The effect of tetracycline on levels of oral contraceptives

U.S. Medical Eligibility Criteria for Contraceptive Use, 2024

The 2024 U.S. Medical Eligibility Criteria for Contraceptive Use (U.S. MEC) comprises recommendations for the use of specific contraceptive methods by persons who have certain characteristics or medical conditions. These recommendations for health care providers were updated by CDC after review of the scientific evidence and a meeting with national experts in Atlanta, Georgia, during January 25-27, 2023. The information in this report replaces the 2016 U.S. MEC (CDC. U.S. Medical Eligibility Criteria for Contraceptive Use, 2016. MMWR 2016:65[No. RR-3]:1-103). Notable updates include 1) the addition of recommendations for persons with chronic kidney disease; 2) revisions to the recommendations for persons with certain characteristics or medical conditions (i.e., breastfeeding, postpartum, postabortion, obesity, surgery, deep venous thrombosis or pulmonary embolism with or without anticoagulant therapy, thrombophilia, superficial venous thrombosis, valvular heart disease, peripartum cardiomyopathy, systemic lupus erythematosus, high risk for HIV infection, cirrhosis, liver tumor, sickle cell disease, solid organ transplantation, and drug interactions with antiretrovirals used for prevention or treatment of HIV infection); and 3) inclusion of new contraceptive methods, including new doses or formulations of combined oral contraceptives, contraceptive patches, vaginal rings, progestin-only pills, levonorgestrel intrauterine devices, and vaginal pH modulator. The recommendations in this report are intended to serve as a source of evidence-based clinical practice guidance for health care providers. The goals of these recommendations are to remove unnecessary medical barriers to accessing and using contraception and to support the provision of person-centered contraceptive counseling and services in a noncoercive manner. Health care providers should always consider the individual clinical circumstances of each person seeking contraceptive services. This report is not intended to be a substitute for professional medical advice for individual patients; when needed, patients should seek advice from their health care providers about contraceptive use.

Drug interactions between non-rifamycin antibiotics and hormonal contraception: a systematic review

OBJECTIVE

The purpose of this study was to determine whether interactions between non-rifamycin antibiotics and hormonal contraceptives result in decreased effectiveness or increased toxicity of either therapy.

STUDY DESIGN

We searched MEDLINE, Embase, clinicaltrials.gov, and Cochrane libraries from database inception through June 2016. We included trials, cohort, case-control, and pharmacokinetic studies in any language that addressed pregnancy rates, pharmacodynamics, or pharmacokinetic outcomes when any hormonal contraceptive and non-rifamycin antibiotic were administered together vs apart. Of 7291 original records that were identified, 29 met criteria for inclusion.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two authors independently assessed study quality and risk of bias using the United States Preventive Services Task Force evidence grading system. Findings were tabulated by drug class.

RESULTS

Study quality ranged from good to poor and addressed only oral contraceptive pills, emergency contraception pills, and the combined vaginal ring. Two studies demonstrated no difference in pregnancy rates in women who used oral contraceptives with and without non-rifamycin antibiotics. No differences in ovulation suppression or breakthrough bleeding were observed in any study that combined hormonal contraceptives with any antibiotic. No significant decreases in any progestin pharmacokinetic parameter occurred during co-administration with any antibiotic. Ethinyl estradiol area under the curve decreased when administered with dirithromycin, but no other drug.

CONCLUSION

Evidence from clinical and pharmacokinetic outcomes studies does not support the existence of drug interactions between hormonal contraception and non-rifamycin antibiotics. Data are limited by low quantity and quality for some drug classes. Most women can expect no reduction in hormonal contraceptive effect with the concurrent use of non-rifamycin antibiotics.

