Why do inadvertent pregnancies occur in oral contraceptive users? Effectiveness of oral contraceptive regimens and interfering factors

The Role of Oral Contraceptive Pills in Hidradenitis Suppurativa: A Cohort Study

There is a need to establish the role of antiandrogens as an alternative or concomitant therapy for hidradenitis suppurativa (HS). Thus, the objectives of this study are (1) to assess the effectiveness of oral contraceptive pills (OCPs) at week 12 in HS women, and (2) to describe the clinical profile of patients receiving oral contraceptive pills (OCPs). A prospective observational study was designed. This study included 100 participants, 50 women with HS who started OCPs for the first time at our HS Clinic and 50 participants without OCP treatment. The main outcome of interest was the percentage of reduction in total abscess and inflammatory nodule (AN) count at week 12. Thirty-three women received combined OCPs and 17 non-combined OCP. HS patients with OCPs treatment were younger (31.7 vs. 40.9 years, p < 0.001), thinner (28.62 vs. 33.35 kg/m²), and have a higher number of areas affected (2.32 vs. 1.38, p = 0.02) than those without OCPs. After 12-weeks of treatment, it was observed that the percentage of AN reduction was higher in HS women receiving OCP than in patients without OCP (53.9% vs. 38.42%, p = 0.049). It was observed that OCP prescription (β = 3.79, p = 0.034) and concomitant therapy (β = 3.91, p = 0.037) were independently associated with a higher % AN when controlling for disease duration, concomitant therapy, and treatment with/without OCP (R² = 0.67). The factors potentially associated with the percentage AN reduction at week 12 in HS women treated with OCPs were disease duration (β = -1.327, p = 0.052), concomitant therapy (β = 11.04, p = 0.079), and HS worsening with the menstrual cycle (β = 10.55, p = 0.087). In conclusion, OCPs might be effective for improving AN count in women with HS. Women whose HS worsens in relation to the menstrual cycle and have a shorter disease may benefit more from the therapeutic effect of OCPs.

Follicle-stimulating hormone (FSH), current suicidal ideation and attempt in female patients with major depressive disorder

Current suicidal ideation and attempts are more commonly found in female patients with major depressive disorder (MDD) than in males. However, little is known about the relationship between activity of female reproductive hormones and suicide. The study population consisted of 490 female MDD patients of age ≥18. They were assessed by the Mini-International Neuropsychiatric Interview. At the same visit, we measured blood Follicle-Stimulating Hormone (FSH), Luteinizing Hormone (LH), estradiol, progesterone, Adrenocorticotropic Hormone (ACTH), cortisol, thyroid hormones, and prolactin. Blood FSH showed a significant difference among female MDD patients with suicide attempt, those with ideation, and those without within the previous month. Post-hoc analysis also showed that FSH was significantly lower in MDD patients with suicide attempt and ideation than those without, whereas other hormones showed no differences between those with and without attempt. FSH was negatively associated with current suicidality scores after adjustment for age and education years in all age groups. FSH was significantly lower in those with current suicide ideation or attempt than those without in age 45 years or under, but not in other age groups. In conclusion, blood FSH is significantly lower in female MDD patients with current suicide attempt or ideation than those without, especially in age 45 years or under.

Quantifying effect of combined oral contraceptive pill on functional ovarian reserve as measured by serum anti-Müllerian hormone and small antral follicle count using three-dimensional ultrasound

OBJECTIVES

Oral contraceptive pills suppress the hypothalomo-pituitary axis, which can affect the ultrasound and endocrine markers used to examine ovarian reserve. The objective of this study was to quantify the ultrasound and endocrine markers of functional ovarian reserve in women using a combined oral contraceptive pill (COCP) for more than a year.

METHODS

This was a prospective case-control study involving healthy volunteers: 34 women using for more than a year a COCP with hormone-free interval (HFI) were compared to 36 normo-ovulatory, age-matched controls who had not used hormonal contraception within the last year. Volunteers using a COCP underwent a 3D ultrasound examination and had a blood sample taken within the first 4 days of active pill ingestion and those in the control group had the scan and blood test in the early follicular phase (days 2-5) of menstrual cycle. The main outcome measure was the difference in antral follicle counts stratified according to size and anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and estradiol (E2) levels.

