Green-blue space exposure changes and impact on individual-level well-being and mental health: a population-wide dynamic longitudinal panel study with linked survey data

Background

Cross-sectional evidence suggests that living near green and blue spaces benefits mental health; longitudinal evidence is limited.

Objectives

To quantify the impact of changes in green and blue spaces on common mental health disorders, well-being and health service use.

Design

A retrospective, dynamic longitudinal panel study.

Setting

Wales, UK.

Participants

An e-cohort comprising 99,682,902 observations of 2,801,483 adults (≥ 16 years) registered with a general practice in Wales (2008-2019). A 5312-strong 'National Survey for Wales (NSW) subgroup' was surveyed on well-being and visits to green and blue spaces.

Main outcome measures

Common mental health disorders, general practice records; subjective well-being, Warwick-Edinburgh Mental Well-being Scale.

Data sources

Common mental health disorder and use of general practice services were extracted quarterly from the Welsh Longitudinal General Practice Dataset. Annual ambient greenness exposure, enhanced vegetation index and access to green and blue spaces (2018) from planning and satellite data. Data were linked within the Secure Anonymised Information Linkage Databank.

Methods

Multilevel regression models examined associations between exposure to green and blue spaces and common mental health disorders and use of general practice. For the National Survey for Wales subgroup, generalised linear models examined associations between exposure to green and blue spaces and subjective well-being and common mental health disorders.

Results and conclusions

Our longitudinal analyses found no evidence that changes in green and blue spaces through time impacted on common mental health disorders. However, time-aggregated exposure to green and blue spaces contrasting differences between people were associated with subsequent common mental health disorders. Similarly, our cross-sectional findings add to growing evidence that residential green and blue spaces and visits are associated with well-being benefits: Greater ambient greenness (+ 1 enhanced vegetation index) was associated with lower likelihood of subsequently seeking care for a common mental health disorder [adjusted odds ratio (AOR) 0.80, 95% confidence interval, (CI) 0.80 to 0.81] and with well-being with a U-shaped relationship [Warwick-Edinburgh Mental Well-being Scale; enhanced vegetation index beta (adjusted) -10.15, 95% CI -17.13 to -3.17; EVI2 beta (quadratic term; adj.) 12.49, 95% CI 3.02 to 21.97]. Those who used green and blue spaces for leisure reported better well-being, with diminishing extra benefit with increasing time (Warwick-Edinburgh Mental Well-being Scale: time outdoors (hours) beta 0.88, 95% CI 0.53 to 1.24, time outdoors2 beta -0.06, 95% CI -0.11 to -0.01) and had 4% lower odds of seeking help for common mental health disorders (AOR 0.96, 95% CI 0.93 to 0.99). Those in urban areas benefited most from greater access to green and blue spaces (AOR 0.89, 95% CI 0.89 to 0.89). Those in material deprivation benefited most from leisure time outdoors (until approximately four hours per week; Warwick-Edinburgh Mental Well-being Scale: time outdoors × in material deprivation: 1.41, 95% CI 0.39 to 2.43; time outdoors2 × in material deprivation -0.18, 95% CI -0.33 to -0.04) although well-being remained generally lower.

Limitations

Longitudinal analyses were restricted by high baseline levels and limited temporal variation in ambient greenness in Wales. Changes in access to green and blue spaces could not be captured annually due to technical issues with national-level planning datasets.

Future work

Further analyses could investigate mental health impacts in population subgroups potentially most sensitive to local changes in access to specific types of green and blue spaces. Deriving green and blue spaces changes from planning data is needed to overcome temporal uncertainties.

Funding

This project was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (Project number 16/07/07) and will be published in full in Public Health Research; Vol. 11, No. 10. Sarah Rodgers is part-funded by the NIHR Applied Research Collaboration North West Coast.

Contraceptive use and pregnancy planning in Britain during the first year of the COVID-19 pandemic: findings from a large, quasi-representative survey (Natsal-COVID)

BACKGROUND

Contraceptive services were significantly disrupted during the COVID-19 pandemic in Britain. We investigated contraception-related health inequalities in the first year of the pandemic.

METHODS

Natsal-COVID Wave 2 surveyed 6658 adults aged 18-59 years between March and April 2021, using quotas and weighting to achieve quasi-representativeness. Our analysis included sexually active participants aged 18-44 years, described as female at birth. We analysed contraception use, contraceptive switching due to the pandemic, contraceptive service access, and pregnancy plannedness.

RESULTS

Of 1488 participants, 1619 were at risk of unplanned pregnancy, of whom 54.1% (51.0%-57.1%) reported routinely using effective contraception in the past year. Among all participants, 14.3% (12.5%-16.3%) reported switching or stopping contraception due to the pandemic. 3.2% (2.0%-5.1%) of those using effective methods pre-pandemic switched to less effective methods, while 3.8% (2.5%-5.9%) stopped. 29.3% (26.9%-31.8%) of at-risk participants reported seeking contraceptive services, of whom 16.4% (13.0%-20.4%) reported difficulty accessing services. Clinic closures and cancelled appointments were commonly reported pandemic-related reasons for difficulty accessing services. This unmet need was associated with younger age, diverse sexual identities and anxiety symptoms. Of 199 pregnancies, 6.6% (3.9%-11.1%) scored as 'unplanned'; less planning was associated with younger age, lower social grade and unemployment.

CONCLUSIONS

Just under a third of participants sought contraceptive services during the pandemic and most were successful, indicating resilience and adaptability of service delivery. However, one in six reported an unmet need due to the pandemic. COVID-induced inequalities in service access potentially exacerbated existing reproductive health inequalities. These should be addressed in the post-pandemic period and beyond.

Ambient greenness, access to local green spaces, and subsequent mental health: a 10-year longitudinal dynamic panel study of 2·3 million adults in Wales

BACKGROUND

Living in greener areas, or close to green and blue spaces (GBS; eg, parks, lakes, or beaches), is associated with better mental health, but longitudinal evidence when GBS exposures precede outcomes is less available. We aimed to analyse the effect of living in or moving to areas with more green space or better access to GBS on subsequent adult mental health over time, while explicitly considering health inequalities.

METHODS

A cohort of the people in Wales, UK (≥16 years; n=2 341 591) was constructed from electronic health record data sources from Jan 1, 2008 to Oct 31, 2019, comprising 19 141 896 person-years of follow-up. Household ambient greenness (Enhanced Vegetation Index [EVI]), access to GBS (counts, distance to nearest), and common mental health disorders (CMD, based on a validated algorithm combining current diagnoses or symptoms of anxiety or depression [treated or untreated in the preceding 1-year period], or treatment of historical diagnoses from before the current cohort [up to 8 years previously, to 2000], where diagnosis preceded treatment) were record-linked. Cumulative exposure values were created for each adult, censoring for CMD, migration out of Wales, death, or end of cohort. Exposure and CMD associations were evaluated using multivariate logistic regression, stratified by area-level deprivation.

FINDINGS

After adjustment, exposure to greater ambient greenness over time (+0·1 increased EVI on a 0-1 scale) was associated with lower odds of subsequent CMD (adjusted odds ratio 0·80, 95% CI 0·80-0·81), where CMD was based on a combination of current diagnoses or symptoms (treated or untreated in the preceding 1-year period), or treatments. Ten percentile points more access to GBS was associated with lower odds of a later CMD (0·93, 0·93-0·93). Every additional 360 m to the nearest GBS was associated with higher odds of CMD (1·05, 1·04-1·05). We found that positive effects of GBS on mental health appeared to be greater in more deprived quintiles.

INTERPRETATION

Ambient exposure is associated with the greatest reduced risk of CMD, particularly for those who live in deprived communities. These findings support authorities responsible for GBS, who are attempting to engage planners and policy makers, to ensure GBS meets residents' needs.

FUNDING

National Institute for Health and Care Research Public Health Research programme.

Variation in availability and use of surgical care for female urinary incontinence: a mixed-methods study

Background

Urinary incontinence affects between 25% and 45% of women. The availability and quality of services is variable and inequitable, but our understanding of the drivers is incomplete.

Objectives

The objectives of the study were to model patient, specialist clinician, primary and secondary care, and geographical factors associated with referral and surgery for urinary incontinence, and to explore women’s experiences of urinary incontinence and expectations of treatments.

Design

This was a mixed-methods study.

Setting

The setting was NHS England.

Participants

Data were collected from all women with a urinary incontinence diagnosis in primary care data, and all women undergoing mid-urethral mesh tape surgery for stress urinary incontinence were included. Interviews were also carried out with 28 women from four urogynaecology clinics who were deciding whether or not to have surgery, and surveys were completed by 245 members of the Royal College of Obstetricians and Gynaecologists with a specialist interest in urinary incontinence.

Data sources

The sources were patient-level data from Hospital Episode Statistics, the Clinical Practice Research Datalink and the Office for National Statistics mortality data linked to Hospital Episode Statistics. Interviews were conducted with women. An online vignette survey was conducted with members of the Royal College of Obstetricians and Gynaecologists.

Main outcome measures

The main outcome measures were the rates of referral from primary to secondary care and surgery after referral, the rates of stress urinary incontinence surgery by geographical area, the risk of mid-urethral mesh tape removal and reoperation after mid-urethral mesh tape insertion.

