CYP3A activity: towards dose adaptation to the individual

INTRODUCTION

Co-medication, gene polymorphisms and co-morbidity are main causes for high variability in expression and function of the CYP3A isoenzymes. Pharmacokinetic variability is a major source of interindividual variability of drug effect and response of CYP3A substrates. While CYP3A genotyping is of limited use, direct testing of enzyme function ('phenotyping') may be more promising to achieve individualized dosing of CYP3A substrates.

AREAS COVERED

We will discuss available phenotyping strategies for CYP3A isoenzymes and causes of intra- and interindividual variability of CYP3A. The impact of phenotyping on the dose selection and pharmacokinetics of CYP3A substrates (docetaxel, irinotecan, tyrosine kinase inhibitors, ciclosporin, tacrolimus) are reviewed. Pubmed searches were conducted during March-November 2015 to retrieve articles related to CYP3A enzyme, phenotyping, drug interactions with CYP3A probe substrates, and phenotyping-guided dosing algorithms.

EXPERT OPINION

While ample data is available on the choice appropriate phenotyping drugs (midazolam, alfentanil, aplrazolam, buspirone, triazolam), less clinical trial data is available concerning strategies to usefully guide dosing in the clinical practice. Implementation into the clinical routine necessitates further research to identify (1) an easy-to-use and cheap test for CYP3A activity that (2) adequately predicts drug exposure to (3) allow a sound decision on dose adaptation and hence (4) improve clinical outcome and/or reduce the intensity or frequency of adverse drug effects.

Willingness to pay for health insurance among the elderly population in Germany

INTRODUCTION

All elderly Germans are legally obliged to have health insurance. About 90 % of this population are members of social health insurances (SHI) whose premiums are generally income-related and independent of health status. For most of these members, holding social health insurance is mandatory. As a consequence, genuine information about preferences for health insurance is not available. The aim of this study was therefore to determine and analyze the willingness to pay (WTP) for health insurance among elderly Germans.

METHODS

Data from a population-based 8-year follow-up of a large cohort study conducted in the Saarland, Germany was used. Participants aged 57-84 years passed a geriatric assessment and responded to a health economic questionnaire. Individuals' WTP was elicited based on a contingent valuation method with a payment card.

RESULTS

Mean monthly WTP per capita for health insurance amounted to €260. This corresponded to about 20% of individual disposable income. Regression analyses showed that WTP increased significantly with higher income, male gender, higher educational level, and privately insured status. In contrast, neither increasing morbidity level nor higher individual health care costs influenced WTP significantly.

DISCUSSION

The relatively large extent of average WTP for health insurance indicates that the elderly would probably accept higher contributions to SHI rather than policy efforts to reduce contributions. The identified determinants of WTP might indicate that elderly generally approve the principle of solidarity of the SHI with contributions depending on income rather than morbidity.

Age-Dependent Impact of Medication Underuse and Strategies for Improvement

Background: Medication underuse is common in aging populations and, because of the growing risk for competing deaths, the benefit of preventive medicines gradually vanishes with advancing age, thus limiting their success. Objective: To estimate the optimum time of initiation of the secondary prevention of cardiovascular events, we examined the impact of appropriate pharmacotherapy for different starting ages at which it is implemented. Methods: In the competing risk framework, we obtained the population's life course from life tables, combined it with effect estimates quantifying the real-world effectiveness of secondary prevention, and compared the outcome of patients not receiving appropriate treatment (underuse) with those receiving preventive medicines that have demonstrated a reduction in the transition to serious cardiovascular events (START criteria). Starting at the age of 55 years, the population proportions of the distinct states of the framework were calculated for each year of chronological age in subgroups of appropriate treatment and underuse. These proportions were used over a follow-up period to estimate measures of treatment effectiveness and risks of underuse. Results: Despite increasing relative effectiveness with advancing age, benefits measured by patient-relevant endpoints, such as life years gained (LYG) or gained quality-adjusted life years (QALYs), markedly dropped after the starting age of 75 years, but even at an initiation age of 85 years, QALYs gained exceeded 1 year. Conclusion: Interventions targeting medication underuse may achieve considerable benefits at any stage of later life, while the benefit is probably largest if appropriate treatment is started before 75 years.