Role of enterohepatic recirculation in drug disposition: cooperation and complications

Enterohepatic recirculation (EHC) concerns many physiological processes and notably affects pharmacokinetic parameters such as plasma half-life and AUC as well as estimates of bioavailability of drugs. Also, EHC plays a detrimental role as the compounds/drugs are allowed to recycle. An in-depth comprehension of this phenomenon and its consequences on the pharmacological effects of affected drugs is important and decisive in the design and development of new candidate drugs. EHC of a compound/drug occurs by biliary excretion and intestinal reabsorption, sometimes with hepatic conjugation and intestinal deconjugation. EHC leads to prolonged elimination half-life of the drugs, altered pharmacokinetics and pharmacodynamics. Study of the EHC of any drug is complicated due to unavailability of the apposite model, sophisticated procedures and ethical concerns. Different in vitro and in vivo methods for studies in experimental animals and humans have been devised, each having its own merits and demerits. Involvement of the different transporters in biliary excretion, intra- and inter-species, pathological and biochemical variabilities obscure the study of the phenomenon. Modeling of drugs undergoing EHC has always been intricate and exigent models have been exploited to interpret the pharmacokinetic profiles of drugs witnessing multiple peaks due to EHC. Here, we critically appraise the mechanisms of bile formation, factors affecting biliary drug elimination, methods to estimate biliary excretion of drugs, EHC, multiple peak phenomenon and its modeling.

Profiling and hormonal therapy for acne in women

Acne vulgaris is the most common condition treated by physicians worldwide. Though most acne patients remit spontaneously, for the ones that do not or are unresponsive to conventional therapy or have obvious cutaneous signs of hyperandrogenism, hormonal therapy is the next option in the therapeutic ladder. It is not strictly indicated for only those patients who have cutaneous or biochemical evidence of hyperandrogenism, but can be used even without any evidence of hyperandrogenism, for therapy-resistant acne. It can be prescribed as monotherapy, but when used in combination with other conventional therapies, it may prove to be more beneficial. Hormonal evaluation is a prerequisite for hormonal therapy, to identify the cause behind hyperandrogenism, which may be ovarian or adrenal. This article reviews guidelines for patient selection and the various available hormonal therapeutic options, their side-effect profile, indications and contraindications, and various other practical aspects, to encourage dermatologists to become comfortable prescribing them.

Antibiotics and oral contraceptives: new considerations for dental practice

The aim of this paper is to highlight a change in guidance relating to possible interactions between antibiotics and oral contraceptives. Until recently, dentists have been advised to warn women taking the combined oral contraceptive pill of the routine need to use additional contraceptive measures while taking courses of broad spectrum antibiotics. Recent guidance relating to this issue has changed and dentists may not be aware of this. This paper reminds dentists of the previous guidelines and related evidence, reviews the pharmacokinetics of hormonal contraception and presents them with the latest evidence-based guidance. This should change their clinical practice.

Estradiol valerate/dienogest: a novel combined oral contraceptive

BACKGROUND

Estradiol valerate/dienogest (E2V/DNG) is a combined oral contraceptive (COC) with 2 new hormonal entities and a unique 4-phasic dosing regimen indicated for women to prevent pregnancy.

OBJECTIVE

The purpose of this article is to review the pharmacology, pharmacokinetics, clinical efficacy, tolerability, and cost of E2V/DNG.

METHODS

MEDLINE (1966-June 2011) and EMBASE (1966-June 2011) were searched for original research and review articles published in the English language using the terms Natazia or Qlaira or estradiol valerate and dienogest. The reference lists of identified articles were reviewed for additional pertinent publications. Abstracts from the 2005 to 2011 American Society of Reproductive Medicine and American College of Obstetricians and Gynecologists meetings were searched using the same terms.

RESULTS

The search provided 56 articles that addressed the pharmacology, pharmacokinetics, pharmacodynamics, clinical efficacy, and tolerability of E2V/DNG in women of reproductive age. Articles reporting efficacy or tolerability in the setting of menopause were excluded. The initial efficacy of E2V/DNG on ovulation inhibition was investigated in 2 prospective, randomized, open-label, Phase II dose-finding studies. The dose that was approved by the Food and Drug Administration resulted in 3.13% of women ovulating in the second cycle of treatment (90% CI, 0.2%-6.05%). Rate of pregnancy prevention with this agent was reported with a Pearl Index ranging from 0.73 to 1.27 (unadjusted) to 0.34 to 0.72 (adjusted for method failure only). The mean duration of withdrawal bleeding was 4.3 days (range, 4.0-4.6 days) among 2266 women receiving 13 treatment cycles. Adverse events reported in >1% of patients included abdominal pain, acne, breast pain, dysmenorrhea, emotional lability, headache, nausea, and weight increase.

