Gestodene and Amoxicillin: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Jul 11, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amoxicillin
Gestodene
No brand names on record
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced efficacy of oral contraceptive
Interaction Deep Dive
Concomitant use of amoxicillin and oral contraceptives may result in reduced combined estrogen/progesterone contraceptive efficacy, due to lower estrogen reabsorption12. Concomitant use has been associated with unintended pregnancies and menstrual changes 3. However, systemic exposure to ethinyl estradiol/etonogestrel was not different when the vaginal ring was used with or without a 10-day course of amoxicillin during a randomized, crossover study (n=15) 5. Furthermore, in a large retrospective chart review, there was no significant difference in oral contraceptive (OC) failure rates among women who received OC with or without concomitant antibiotics, including penicillins 4.
Why it happens (mechanism)
Alteration in gut flora, leading to reduced estrogen reabsorption
Literature reports
3 reports — tap to read
a) Systemic exposure of ethinyl estradiol/etonogestrel with use of the vaginal ring contraceptive was not affected by concomitant use of amoxicillin in a randomized, 2-way crossover study in healthy women volunteers (n=15). Following synchronization of menstrual cycles by 21 to 28 days and a 7-day ring-free period, volunteers received the vaginal ring for 21 days with or without amoxicillin 875 mg orally twice daily for 10 days (mean age, 29.9 +/- 5.8 years). After a 7-day ring-free washout period, subjects crossed over to the opposite treatment arm. With administration of the vaginal ring alone, the mean AUC of ethinyl estradiol, measured at 12 hours, day 9 to 10, day 10, and day 21, was 0.328 +/- 0.092 nanograms x hr/mL, 0.266 +/- 0.0874 nanograms x hr/mL, 5.86 +/- 1.77 nanograms x hr/mL, and 11.7 +/- 3.86 nanograms x hr/mL, respectively. With administration of the ring plus amoxicillin, the mean AUC of ethinyl estradiol was 0.328 +/- 0.0757 nanograms x hr/mL, 0.252 +/- 0.0935 nanograms x hr/mL, 5.49 +/- 1.67 nanograms x hr/mL, and 11.3 +/- 3.57 nanograms x hr/mL, respectively. The AUC interaction/control ratio (ring with amoxicillin to ring alone) also showed absence of drug interaction. At 12 hours, day 9 to 10, day 10, and day 21, the interaction/control ratio was 1.01 (90% CI, 0.87 to 1.18), 0.96 (90% CI, 0.84 to 1.09), 0.95 (90% CI, 0.85 to 1.06), and 0.98 (90% CI, 0.88 to 1.09), respectively. The etonogestrel plasma concentrations and interaction/control ratio demonstrated similar findings at all time points 5.
b) There was no significant difference in oral contraceptive (OC) failure rates among women who received OC with or without concomitant antibiotics, including penicillins; and the OC failure rate in both groups did not exceed a typical contraceptive failure rate of 1% to 3% in a retrospective chart review and follow-up survey. Of 356 women who received antibiotics and OC concurrently over 311.2 woman-years, 5 pregnancies occurred yielding a rate of 1.6 pregnancies per 100 woman-years or a 1.6%/year failure rate. Of 425 control patients who received OC without antibiotics for 1244.9 woman-years, 12 pregnancies occurred yielding a rate of 0.96 pregnancies per 100 woman-years or 0.96%/year failure rate. The difference in failure rate between these groups was not significant (95% CI on the difference, -0.81 to 2.1; p=0.4) and ruled out a substantial difference (greater than 2.1% per year). The women in the control group consisted of 263 women who received OC but did not concomitantly use OC with antibiotics and 162 OC users who never concomitantly used antibiotics. Among women who never concomitantly used antibiotics (n=162) over 551.2 woman-years, 7 pregnancies occurred, yielding a rate of 1.3 pregnancies per 100 woman-years or 1.3%/year failure rate 4.
c) Concomitant use of amoxicillin and oral contraceptives has been associated with unintended pregnancies and menstrual changes 637.
Common questions
Can I take Gestodene and Amoxicillin together?
Reduced efficacy of oral contraceptive Always confirm with your pharmacist or prescriber before making any change.
How serious is the Gestodene and Amoxicillin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Gestodene or Amoxicillin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (7)
- Product Information: amoxicillin oral capsules, oral suspension, oral chewable tablets, amoxicillin oral capsules, oral suspension, oral chewable tablets. Teva Pharmaceuticals USA (per DailyMed), Sellersville, PA, 2013. DailyMed
- Product Information: AMOXICILLIN oral capsules, amoxicillin oral capsules. Micro Labs USA, Inc. (per Dailymed), Somerset, NJ, 2024. DailyMed
- Back DJ, Breckenridge AM, Crawford FE, et al: Interindividual variation and drug interactions with hormonal steroid contraceptives. Drugs 1981; 21:46-61. PubMed
- Helms SE, Bredle DL, Zajic J, et al: Oral contraceptive failure rates and oral antibiotics. J Am Acad Dermatol 1997; 36(5 Pt 1):705-710. DOI
- Dogterom P, van den Heuvel MW, & Thomsen T: Absence of pharmacokinetic interactions of the combined contraceptive vaginal ring NuvaRing with oral amoxicillin or doxycycline in two randomised trials. Clin Pharmacokinet 2005; 44(4):429-438. DOI
- Szoka PR & Edgren RA: Drug interactions with oral contraceptives: compilation and analysis of an adverse experience report database. Fertil Steril 1988; 49(5 suppl 2):31S-38S.
- True RJ: Interactions between antibiotics and oral contraceptives (letter). JAMA 1982; 247:1408. DOI
Keep reading about Amoxicillin
Keep reading about Gestodene
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