[Formal prescribing errors are substantially reduced in electronic prescribing and after teaching sessions]

INTRODUCTION

Prescription forms enable the communication between physicians and pharmacists. Hence, incorrectly issued prescriptions may result in delay of health-care delivery, additional workload, and potentially adverse patient outcomes. We aimed to evaluate the formal prescription quality in our outpatient clinics (OC) before and after performing teaching sessions and using an electronic prescription system to replace handwritten prescriptions.

METHODS

All OCs of a university hospital were offered a short teaching session on how to issue prescriptions correctly and how to use the electronic prescription system. During four weeks before and after the teaching, we anonymously collected all prescriptions of the OCs in 20 surrounding community pharmacies and assessed whether they were error-free, required an intervention by the pharmacist, additional clarification by the OC, or had to be reissued.

RESULTS

After the intervention, the absolute fraction of formally error-free prescriptions increased by 12.9% from 52.9% (516/976) to 65.8% (713/1084, p < 0.001; d = 12,9% 95% confidence interval [8,7%; 17,1%]). Largest improvements were seen in prescriptions requiring clarification by the OC (224/976 prescriptions at baseline versus 93/1084 post-intervention, p < 0.001). The fraction of electronic prescriptions increased from 34.9% (341/976) to 46.9% (509/1084, p < 0.001, d = 12,0% 95% confidence interval [7,8%; 16,2%]) with electronic prescriptions consistently being of higher formal quality than handwritten prescriptions.

CONCLUSION

After increased use of electronic prescribing and teaching courses, formal prescription quality was significantly improved.

Quality of antenatal and childbirth care in rural health facilities in Burkina Faso, Ghana and Tanzania: an intervention study

OBJECTIVE

To assess the impact of an intervention consisting of a computer-assisted clinical decision support system and performance-based incentives, aiming at improving quality of antenatal and childbirth care.

METHODS

Intervention study in rural primary healthcare (PHC) facilities in Burkina Faso, Ghana and Tanzania. In each country, six intervention and six non-intervention PHC facilities, located in one intervention and one non-intervention rural districts, were selected. Quality was assessed in each facility by health facility surveys, direct observation of antenatal and childbirth care, exit interviews, and reviews of patient records and maternal and child health registers. Findings of pre- and post-intervention and of intervention and non-intervention health facility quality assessments were analysed and assessed for significant (P < 0.05) quality of care differences.

RESULTS

Post-intervention quality scores do not show a clear difference to pre-intervention scores and scores at non-intervention facilities. Only a few variables had a statistically significant better post-intervention quality score and when this is the case this is mostly observed in only one study-arm, being pre-/post-intervention or intervention/non-intervention. Post-intervention care shows similar deficiencies in quality of antenatal and childbirth care and in detection, prevention, and management of obstetric complications as at baseline and non-intervention study facilities.

CONCLUSION

Our intervention study did not show a significant improvement in quality of care during the study period. However, the use of new technology seems acceptable and feasible in rural PHC facilities in resource-constrained settings, creating the opportunity to use this technology to improve quality of care.

[Which Factors Affect Out-of-pocket Payments for Health Care Services Among Elderly Germans? Results of a Longitudinal Study]

Background: In Germany, out-of-pocket payments (OOPP) account for a large proportion of total health expenditure. However, there are only few investigations on how morbidity-related, sociodemographic and lifestyle factors affect OOPP particularly in the older population. The aim of this study was to identify factors affecting OOPP for health care services among elderly Germans in a longitudinal setting. Methods: This longitudinal study used data from 2 follow-up waves (3-year interval) from a population-based prospective cohort study (ESTHER study) collected in Saarland, Germany. At the first follow-up wave, subjects were between 57 and 84 years old. Participants provided comprehensive data including individual OOPP for the preceding 3 months. Fixed effects (FE) regressions were used to determine factors affecting OOPP. Results: Mean individual OOPP (3-month period) rose from € 119 (first wave) to € 136 (second wave). Longitudinal regressions showed that higher morbidity did not affect OOPP. Moreover, changes in sociodemographic as well as lifestyle factors were not related to changes in OOPP. Solely, exemption of OOPP reduced the dependent variable significantly. Conclusion: In contrast to cross-sectional findings for Germany, OOPP are not related to morbidity and income in this study. This underlines the complex nature of OOPP in old age and the need for longitudinal studies to gain some insight into the underlying causal factors.

[Use and potential risks of over-the-counter analgesics]

BACKGROUND AND AIM

We investigated the use of prescription and non-prescription (over-the-counter, OTC) analgesics and the associated risks in elderly patients with multiple morbidities.