RESULTS

There were no significant differences in the number of small antral follicles measuring 2-6 mm. The COCP group had significantly fewer antral follicles measuring ≥ 6 mm (P < 0.001) and had significantly smaller ovaries (P < 0.001), which also had lower vascular indices than the control group (P < 0.05). While serum FSH, LH and E2 levels were significantly lower in the COCP group (P < 0.05), there was no significant difference in serum AMH levels between the two groups.

CONCLUSIONS

Prolonged use of COCP suppressed pituitary gonadotropins and antral follicle development beyond 6 mm, but had no effect on levels of serum AMH and number of small antral follicles.

Contraceptive choices, pregnancy rates, and outcomes in a microbicide trial

OBJECTIVE

Women who become pregnant during the conduct of biomedical human immunodeficiency virus prevention trials are taken off the study product for safety reasons. High pregnancy rates can compromise statistical integrity in these trials. The comprehensive contraceptive curriculum developed for the Centre for the AIDS Programme of Research in South Africa (CAPRISA) 004 trial was evaluated for its ability to enhance contraceptive uptake, reduce pregnancy rates, and preserve statistical integrity.

METHODS

Contraceptive- and pregnancy-related eligibility criteria were specified in the protocol. We enrolled women who opted for a nonbarrier method of contraceptive and provided hormonal contraceptives onsite at no cost. At each monthly study visit, we provided pregnancy prevention counseling and performed pregnancy testing. Study product was withheld on pregnancy diagnosis, but women continued with monthly follow-up.

RESULTS

Contraceptive use was high throughout the study with 100% uptake at baseline and 94.71% use after a mean of 18 months follow-up at exit. Injectable progestins, particularly medroxyprogesterone acetate, remained the preferred choice of contraceptive. After 30 months of follow-up, 54 pregnancies were reported out of 889 participants, giving a pregnancy incidence rate of 3.95 per 100 woman-years (95% confidence interval 2.96-5.17). Of all pregnancies, two thirds (64.81%) resulted in a full-term live birth, whereas 18.52% and 11.11% pregnancies culminated as miscarriage and terminated pregnancies, respectively. There were no congenital anomalies in the early neonatal period. Pregnancies resulted in 1.56% of woman-years of study follow-up lost as a result of temporary product withdrawal.

CONCLUSION

The CAPRISA 004 contraceptive curriculum was an effective strategy for maintaining low pregnancy rates, thereby minimizing product withdrawal and loss of follow-up time.

LEVEL OF EVIDENCE

III.

Menstrual suppression for adolescents with developmental disabilities

The approach to menstrual suppression for adolescents with developmental disabilities has evolved considerably over the years due to changing philosophies and evolving treatment options. We review the medical management options available for menstrual suppression with a focus on the needs and treatment of adolescents with developmental disabilities.

Long-Cycle Treatment with Oral Contraceptives

The conventional regimen of oral contraceptive (OC) use mimics the natural cycles by causing regular withdrawal bleeding, which can be avoided by omission of the hormone-free interval of 7 days. Consequently, long-cycle regimens with continuous administration of OCs for 3 or 6 months followed by a hormone-free interval of 7 days may reduce the frequency of menstruations and cycle-dependent complaints. Surveys have revealed that, despite a higher rate of irregular bleeding, the majority of women prefer the long-cycle regimen to the conventional OC regimen with regular bleeds every 4 weeks because it may improve quality of life. As this regimen increases the contraceptive efficacy to a large degree, continuous treatment with OCs may prevent unintended pregnancies in women who miss a pill or are concomitantly treated with drugs that are able to impair the efficacy of OCs. Postponement of withdrawal bleeding may also reduce or prevent menses-associated disorders such as hypermenorrhoea and dysmenorrhoea, and have beneficial effects in patients with haemorrhagic diathesis, endometriosis, uterine leiomyoma and polycystic ovary syndrome. Continuous use of OCs prevents the cyclic fluctuations of serum levels of ethinylestradiol and progestogen and, hence, the cyclic variations of metabolic serum parameters. Although the long-cycle regimen is initially associated with an elevated rate of irregular bleeding, the total number of bleeding days that require sanitary product protection is lower than during conventional OC treatment. Many physicians tend to prescribe extended OC cycles for postponement of menstruation or reduction of frequency of regular bleeding. This review summarises and examines the available data on OC long-cycle regimens. The data suggest that the rate of treatment-related side effects with OCs according to the long-cycle regimen is similar to that of conventional OC regimens. However, clinical trials are necessary to assess the impact of long-term OC long cycles on safety, particularly the risk of cancer and cardiovascular disease, and fertility after discontinuation of treatment.