Results

Almost half (45.8%) of women with a new urinary incontinence diagnosis in primary care were referred to a urinary incontinence specialist: 59.5% of these referrals were within 30 days of diagnosis. In total, 14.2% of women referred to a specialist underwent a urinary incontinence procedure (94.5% of women underwent a stress urinary incontinence procedure and 5.5% underwent an urgency urinary incontinence procedure) during a follow-up period of up to 10 years. Not all women were equally likely to be referred or receive surgery. Both referral and surgery were less likely for older women, those who were obese and those from minority ethnic backgrounds. The stress urinary incontinence surgery rate was 40 procedures per 100,000 women per year, with substantial geographical variation. Among women undergoing mid-urethral mesh tape insertion for stress urinary incontinence, the 9-year mesh tape removal rate was 3.3%. Women’s decision-making about urinary incontinence surgery centred on perceptions of their urinary incontinence severity and the seriousness/risk of surgery. Women judged urinary incontinence severity in relation to their daily lives and other women’s experiences, rather than frequency or quantity of leakage, as is often recorded and used by clinicians. Five groups of UK gynaecologists could be distinguished who differed mainly in their average inclination to recommend surgery to hypothetical urinary incontinence patients. The gynaecologists’ recommendations were also influenced by urinary incontinence subtype and the patient’s history of previous surgery.

Limitations

The primary and secondary care data lacked information on the severity of urinary incontinence.

Conclusions

There was substantial variation in rates of referrals, surgery, and mesh tape removals, both geographically and between women of different ages and women from different ethnic backgrounds. The variation persisted after adjustment for factors that were likely to affect women’s preferences. Growing safety concerns over mid-urethral mesh tape surgery for stress urinary incontinence during the period from which the data are drawn are likely to have introduced more uncertainty to women’s and clinicians’ treatment decision-making.

Future work

Future work should capture outcomes relevant to women, including ongoing urinary incontinence and pain that is reported by women themselves, both before and after mesh and non-mesh procedures, as well as following conservative treatments. Future research should examine long-term patient-reported outcomes of treatment, including for women who do not seek further health care or surgery, and the extent to which urinary incontinence severity explains observed variation in referrals and surgery.

Funding

This project was funded by the National Institute for Health Research (NIHR) Health Services and Delivery Research programme and will be published in full in Health Services and Delivery Research; Vol. 9, No. 7. See the NIHR Journals Library website for further project information.

Uptake and outcomes of robotic gynaecological surgery in England (2006-2018): an account of Hospital Episodes Statistics (HES)

This was a retrospective study to review the uptake and outcomes of robotic gynaecological surgery in England between 1st April 2006 and 31st March 2018, analysing Hospital Episode Statistics form National Health Service hospitals in England. Women aged 18 years and above who had elective gynaecological surgery were included and those who had undergone robotic gynaecology surgery were included. Robotic gynaecological procedures were defined as procedures that used a robotic minimal access approach for hysterectomy, adnexal surgery and urogynaecological surgery (sacrocolpopexy, sacrohysteropexy and colposuspension). Numbers of procedures were reviewed by year and mapped to the 44 NHS healthcare regions. Length of stay (nights in hospital), laparotomy (conversion during primary procedure or after return to theatre for management of complication), and 30-day emergency readmission rates were calculated by year and procedure type. Overall 527,217 elective gynaecological procedures were performed in the English NHS (1st April 2006 and 31st March 2018), of which 4384 (0.83%) were performed with robotic assistance (3864 (88%) hysterectomy, 706 (16%) adnexal surgery, 192 (4%) urogynaecological surgery). There was gradual rise in the uptake of robotic surgery but there was a marked geographical variation. Median (IQR) length of stay (LOS) was 1(1-2) night, laparotomy rate was 0.3% and 30-day emergency readmission rate was 4.7%. LOS was statistically, but not clinically, different across time. Other outcomes did not differ by year. Robotic gynaecological procedures are increasingly being used in the English NHS, predominantly for hysterectomy, although in small proportions (2.6% in the most recent study year). There was wide geographical variation in robotic uptake across England and overall, outcomes were comparable to those reported in other countries.

Determinants of referral of women with urinary incontinence to specialist services: a national cohort study using primary care data from the UK

BACKGROUND

Female urinary incontinence is underdiagnosed and undertreated in primary care. There is little evidence on factors that determine whether women with urinary incontinence are referred to specialist services. This study aimed to investigate characteristics associated with referrals from primary to specialist secondary care for urinary incontinence.

METHODS

We carried out a cohort study, using primary care data from over 600 general practices contributing to the Clinical Practice Research Datalink (CPRD) in the United Kingdom. We used multi-level logistic regression to estimate adjusted odds ratios (aOR) that reflect the impact of patient and GP practice-level characteristics on referrals to specialist services in secondary care within 30 days of a urinary incontinence diagnosis. All women aged ≥18 years newly diagnosed with urinary incontinence between 1 April 2004 and 31 March 2013 were included. One-year referral was estimated with death as competing event.

RESULTS

Of the 104,466 included women (median age: 58 years), 28,476 (27.3%) were referred within 30 days. Referral rates decreased with age (aOR 0.34, 95% CI 0.31-0.37, comparing women aged ≥80 with those aged 40-49 years) and was lower among women who were severely obese (aOR 0.84, 95% CI 0.78-0.90), smokers (aOR 0.94, 95% CI 0.90-0.98), women from a minority-ethnic backgrounds (aOR 0.76, 95% CI 0.65-0.89 comparing Asian with white women), women with pelvic organ prolapse (aOR 0.77, 95% CI 0.68-0.87), and women in Scotland (aOR 0.60, 95% CI 0.46-0.78, comparing women in Scotland and England). One-year referral rate was 34.0% and the pattern of associations with patient characteristics was almost the same as for 30-day referrals.

CONCLUSIONS

About one in four women with urinary incontinence were referred to specialist secondary care services within one month after a UI diagnosis and one in three within one year. Referral rates decreased with age which confirms concerns that older women with UI are less likely to receive care according to existing clinical guidelines. Referral rates were also lower in women from minority-ethnic backgrounds. These finding may reflect clinicians' beliefs about the appropriateness of referral, differences in women's preferences for treatment, or other factors leading to inequities in referral for urinary incontinence.

Sexual mixing in opposite-sex partnerships in Britain and its implications for STI risk: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3)

Background

The extent to which individuals are similar to their sexual partners influences STI-transmission probabilities, yet there is a dearth of empirical data, especially those representative of the population.

Methods

Analyses of data reported by 10 759 sexually active people aged 16–74 y interviewed for a British national probability survey undertaken in 2010–12. Computer-assisted self-interviews asked about partner numbers and characteristics of participants’ three most recent partnerships (MRPs). Opposite-sex MRPs were weighted to represent all such partnerships in the past year (N = 16 451). Estimates of disassortative age mixing (≥±5-y difference), ethnic mixing (partner of a different ethnic group) and geographical mixing (partner from a different region/country when they first met) were calculated, stratified by gender, age group and partnership status (casual/steady). Multivariable regression examined how these disassortative mixing measures were associated with STI-risk measures: condom use at first sex together at the partnership-level and, at the participant-level, STI-risk perception and reporting STI diagnoses.

Results

Disassortative age mixing occurred in around one-third of opposite-sex partnerships, with men ≥5 y older in most cases, although this proportion varied by participant’s gender and age group. Ethnic mixing occurred less frequently (11.3% of men’s and 8.6% of women’s partnerships) as did geographical mixing (14.1 and 16.3%, respectively). Disassortative mixing was more common among casual vs steady partnerships. Condom use at first sex was less likely in women’s partnerships that were age-disassortative [adjusted odds ratio (AOR): 0.79, 95% confidence interval (CI): 0.69–0.95], whereas men reporting disassortative ethnic mixing were more likely to perceive themselves at STI risk (AOR: 1.76, 95% CI: 1.23–2.52) and report STI diagnoses (AOR: 2.37, 95% CI: 1.22–4.59).

Conclusions

Disassortative mixing, although uncommon among opposite-sex partnerships in Britain, is independently associated with STI risk, warranting consideration in STI-prevention efforts.

Geographical variation in rates of surgical treatment for female stress urinary incontinence in England: a national cohort study

OBJECTIVE

To examine geographic variation in use of surgery for female stress urinary incontinence (SUI), mainly midurethral mesh tape insertions, in the English National Health Service (NHS).

DESIGN

National cohort study.

SETTING

NHS hospitals.

PARTICIPANTS

27 997 women aged 20 years or older who had a first SUI surgery in an English NHS Hospital between April 2013 and March 2016 and a diagnosis of SUI at the same time as the procedure.

METHODS

Multilevel Poisson regression was used to adjust for geographic differences in age, ethnicity, prevalence of long-term illness and socioeconomic deprivation.

PRIMARY OUTCOME MEASURE

Rate of surgery for SUI per 100 000 women/year at two geographic levels: Clinical Commissioning Group (CCG; n=209) and Sustainability and Transformation Partnership (STP; n=44).

RESULTS

The rate of surgery for SUI was 40 procedures per 100 000 women/year. Risk-adjusted rates ranged from 20 to 106 procedures per 100 000 women/year across CCGs and 24 to 69 procedures per 100 000 women/year across the STP areas. These regional differences were only partially explained by demographic characteristics as adjustment reduced variance of surgery rates by 16% among the CCGs and 35% among the STPs.

CONCLUSIONS

Substantial geographic variation exists in the use of surgery for female SUI in the English NHS, suggesting that women in some areas are more likely to be treated compared with women with the same condition in other areas. The variation reflects differences in how national guidelines are being interpreted in the context of the ongoing debate about the safety of SUI surgery.

Association of Timing of Sexual Partnerships and Perceptions of Partners' Concurrency With Reporting of Sexually Transmitted Infection Diagnosis

IMPORTANCE

The timing of sexual partnerships is important for sexually transmitted infection (STI) transmission potential. Studies often measure timing as whether partnerships overlap in time (concurrency), but this measure does not account for how STI risk from previous partners can be carried forward into future partnerships even when there is a time gap between them (serial monogamy) if the infectious period is greater than this time gap.

OBJECTIVE

To examine the association of the timing of partnerships, measured as the time gap or time overlap between partners, and perceptions of partners' concurrency with STI transmission.

DESIGN, SETTING, AND PARTICIPANTS

This survey study that was conducted in 2017 included 8867 participants in Britain aged 16 to 44 years who reported 1 or more sexual partners in the 5 years before the interview. Data were collected from 2010 to 2012 from Britain's third National Survey of Sexual Attitudes and Lifestyles (Natsal-3), a large probability survey (response rate, 57.7%) designed to be broadly representative of the general population.