CONCLUSIONS

Estradiol valerate/dienogest is a new contraceptive formulation. It offers efficacy, tolerability, and an acceptable safety profile with a potentially better bleeding pattern than levonorgestrel-containing COCs. This COC may be especially useful for older women of reproductive age who are adherent to therapy and looking for shorter and/or lighter menstrual cycles. Studies will need to be performed to determine whether clinically significant differences in outcomes exist among E2V/DNG and other available COCs.

A randomized controlled trial of subantimicrobial-dose doxycycline to prevent unscheduled bleeding with continuous oral contraceptive pill use

BACKGROUND

Unscheduled bleeding is the main side effect of continuous oral contraceptive pills (OCPs) and has been correlated with the up-regulation of matrix metalloprotineases (MMPs). The study objective was to determine if prophylactic administration of doxycycline (an MMP inhibitor at low subantimicrobial doses) would prevent unscheduled bleeding during the initiation of a continuous OCP.

STUDY DESIGN

Subjects using cyclic hormonal contraceptives (combined OCPs, patch or ring) without unscheduled bleeding were switched to continuous OCPs (20 mcg ethinyl estradiol/100 mcg levonorgestrel). They were randomized to receive daily doxycycline [sustained-release subantimicrobial dose (40 mg daily)] or placebo for the first 84 days and then observed for an additional 28 days on the continuous OCP alone. The number of bleeding/spotting days and the time in days it took to achieve amenorrhea were compared using a t test.

RESULTS

Sixty-five subjects were randomized. Although the use of doxycycline did not significantly decrease the number of mean bleeding/spotting days in the first 84 days of the study [doxycycline 14.75 (SE 2.30), placebo 17.78 (2.31), p=.36], women who received doxycycline had a significantly earlier onset of amenorrhea [mean last day of bleeding/spotting doxycycline 61.7 (7.7), placebo 85.2 (6.7), p=.03].

CONCLUSION

The coadministration of subantimicrobial-dose doxycycline during initiation of continuous OCPs results in a significant reduction in the length of time needed to achieve amenorrhea.

Treatment of unscheduled bleeding in continuous oral contraceptive users with doxycycline: a randomized controlled trial

OBJECTIVE

To estimate whether doxycycline, a matrix metalloproteinase inhibitor, would decrease unscheduled bleeding associated with initiation of a continuous oral contraceptive pill.

METHODS

Participants initiating a continuous oral contraceptive pill (20 micrograms of ethinyl estradiol/90 micrograms of levonorgestrel) were randomly assigned to receive either doxycycline (100 mg orally twice daily) or placebo taken for 5 days at the onset of each bleeding or spotting episode during the first 84 days of the study period. For the final 28 days of the study, participants were observed on the oral contraceptive pill alone. The primary outcome was the number of bleeding and spotting days. A sample size of 66 (33 in each arm) was calculated to detect a 50% reduction in bleeding (beta=0.80, alpha=0.05) and accounted for a 30% dropout rate.

RESULTS

Sixty-six women were randomly assinged (33 in each study group). There were no significant differences during the 84-day treatment in bleeding or spotting days (doxycycline [mean {standard error}, placebo, P=.32) or the length of the longest bleeding or spotting episode (doxycycline, placebo, P=.70) between study groups. Similarly, no significant differences in bleeding patterns existed between groups during the final 28 days.

CONCLUSION

Doxycycline, administered once bleeding has started, does not decrease unscheduled bleeding or shorten episodes of unscheduled bleeding in continuous oral contraceptive pill users.

LEVEL OF EVIDENCE

I.

Safety and efficacy of doxycycline in the treatment of rosacea

Rosacea is a common, chronic, skin condition characterized by recurrent episodes of facial flushing, transient or persistent erythema, papules, pustules, and telangiectasias, in a symmetrical facial distribution. The etiology of rosacea remains unknown and this condition represents a therapeutic challenge because of its chronic nature, progression, potential for disfigurement and psychological impact. Although there is no curative therapy for rosacea, the most widely used systemic agents are oral tetracycline derivatives, including tetracycline, doxycycline, and minocycline. This article reviews the available evidence for the use of doxycycline, a second-generation tetracycline, in the treatment or rosacea.