Oral contraceptive efficacy and antibiotic interaction: a myth debunked

The purpose of this study was to review the pharmacokinetic and clinical literature regarding the efficacy of oral contraceptives when used concomitantly with antibiotic therapy. Relevant literature was identified by searching MEDLINE and EMBASE. Other sources were located by consulting the bibliographies of the material collected from MEDLINE and EMBASE. Pharmacokinetic evidence demonstrates that plasma levels of oral contraceptive steroids are unchanged with the concomitant administration of antibiotics, including ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, temafloxacin, and tetracycline. However, reduced steroid levels have been reported in women taking rifampin with oral contraceptives. Clinical reports of contraceptive failure with antibiotic use are retrospective, have multiple potential biases, and are not supported by pharmacokinetic data. Available scientific and pharmacokinetic data do not support the hypothesis that antibiotics (with the exception of rifampin) lower the contraceptive efficacy of oral contraceptives.

Charcoal treatment and risk of escape ovulation in oral contraceptive users

Ovulatory potential was studied during the use of two oral contraceptive pill preparations, after repeated mid-cycle administration of activated charcoal. Eleven women used monophasic pills containing gestodene, 75 microgram, plus ethinyl oestradiol, 30 microgram, or norethisterone acetate, 1 mg, plus ethinyl oestradiol, 30 microgram, for 4 months each, in randomized order. During both pill treatments the third cycle was a control cycle, and during the fourth cycle of both pill types, 5 g of activated charcoal was ingested four times a day, starting 3 h after pill intake, on cycle days 12, 13 and 14. Ovarian activity was monitored by intravaginal ultrasonography of follicles and by measurements of serum concentrations of LH, FSH, oestradiol and progesterone throughout the control and charcoal-treatment cycles of both pill treatments. None of the women ovulated. Follicular activity seen in two women did not correlate with charcoal administration. It is concluded that the possible enterohepatic recirculation of gestodene and norethisterone is not of clinical importance. Repeated charcoal treatment, when administered 3 h after but at least 12 h before pill intake, can be used to treat diarrhoea in women taking oral contraceptives.

Pharmacokinetic drug interactions between oral contraceptives and second-generation anticonvulsants

Drug interactions between oral contraceptives (OCs) and traditional anticonvulsants have been well described. However, in the past decade, a number of new anticonvulsants have been developed, as well as modifications made in the composition of the OC preparations themselves. Additionally, anticonvulsants are increasingly employed in the therapy of nonseizure-related disorders, placing more women at risk of potential drug interactions that may lead to contraceptive failure. Second-generation anticonvulsants include felbamate, gabapentin, lamotrigine, oxcarbazepine, tiagabine, topiramate, vigabatrin and zonisamide. Most have been approved for adjunctive management of seizures refractory to therapy with traditional anticonvulsants. On the basis of available study data in women receiving concomitant OC preparations, gabapentin, lamotrigine, tiagabine and vigabatrin may be administered without significant pharmacokinetic interactions that potentially diminish contraceptive efficacy. However, additional or alternative contraceptive measures, including using OCs with higher estrogen content, are recommended when using felbamate, oxcarbazepine and topiramate, as these agents have demonstrated enzyme-inducing activity leading to reduced plasma steroid concentrations. The effects of zonisamide in women receiving OCs have yet to be reported. It is important to characterise the properties [e.g. substrate and enzyme activity (particularly cytochrome P450 3A4 induction)] of new anticonvulsants and recognise their potential to interfere with OCs. However, a pharmacokinetic interaction does not in itself indicate loss of OC efficacy. Contraceptive failure should be measured by changes in ovarian hormone concentrations, maturation of ovarian follicle(s) or ovulation.