EXPOSURES

Gaps between participants' 3 or fewer most recent partners in the past 5 years were calculated from dates of the last sexual encounter with former partners and the first sexual encounter with subsequent partners. Negative gaps denote overlapping partnerships (concurrency); positive gaps denote serial monogamy. Participant perception of most recent partner concurrency was proxied by asking participants whether they knew or thought that their partners had had sex with other partners since their first sexual encounter together.

MAIN OUTCOMES AND MEASURES

Reported STI diagnosis in the past 5 years.

RESULTS

Of 8867 participants eligible for this analysis, 3509 (39.6%) were male and 5158 (58.2%) were female, with a mean age of 28 years. Overall, 48.1% of males and 39.5% of females reported 2 or more partners and 1 or more time gaps. The median time gap was 2 months (interquartile range, -3 months to 8 months). Although 67.0% of the time gaps were 1 month or more, many were sufficiently short time gaps for STI transmission. The time gap was independently associated with STI diagnosis, without a significant decrease in likelihood until the time gap was 4 months or more for females (adjusted odds ratio [OR]: 0.39, 95% CI, 0.19-0.81) and 6 months or more for males (adjusted OR: 0.42, 95% CI, 0.20-0.85) compared with time overlaps of 2 years or more. Participant perception of partners' concurrency (reported by half of the participants) was independently associated with STI diagnosis among females (reporting no partner concurrency vs reporting partner concurrency: adjusted OR, 0.32; 95% CI, 0.22-0.49).

CONCLUSIONS AND RELEVANCE

The findings suggest that the gap between partners is often sufficiently small to permit STI transmission and that many people, although themselves monogamous, have partners who are not, which itself is associated with an increase in the risk of STI acquisition. Public health practitioners should communicate these epidemiological facts, and researchers should develop measures that better capture the risk of STI transmission from partners.

Long-term Rate of Mesh Sling Removal Following Midurethral Mesh Sling Insertion Among Women With Stress Urinary Incontinence

Importance

There is concern about outcomes of midurethral mesh sling insertion for women with stress urinary incontinence. However, there is little evidence on long-term outcomes.

Objective

To examine long-term mesh removal and reoperation rates in women who had a midurethral mesh sling insertion for stress urinary incontinence.

Design, Setting, and Participants

This population-based retrospective cohort study included 95 057 women aged 18 years or older who had a first-ever midurethral mesh sling insertion for stress urinary incontinence in the National Health Service hospitals in England between April 1, 2006, and December 31, 2015. Women were followed up until April 1, 2016.

Exposures

Patient and hospital factors and retropubic or transobturator mesh sling insertions.

Main Outcomes and Measures

The primary outcome was the risk of midurethral mesh sling removal (partial or total) and secondary outcomes were reoperation for stress urinary incontinence and any reoperation including mesh removal, calculated with death as competing risk. A multivariable Fine-Gray model was used to calculate subdistribution hazard ratios as estimates of relative risk.

Results

The study population consisted of 95 057 women (median age, 51 years; interquartile range, 44-61 years) with first midurethral mesh sling insertion, including 60 194 with retropubic insertion and 34 863 with transobturator insertion. The median follow-up time was 5.5 years (interquartile range, 3.2-7.5 years). The rate of midurethral mesh sling removal was 1.4% (95% CI, 1.3%-1.4%) at 1 year, 2.7% (95% CI, 2.6%-2.8%) at 5 years, and 3.3% (95% CI, 3.2%-3.4%) at 9 years. Risk of removal declined with age. The 9-year removal risk after transobturator insertion (2.7% [95% CI, 2.4%-2.9%]) was lower than the risk after retropubic insertion (3.6% [95% CI, 3.5%-3.8%]; subdistribution hazard ratio, 0.72 [95% CI, 0.62-0.84]). The rate of reoperation for stress urinary incontinence was 1.3% (95% CI, 1.3%-1.4%) at 1 year, 3.5% (95% CI, 3.4%-3.6%) at 5 years, and 4.5% (95% CI, 4.3%-4.7%) at 9 years. The rate of any reoperation, including mesh removal, was 2.6% (95% CI, 2.5%-2.7%) at 1 year, 5.5% (95% CI, 5.4%-5.7%) at 5 years, and 6.9% (95% CI, 6.7%-7.1%) at 9 years.

Conclusions and Relevance

Among women undergoing midurethral mesh sling insertion, the rate of mesh sling removal at 9 years was estimated as 3.3%. These findings may guide women and their surgeons when making decisions about surgical treatment of stress urinary incontinence.

A step-wise approach to developing indicators to compare the performance of maternity units using hospital administrative data

Hospital administrative data are attractive for comparing performance of maternity units because of their often large sample sizes, lack of selection bias and the relatively low costs of accessing these data compared with conducting primary data collection. However, using administrative data to develop indicators can also present challenges including varying data quality, the limited detail on clinical risk factors and a lack of structural and user experience measures. This review illustrates how to develop performance indicators for maternity units using hospital administrative data, including methods to address the challenges that administrative data pose.

TWEETABLE ABSTRACT

How to develop maternity indicators from administrative data.

Sexual identity, attraction and behaviour in Britain: The implications of using different dimensions of sexual orientation to estimate the size of sexual minority populations and inform public health interventions

BACKGROUND

Sexual orientation encompasses three dimensions: sexual identity, attraction and behaviour. There is increasing demand for data on sexual orientation to meet equality legislation, monitor potential inequalities and address public health needs. We present estimates of all three dimensions and their overlap in British men and women, and consider the implications for health services, research and the development and evaluation of public health interventions.

METHODS

Analyses of data from Britain's third National Survey of Sexual Attitudes and Lifestyles, a probability sample survey (15,162 people aged 16-74 years) undertaken in 2010-2012.

FINDINGS

A lesbian, gay or bisexual (LGB) identity was reported by 2·5% of men and 2·4% of women, whilst 6·5% of men and 11·5% of women reported any same-sex attraction and 5·5% of men and 6·1% of women reported ever experience of same-sex sex. This equates to approximately 547,000 men and 546,000 women aged 16-74 in Britain self-identifying as LGB and 1,204,000 men and 1,389,000 women ever having experience of same-sex sex. Of those reporting same-sex sex in the past 5 years, 28% of men and 45% of women identified as heterosexual.

INTERPRETATION

There is large variation in the size of sexual minority populations depending on the dimension applied, with implications for the design of epidemiological studies, targeting and monitoring of public health interventions and estimating population-based denominators. There is also substantial diversity on an individual level between identity, behaviour and attraction, adding to the complexity of delivering appropriate services and interventions.

Sexual health clinic attendance and non-attendance in Britain: findings from the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3)

Objectives

In Britain, sexual health clinics (SHCs) are the most common location for STI diagnosis but many people with STI risk behaviours do not attend. We estimate prevalence of SHC attendance and how this varies by sociodemographic and behavioural factors (including unsafe sex) and describe hypothetical service preferences for those reporting unsafe sex.

Methods

Complex survey analyses of data from Britain’s third National Survey of Sexual Attitudes and Lifestyles, a probability survey of 15 162 people aged 16–74 years, undertaken 2010–2012.

Results

Overall, recent attendance (past year) was highest among those aged 16–24 years (16.6% men, 22.4% women), decreasing with age (<1.5% among those 45–74 years). Approximately 15% of sexually-active 16–74 year olds (n=1002 men; n=1253 women) reported ‘unsafe sex’ (condomless first sex with a new partner and/or ≥2 partners and no condom use, past year); >75% of these had not attended a SHC (past year). However, of non-attenders aged 16–44 years, 18.7% of men and 39.0% of women reported chlamydia testing (past year) with testing highest in women aged <25 years. Of those aged 16–44 years reporting unsafe sex, the majority who reported previous SHC attendance would seek STI care there, whereas the majority who had not would use general practice.

Conclusion

While most reporting unsafe sex had not attended a SHC, many, particularly younger women, had tested for chlamydia suggesting engagement with sexual health services more broadly. Effective, diverse service provision is needed to engage those at-risk and ensure that they can attend services appropriate to their needs.

Actual and preferred contraceptive sources among young people: findings from the British National Survey of Sexual Attitudes and Lifestyles

OBJECTIVE

To describe actual and preferred contraceptive sources among young people in Britain and whether discordance between these is associated with markers of sexual risk behaviour or poor sexual health.

DESIGN

Cross-sectional probability sample survey.

SETTING

British general population.

PARTICIPANTS

3869 men and women aged 16-24 years interviewed for the third National Survey of Sexual Attitudes and Lifestyles (Natsal-3) between 2010 and 2012.

MAIN OUTCOME MEASURES

Reported source of contraceptive method(s) and preferred source if all were available and easily accessible.

RESULTS

Of the 75% of young people (aged 16-24) who were heterosexually active (1619 women, 1233 men), >86% reported obtaining contraceptives in the past year. Most common sources were general practice (women, 63%) and retail (men, 60%): using multiple sources was common (women 40%, men 45%). Healthcare sources were preferred by 81% of women and 57% of men. Overall, 32% of women and 39% of men had not used their preferred source. This discordance was most common among men who preferred general practice (69%) and women who preferred retail (52%). Likelihood of discordance was higher among women who usually used a less effective contraceptive method or had an abortion. It was less likely among men who usually used a less effective method of contraception and men who were not in a steady relationship.

CONCLUSIONS

Most young people in Britain obtained contraception in the past year but one-third had not used their preferred source. Healthcare sources were preferred. Discordance was associated with using less effective contraception and abortion among young women. Meeting young people's preference for obtaining contraception from healthcare sources could improve uptake of effective contraception to reduce unwanted pregnancies.

