A model to detect interactions between roxithromycin and 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.

Predicted Pharmacokinetic Interactions Between Hormonal Contraception and Single or Intermittently Dosed Rifampicin

The scale-up of rifampicin-based prevention regimens is an essential part of the global leprosy strategy. Daily rifampicin may reduce the effectiveness of the oral contraceptive pill (OCP), but little is known about the effects of rifampicin at the less frequent dosing intervals used for leprosy prophylaxis. As many women of reproductive age rely on OCP for family planning, evaluating the interaction with less-than-daily rifampicin regimens would enhance the scalability and acceptability of leprosy prophylaxis. Using a semi-mechanistic pharmacokinetic model of rifampicin induction, we simulated predicted changes in OCP clearance when coadministered with varying rifampicin dosing schedules. Rifampicin given as a single dose (600 or 1200 mg) or 600 mg every 4 weeks was not predicted to result in a clinically relevant interaction with OCP, defined as a >25% increase in clearance. Simulations of daily rifampicin were predicted to increase OCP clearance within the range of observed changes previously reported in the literature. Therefore, our findings suggest that OCP efficacy will be maintained when coadministered with rifampicin-based leprosy prophylaxis regimens of 600 mg once, 1200 mg once, and 600 mg every 4 weeks. This work provides reassurance to stakeholders that leprosy prophylaxis can be used with OCP without any additional recommendations for contraception prevention.

The effect of rifampin on serum etonogestrel concentrations and biomarkers of ovulation among contraceptive implant users: A pharmacokinetic and pharmacodynamic study

OBJECTIVES

Rifampin, a strong CYP3A inducer, is the gold standard for evaluating CYP3A-mediated drug-drug interactions. We aimed to evaluate the pharmacokinetic and pharmacodynamic effects of a short course (2 weeks) of rifampin on serum etonogestrel (ENG) concentrations and serologic measures of ovarian activity (endogenous estradiol [E2] and progesterone [P4]) among ENG implant users.

STUDY DESIGN

We enrolled healthy females using ENG implants for 12 to 36 months. We measured baseline serum ENG concentrations using a validated liquid chromatography mass-spectrometry assay and baseline E2 and P4 concentrations using chemiluminescent immunoassays. After 2 weeks of rifampin 600 mg daily, we repeated ENG, E2, and P4 measurements. We compared pre- and post-rifampin serum measurements using paired Wilcoxon signed-rank tests.

RESULTS

Fifteen participants completed all study procedures. Participants' median age was 28.2 years (range 21.8-34.1), median body-mass index was 25.2 kg/m2 (range 18.9-37.3), and median duration of implant use was 22 months (range 12-32). All participants experienced significant decreases from baseline ENG concentrations (median 164.0 pg/mL [range 94.4-265.0]) to post-rifampin measurements (median 47.8 pg/mL [range 24.7-82.8]) (p < 0.001). Serum E2 concentrations also significantly increased with rifampin exposure (median 73 pg/mL vs 202 pg/mL, p = 0.003); increases in serum P4 concentrations were not statistically significant (p = 0.19). Three participants (20%) experienced increased luteal activity, with one presumptively ovulating post-rifampin (P4 = 15.8 ng/mL).

CONCLUSIONS

With only short exposure to a strong CYP3A inducer, ENG implant users experienced clinically significant decreases in serum ENG concentrations that led to changes in biomarkers indicative of waning suppression of ovulation.

IMPLICATIONS

Even a short, 2-week course of treatment with rifampin places etonogestrel contraceptive implant users at risk for decreased contraceptive efficacy. Clinicians should counsel patients using etonogestrel implants considering any duration of rifampin therapy on the need for backup nonhormonal contraception or the use of an intrauterine device to avoid unintended pregnancies.

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

BACKGROUND

Rifamycin antibiotics are commonly used for treatment of tuberculosis, but may reduce the effectiveness of hormonal contraception (HC).

OBJECTIVES

To determine whether interactions between rifamycins and HC result in decreased effectiveness or increased toxicity of either therapy.

SEARCH STRATEGY

We searched MEDLINE, Embase, Cochrane and clinicaltrials.gov through May 2017.