METHODS

Pain medication use was evaluated from the baseline data (2008/2009) of the MultiCare cohort enrolling elderly patients with multiple morbidities who were treated by primary care physicians (trial registration: ISRCTN89818205). We considered opioids (N02A), other analgesics, and antipyretics (N02B) as well as nonsteroidal anti-inflammatory drugs (NSAIDs; M01A). OTC use, duplicate prescription, dosages, and interactions were examined for acetylsalicylic acid, diclofenac, (dex)ibuprofen, naproxen, and acetaminophen.

RESULTS

Of 3,189 patients with multiple morbidities aged 65-85 years, 1,170 patients reported to have taken at least one prescription or non-prescription analgesic within the last 3 months (36.7 %). Of these, 289 patients (24.7 % of 1,170) took at least one OTC analgesic. Duplicate prescription was observed in 86 cases; 15 of these cases took the analgesics regularly. In two cases, the maximum daily dose of diclofenac was exceeded due to duplicate prescription. In 235 cases, patients concurrently took a drug with a potentially clinically relevant interaction. In 43 cases (18.3 % of 235) an OTC analgesic, usually ibuprofen, was involved.

DISCUSSION

About one third of the elderly patients took analgesics regularly or as needed. Despite the relatively high use of OTC analgesics, the proportions of duplicate prescription, medication overdoses, and adverse interactions due to OTC products was low.

Midazolam microdose to determine systemic and pre-systemic metabolic CYP3A activity in humans

AIM

We aimed to establish a method to assess systemic and pre-systemic cytochrome P450 (CYP) 3A activity using ineffective microgram doses of midazolam.

METHODS

In an open, one sequence, crossover study, 16 healthy participants received intravenous and oral midazolam at microgram (0.001 mg intravenous and 0.003 mg oral) and regular milligram (1 mg intravenous and 3 mg oral) doses to assess the linearity of plasma and urine pharmacokinetics.

RESULTS

Dose-normalized AUC and Cmax were 37.1 ng ml(-1 ) h [95% CI 35.5, 40.6] and 39.1 ng ml(-1) [95% CI 30.4, 50.2] for the microdose and 39.0 ng ml(-1 ) h [95% CI 36.1, 42.1] and 37.1 ng ml(-1) [95% CI 26.9, 51.3] for the milligram dose. CLmet was 253 ml min(-1) [95% CI 201, 318] vs. 278 ml min(-1) [95% CI 248, 311] for intravenous doses and 1880 ml min(-1) [95% CI 1590, 2230] vs. 2050 ml min(-1) [95% CI 1720, 2450] for oral doses. Oral bioavailability of a midazolam microdose was 23.4% [95% CI 20.0, 27.3] vs. 20.9% [95% CI 17.1, 25.5] after the regular dose. Hepatic and gut extraction ratios for microgram doses were 0.44 [95% CI 0.39, 0.49] and 0.53 [95% CI 0.45, 0.63] and compared well with those for milligram doses (0.43 [95% CI 0.37, 0.49] and 0.61 [95% CI 0.53, 0.70]).

CONCLUSION

The pharmacokinetics of an intravenous midazolam microdose is linear to the applied regular doses and can be used to assess safely systemic CYP3A activity and, in combination with oral microdoses, pre-systemic CYP3A activity.

Loneliness in the elderly is associated with the use of psychotropic drugs

OBJECTIVE

The aim of this study was to evaluate the association between loneliness in elderly people with the use of psychotropic drugs.

METHODS

A subsample of 3111 participants (ages 55-85) of the large population-based German ESTHER study was included in the study. Loneliness was measured by using a three-item questionnaire. Two subgroups were defined according to their degrees of loneliness. Psychotropic drugs were categorized by study doctors. Logistic regression analyses were conducted to determine the association between loneliness subgroups and the use of psychotropic drugs adjusted for psychosocial variables, multimorbidity, depression, anxiety, and somatic symptom severity.

RESULTS

Of the participants 14.1% (95%-CI = [12.9; 15.4]) were estimated to have a high degree of loneliness (women > men); 19% (95%-CI = [17.6; 20.4]) of the participants used psychotropic drugs, 8.4% (95%-CI = [7.5; 9.5]) antidepressants. Logistic regression analysis showed that more lonely participants had significantly higher odds for using psychotropic drugs (OR: 1.495; 95%-CI = [1.121; 1.993]). Depression severity, somatic symptom severity, and female gender were also positively associated with the use of psychotropic drugs.