Pharmacokinetic interaction of tetracycline with centchroman in healthy female volunteers

OBJECTIVES

We aimed to investigate the effect of tetracycline coadministration, with and without lactic acid bacillus spores supplementation, on the pharmacokinetics of centchroman, a nonsteroidal oral contraceptive, in healthy female volunteers.

PARTICIPANTS AND METHODS

The study was a single-centre, single-blinded, randomised, parallel treatment study in healthy female subjects of reproductive age randomised to two groups (11 subjects in each group). On day 1, subjects were given either a single oral dose of centchroman 30 mg with tetracycline 250 mg (group A) or a single dose of centchroman 30 mg, tetracycline 250 mg and one tablet containing 60 million lactic acid bacillus spores (group B). Tetracycline (250 mg three times daily) and lactic acid bacillus spores (one tablet three times daily) were continued for 3 days. Serial blood samples were collected and analysed by high performance liquid chromatography. The pharmacokinetic parameters were compared with the control data reported previously from this laboratory.

RESULTS

Coadministration of tetracycline yielded significantly higher maximum plasma concentrations (C(max)) [35%] and a shorter time to reach C(max) (t(max)) values for centchroman (42%) than those obtained in the control group of females (p < 0.05). Inclusion of lactic acid bacillus spores in the regimen resulted in similar effects with increased C(max) (47%) and area under the concentration-time curve from time zero to infinity (34%) of centchroman (p < 0.05) with a significant decrease in t(max). Other parameters such as half-life, apparent clearance, apparent volume of distribution and mean residence time of centchroman were not affected by either of the treatments.

CONCLUSIONS

The apparent effects of either of the regimens on centchroman pharmacokinetics seem to be of little clinical relevance in terms of increased rate or extent of availability. It can be concluded that this tetracycline-containing regimen is unlikely to alter the contraceptive efficacy of centchroman in humans.

Antibiotics and oral contraceptives

With the exception of rifampin-like drugs, there is a lack of scientific evidence supporting the ability of commonly prescribed antibiotics, including all those routinely employed in outpatient dentistry, to either reduce blood levels and/or the effectiveness of oral contraceptives. To date, all clinical trials studying the effects of concomitant antibiotic therapy (with the exception of rifampin and rifabutin) have failed to demonstrate an interaction. Like all drugs, oral contraceptives are not 100% effective with the failure rate in the typical United States population reported to be as high as 3%. It is thus possible that the case reports of unintended pregnancies during antibiotic therapy may simply represent the normal failure rate of these drugs. Considering that both drug classes are prescribed frequently to women of childbearing potential, one would expect a much higher rate of oral contraceptive failure in this group of patients if a true drug:drug interaction existed. On the other hand, if the interaction does exist but is a relatively rare event, occurring in, say, 1 in 5000 women, clinical studies such as those described in this article would not detect the interaction. The pharmacokinetic studies of simultaneous antibiotic and oral contraceptive ingestion, and the retrospective studies of pregnancy rates among oral contraceptive users exposed to antibiotics, all suffer from one potential common weakness, i.e., their relatively small sample size. Sample sizes in the pharmacokinetic trials ranged from 7 to 24 participants, whereas the largest retrospective study of pregnancy rates still evaluated less than 800 total contraceptive users. Still, the incidence of such a rare interaction would not differ from the accepted normal failure rate of oral contraceptive therapy. The medico-legal ramifications of what looks like at best a rare interaction remains somewhat "murky." On one hand, we have medico-legal experts advising the profession to exercise caution and warn all oral contraceptive users of a potential reduction in efficacy during antibiotic therapy. These opinions are not evidence-based and rely heavily on one or two legal proceedings that cannot even be substantiated. On the other hand, there is one recently published legal proceeding in which the outcome was in favor of the oral surgeon. There is clearly a need for additional scientific research in oral contraceptive users that incorporates larger sample sizes, different time courses (prophylactic use versus standard 7-10 day use versus extended use), and different delivery systems (systemic administration versus local-controlled delivery) of antibiotic therapy. Though experts on this topic still recommend informing oral contraceptive users of the potential for a rare interaction, and for clinicians to advise them to employ additional barrier techniques of birth control during antibiotic therapy and for at least 1 week beyond the last dose [40], it is hoped that a set of guidelines regarding this controversy will eventually be published that is evidence-based, and not solely the results of anecdotal reports, expert opinions, and legal proceedings.