SELECTION CRITERIA

We included trials, cohort, and case-control studies addressing pregnancy rates, pharmacodynamics or pharmacokinetic (PK) outcomes when HC and rifamycins were administered together versus apart. Of 7291 original records identified, 11 met inclusion criteria after independent review by two authors.

DATA COLLECTION AND ANALYSIS

Two authors independently abstracted study details and assessed study quality using the United States Preventive Services Task Force grading system. Findings are reported descriptively.

MAIN RESULTS

Studies only addressed combined oral contraceptives (COCs) and none reported pregnancy rates. Quality ranged from good to poor. Rifampin increased the frequency of ovulation in two of four studies, and reduced estrogen and/or progestin exposure in five studies. Rifabutin led to smaller PK changes than rifampin in two studies. In one study each, rifaximin and rifalazil did not alter hormone PK.

CONCLUSIONS

No studies evaluated pregnancy risk or non-oral HCs. PK and ovulation outcomes support a clinically concerning drug interaction between COCs and rifampin, and to a lesser extent rifabutin. Data are limited for other rifamycins.

TWEETABLE ABSTRACT

Rifampin and rifabutin reduce systemic exposure of oral contraceptives, but no studies have evaluated pregnancy risk.

Use of Dicloxacillin and Risk of Pregnancy among Users of Oral Contraceptives

The antibiotic dicloxacillin has been shown to induce drug-metabolizing CYP enzymes to a clinically relevant extent. In this study, we investigated whether the use of dicloxacillin confers an increased risk of unwanted pregnancy among oral contraceptive users. The study population comprised Danish women falling pregnant (1997-2015) during oral contraceptive use, defined as having filled a prescription for an oral contraceptive within 120 days both before and after the estimated date of conception. Data were analysed using a case-crossover approach. For each woman, we assessed the use of dicloxacillin preceding the date of conception and during 10 previous control periods and estimated the odds ratio for such unintended pregnancies associated with the use of dicloxacillin. Among 364 women using dicloxacillin prior to conception, 40 (11%) were exposed to dicloxacillin at the time of conception, yielding an odds ratio (OR) associating use of dicloxacillin to unintended pregnancy of 1.18 (95% CI 0.84-1.65). Supplementary and sensitivity analyses generally returned similar estimates, except for a slightly increased risk among users of progestogen-only oral contraceptives (OR 1.83, 95% CI 0.63-5.34). Analysis of other antibiotics as negative controls yielded results close to unity (ORs ranging from 0.83 to 1.13). In conclusion, our study found no evidence for an increased risk of oral contraceptive failure when using dicloxacillin. However, acknowledging study limitations, we suggest the use of supplementary barrier methods during treatment with dicloxacillin, until our findings are confirmed in further studies.

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.

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.

Influence of endogenous progesterone on alprazolam pharmacodynamics

The results of a recently completed study demonstrated that postmenopausal women were more sensitive to triazolam-induced psychomotor performance impairment when progesterone was administered concomitantly. That clinical evidence agrees with the emerging in vitro information regarding the rapid membrane effects of a progesterone metabolite that positively modulates the gamma-aminobutyric acid-A-benzodiazepine receptor complex. The objective of this study in premenopausal women was to determine whether the response to a benzodiazepine is altered when endogenous progesterone concentrations are high (luteal phases of a menstrual cycle) compared with when progesterone concentrations are low (follicular phases of a menstrual cycle). The pharmacokinetics and pharmacodynamics of oral alprazolam were evaluated in twelve healthy, normally menstruating women who were not receiving oral contraceptive agents. On two separate occasions, once during each phase of the menstrual cycle, the women randomly received an oral alprazolam 2-mg dose. Blood samples were collected, and psychomotor performance tests were conducted at selected times before and after dosing. These data show that fluctuations of endogenous progesterone across the menstrual cycle do not influence alprazolam pharmacodynamics. Despite endogenous progesterone concentrations being significantly higher during the midluteal than during the midfollicular drug administrations, no differences were observed in either the digit-symbol substitution test, card sorting by suit, or sedation scores on these two occasions. No pharmacokinetic differences were observed between the two menstrual cycle-phase drug administrations. In conclusion, the lack of changes during the menstrual cycle in demonstrable cognitive impairment and pharmacokinetics after alprazolam administration is reassuring. This implies that a dose adjustment made on the basis of menstrual timing is not required.