CONCLUSION

A high degree of subjective loneliness in the elderly is associated with the use of psychotropic drugs, even after adjustment for somatic and psychological comorbidities and psychosocial variables.

Quantitative bile acid profiling by liquid chromatography quadrupole time-of-flight mass spectrometry: monitoring hepatitis B therapy by a novel Na(+)-taurocholate cotransporting polypeptide inhibitor

A novel analytical approach for the targeted profiling of bile acids (BAs) in human serum/plasma based on liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) is presented. Reversed-phase chromatography enabled the baseline separation of 15 human BA species which could be readily detected by accurate mass analysis in negative ion mode. Blood proteins were removed by methanol precipitation in the presence of deuterium-labeled internal standards which allowed BA quantification in 50 μl plasma/serum. The assay was validated according to FDA guidance achieving quantification limits from 7.8 to 156 nM. Calibration curves prepared in charcoal-stripped serum/plasma showed excellent regression coefficients (R (2) > 0.997) and covered quantities from 7.8 to 10,000 nM depending on the analyzed species. Intra- and inter-day accuracy and precision were below 15 % for all analytes. Apparent extraction recoveries were above 97 %, and ion suppression rates were between 4 and 53 %. Mean BA level in serum/plasma from healthy volunteers ranged from 11 ± 4 nM (tauroursodeoxycholic acid) to 1321 ± 1442 nM (glycochenodeoxycholic acid). As a proof of concept, the assay was applied to plasma samples derived from a clinical phase I study of myrcludex B, a novel first-in-class virus entry inhibitor for the treatment of chronic hepatitis B and D. The results demonstrate that myrcludex-induced inhibition of the hepatic BA transporter Na(+)-taurocholate cotransporting polypeptide (NTCP) significantly affects plasma BA level. These observations provide novel insights into drug-induced metabolic responses and will be indispensable for the assessment of side effects and dose-finding processes during future clinical trials.

The impact of pharmaceutical care interventions for medication underuse in older people: a systematic review and meta-analysis

AIMS

The aim of the present study was to conduct a meta-analysis of controlled trials assessing the impact of pharmaceutical care interventions (e.g. medication reviews) on medication underuse in older patients (≥65 years).

METHODS

The databases MEDLINE and EMBASE were searched for controlled studies, and data on interventions, patient characteristics and exposure, and outcome assessment were extracted. Risk of bias was assessed using the Cochrane Collaboration's 'risk of bias' table. Results from reported outcomes were synthesized in multivariate random effects meta-analysis, subgroup meta-analysis and meta-regression.

RESULTS

From 954 identified articles, nine controlled studies, mainly comprising a medication review, were included (2542 patients). These interventions were associated with significant reductions in the mean number of omitted drugs per patient (estimate from six studies with 1469 patients: - 0.44; 95% confidence interval -0.61, -0.26) and the proportion of patients with ≥1 omitted drugs (odds ratio from eight studies with 1833 patients: 0.29; 95% confidence interval 0.13, 0.63). The only significant influential factor for improving success was the utilization of explicit screening instruments when conducting a medication review (P = 0.033).

CONCLUSION

Pharmaceutical care interventions, including medication reviews, can significantly reduce medication underuse in older people. The use of explicit screening instruments alone or in combination with implicit reasoning is strongly recommendable for clinical practice.

St. John's wort treatment in women bears risks beyond pharmacokinetic drug interactions

We analyzed adverse events in a clinical phase I trial to assess dose-dependent metabolic effects of St. John's wort co-administered with rifampicin in 12 healthy volunteers. Within 3-6 days after increasing the St. John's wort dose from 300 to 600 mg TID, five of six female participants developed ambient temperature-dependent allodynia and paresthesia in sun-exposed areas (back of the hands and perioral and nasal area). Aggravation of symptoms resulted in persistence of paresthesia and phototoxic erythrodermia. None of the male participants showed any of these effects. Gender, duration of treatment, dose, and solar exposure seem to be extrinsic and host factors facilitating St. John's wort-induced neuropathy. The risk to develop this adverse effect is almost exclusively present in women.

Tailoring of alerts substantially reduces the alert burden in computerized clinical decision support for drugs that should be avoided in patients with renal disease

OBJECTIVE

Electronic alerts are often ignored by physicians, which is partly due to the large number of unspecific alerts generated by decision support systems. The aim of the present study was to analyze critical drug prescriptions in a university-based nephrology clinic and to evaluate the effect of different alerting strategies on the alert burden.