Effects of rifabutin and rifampicin on the pharmacokinetics of ethinylestradiol and norethindrone

This open-label, randomized, three-way crossover study of 28 healthy premenopausal women was conducted to compare the impact of concomitant rifabutin and rifampicin on the safety, pharmacokinetics, and pharmacodynamics of the oral contraceptives ethinylestradiol and norethindrone (Ortho-Novum 1/35; Ortho Pharmaceutical, Raritan, NJ). Each participant received oral contraceptives daily for 21 days for the first control cycle, then was randomized to one of two sequences to receive oral contraceptives with concomitant rifampicin and rifabutin at equal doses of 300 mg/day for 10 days. Ethinylestradiol, norethindrone, follicle stimulating hormone (FSH), luteinizing hormone (LH), progesterone, rifampicin, and rifabutin (and metabolite) were measured in plasma over the same time frames in all three cycles. Safety was assessed from before the beginning to the end of each cycle. Twenty-two subjects completed all three cycles. Compared with the control cycle, rifabutin and rifampicin significantly altered the disposition of the oral contraceptive. Area under the concentration-time curve from 0 to 24 hours (AUC0-24) and maximum plasma concentration (Cmax) of ethinylestradiol decreased by 64% and 42%, respectively, after coadministration with rifampicin and by 35% and 20%, respectively, after coadministration with rifabutin. The AUC0-24 of norethindrone decreased by 60% and 20% after coadministration with rifampicin and rifabutin, respectively. Unlike progesterone levels, FSH and LH levels increased during coadministration with rifampicin and rifabutin. The incidence of spotting was significantly higher after coadministration with rifampicin (36.4%) and rifabutin (21.7%) than during the control cycle (3.7%). Although both rifampicin and rifabutin affected the pharmacokinetics of ethinylestradiol and norethindrone, the magnitude of this effect was more pronounced with rifampicin. Likewise, the fact that the highest incidence of spotting occurred with rifampicin was consistent with higher metabolic induction by rifampicin. Despite the fact that there was no change in progesterone levels, it is recommended that patients be advised to use additional contraceptive methods while receiving rifabutin or rifampicin with oral contraceptives to prevent inadvertent pregnancy.

Omitting the first oral contraceptive pills of the cycle does not automatically lead to ovulation

OBJECTIVE

Our purpose was to test the hypothesis that omitting the first three pills of the contraceptive cycle leads to ovulation.

STUDY DESIGN

Ninety-nine women, randomly assigned to 1 of 3 treatments of combined oral contraceptives, completed the study. Treatments contained ethinyl estradiol and either monophasic gestodene, triphasic gestodene, or monophasic desogestrel. Pituitary-ovarian activity was monitored by ultrasonography of the ovaries and assay of serum concentrations of estradiol, progesterone, and follicle-stimulating hormone over 1 normal cycle (study period 1) and 1 cycle after an extended pill-free interval of 10 days (study period 2).

RESULTS

None of the women experienced normal ovulation as evaluated by ultrasonography and serum progesterone concentrations. However, follicle-stimulating hormone reached a maximal serum concentration in most women during the first 7 pill-free days, indicating complete pituitary recovery, and increases in serum estradiol concentrations were seen in each woman although with marked interindividual variation. During study period 2 we found follicles of >18 mm in 24%, 24%, and 40% of the monophasic gestodene, triphasic gestodene, and monophasic desogestrel groups, respectively.

CONCLUSIONS

Follicular growth up to preovulatory size is common in women missing the first one to three pills of their contraceptive cycle. Although this creates the prerequisite for ovulation, normal ovulation did not occur when pill omissions were limited to only 3 days.

Compliance and oral contraceptives: a review

Compliance difficulties are more common among oral contraceptive (OC) users than generally appreciated by clinicians, in part because unintended pregnancy is a relatively infrequent consequence and in part because more common manifestations such as spotting and bleeding may not be recognized as resulting from poor compliance. While improving compliance is a shared responsibility of patients, clinicians, and manufacturers, the clinician is the focal point for these efforts. Counseling must be individualized, which requires knowledge of factors that predict compliance and an understanding of the patient's decision-making process as it relates to medications. Most OC compliance research has focused on adolescents, where predictors of poor compliance include multiple sex partners, low evaluation of personal health, degree of concern about pregnancy, and previous abortion. Good compliance has been linked with patient satisfaction with the clinician, the absence of certain side effects, establishing a regular daily routine to take OCs, and reading information distributed with OC packaging.

The combined oral contraceptive pill: what advice should we give when tablets are missed?