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.

Macrolide antibiotics in paediatric infectious diseases

Erythromycin and other macrolides have enjoyed a renaissance in the 1970s, 1980s and 1990s secondary to the discovery of "new' pathogens such as Chlamydia, Legionella, Campylobacter and Mycoplasma spp. Erythromycin is an important therapeutic agent in the paediatric age group for several reasons: (a) it exhibits proven efficacy for a wide range of infections (upper and lower respiratory tract infections, skin/skin structure infections, prophylaxis of endocarditis/acute rheumatic fever/ophthalmia neonatorum and pre-colonic surgery, campylobacteriosis, chlamydial and ureaplasmal infections, diphtheria, whooping cough, streptococcal pharyngitis) and gastrointestinal (GI) dysmotility states; (b) intravenous formulations are widely available; and (c) it is available in a number of formulations as a generic product, which is likely to result in significant cost savings. Nevertheless, erythromycin and similar earlier macrolides are characterised by a number of drawbacks including a narrow spectrum of antimicrobial activity, unfavourable pharmacokinetic properties and poor GI tolerability. Newer macrolides such as clarithromycin and azithromycin are useful in serving the needs of paediatric patients who are erythromycin-intolerant or who have infections caused by organisms that are intrinsically erythromycin-resistant, or for which a high percentage of strains are resistant (e.g. Haemophilus influenzae, Helicobacter pylori, Mycobacterium avium complex). In addition, these newer macrolides may be considered as alternatives to oral amoxicillin-clavulanic acid, second or third generation cephalosporins, or erythromycin plus sulphonamide in this patient population. Selection between specific macrolides and between macrolides and other antibiotics in the paediatric population is likely to depend, at least for the immediate future, on separate comparisons of product availability, cost, effectiveness and tolerability profiles.

The influence of endogenous and exogenous sex hormones in adolescents with attention to oral contraceptives and anabolic steroids

The endogenous sex hormones produce dispositional changes in the developing child as well as imparting unique male and female dispositional patterns. Age-related changes have been observed for digoxin disposition and caffeine and theophylline metabolism. These age-related dispositional changes have led to age-dependent dosing recommendations. Studies with caffeine and antipyrine indicate that this change in drug disposition occurs over a short period of time, is seen earlier in girls than in boys, and is related to pubertal (Tanner) stage and the "growth spurt". Significant changes in endogenous sex hormone concentrations occur during the menstrual cycle and during pregnancy, leading to alterations in drug binding, distribution, and clearance. Oral contraceptives (OCs) inhibit the metabolism of certain drugs resulting in toxicity or lack of efficacy. Rifampin induces the OC metabolism, resulting in decreased clinical effectiveness. Most studies did not examine these kinetic and dynamic interactions between adult and adolescent users. It is estimated that there are over 45 anabolic steroid compounds available for abuse by athletes, and their use is increasing among male and female adolescents. Although the adolescent is at increased risk of developing adverse effects from these agents, a systematic evaluation of the long-term effects of anabolic steroid abuse has not been undertaken in this population. Further research is needed regarding the influence of endogenous and exogenous hormones on adolescent drug kinetics and dynamics. Because of their frequency of use among adolescents, OCs and anabolic steroids require particular emphasis.

Roxithromycin. An update of its antimicrobial activity, pharmacokinetic properties and therapeutic use