METHODS

In a prospective observational study, two advanced strategies to automatically generate alerts were applied when medication regimens were entered for discharge letters, outpatient clinic letters, and written prescriptions and compared to two basic reference strategies. Strategy A generated alerts whenever drug-specific information was available, whereas strategy B generated alerts only when the estimated glomerular filtration rate of a patient was below a drug-specific value. Strategies C and D included further patient characteristics and drug-specific information to generate even more specific alerts.

RESULTS

Overall, 1012 medication regimens were entered during the observation period. The average number of alerts per drug preparation in medication regimens entered for letters was 0.28, 0.080, 0.019, and 0.011, when using strategy A, B, C, or D (P<0.001, for comparison between the strategies), leading to at least one alert in 87.5%, 39.3%, 13.5%, or 7.81 % of the regimens. Similar average numbers of alerts were observed for medication regimens entered for written prescriptions.

CONCLUSIONS

The prescription of potentially hazardous drugs is common in patients with renal impairment. Alerting strategies including patient and drug-specific information to generate more specific alerts have the potential to reduce the alert burden by more than 90 %.

Anti-angiogenic activity of VXM01, an oral T-cell vaccine against VEGF receptor 2, in patients with advanced pancreatic cancer: A randomized, placebo-controlled, phase 1 trial

VEGFR-2 is expressed on tumor vasculature and a target for anti-angiogenic intervention. VXM01 is a first in kind orally applied tumor vaccine based on live, attenuated Salmonella bacteria carrying an expression plasmid, encoding VEGFR-2. We here studied the safety, tolerability, T effector (Teff), T regulatory (Treg) and humoral responses to VEGFR2 and anti-angiogenic effects in advanced pancreatic cancer patients in a randomized, dose escalation phase I clinical trial. Results of the first 3 mo observation period are reported. Locally advanced or metastatic, pancreatic cancer patients were enrolled. In five escalating dose groups, 30 patients received VXM01 and 15 placebo on days 1, 3, 5, and 7. Treatment was well tolerated at all dose levels. No dose-limiting toxicities were observed. Salmonella excretion and salmonella-specific humoral immune responses occurred in the two highest dose groups. VEGFR2 specific Teff, but not Treg responses were overall increased in vaccinated patients. We furthermore observed a significant reduction of tumor perfusion after 38 d in vaccinated patients together with increased levels of serum biomarkers indicative of anti-angiogenic activity, VEGF-A, and collagen IV. Vaccine specific Teff responses significantly correlated with reductions of tumor perfusion and high levels of preexisting VEGFR2-specific Teff while those showing no antiangiogenic activity had low levels of preexisting VEGFR2 specific Teff, showed a transient early increase of VEGFR2-specific Treg and reduced levels of VEGFR2-specific Teff at later time points - pointing to the possibility that early anti-angiogenic activity might be based at least in part on specific reactivation of preexisting memory T cells.

Clarithromycin substantially increases steady-state bosentan exposure in healthy volunteers

AIMS

The aim of this study was to assess the effect of the cytochrome P450 (CYP) 3A4 and organic anion-transporting polypeptide (OATP) 1B1 inhibitor clarithromycin on the pharmacokinetics of bosentan. We also aimed to evaluate the impact of CYP2C9 and SLCO1B1 (encoding for OATP1B1) genotypes and their combination.

METHODS

We assessed the effect of the OATP and CYP3A inhibitor clarithromycin on bosentan pharmacokinetics at steady state and concurrently quantified changes of CYP3A activity using midazolam as a probe drug. Sixteen healthy volunteers received therapeutic doses of bosentan (125 mg twice daily) for 14 days and clarithromycin (500 mg twice daily) concomitantly for the last 4 days, and bosentan pharmacokinetics was assessed on days 1, 10 and 14.

RESULTS

Clarithromycin significantly increased bosentan area under the plasma concentration-time curve of the dosing interval 3.7-fold and peak concentration 3.8-fold in all participants irrespective of the genotype. Clarithromycin also reduced CYP3A activity (midazolam clearance) in all participants; however, these changes were not correlated to the changes of bosentan clearance.

CONCLUSIONS

Clarithromycin substantially increases the exposure to bosentan, suggesting that dose reductions may be necessary.