Efficacy of a low-dose oral contraceptive containing 20 microg of ethinyl estradiol and 100 microg of levonorgestrel for the treatment of moderate acne: A randomized, placebo-controlled trial

BACKGROUND

Acne is a multifactorial disease in which androgens appear to play an important role. A low-dose oral contraceptive containing 20 microg of ethinyl estradiol and 100 microg of levonorgestrel (EE/LNG) has been shown to improve biochemical markers of androgenicity. Lowering bioavailable androgens may improve acne.

OBJECTIVE

The aim of this study was to evaluate the efficacy and safety of a low-dose oral contraceptive containing 20 microg of EE and 100 microg of LNG for the treatment of moderate acne.

METHODS

In a randomized, double-blind, placebo-controlled clinical trial, healthy female subjects (n = 371; >/=14 years old) with regular menstrual cycles and moderate facial acne were randomly assigned to receive EE/LNG or placebo for 6 cycles of 28 days. Acne lesion counts and clinician global assessment were performed at the end of each cycle. Patient self-assessments were collected and biochemical markers of androgenicity were also measured.

RESULTS

At the end of the study, the number of inflammatory and total lesions was significantly lower with EE/LNG compared with placebo (P <.05). Patients in the EE/LNG group also had significantly better scores for clinician global and patient self-assessments than those in the placebo group (P <.05). Biochemical markers of androgenicity improved during EE/LNG treatment compared with placebo and baseline values.

CONCLUSION

A low-dose oral contraceptive containing EE/LNG is effective and safe for the treatment of moderate acne.

Oral contraceptives as anti-androgenic treatment of acne

Although acne is seldom associated with high serum levels of androgens, it has been shown that female acne patients have definite increases in ovarian and adrenal androgen levels when compared to appropriate controls. As shown in several pilot and in multiple open and comparative studies, oral contraceptives (OCs) are effective in causing a significant regression of mild to moderate acne. These results have been confirmed by multicentre randomized trials where low-dose OCs did not cause side effects different from those of the placebo-controlled group. The beneficial effect of OCs is related to a decrease in ovarian and adrenal androgen precursors; to an increase in sex hormone-binding globulin (SHBG), which limits free testosterone; and to a decrease in 3a-androstenediol glucuronide conjugate, the catabolite of dihydrotestosterone (DHT) formed in peripheral tissues. The estrogen-progestin combination containing cyproterone acetate (CPA) is particularly effective in treating acne, since this progestin also has a direct peripheral anti-androgenic action in blocking the androgen receptor. Only two open studies and one randomized study on small numbers of patients have reported some efficacy of spironolactone used alone or in combination with an OC in the treatment of acne. The new non-steroidal anti-androgens flutamide and finasteride are being evaluated for the treatment of hirsutism. Oral antibiotics are prescribed to patients with inflammatory lesions, where they are effective in decreasing the activity of microbes, the activity of microbial enzymes, and leukocyte chemotaxis. Concomitant intake of an OC and an antibiotic usually prescribed for acne does not impair the contraceptive efficacy of the OC. A second effective contraceptive method should be used whenever there would be decreased absorption or efficacy of the OC (digestive problems, breakthrough bleeding), lack of compliance and use of a type or dose of antibiotic different from that usually prescribed for acne.Overall, the various approaches for the treatment of acne depend on the needs of the patient and on the therapeutic objectives. Low-dose OCs are effective in improving acne and have side effects similar to placebo. They can be used alone or in combination with other anti-acne agents. The physician prescribing an OC as an anti-androgen intervention should take into account the multiple factors involved in acne and be familiar with current non-hormonal agents for treating mild to moderate acne. Individuals presenting with moderate to severe acne, or not responding to an estrogen-progestin combination, should be referred to a dermatologist.