Despite more than 30 years' experience with the pill, being by far the most thoroughly studied drug ever, we must conclude that there still is a remarkable paucity of data that would allow us to assess unambiguously its margins of efficacy. The physiological studies on which we must rely encompass limited numbers of subjects and are unlikely to include sufficient representatives of the vulnerable minority of women that really matter. Even though we realise that this vulnerable minority is there, we still cannot do better than to hypothesise about their characteristics, let alone identify them in advance. This lack of knowledge has contributed to the existence of diverging views on how to advise the general population of pill takers about missed tablets. Against this background, we felt there was a need to make an inventory of the existing data and, subsequently, to incorporate them in advice that in our opinion is most appropriate in the current state of knowledge. We have come to the conclusion, in contrast to what is often held, that it is not the number of tablets missed, but rather the timing relative to the pill-free interval that determines the impact of noncompliance. We further conclude that shortening of the pill-free interval to five or six days could substantially improve the efficacy of the pill: at the low doses currently used in oral contraceptives the total steroid burden would not be substantially increased, while still allowing withdrawal bleeding to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Practical problems which women encounter with available contraception in Australia

Australian women face major difficulties with contraception because of the limited range of choices, the need for meticulous attention to compliance with most available methods and because of cost limitations for a significant minority of the population. The most commonly used methods are oral contraceptive pills and barrier methods, and each has substantial compliance problems which can be minimized with care and counselling. There is an urgent need for a wider range of options in Australia and for good information and publicity about them. Present progress in this direction gives some hope for the near future.

Introducing the low-dose pill to Bangladesh; issues of continuation and failure

In response to government plans to introduce a low-dose pill to the national family planning program of Bangladesh, a comparison of the performance of low-dose and standard-dose pills among a rural Bangladeshi population was conducted. Continuation rates were found to be better among users of the low-dose pill and there was no evidence that failure rates were higher. The relative risk (standard-dose vs. low-dose) over the first 30 months following adoption was 1.25 for first method continuation, and 1.29 for extended use failure. This paper, thus, provides evidence that low-dose pills may be a suitable method of contraception for rural Bangladeshi women.

Should oral contraceptives be available without prescription?

In this paper, it is argued that oral contraceptives should be available without prescription. Prescription status entails heavy costs, including the dollar, time, and psychological costs of visiting a physician to obtain a prescription, the financial and human costs of unintended pregnancies that result from the obstacle to access caused by medicalization of oral contraceptives, and administrative costs to the health care system. After a review and evaluation of the reasons for strict medical control of oral contraceptives in the United States, safety concerns anticipated in response to the proposal discussed here are addressed. Also, concerns that prescription status is necessary for efficacious use are evaluated. It is concluded that neither safety nor efficacy considerations justify prescription status for oral contraceptives. Revised package design and patient labeling could allow women to screen themselves for contraindications, to educate themselves about danger signs, and to use oral contraceptives safely and successfully. Several alternatives to providing oral contraceptives by prescription with current package design and labeling and selling them over the counter are suggested; the proposals discussed would make these safe and effective contraceptives easier to obtain and to use.

The safety and efficacy issues of progestin-only oral contraceptives--an epidemiologic perspective

Progestogen-only oral contraceptives (POCs) are generally considered a good contraceptive choice for brestfeeding women and for women who want to use an oral form of contraception, but are not suited for, or cannot tolerate the side effects of, estrogen-containing preparations. However, a number of POCs' safety, efficacy and other related issues remain to be addressed. This paper reviews recent literature and evaluates these issues from an epidemiologic perspective. The small number of users imposes severe limitations in designing epidemiologic studies to address POCs' long-term safety issues, but available information suggests POCs are at least as safe as, if not safer than, COCs. Compared to COCs, POCs are more likely to cause menstrual disturbances which, in turn, could affect their acceptability and lead to poor compliance and hence higher pregnancy rates. POCs' efficacy has been estimated to be between 1.4 and 4.3 pregnancies per 100 woman-years of use. Lower pregnancy rates approaching those of COCs have been reported in centers with good counseling. POCs' benefits outweigh their risks. However, more studies are needed to further address POCs' safety and efficacy issues.