Changes in conceptions in women younger than 18 years and the circumstances of young mothers in England in 2000-12: an observational study

BACKGROUND

In 2000, a 10-year Teenage Pregnancy Strategy was launched in England to reduce conceptions in women younger than 18 years and social exclusion in young parents. We used routinely collected data and data from Britain's National Surveys of Sexual Attitudes and Lifestyles (Natsal) to examine progress towards these goals.

METHODS

In this observational study, we used random-effects meta-regression to analyse the change in conception rates from 1994-98 to 2009-13 by top-tier local authorities in England, in relation to Teenage Pregnancy Strategy-related expenditure per head, socioeconomic deprivation, and region. Data from similar probability sample surveys: Natsal-1 (1990-91), Natsal-2 (1999-2001), and Natsal-3 (2010-12) were used to assess the prevalence of risk factors and their association with conception in women younger than 18 years in women aged 18-24 years; and the prevalence of participation in education, work, and training in young mothers.

FINDINGS

Conception rates in women younger than 18 years declined steadily from their peak in 1996-98 and more rapidly from 2007 onwards. More deprived areas and those receiving greater Teenage Pregnancy Strategy-related investment had higher rates of conception in 1994-98 and had greater declines to 2009-13. Regression analyses assessing the association between Teenage Pregnancy Strategy funding and decline in conception rates in women younger than 18 years showed an estimated reduction in the conception rate of 11.4 conceptions (95% CI 9.6-13.2; p<0.0001) per 1000 women aged 15-17 years for every £100 Teenage Pregnancy Strategy spend per head and a reduction of 8.2 conceptions (5.8-10.5; p<0.0001) after adjustment for socioeconomic deprivation and region. The association between conception in women younger than 18 years and lower socioeconomic status weakened slightly between Natsal-2 and Natsal-3. The prevalence of participation in education, work, or training among young women with a child conceived before age 18 years was low, but the odds of them doing so doubled between Natsal-2 and Natsal-3 (odds ratio 1.99, 95% CI 0.99-4.00).

INTERPRETATION

A sustained, multifaceted policy intervention involving health and education agencies, alongside other social and educational changes, has probably contributed to a substantial and accelerating decline in conceptions in women younger than 18 years in England since the late 1990s.

FUNDING

Medical Research Council, Wellcome Trust, Economic and Social Research Council, and Department of Health.

The gender dimensions of social networks and help-seeking behaviors of young adults in Soweto, South Africa

Background

Young people constitute a major proportion of the general population and are influenced by a variety of factors, especially in regards to seeking help. An understanding of help-seeking behaviors among young people is important for designing and implementing effective targeted health services.

Methods

We conducted in-depth interviews with 23 young adults aged 21–22 years in Soweto, South Africa, to explore the gender dimensions of social networks and help-seeking behaviors.

Results

We found that young men had larger peer social networks than young women and that young women's social networks centered on their households. For general health, both young men and young women often sought help from an older, maternal figure. However, for sexual health, young men consulted their group of peers, whereas young women were more likely to seek information from one individual, such as an older female friend or family member.

Conclusion

These differences in help-seeking behaviors have important implications for the delivery of health information in South Africa and how health promotion is packaged to young men and women, especially for sexual and reproductive health issues. Peer educators might be very effective at conveying health messages for young men, whereas women might respond better to health information presented in a more confidential setting either through community health workers or mHealth technologies. Provision of or linkage to health services that is consistent with young people's health-seeking behavior, such as using peer educators and community health care workers, may increase the reach and utilization of these services among young people.

Evaluating youth-friendly health services: young people's perspectives from a simulated client study in urban South Africa

Background

Few youth-friendly health services worldwide have been scaled up or evaluated from young people’s perspectives. South Africa’s Youth Friendly Services (YFS) programme is one of the few to have been scaled up. This study investigated young people’s experiences of using sexual and reproductive health services at clinics providing the YFS programme, compared to those that did not, using the simulated client method.

Design

Fifteen primary healthcare clinics in Soweto were randomly sampled: seven provided the YFS programme. Simulated clients conducted 58 visits; young men requested information on condom reliability and young women on contraceptive methods. There were two outcome measures: a single measure of the overall clinic experience (clinic visit score) and whether or not simulated clients would recommend a clinic to their peers. The clinic visit score was based on variables relating to the simulated clients’ interactions with staff, details of their consultation, privacy, confidentiality, the healthcare workers’ characteristics, and the clinic environment. A larger score corresponds to a worse experience than a smaller one. Multilevel regression models and framework analysis were used to investigate young people’s experiences.

Results

Health facilities providing the YFS programme did not deliver a more positive experience to young people than those not providing the programme (mean difference in clinic visit score: −0.18, 95% CI: −0.95, 0.60, p=0.656). They were also no more likely to be recommended by simulated clients to their peers (odds ratio: 0.48, 95% CI: 0.11, 2.10, p=0.331). More positive experiences were characterised by young people as those where healthcare workers were friendly, respectful, knew how to talk to young people, and appeared to value them seeking health information. Less positive experiences were characterised by having to show soiled sanitary products to obtain contraceptives, healthcare workers expressing negative opinions about young people seeking information, lack of privacy, and inadequate information.

Conclusions

The provision and impact of the YFS programme are limited. Future research should explore implementation. Regular training and monitoring could enable healthcare workers to address young people’s needs.

The effectiveness of youth centers in increasing use of sexual and reproductive health services: a systematic review

This study presents findings from a systematic review of the evidence regarding the effectiveness of youth centers in increasing use of sexual and reproductive health (SRH) services in lower- and middle-income countries. Evidence from peer-reviewed and gray literature between 1990 and 2010 was reviewed. After the screening of 3,769 citations, 21 studies reporting on 17 youth center programs were included, and were ranked by strength of evidence. Considerable consistency in findings across studies was observed. Youth centers generally served a relatively small proportion of young people living nearby. The main users were young men attending school or college, with a significant proportion older than the target age. Users of the on-site SRH services were predominantly young women, with a significant proportion older than the target age group. Uptake of services was generally low. Despite widespread emphasis on youth centers as a strategy for encouraging young people to access SRH services, results from these studies have not been encouraging, and cost-effectiveness for these purposes is likely to be low.

Bioavailability and therapeutic activity of alicaforsen (ISIS 2302) administered as a rectal retention enema to subjects with active ulcerative colitis

BACKGROUND

Alicaforsen is a phosphorothioate-modified antisense oligodeoxynucleotide designed to sequence-specifically reduce intercellular adhesion molecule 1 messenger RNA levels.

AIMS

To determine the systemic and local bioavailability of alicaforsen, and its activity when administered as a once daily enema in subjects with active ulcerative colitis. METHODS An open-label study was conducted to assess the relative absorption (local and systemic pharmacokinetics) and pharmacologic activity of alicaforsen enema in subjects with active ulcerative colitis. Fifteen subjects received nightly enemas of alicaforsen (240 mg) for a treatment period of 6 weeks. Alicaforsen concentrations in plasma and colonic tissue biopsies were determined. Disease activity index and multiple measurements including endoscopy were used to assess alicaforsen activity in these subjects.

RESULTS

Plasma concentrations of parent alicaforsen represented < 0.6% mean bioavailability when compared with historical intravenous area under the plasma concentration-time curves. Concentrations of the intact oligonucleotide in mucosal colonic tissue biopsies were orders of magnitude higher than those observed in plasma. A 46% reduction in mean Disease Activity Index and 33% rate of remission as defined by complete mucosal healing were observed at the end of treatment. Conclusion These data confirm that alicaforsen enema provides local treatment for a local disease with little meaningful systemic exposure.

Oral bioavailability and multiple dose tolerability of an antisense oligonucleotide tablet formulated with sodium caprate

In vivo study was performed to determine the tolerability and pharmacokinetics of ISIS 104838, a phosphorothioate antisense oligonucleotide targetting human tumour necrosis factor alpha (TNF-alpha) mRNA, following multi-dose administration via intravenous and oral routes. Oral tablet formulations of ISIS 104838 were pre-formulated with the permeation enhancer, sodium caprate, in an enteric-coated solid dosage form. The average plasma bioavailability of ISIS 104838 was 1.4% relative to IV. The tissue distribution profile was similar following both routes of administration, with highest concentrations observed in the kidney followed by the liver, lymph nodes and spleen. Plasma bioavailability underestimated the tissue accumulation of ISIS 104838 observed 1 day after the last dose. Mean systemic tissue bioavailability ranged from 2.0 to 4.3%, relative to IV tissues, and was dependent on tissue type. No marked differences were noted in the pharmacokinetic parameters following multi-dosing either via intravenous or oral routes. All formulations administered were well tolerated. This paper reports the first evaluation of solid oral dosage forms comprising sodium caprate and an antisense oligonucleotide. Furthermore, this study demonstrates the oral delivery of ISIS 104838 from solid oral dose formulations, with the achievement of comparable tissue concentrations of the oligonucleotide to that of the intravenous treatment.

A Phase I trial of H-ras antisense oligonucleotide ISIS 2503 administered as a continuous intravenous infusion in patients with advanced carcinoma

BACKGROUND

Abnormal expression of Ras proteins frequently is found with oncogenic transformation making ras a promising therapeutic target. ISIS 2503 is a 20-base antisense phosphorothioate oligodeoxyribonucleotide that specifically downregulates H-ras expression and inhibits tumor cell growth in preclinical studies. Here, the authors report an initial clinical study of the safety and tolerability of an intravenous infusion of ISIS 2503 in patients with advanced cancer.