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.

Interaction between broad-spectrum antibiotics and the combined oral contraceptive pill. A literature review

There is considerable variation in opinion about the importance of drug interactions between the combined oral contraceptive pill (COCP) and broad-spectrum antibiotics. Clinical practice varies widely, especially between doctors in Europe and those in the US. Rifampicin and griseofulvin induce hepatic enzymes and do appear to have a genuine interaction with the COCP, leading to reduced efficacy. The situation with the broad-spectrum antibiotics is less clear. There are relatively few prospective studies of the pharmacokinetics of concurrent COCP and antibiotic use and few, if any, demonstrate a convincing basis for any reduced contraceptive efficacy. There is evidence, however, that variable contraceptive steroid handling could make some women, at some times, more susceptible to COCP failure. Given the serious consequences of unwanted pregnancy, the cautious approach of using additional or alternative contraception during short courses of broad-spectrum antibiotics and the initial weeks of long-term antibiotic administration may be justified to safeguard the few unidentifiable women who may be at risk. Conflicting opinion and advice is potentially confusing to both professionals and patients, and instructions for additional precautions during and after concurrent COCP and antibiotic use are complicated. Many women are ignorant of, or confused about, the circumstances that can cause OC to fail. Health professionals who prescribe the COCP must continue to strive to educate women about the mode of action and about the times when there is the greatest danger of failure. Professionals who feel that concurrent antibiotic use represents a real threat to contraceptive efficacy of the COCP should be prepared to present the advice for additional contraceptive precautions in a simple and consistent way, backed up with written information and reinforced at regular intervals.

Adverse drug interactions in dental practice: interactions involving antibiotics. Part II of a series

BACKGROUND

The prudent use of antibiotics is an integral part of dental practice. While these agents generally are considered safe in the dental setting, their use can result in interactions that can lead to serious morbidity in dental patients.

METHODS

The faculty of a symposium entitled "Adverse Drug Interactions in Dentistry: Separating the Myths From the Facts" did an extensive literature review on drug interactions. Through this, they were able to establish a significance rating of alleged adverse drug interactions as they relate to dentistry, based on their scientific documentation and severity of effect. The author of this article focused on antibiotics.

RESULTS

Most of the reported drug interactions discussed in this article are well-documented by clinical studies. It is particularly important that dentists be aware of the potentially serious and life-threatening interactions of the antibiotics erythromycin, clarithromycin and metronidazole, and of the antifungal agents ketoconazole and itraconazole, with a host of other drugs whose metabolism is impaired by these antimicrobial agents. In contrast, the alleged ability of commonly employed antibiotics to reduce the effectiveness of oral contraceptive agents is not adequately supported by clinical research. It still is recommended, however, that clinicians discuss this possible interaction with their patients, as it might represent a relatively rare event that cannot be discerned in clinical trials.

CONCLUSIONS

Potentially serious adverse drug interactions can occur between antimicrobial agents used in dental practice and other drugs patients are taking for a variety of medical conditions.

CLINICAL IMPLICATIONS

It is important that dentists stay abreast of potential drug interactions involving antibiotics to avoid serious morbidity among their patients.

Dispelling myths about acne

Virtually no one escapes adolescence and early adulthood unscathed by acne. However, advanced methods of therapy are now available to deal with all but the most recalcitrant forms of the condition. Unfortunately, stereotypical notions about causes and treatments still persist, and as Dr Landow points out, patient education to dispell these myths is an important part of management.

Oral contraceptive failure rates and oral antibiotics

BACKGROUND

Despite anecdotal evidence of a possibility of decreased effectiveness of oral contraceptives (OCs) with some antibiotics, it is not known whether antibiotic use in dermatologic practices engenders any increased risk of accidental pregnancy.

OBJECTIVE

Our purpose was to examine the effect of commonly prescribed oral antibiotics (tetracyclines, penicillins, cephalosporins) on the failure rate of OCs.