High-dose and low-dose combined oral contraceptives: protection against epithelial ovarian cancer and the length of the protective effect. The WHO Collaborative Study of Neoplasia and Steroid Contraceptives

The relations between use of high-dose and low-dose combined oral contraceptives and epithelial ovarian cancer were compared in an international hospital-based case-control study. 393 cases from seven countries were compared with 2561 matched controls. The odds ratio (OR) was somewhat lower for women who used high-dose oestrogen oral contraceptives (OR = 0.68) than for women who used low-dose preparations (OR = 0.81) although the difference could have occurred by chance. After controlling for time since last use, risk was slightly lower for long-term users of high-dose preparations than for long-term users of low-dose pills. Both high-dose and low-dose oral contraceptives protect against ovarian cancer, but the degree of protection may be slightly weaker for the newer, low-dose products.

Interchangeability of low-dose oral contraceptives. Are current bioequivalent testing measures adequate to ensure therapeutic equivalency?

Current Food and Drug Administration guidelines for assessing the differences in bioavailability between generic oral contraceptives and brand-name products are inadequate to ensure therapeutic equivalence. The guidelines do not take into account those women who may have blood levels of active ingredients well outside the range of acceptability. Due to the narrow therapeutic range of steroids, these women may become pregnant or experience an increased incidence of breakthrough bleeding. Furthermore, oral contraceptive packaging is unique to each manufacturer, and any change in brands (and therefore packaging) can easily negate the sequential administration of the appropriate tablet. These are among the reasons proposed for placing oral contraceptives in the critical drug category, in which generic substitution and interchangeability of products should not be allowed.

Cycle control on low-dose oral contraceptives: a comparative trial

Cycle control was studied comparing the monophasic oral contraceptive Loestrin with three low-dose phasic preparations (Triphasil, Ortho 10/11 and Ortho 7/7/7) in 391 women of whom 300 completed 6 cycles. Loestrin subjects had a rate of occurrence (31% of cycles) for intermenstrual bleeding (IMB) comparable to the rates for subjects on the phasic preparations (36%, 37% and 37%, respectively). Triphasil subjects had lower rates than the Ortho 10/11 and Ortho 7/7/7 subjects (p less than 0.01) in cycle one when all subjects were analyzed and in pre-study users when continuing menstrual flow (CMF) episodes were not included as IMB. IMB was a cause for dropping out of the study in 7% of subjects who were evenly distributed between groups. There were no differences between groups for BTB when perceived by subjects as a side effect. Spotting was perceived as a side effect more often with Ortho 10/11 and Ortho 7/7/7 use than with Triphasil (p less than 0.01). Loestrin, Ortho 10/11 and Ortho 7/7/7 subjects were more likely to report amenorrhea (p less than 0.001) and less likely to report leg cramps (p less than 0.01) compared to those on Triphasil. Triphasil subjects were less likely to report acne than subjects on Ortho 7/7/7 (p less than 0.01).

Pharmacokinetic drug interactions with oral contraceptives

Oral contraceptive steroids are used by an estimated 60 to 70 million women world-wide. Over the past 20 years there have been both case reports and clinical studies on the topic of drug interactions with these agents. Some of the interactions are of definite therapeutic relevance, whereas others can be discounted as being of no clinical significance. Pharmacological interactions between oral contraceptive steroids and other compounds may be of 2 kinds: (a) drugs may impair the efficacy of oral contraceptive steroids, leading to breakthrough bleeding and pregnancy (in a few cases, the activity of the contraceptive is enhanced); (b) oral contraceptive steroids may interfere with the metabolism of other drugs. A number of anticonvulsants (phenobarbital, phenytoin, carbamazepine) are enzyme-inducing agents and thereby increase the clearance of the oral contraceptive steroids. Valproic acid has no enzyme-inducing properties, and thus women on this anticonvulsant can rely on their low dose oral contraceptive steroids for contraceptive protection. Researchers are now beginning to unravel the molecular basis of this interaction, with evidence of specific forms of cytochrome P450 (P450IIC and IIIA gene families) being induced by phenobarbital. Rifampicin, the antituberculous drug, also induces a cytochrome P450 which is a product of the P450IIIA gene subfamily. This isozyme is one of the major forms involved in 2-hydroxylation of ethinylestradiol. Broad spectrum antibiotics have been implicated in causing pill failure; case reports document the interaction, and general practitioners are convinced that it is real. The problem remains that there is still no firm clinical pharmacokinetic evidence which indicates that blood concentrations of oral contraceptive steroids are altered by antibiotics. However, perhaps this should not be a surprise, given that the incidence of the interaction may be very low. It is suggested that an individual at risk will have a low bioavailability of ethinylestradiol, a large enterohepatic recirculation and gut flora particularly susceptible to the antibiotic being used. Two drugs, ascorbic acid (vitamin C) and paracetamol (acetaminophen), give rise to increased blood concentrations of ethinylestradiol due to competition for sulphation. The interactions could have some significance to women on oral contraceptive steroids who regularly take high doses of either drug. Although on theoretical grounds adsorbents (e.g. magnesium trisilicate, aLuminium hydroxide, activated charcoal and kaolin) could be expected to interfere with oral contraceptive efficacy, there is no firm evidence that this is the case. Similarly, there is no evidence that smoking alters the pharmacokinetics of oral contraceptive steroids. These agents are now well documented as being able to alter the pharmacokinetics of other concomitantly administered drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Inadvertent pregnancies in oral contraceptive users