METHODS

A continuous intravenous infusion of ISIS 2503 was administered for 14 days every 3 weeks to 23 patients with a variety of solid tumors refractory to standard therapy. The dose of ISIS 2503 was increased in sequential cohorts of patients, as toxicity allowed, until a final dose of 10.0 mg/kg/day of body weight was reached. Toxicity was scored by the National Cancer Institute's Common Toxicity Criteria, and tumor response was monitored after every two treatment cycles. Pharmacokinetic studies were performed in some of the patients up to, and including, the final dose of 10 mg/kg/day/day of body weight. Levels of H-ras mRNA expression also were determined in the circulating lymphocytes of some patients by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

A total of 23 patients received 63 cycles of ISIS 2503 at escalating doses to 10.0 mg/kg/day without dose-limiting toxicity and only minimal side effects. Four patients had stabilization of their disease for 6-10 cycles. No consistent decreases in H-ras mRNA levels were observed in peripheral blood lymphocytes.

CONCLUSIONS

ISIS 2503, an antisense oligonucleotide against H-ras, was well tolerated as a single agent at doses up to 10.0 mg/kg/day by 14-day continuous intravenous infusion. Several patients had stabilization of disease, suggesting that ISIS 2503 had some tumor growth inhibitory effects and future trials of ISIS 2503 in combination with chemotherapy should be considered.

Drug properties of second-generation antisense oligonucleotides: how do they measure up to their predecessors?

Antisense technology has progressed beyond the point of using only phosphorothioate oligodeoxynucleotides as therapeutic agents to looking at antisense molecules that contain additional chemical modifications as the next generation of therapeutic agents. These modifications are intended to improve the overall therapeutic properties by increasing potency, optimizing pharmacokinetic properties and improving the safety profile. This review will focus on the non-clinical pharmacokinetic and safety properties of 2'-O-methoxyethyl-modified oligonucleotides. Implications on the convenience and safe use of these compounds as therapeutic agents will be discussed.

A Phase I trial of H-ras antisense oligonucleotide ISIS 2503 administered as a continuous intravenous infusion in patients with advanced carcinoma

BACKGROUND

Abnormal expression of Ras proteins frequently is found with oncogenic transformation making ras a promising therapeutic target. ISIS 2503 is a 20-base antisense phosphorothioate oligodeoxyribonucleotide that specifically downregulates H-ras expression and inhibits tumor cell growth in preclinical studies. Here, the authors report an initial clinical study of the safety and tolerability of an intravenous infusion of ISIS 2503 in patients with advanced cancer.

METHODS

A continuous intravenous infusion of ISIS 2503 was administered for 14 days every 3 weeks to 23 patients with a variety of solid tumors refractory to standard therapy. The dose of ISIS 2503 was increased in sequential cohorts of patients, as toxicity allowed, until a final dose of 10.0 mg/kg/day of body weight was reached. Toxicity was scored by the National Cancer Institute's Common Toxicity Criteria, and tumor response was monitored after every two treatment cycles. Pharmacokinetic studies were performed in some of the patients up to, and including, the final dose of 10 mg/kg/day/day of body weight. Levels of H-ras mRNA expression also were determined in the circulating lymphocytes of some patients by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

A total of 23 patients received 63 cycles of ISIS 2503 at escalating doses to 10.0 mg/kg/day without dose-limiting toxicity and only minimal side effects. Four patients had stabilization of their disease for 6-10 cycles. No consistent decreases in H-ras mRNA levels were observed in peripheral blood lymphocytes.

CONCLUSIONS

ISIS 2503, an antisense oligonucleotide against H-ras, was well tolerated as a single agent at doses up to 10.0 mg/kg/day by 14-day continuous intravenous infusion. Several patients had stabilization of disease, suggesting that ISIS 2503 had some tumor growth inhibitory effects and future trials of ISIS 2503 in combination with chemotherapy should be considered.

Pharmacokinetics of phosphorothioate antisense oligodeoxynucleotides

Phosphorothioate (PS) oligodeoxynucleotides represent the class of antisense drugs most advanced in development and clinical testing. Exploitation of antisense oligonucleotide technology for development of rationally designed therapeutic drugs has presented a unique set of challenges, some of which relate to their pharmacokinetic behavior in vivo. Pharmacokinetic studies of PS oligodeoxynucleotides demonstrate that they are well absorbed from parenteral sites, rapidly distributed broadly to all peripheral tissues, do not cross the blood-brain barrier, and are eliminated primarily by slow metabolism in tissues. In general, the pharmacokinetic properties of this class of compounds appear to be largely driven by chemistry rather than sequence.

Pharmacokinetic properties of 2'-O-(2-methoxyethyl)-modified oligonucleotide analogs in rats

Plasma pharmacokinetics, biodistribution, excretion, and metabolism of four modified 20-mer antisense oligonucleotides targeted to human intercellular adhesion molecule-1 mRNA have been characterized in rats and compared with a first-generation phosphorothioate oligodeoxynucleotide (PS ODN), ISIS 2302. The modified oligonucleotides contained 2'-O-(2-methoxyethyl) (2'-O-MOE) ribose sugar modifications on all or a portion of the nucleotides in the antisense sequence. The 2'-O-MOE-modified oligonucleotides were resistant to nuclease metabolism in both plasma and tissue. In general, plasma pharmacokinetics was not substantially altered by addition of the 2'-O-MOE modification to PS ODN. Thus, plasma clearance was dominated by distribution to tissues, broadly, with less than 10% of the administered dose excreted in urine or feces over 24 h. However, the 2'-O-MOE modification combined with the phosphodiester (PO) backbone exhibited 10-fold more rapid plasma clearance, with approximately 50% of the dose excreted in urine as intact oligonucleotide. Consistent with its rapid and extensive excretion, the PO 2'-O-MOE modification distributed to very few organs in any substantial amount with the exception of the kidney. Oligonucleotides that contained phosphorothioate backbones were highly bound to plasma proteins. Indeed, the primary characteristic that resulted in the most marked alterations in pharmacokinetics appeared to be the affinity and capacity of these compounds to bind plasma proteins. A balance of greater stability supplied by the 2'-O-MOE modification together with maintenance of plasma protein binding appears to be necessary to ensure favorable pharmacokinetics of this new generation of antisense oligonucleotides.

Absolute bioavailability of 2'-O-(2-methoxyethyl)-modified antisense oligonucleotides following intraduodenal instillation in rats

Three modified 20-mer antisense oligonucleotides targeted to human intercellular adhesion molecule-1 mRNA were characterized for their presystemic stability and oral bioavailability compared with a first-generation phosphorothioate oligodeoxynucleotide (PS ODN), ISIS 2302. The three modified oligonucleotides contained 2'-O-(2-methoxyethyl) (2'-O-MOE) ribose sugar modifications on a portion, or on all of the nucleotides in the antisense sequence. In vitro metabolism studies conducted in various gastrointestinal and digestive tissue preparations indicated substantial improvement in stability of 2'-O-MOE-modified oligonucleotides. In addition, in vivo presystemic stability of these oligonucleotides was monitored in rats following intraduodenal administration. By 8 h after administration, only chain-shortened metabolites of the PS ODN were recovered in the gastrointestinal contents. In contrast, approximately 50% of the 2'-O-MOE ribose-modified (partial) compound remained intact (20-mer) by 8 h following administration. Both of the fully modified compounds (2'-O-MOE PO and PS) were completely stable with no measurable metabolites observed within 8 h of administration. The rank order of bioavailability was ISIS 11159 (full PS, full MOE) < ISIS 2302 (PS ODN) < ISIS 16952 (full PO, full MOE) < ISIS 14725 (full PS, partial MOE); the absolute plasma concentration bioavailability was measured in reference to intravenous dosing in the rat and was estimated at 0.3, 1.2, 2.1, and 5.5%, respectively. The optimal oligonucleotide chemistry for improved permeability and resulting bioavailability was the partially modified 3' hemimer 2'-O-MOE phosphorothioate oligonucleotide (ISIS 14725). Improved presystemic stability coupled with improved permeability were likely responsible for the remarkable improvement in the oral bioavailability of this compound.

Comparison of pharmacokinetics and tissue disposition of an antisense phosphorothioate oligonucleotide targeting human Ha-ras mRNA in mouse and monkey

The plasma pharmacokinetics and tissue disposition of ISIS 2503 were studied in mice following single and multiple bolus intravenous (iv) injections of 1-50 mg/kg, and in monkeys following single and multiple 2-h iv infusions of 1-10 mg/kg and bolus iv injections of 1 mg/kg of ISIS 2503. ISIS 2503 and its metabolites were measured in plasma, urine, and tissues using solid-phase extraction followed by capillary gel electrophoresis (CGE). In both species, the plasma clearance of ISIS 2503 was characterized by rapid distribution to tissues, and to a lesser extent, metabolism. The plasma clearance in mice was at least two-fold more rapid than in monkeys at equivalent doses. The plasma disposition (t1/2) increased with dose. The highest concentrations of oligonucleotide were consistently observed in the kidney and liver in both species. At equivalent doses, tissue concentrations in monkeys were much higher than tissue concentrations in mice. Urinary excretion of total oligonucleotide was a minor elimination pathway in both species at doses < 10 mg/kg. However, urinary excretion of total oligonucleotide in mice was increased to 12-29% as dose increased from 20 to 50 mg/kg.

Pharmacokinetics and pharmacodynamics of an antisense phosphorothioate oligonucleotide targeting Fas mRNA in mice

ISIS 22023 is a modified phosphorothioate antisense oligonucleotide targeting murine Fas mRNA. Treatment of mice with ISIS 22023 reduced Fas expression in liver in a concentration-dependent and sequence-specific manner, which completely protected mice from fulminant death induced by agonistic Fas antibody. In this study, we characterized the relationships in mice between total dose administered, dose to the target organ, and ultimately, the intracellular concentration within target cell types to the pharmacologic activity of ISIS 22023. After subcutaneous injection, ISIS 22023 distributed to the liver rapidly and remained in the liver with the t(1/2) ranging from 11 to 19 days, depending on dose. There were apparent differences in patterns of uptake and elimination in different types of liver cells. Oligonucleotide appeared within hepatocytes rapidly, whereas the peak concentrations in Kupffer cells were delayed until 2 days after dose administration. Hepatocytes cleared oligonucleotide the most rapidly, whereas Kupffer cells appeared to retain oligonucleotide longer. The reduction of Fas mRNA levels (pharmacodynamic response) paralleled the increase of oligonucleotide concentration in mouse liver with maximum mRNA reduction of 90% at 2 days after a single 50 mg/kg subcutaneous administration. Moreover, the pharmacodynamics of ISIS 22023 correlated better with the pharmacokinetics in hepatocytes, supporting the concept that the presence of oligonucleotide in target cells results in reductions in mRNA and, ultimately, pharmacologic activity. These results provide a comprehensive understanding of the kinetics of an antisense drug at the site of action and demonstrate that the reductions in mRNA induced by this antisense oligonucleotide correlate with its concentrations in cell targets.