METHODS

The records from three dermatology practices were reviewed, and 356 patients with a history of combined oral antibiotic/OC use were surveyed retrospectively. Of these patients, 263 also provided "control" data (during the times they used OCs alone). An additional 162 patients provided control data only.

RESULTS

Five pregnancies occurred in 311 woman-years of combined antibiotic/OC exposure (1.6% per year failure rate) compared with 12 pregnancies in 1245 woman-years of exposure (0.96% per year) for the 425 control patients. This difference was not significant (p = 0.4), and the 95% confidence interval on the difference (-0.81, 2.1) ruled out a substantial difference (> 2.1% per year). There was also no significant difference between OC failure rates for the women who provided data under both conditions, nor between the two control groups. All our data groups had failure rates below the 3% or higher per year, which are typically found in the United States.

CONCLUSION

The difference in failure rates of OCs when taken concurrently with antibiotics commonly used in dermatology versus OC use alone suggests that these antibiotics do not increase the risk of pregnancy. Physicians and patients need to recognize that the expected OC failure rate, regardless of antibiotic use, is at least 1% per year and it is not yet possible to predict in whom OCs may fail.

Study of the pharmacokinetic interaction between ethinylestradiol and amoxicillin in rabbits

Several antibiotics have been implicated in oral contraception failure when they are administered at the same time as the oral contraceptive (OC) pill. In the present paper, a study about amoxicillin-ethinylestradiol (EE2) pharmacokinetic potential interaction was studied. Two rabbit groups were utilized, the first group received amoxicillin (10 mg/kg) and EE2 (30, 50 and 100 micrograms/kg, respectively), both by intravenous (i.v.) route. The second group received amoxicillin (oral route, 10 mg/kg/day) and EE2 (i.v. route, 100 mu/kg) on day 1, 4 and 8 of antibiotic treatment, respectively. After compartmental (two-compartment open model) and non-compartmental analysis of plasma concentrations, the statistical study (ANOVA p < or = 0.05) revealed that the presence of amoxicillin did not modify the EE2 distribution and elimination pharmacokinetic parameters (by comparison with those obtained in a previous study where EE2 was administered alone). There also were no significant differences with the time of amoxicillin oral treatment.

Contraception. A clinical review for the internist

Effective use of contraception allows couples to control their fertility and, in certain instances, is associated with important noncontraceptive benefits. Surgical sterilization offers safe, effective, and permanent contraception for women and men. Low-dose OCPs offer safe, effective contraception for most women able and willing to take pills consistently. In addition, their use confers a variety of important noncontraceptive benefits. The availability of long-acting progestin injectable and implantable methods has made highly effective and convenient birth control available for women who are not good pill takers as well as for those for whom contraceptive doses of estrogen are contraindicated. Barrier methods are readily available and provide protection against STDs; unfortunately, erratic use is all too often associated with inadequate contraceptive efficacy. IUDs offer convenient, highly effective contraception for appropriate candidates.

A practical approach to antibiotic treatment in women taking oral contraceptives

Clinical situations that require the use of systemic antibiotic therapy are common. Because millions of women choose oral contraceptives for birth control, the potential for interaction between these drugs frequently has to be considered. We review the available information and present a practical approach for dealing with this situation based on sharing responsibility with an educated patient.

Contraception and sexually transmitted diseases: interactions and opportunities

Today "safe sex" means protection from both unintended pregnancy and sexually transmitted disease and human immunodeficiency virus. These parallel complications of sexual activity have serious biologic and clinical sequelae that should be considered at the time of contraceptive selection. In addition, there is ongoing debate regarding potential interactions between antibiotic intervention and contraceptive steroids. This article assesses the impact of hormonal contraception, spermicides, barrier methods, intrauterine devices, and douching on the pathogenesis of sexually transmitted disease and the human immunodeficiency virus infection. It discusses the direct and indirect effects of contraception methods on clinical physiology and host immune responses while also considering the possible consequences on maternal and infant health if pregnancy results from the use of ineffective contraception. Counseling and care for both family planning and infectious disease protection must be provided to all sexually active individuals.