Oral Antibiotics and Nexplanon Efficacy
Most commonly prescribed oral antibiotics (such as amoxicillin, tetracyclines, penicillins, and cephalosporins) do NOT affect the contraceptive efficacy of Nexplanon (etonogestrel implant). 1
Key Evidence on Drug Interactions
The critical distinction is between enzyme-inducing medications versus standard antibiotics:
Standard oral antibiotics used in routine practice do not interfere with Nexplanon. The etonogestrel implant maintains its exceptional effectiveness (failure rate <0.05%) when used with typical antibiotics like amoxicillin, tetracyclines, penicillins, and cephalosporins. 1, 2
Only hepatic enzyme-inducing drugs that act on the cytochrome P450 pathway can impair Nexplanon efficacy. These are primarily certain antiretroviral medications, NOT standard antibiotics. 3
Specific Medications That DO Affect Nexplanon
The following antiretroviral medications (not standard antibiotics) can reduce Nexplanon effectiveness:
Efavirenz - Case reports and pharmacokinetic studies document reduced etonogestrel concentrations and contraceptive failures in patients receiving efavirenz-based therapy. 3
Nevirapine - NIH guidance recommends alternative or additional contraceptive methods, though subsequent studies have not confirmed significant interactions with levonorgestrel. 3
Most protease inhibitors - These require alternative or additional contraceptive methods according to NIH guidance. 3
Clinical Recommendations
For patients on standard oral antibiotics (amoxicillin, tetracyclines, penicillins, cephalosporins):
- No dose adjustments needed for Nexplanon. 1
- No additional contraceptive methods required for pregnancy prevention. 1
- Continue Nexplanon as the sole hormonal contraceptive method. 1
For patients on enzyme-inducing antiretrovirals:
- Use alternative or additional contraceptive methods during treatment and for the duration of the implant if exposed to efavirenz, nevirapine, or most protease inhibitors. 3
Important Caveats
Backup contraception is needed for the first week after Nexplanon insertion regardless of antibiotic use - this applies to all patients to ensure full contraceptive efficacy. 1
Dual protection with condoms remains essential - while antibiotics don't affect Nexplanon's pregnancy prevention, condoms are still necessary for STI protection. 3
The baseline Nexplanon failure rate is exceptionally low (<0.05% over 3 years), making it one of the most effective reversible contraceptive methods available even when considering potential drug interactions. 1