Pharmacokinetic and toxicity profile of a phosphorothioate oligonucleotide following inhalation delivery to lung in mice

Antisense oligonucleotides are currently being investigated for the treatment of a variety of diseases. Antisense drugs are being administered primarily by parenteral injection. To explore more convenient patient delivery methods, we have characterized the tissue kinetics and tolerability of an inhaled aerosol formulation of a phosphorothioate oligonucleotide in mice. Concentrations of oligonucleotide in bronchioalveolar lavage fluid, plasma, and tissue and immunohistochemical localization were used to assess deposition and pharmacokinetic parameters. Significant concentrations of oligonucleotide in lung, as well as systemic tissues, were measured following a pulmonary dose of 12 mg/kg. Doses as low as 1-3 mg/kg also produced significant concentrations of oligonucleotide (>50 microg oligonucleotide per gram of tissue), and these were maintained in the lung with a halflife of 20 hours or greater. Oligonucleotide was localized to bronchiolar epithelium and alveolar epithelium and endothelium. Toxicity was mild at the 12 mg/kg level and minimal to absent at doses of 3 mg/kg or below. Based on a favorable pharmacokinetic profile and a relative lack of toxicity, inhalation delivery appears to be a therapeutic option for antisense oligonucleotides.

A phase I trial of c-Raf kinase antisense oligonucleotide ISIS 5132 administered as a continuous intravenous infusion in patients with advanced cancer

Raf proteins play a central role in the mitogen-activated protein kinase signaling pathway and hence are involved in oncogenic transformation and tumor cell proliferation. ISIS 5132 is a 20-base antisense phosphorothioate oligodeoxyribonucleotide that specifically down-regulates c-raf expression. We report here an initial study of the safety and tolerability of an i.v. infusion of ISIS 5132 in patients with advanced cancer. A continuous i.v. infusion of ISIS 5132 was administered for 21 days every 4 weeks to 34 patients with a variety of solid tumors refractory to standard therapy. The dose of ISIS 5132 was increased in sequential cohorts of patients, as toxicity allowed, until a final dose of 5.0 mg/kg body weight was reached. Toxicity was scored by common toxicity criteria, and tumor response was monitored. Pharmacokinetic studies were performed for 30 patients treated at doses of < or =4.0 mg/kg/day. The initial dose of ISIS 5132 was 0.5 mg/kg body weight and was successfully increased incrementally to 5.0 mg/kg body weight. Toxicities through the 4.0 mg/kg dose level were not dose limiting. Side effects were minimal and could not be specifically related to ISIS 5132. Two patients had prolonged stabilization of their disease, and one patient with ovarian carcinoma had a significant response with a 97% reduction in CA-125 levels. ISIS 5132, an antisense oligonucleotide against c-raf, was well tolerated at doses up to and including 4.0 mg/kg/day by 21-day continuous i.v. infusion and demonstrated antitumor activity at the doses tested.

Absorption of antisense oligonucleotides in rat intestine: effect of chemistry and length

An in situ single-pass perfusion model was used to assess the effect of chemical modification and length on permeability and absorption of various oligonucleotides in rat intestine. Phosphorothioate oligodeoxynucleotides (PS-ODN) were compared with oligoribonucleotides with 2'-methoxyethyl (MOE) or 2'-O-methyl (OMe) modifications. A 25-mer PS-OMe-modified oligonucleotide showed relatively poor permeability in this model, as did unmodified 20-mer PS-ODN (permeability coefficient [P(eff)] = 2-8 X 10(-6)cm/sec). Modifying some or all of the oligonucleotides with 2'-MOE groups on deoxyribose and 5'-methylation of the cytosines substantially increased intestinal permeability of oligonucleotides. Both partially and fully modified PS-MOE oligonucleotides showed a (2-4)-fold increase in permeability as compared with unmodified PS-ODN. The presence of a phosphodiester backbone in MOE-modified compounds led to further increases in intestinal permeability. PS-MOE composed of 6, 8, 10, 12, 14, 16, 18, 20, and 22 nucleotides were also examined. It was found that the permeability of these oligonucleotides increased linearly with decreasing length.

Phase I study of an antisense oligonucleotide to protein kinase C-alpha (ISIS 3521/CGP 64128A) in patients with cancer

Protein kinase C (PKC) is an attractive target in cancer therapy. It is overexpressed in a variety of cancers, and nonspecific inhibitors of PKC have demonstrated antitumor activity. Antisense oligonucleotides targeted against PKC-alpha, which have high specificity, can inhibit mRNA and protein expression as well as the growth of tumors in vitro and in vivo. This Phase I study sought to characterize the safety profile and to determine the maximum tolerated dose of antisense to PKC-alpha when administered by continuous infusion in patients. Patients with incurable malignancies received ISIS 3521, a 20-length phosphorothioate oligodeoxynucleotide specific for PKC-alpha. Treatment was delivered over a period of 21 days by continuous i.v. infusion followed by a 7-day rest period. Doses were increased from 0.5 to 3.0 mg/kg/day. Patients continued on the study until evidence of disease progression or unacceptable toxicity was detected. Between August 1996 and September 1997, 21 patients were treated in five patient cohorts. The maximum tolerated dose was 2.0 mg/kg/day. The dose-limiting toxicities were thrombocytopenia and fatigue at a dose of 3.0 mg/kg/day. Pharmacokinetic measurements showed rapid plasma clearance and dose-dependent steady-state concentrations of ISIS 3521. Evidence of tumor response lasting up to 11 months was observed in three of four patients with ovarian cancer. The recommended dose of ISIS 3521 for Phase II studies is 2.0 mg/kg/day when given over a period of 21 days. Side effects are modest and consist of thrombocytopenia and fatigue. Evidence of antitumor activity provides the rationale for Phase II studies in ovarian cancer and other malignancies.

A nonradioisotope biomedical assay for intact oligonucleotide and its chain-shortened metabolites used for determination of exposure and elimination half-life of antisense drugs in tissue

Rigorous extraction methods coupled with capillary gel electrophoresis (CGE) provide a basis for a nonradiolabel assay for quantitation of intact antisense drug and its numerous chain-shortened metabolites. As part of the validation of the CGE method, we compared the quantitation of unlabeled ISIS 3521 (ISI 641A) and its chain-shortened metabolites with total radioactivity of [(35)S]-ISIS 3521. ISIS 3521 was labeled on the fifth nucleotide linkage from the 5'-end with (35)S by well-established methods. Multiple tissues collected from rats after administration of [(35)S]-ISIS 3521 were assayed by both radiolabel (liquid scintillation spectroscopy) and CGE methods. The CGE method provided accurate quantitation of the drug and its metabolites in kidney cortex and liver tissues. The correlation between methods for multiple tissues over time was excellent with 88.5% of the measurements being statistically equivalent. These data suggest that CGE is an accurate means of quantitating oligonucleotide in tissue and that it compares favorably with traditional radiochemical techniques. Clearance half-lives for total measurable oligonucleotides were equivalent to clearance of total radioactivity in both liver and kidney with the longest clearance half-life associated with the kidney.

Pharmacokinetics and tissue disposition in monkeys of an antisense oligonucleotide inhibitor of Ha-ras encapsulated in stealth liposomes

PURPOSE

This study examined the pharmacokinetics and tissue distribution of an antisense oligonucleotide ISIS 2503, formulated in stealth (pegylated) liposomes (encapsulated) or in phosphate-buffered saline (unencapsulated).

METHODS

Encapsulated or unencapsulated ISIS 2503 was administered to rhesus monkeys by intravenous infusion. The concentrations of ISIS 2503 and metabolites in blood, plasma, and tissue samples were determined by capillary gel electrophoresis.

RESULTS

Plasma concentrations of encapsulated ISIS 2503 decreased mono-exponentially after infusion with a mean half-life of 57.8 hours. In contrast, the concentration of unencapsulated ISIS 2503 in plasma decreased rapidly with a mean half-life of 1.07 hours. Both encapsulated and unencapsulated ISIS 2503 distributed widely into tissues. Encapsulated ISIS 2503 distributed primarily to the reticulo-endothelial system and there were few metabolites observed. In contrast, unencapsulated ISIS 2503 distributed rapidly to tissue with highest concentration seen in kidney and liver. Nuclease-mediated metabolism was extensive for unencapsulated oligonucleotide in plasma and tissues.

CONCLUSIONS

The data suggest that stealth liposomes protect ISIS 2503 from nucleases in blood and tissues, slow tissue uptake, and slow the rate of clearance from the systemic circulation. These attributes may make these formulations attractive for delivering oligonucleotides to sites with increased vasculature permeability such as tumors or sites of inflammation.