Two hundred and nine inadvertent pregnancies in oral contraceptive users were studied to determine the associated factors. The percentage of Pill types also were compared with the market usage over the same period. We found that the classically-suggested cofactors, such as missed pills, late pills, drug ingestion, and gastrointestinal upsets were reported commonly. The triphasic Pills also were represented more frequently than would have been expected from their share of the market.

The effect of deliberate omission of Trinordiol or Microgynon on the hypothalamo-pituitary-ovarian axis

The effect of deliberate omission of a phased formulation pill, Trinordiol (ethinyl estradiol 30 micrograms + levonorgestrel 50 micrograms: 6 tablets; ethinyl estradiol 40 micrograms + levonorgestrel 75 micrograms: 5 tablets; ethinyl estradiol 30 micrograms + levonorgestrel 125 micrograms: 10 tablets) or a low-dose, combined, oral contraceptive pill, Microgynon (ethinyl estradiol 30 micrograms + levonorgestrel 150 micrograms: 21 tablets) on the hypothalamo-pituitary-ovarian axis were studied. Thirty-six women were recruited to the study and divided equally between the two types of pill. Medication was begun on the 8th pill-free day of the cycle and continued for 7 days (Group 1), 14 days (Group 2) or 21 days (Group 3). Levels of FSH, LH, estradiol (E2) and progesterone (P) were measured in plasma on alternate days during the final week of pill therapy, and daily for the 7 days after stopping the pill. For the first 2 weeks of pill therapy, follicular activity, as judged by plasma levels of E2, was greater in women taking Trinordiol than in those taking Microgynon, but was similar in both groups by the third week of pill treatment. Five women taking Trinordiol (2 in Group 1 and 3 in Group 2) had plasma levels of E2 in excess of 500 pmol/l whilst taking the pills, and only 1 patient achieved this degree of follicular activity after stopping the tablets. One woman who had taken 7 days of Trinordiol (Group 1) showed a rise of plasma levels of P to 6.8 nmol/l, but luteinization did not occur in any of the remaining 35 women who took Trinordiol or Microgynon. These findings suggest that follicular activity is less completely suppressed by Trinordiol than Microgynon, at least in the first 2 weeks of pill therapy, but that normal ovulation is still a rare event in the week after cessation of either of these pills, even if only 7 days of medication have been taken.

Suppression of ovarian function by Microgynon 30 in day 1 and day 5 "starters"

The suppression of ovulation during the first treatment cycle with Microgynon 30 (150 micrograms levonorgestrel and 30 micrograms ethinyl oestradiol) for nine subjects starting the "pill" on day 1 of their cycle and five subjects on day 5 was investigated. Serum oestradiol and progesterone levels throughout the cycle and midcycle urinary LH levels were reliably suppressed in all day 1 "starters". Serum progesterone levels and urinary LH levels were also suppressed in day 5 "starters" but one subject produced oestradiol levels within the normal range of ovulatory cycles. Mean oestradiol levels of day 5 "starters" were found to be significantly higher than those of day 1 "starters" (p less than 0.05).

Inhibition of oral contraceptive effectiveness by concurrent antibiotic administration. A review

The use of antibiotics in periodontal therapy has received increasing attention in recent years. Although generally safe, certain antibiotics, including tetracycline and ampicillin, have been shown to interact indirectly with oral contraceptives, with a resultant decrease in oral contraceptive efficacy. This paper reviews the nature of antibiotic-oral contraceptive inter-actions, as well as the precautions that have been suggested for patients taking oral contraceptives for whom certain antibiotics have been prescribed.