Roxithromycin is a derivative of the macrolide antibacterial erythromycin with in vitro antibacterial activity resembling that of the parent compound. The drug has activity against some Staphylococcus spp., many Streptococcus spp., Moraxella (Branhamella) catarrhalis, Mycoplasma pneumoniae, Legionella pneumophila and Chlamydia trachomatis as well as many less common organisms. Measured using recently proposed guidelines, roxithromycin has in vitro activity against Haemophilus influenzae. In comparison with that of its parent compound, the pharmacokinetic profile of roxithromycin is characterised by high plasma, tissue and body fluid concentrations and a long half-life permitting an extended dosage interval. Roxithromycin has proven clinical efficacy in upper and lower respiratory infections, skin and soft tissue infections, urogenital infections and orodental infections, and appears to be as effective as more established treatments including erythromycin, amoxicillin/clavulanic acid and cefaclor. The drug has also shown promise in a variety of more specialised indications including opportunistic infections in human immunodeficiency virus (HIV)-positive patients and as part of a Helicobacter pylori eradication regimen. Roxithromycin is very well tolerated with an overall incidence of adverse events of approximately 4%. Thus, roxithromycin is an attractive therapeutic alternative in its established indications, especially when the option of once-daily administration is considered.

A pharmacokinetic interaction between roxithromycin and midazolam

The interaction between roxithromycin and midazolam was investigated in a double-blind, randomised crossover study of two phases. Ten healthy volunteers were given roxithromycin (300 mg) or placebo once daily for 6 days. On the sixth day they ingested 15 mg midazolam. Plasma samples were collected and psychomotor performance measured for 17 h. Roxithromycin administration significantly increased the area under the plasma midazolam concentration-time curve from 8.3 to 12.2 micrograms.ml-1.min and the elimination half-lives from 1.7 to 2.2 h. In psychomotor performance only minor differences were seen between the treatments in one of the measured psychomotor parameters. Thus, in contrast to the strong interaction between erythromycin and midazolam, the interaction between roxithromycin and midazolam appears less likely to be clinically significant.

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.

Pharmacokinetic drug interactions of macrolides

The macrolide antibiotics include natural members, prodrugs and semisynthetic derivatives. These drugs are indicated in a variety of infections and are often combined with other drug therapies, thus creating the potential for pharmacokinetic interactions. Macrolides can both inhibit drug metabolism in the liver by complex formation and inactivation of microsomal drug oxidising enzymes and also interfere with microorganisms of the enteric flora through their antibiotic effects. Over the past 20 years, a number of reports have incriminated macrolides as a potential source of clinically severe drug interactions. However, differences have been found between the various macrolides in this regard and not all macrolides are responsible for drug interactions. With the recent advent of many semisynthetic macrolide antibiotics it is now evident that they may be classified into 3 different groups in causing drug interactions. The first group (e.g. troleandomycin, erythromycins) are those prone to forming nitrosoalkanes and the consequent formation of inactive cytochrome P450-metabolite complexes. The second group (e.g. josamycin, flurithromycin, roxithromycin, clarithromycin, miocamycin and midecamycin) form complexes to a lesser extent and rarely produce drug interactions. The last group (e.g. spiramycin, rokitamycin, dirithromycin and azithromycin) do not inactivate cytochrome P450 and are unable to modify the pharmacokinetics of other compounds. It appears that 2 structural factors are important for a macrolide antibiotic to lead to the induction of cytochrome P450 and the formation in vivo or in vitro of an inhibitory cytochrome P450-iron-nitrosoalkane metabolite complex: the presence in the macrolide molecules of a non-hindered readily accessible N-dimethylamino group and the hydrophobic character of the drug. Troleandomycin ranks first as a potent inhibitor of microsomal liver enzymes, causing a significant decrease of the metabolism of methylprednisolone, theophylline, carbamazepine, phenazone (antipyrine) and triazolam. Troleandomycin can cause ergotism in patients receiving ergot alkaloids and cholestatic jaundice in those taking oral contraceptives. Erythromycin and its different prodrugs appear to be less potent inhibitors of drug metabolism. Case reports and controlled studies have, however, shown that erythromycins may interact with theophylline, carbamazepine, methylprednisolone, warfarin, cyclosporin, triazolam, midazolam, alfentanil, disopyramide and bromocriptine, decreasing drug clearance. The bioavailability of digoxin appears also to be increased by erythromycin in patients excreting high amounts of reduced digoxin metabolites, probably due to destruction of enteric flora responsible for the formation of these compounds. These incriminated macrolide antibiotics should not be administered concomitantly with other drugs known to be affected metabolically by them, or at the very least, combined administration should be carried out only with careful patient monitoring.(ABSTRACT TRUNCATED AT 400 WORDS)