Preclinical evaluation of the effects of a novel antisense compound targeting C-raf kinase in mice and monkeys

CGP 69846A (ISIS 5132) is an antisense phosphorothioate oligodeoxynucleotide which targets human C-raf kinase and is currently being developed as an antineoplastic agent. The toxicity of this compound was evaluated in mice and monkeys following repeated i.v. injections or infusions for 4 weeks at doses up to 100 mg/kg. Because CGP 69846A is inactive in the mouse, ISIS 11061, the murine-specific homologue targeting C-raf kinase mRNA was evaluated concurrently with CGP 69846A to assess the potential toxicity associated with reduced C-raf expression. There were no toxicities that differentiated ISIS 11061 from CGP 69846A in mice. Effects in mice included hepatomegaly and hepatocellular degeneration at the high dose of 100 mg/kg CGP 69846A that potentially resulted in lethality. Other effects which were observed at 20 and 100 mg/kg included mononuclear cell infiltrates in multiple organs, extramedullary hematopoiesis in the spleen and liver, an increase in bone marrow cellularity, an increase in white blood cells, a decrease in platelet counts, and Kupffer cell hyperplasia. These alterations were reversible following a recovery period. No adverse effects in mice were observed with doses < or = 10 mg/kg. In monkeys, administration of 10 mg/kg of CGP 69846A was associated with effects observed with other P = S ODNs, namely, prolongation of activated partial thromboplastin time (APTT) and activation of complement. These effects were transient and correlated with plasma concentrations of CGP 69846A. Below a concentration of 35 micrograms/ml of intact CGP 69846A the prolongation of APTT was less than 50% and levels of complement split products were not increased. All monkeys tolerated complement activation with no evidence of treatment-related clinical signs. Complement and coagulation were not affected by the lower doses of 1 and 3 mg/kg. No histopathology or alteration in hematology or serum chemistry was induced by doses up to 10 mg/kg in monkeys. The plasma and tissue deposition of CGP 69846A were characterized in mice and monkeys and toxicity was dependent on dose of CGP 69846A. In the present preclinical evaluation of toxicity in mice and monkeys, CGP 69846A is well tolerated at doses targeted for clinical trials. Toxicities induced by CGP 69846A in monkeys and mice occurred at doses of 10 mg/kg and greater. Effects induced by CGP 69846A were not unique and have been observed previously with other phosphorothioate oligodeoxynucleotides.

Bioavailability of intranasal promethazine dosage forms in dogs

Intramuscular promethazine (PMZ) is used aboard the US Space Shuttle to ameliorate symptoms of space motion sickness. Bioavailability after an oral dose of PMZ during space flight is thought to be impaired because of gastrointestinal disturbances associated with weightlessness and space motion sickness. In an attempt to find an alternative dosage form for use in space, we evaluated two intranasal (i.n.) dosage forms of PMZ in dogs for absorption and bioavailability relative to that of an equivalent intramuscular dose. Promethazine (5 mg kg-1) was administered as two intranasal dosage forms and as an intramuscular (i.m.) dose to three dogs in a randomised cross-over design. Serial blood samples were taken and analysed for PMZ concentrations and the absorption and bioavailability of PMZ were calculated for the three dosage forms. PMZ absorption from the carboxymethyl cellulose microsphere i.n. dosage form was more rapid and complete than from the myverol cubic gel formulation or from an i.m. injection. Bioavailability of the microsphere formulation was also greater than that of the gel formulation (AUC 3009 vs 1727 ng h ml-1). The bioavailability of the two i.n. dosage forms (relative to that of the i.m. injection) were 94% (microsphere) and 54% (gel). The i.n. microsphere formulation of PMZ offers great promise as an effective non-invasive alternative for treating space motion sickness due to its rapid absorption and bioavailability equivalent to the i.m. dose.

Pharmacokinetics and metabolism in mice of a phosphorothioate oligonucleotide antisense inhibitor of C-raf-1 kinase expression

The plasma and tissue disposition of CGP 69846A (ISIS 5132) was characterized in male CD-1 mice following iv bolus injections administered every other day for 28 days (total of 15 doses). The doses ranged from 0.8 mg/kg to 100 mg/kg. Urinary excretion of oligonucleotide was also monitored over a 24-hr period following single dose administration over the same dose range. Pharmacokinetic plasma profiles were determined following single dose administration (dose 1) and after multiple doses (dose 15) at doses of 4 and 20 mg/kg. Concentrations in kidney, liver, spleen, heart, lung, and lymph nodes were characterized following doses 1, 8, and 15 for all doses. Capillary gel electrophoresis was used to quantitate intact (full-length) oligonucleotide and its metabolites (down to N - 11 base deletions) in both plasma and tissue at all time points. The plasma and tissue disposition of CGP 69846A was characterized by a rapid distribution into all tissues analyzed. Rapid plasma clearance of the parent oligonucleotide (9.3-14.3 ml/min/kg) was predominantly the result of distribution to tissue and, to a lesser extent, metabolism. Appearance and pattern of chain-shortened metabolites seen in plasma and tissue were consistent with predominantly exonuclease-mediated base deletion. No measurable accumulation of oligonucleotide was observed in plasma following multiple-dose administration, but both the liver and the kidney exhibited 2-3-fold accumulations. In general, the tissues exhibited half-lives for the elimination of parent oligonucleotide of 16-60 hr compared with plasma half-lives of 30-45 min. After repeated administrations, significant decreases in plasma clearance and volume of distribution at steady state (Vss) were observed following dose 15 at the dose of 20 mg/kg but not at the dose of 4 mg/kg. Changes in tissue accumulation and evidence for saturation of tissue distribution at the high doses may explain the plasma disposition changes observed in the absence of alteration of metabolism or plasma accumulation. Urinary excretion was a minor pathway for elimination of oligonucleotide over the 24-hr period immediately following iv administration. However, the amount of oligonucleotide excreted in the urine increased as a function of dose from less than 1% to approximately 13% of the administered dose over a dose range of 0.8 mg/kg to 100 mg/kg.

Phase I safety and pharmacokinetic profile of an intercellular adhesion molecule-1 antisense oligodeoxynucleotide (ISIS 2302)

Healthy male volunteers received single or multiple intravenous infusions of an intercellular adhesion molecule-1 antisense phosphorothioate oligodeoxynucleotide, ISIS 2302, in a rising-dose (0.06-2.00 mg/kg infused over 2 hr), double-blind, placebo-controlled trial. Brief, dose-related increases in activated partial thromboplastin time were seen at the time of peak plasma concentration (C(max)). Clinically insignificant increases in C3a were seen after higher, repeated doses, but C5a, blood pressure and pulse were unaffected. No adverse events or other laboratory abnormalities were related to treatment with the drug. ISIS 2302 C(max) was linearly related to dose and occurred at the end of infusion. Plasma half-life for intact drug (53-54 min) and total oligonucleotide (67-74 min) were similar at the two doses (0.5 and 2.0 mg/kg) at which extensive pharmacokinetic data were collected. Nonlinear changes in area under the plasma concentration/time curve and steady-state volume of distribution with increasing dose suggested a saturable component to disposition. Metabolites co-migrating with n-1, n-2 and n-3 chain-shortened versions of ISIS 2302 appeared very rapidly in plasma, and disposition and metabolism appeared unaltered by repeated dosing. ISIS 2302 was well tolerated and behaved reproducibly with respect to plasma pharmacokinetics and expected side effects.

The comparative metabolism of diisopropyl methylphosphonate in mink and rats

This study reports the metabolism of carbon-14labeled diisopropyl methylphosphonate (DIMP) in mink and rats, undertaken to better understand the dose-related mortality reported for mink in a previous study. In both male and female mink and rats, DIMP was rapidly absorbed after oral administration; it was metabolized by a saturable pathway to a single metabolite, isopropyl methylphosphonate (IMPA), which was rapidly excreted, primarily in the urine (90%). Fecal radioactivity, also identified as IMPA, was 1.7-3.1% of the administered dose. Female rats had a slower rate of conversion of DIMP to IMPA and less total excretion of IMPA than male rats. Metabolism of DIMP administered intravenously was not very different from that given orally in both species. These data indicate that mink absorb, metabolize, and excrete DIMP (as IMPA) in a manner very similar to mice, rats, and dogs.

Characterization of WR-1065 absorption in the rat small intestine

A circulating in situ rat small intestine absorption model was used to study the lumenal metabolism and absorption of [14C]WR-1065. WR-1065 was found to be more tissue reactive and toxic than its phosphorylated form, ethiofos, at equimolar perfusate concentrations. The disappearance profiles of the radiolabeled drug and free WR-1065 indicate that WR-1065 is extensively metabolized in the intestinal lumen prior to absorption. Coadministration of disodium ethylenediaminetetraacetic acid enhances the absorption of the free thiol although not to the same extent as seen with ethiofos. Perfusion of WR-1065 in citrate buffer decreased lumenal degradation of the drug but resulted in decreased absorption. The total material converted to WR-1065 portal blood profiles following ethiofos and WR-1065 perfusion were altered possibly due to distribution and metabolism differences. This study coupled with earlier work completed on ethiofos have increased our understanding of the significant barriers to absorption observed following oral administration of these compounds.

Characterization of ethiofos absorption in the rat small intestine

The absorption characteristics of ethiofos were studied using the rat in situ intestine circulating perfusion technique. Slow absorption kinetics were observed for ethiofos with varying rates of absorption and metabolism/degradation in situ as a function of buffer and absorption enhancers. In most cases less than 10 per cent of the radiolabeled compound is lost from the circulating perfusate in 90 min. In addition, over the same time period greater than 40 per cent of the intact parent compound was lost by degradation. Much of the difference can be accounted for in the formation of the free thiol metabolite. WR-1065, suggesting ester hydrolysis or metabolic activity. Good stability was observed in all perfusate systems ex vivo indicating that the degradation occurs in situ. The disodium salt of ethylenediaminetetraacetic acid (EDTA) was shown to be an effective absorption enhancer of ethiofos. The enhancement of intestinal absorption by EDTA was dose-dependent resulting in a 20-fold increase in blood levels of ethiofos in the portal blood. Follow-up studies in the rhesus monkey confirm this observation. Salicylate and dimethylsulfoxide (DMSO) also resulted in absorption enhancement although to a lesser degree than that seen after EDTA treatment. Addition of several alkaline phosphatase inhibitors did not significantly improve absorption of ethiofos in the rat small intestine. Proposed mechanism(s) for intestinal absorption and absorption enhancement of ethiofos are discussed.

RIA-linked microdialysis sampling in the awake rat: application to free-drug pharmacokinetics of hydrocortisone

The purpose of this research was to combine microdialysis sampling techniques with a highly sensitive radioimmunoassay (RIA) to study the in vivo kinetic response of pharmacologically important substances. This technique allowed for a dense sampling regimen from an awake, free-roaming experimental animal with no loss of blood and with rapid analysis of the dialysate. An important methodological criterion for accurate quantitation of a test drug in the extracellular space was knowledge of the relative recovery of the sampling system at the time of experimentation. Accordingly, the factors which influenced the recovery of drug during dense in vivo microdialysis sampling were examined and an analytical technique was developed to measure the instantaneous recovery of drug from the extracellular space. This information was applied to in vivo (iv) sampling experiments on anaesthetized and awake, free-roaming rats following bolus and multiple long-term iv administrations of the highly protein bound steroid (i.e. greater than 90%), hydrocortisone-21-phosphate. These studies indicated that unbound hydrocortisone levels as determined by the RIA-linked microdialysis (RIALM) technique fluctuated rapidly between each 2-min sampling interval, but nevertheless decreased to predose endogenous concentrations in a first-order fashion (t1/2 = 17-29 min). The rapid fluctuations of unbound hydrocortisone may reflect real pharmacokinetic or pharmacodynamic phenomena, attributed, perhaps, to reequilibration of the unbound drug pool with proteins and tissues in the blood.

Pharmacokinetics and disposition of WR-1065 in the rhesus monkey

The pharmacokinetics of WR-1065 [S-2-(3-aminopropylamino)ethanethiol] were investigated following iv, intraduodenal, and intraportal administrations in the rhesus monkey. Pharmacokinetic parameters were estimated by compartmental modeling of plasma concentration data from 10-min and 120-min iv infusions. Higher apparent volumes of distribution (Vc and Vss) and higher mean residence time (MRT) were observed at the slower infusion rate but a constant total dose. The values reflect a change in the distribution of WR-1065, possibly due to to saturation of binding in plasma and tissue. However, clearance remained unchanged. For a monkey administered approximately twice the 60 mg/kg dose infused over 120 min, data analysis indicates a disproportional increase in AUC and a substantial decrease in clearance. Low and erratic plasma concentrations of free drug (analytically determined without reductive cleavage) were observed following intraduodenal administration of WR-1065, demonstrating the drug's poor oral bioavailability. Results of intraduodenal administrations of radiolabeled drug indicated than an appreciable amount of the radiolabel in the dose reached the systemic circulation. However, after either intraduodenal or iv administration, only 31% of the AUC (radiolabel) could be accounted for as total (free and disulfide-bound) WR-1065 by specific analysis in separate experiments. Low levels of total cysteamine strongly suggest it to be a minor contributor to the disposition of the drug. Free WR-1065 AUC values following intraportal administration were similar to values obtained after iv administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraduodenal administration of ethiofos (WR-2721): dose proportionality study in the rhesus monkey

A dose progression crossover study of ethiofos (WR-2721) was conducted in three healthy male rhesus monkeys. Each subject was tested with three single intraduodenal doses containing 150, 300, and 600 mg/kg. Blood samples were drawn as a function of time and the concentrations of ethiofos, WR-1065 (free thiol metabolite), and total drug convertible to the free thiol (total WR-1065) were determined by HPLC using electrochemical detection. Ethiofos levels in plasma were usually below quantifiable limits of detection (0.23 mumol/L) at all three dose levels, but free WR-1065 plasma levels increased with increasing dose. Analysis of the free WR-1065 bioavailability values indicated large variability and an unpredictable dose response among subjects. Bound WR-1065 appears to reach saturable levels over the dose range, suggesting a saturable pool of binding sites in plasma. The time-to-peak plasma levels for WR-1065 were variable regardless of the administered dose and ranged from 1.0-2.5 hours. The high variability in the data may be a result of poor permeability or absorption of the parent compound (ethiofos), saturable binding to a variable pool of binding sites in plasma and/or high first-pass metabolism of ethiofos involving the gut lumen, gut wall (epithelium), and liver.

Relative bioavailability of almitrine bismesylate in humans

Bioavailability and bioequivalency studies of almitrine bismesylate from U.S. manufactured film coated, waxed, 50 mg tablets were compared in 34 normal healthy volunteers to 50 mg European film coated, waxed and unwaxed, tablets and a 0.5 per cent (w/v) oral reference solution of almitrine bismesylate in d,l malic acid. The U.S. manufactured formulations were 85.88 and 87.85 per cent of the calculated mean area under the individual concentration-time curve for almitrine bismesylate reference solution compared to 88.40 and 88.86 per cent for the waxed and unwaxed film coated European tablets, respectively. The mean peak plasma concentrations for the U.S. formulations were 176.3 ng ml-1 and 180.1 ng ml-1 compared to 196.3 and 200.1 ng ml-1 for the waxed and unwaxed European formulations, respectively. Mean time to peak plasma concentrations for the two U.S. formulations and the waxed and unwaxed European formulations were 3.22, 3.33, 3.06, and 3.26 h, respectively. In addition, the oral reference solution yielded a mean peak plasma concentration of 222.8 ng ml-1 and a mean time to peak plasma concentration of 2.68 h. Analysis of variance and multiple range comparisons (p less than 0.05) indicated that the tablet formulations were bioequivalent. The results of this study show that the U.S. formulated almitrine bismesylate tablets exceed 85 per cent relative bioavailability with respect to the oral reference solution and are bioequivalent compared to the marketed standard European tablet formulations.

Single oral dose proportionality pharmacokinetics of almitrine bismesylate in humans

A single-blind study was conducted in 10 healthy male subjects. Each subject was tested with four single oral doses of capsules containing 25, 50, 100, 200mg almitrine bismesylate and one dose of placebo. Blood samples were drawn as a function of time and the concentration of almitrine in plasma was determined by gas chromatography utilizing nitrogen-phosphorus detection. Linear regression analysis of the data suggested that a deviation from linearity existed between the area under the plasma concentration time curves and the dose (R = 0.96). Linear analysis of the individual data indicates that a slight negative deviation from linearity is apparent for the 200 mg dose. The same trend was observed for the mean maximum almitrine plasma concentration, Cmax, which ranged from 38.9 +/- 11.8 to 286.2 +/- 99.1 ng ml-1 for the 25 and 200 mg dose, respectively. The time to peak was relatively constant regardless of the administered dose and ranged from 2.4 +/- 0.5 h to 2.8 +/- 0.8 h. Good agreement was obtained between the observed bioavailability parameters and those predicted from the nonlinear fit of the data. Further kinetic analysis of the data revealed mean total body clearance over fraction of dose absorbed ranging from 268.2 +/- 132.8 to 436.4 +/- 191.4 ml min-1 for doses 50 and 200mg, respectively.

One year administration of almitrine bismesylate (Vectarion) to chronic obstructive pulmonary disease patients: pharmacokinetic analysis

A double blind study utilizing orally administered almitrine bismesylate was conducted involving 36 stable chronic obstructive pulmonary disease (COPD) patients with hypoxia and with and without hypercapnia. The patients received 50 mg tablets twice daily for 360 days. Blood samples were taken both at predose and 3 hours postdose at different periods throughout 1 year dosage regimen and plasma levels were analyzed by a GLC method using a nitrogen-phosphorous detector. Plasma almitrine concentrations indicate large variability at each time sample. Results suggest an increasing trend in the almitrine plasma levels as a function of time. Plasma almitrine levels increased significantly (p less than 0.01) between test day 14 and test day 360 (243 +/- 213 per cent and 199 +/- 170 per cent for predose and 3h postdose samples, respectively) indicating that steady state is not achieved by day 14. Almitrine plasma levels appear to stabilize between test day 90 and test day 180. The effective multiple dose half-life for almitrine bismesylate in plasma is estimated to be 32 days. About half of the patients exhibited steady state peak plasma almitrine levels above 500 ng ml-1. In addition, 19 per cent of the patients achieved maximum apparent steady state almitrine levels greater than 700 ng ml-1. Mean accumulation was estimated to be 4.21 +/- 1.98 at one year.

The disposition of ethiofos (WR-2721) in the isolated perfused rat liver

We have investigated the disposition of ethiofos (20 mg, 4 microCi [14C]ethiofos) in the isolated perfused rat liver preparation to determine the hepatic contribution to the poor oral bioavailability of the drug. Ethiofos clearance (10.6 +/- 3.3 ml h-1) was only a small fraction (1.2 +/- 0.03%) of the perfusate flow rate. The elimination half-life was calculated at 7.1 +/- 1.9 h. The area under curve, AUC0-4 h, for ethiofos (2858 +/- 314 nM h ml-1) was not significantly different from that of 14C (3038 +/- 692 nM h ml-1) or total material convertible to WR-1065 (total WR-1065, 3324 +/- 612 nM h ml-1), indicating a low level of metabolism. The AUC0-4 h for free WR-1065 (37.5 +/- 23.3 nM h ml-1) was less than 2% of ethiofos. Biliary elimination of ethiofos, WR-1065, and 14C was below 1%. At 4 h postdose, 7.9 +/- 1.9% of the dose of radioactivity remained in the liver. Less than 1.5% could be identified as ethiofos (0.12 +/- 0.09%) or total WR-1065 (1.09 +/- 0.05%). Ethiofos, 14C, and total WR-1065 were approximately evenly distributed between the 10,000-g pellet and supernatant. However, significantly more ethiofos, WR-1065, and 14C were recovered from the 105,000-g supernatant compared with the pellet. In summary, both the metabolism and biliary elimination of ethiofos and its derivatives were sparing. Hence it is likely that in the rat, the contribution of the liver to the presystemic biotransformation and poor bioavailability of ethiofos is relatively minor.