Nexplanon is one of the most effective birth control methods available, but certain medications, supplements, and health conditions can reduce how well it works or make it unsafe to use. Knowing what to avoid helps you stay protected for the full duration of your implant.
Medications That Reduce Effectiveness
The biggest practical risk with Nexplanon is taking a medication that speeds up how quickly your body breaks down the hormone it releases. Nexplanon works by steadily releasing a progestin called etonogestrel into your bloodstream. Certain drugs rev up liver enzymes that process this hormone faster than normal, dropping your blood levels low enough that the implant may not prevent pregnancy.
The FDA lists these specific medications as problematic:
- Seizure medications: carbamazepine, oxcarbazepine, phenytoin, felbamate, topiramate
- Antibiotics and antifungals: rifampin (used for tuberculosis), griseofulvin (an antifungal)
- Sedatives: barbiturates
- Other: bosentan (used for pulmonary arterial hypertension)
If you need long-term treatment with any of these, the FDA recommends removing the implant entirely and switching to a birth control method that isn’t affected by these interactions, such as a copper IUD. For short courses, your provider may recommend backup contraception like condoms for the duration of treatment and for a period afterward.
HIV medications are a separate concern. Both protease inhibitors and non-nucleoside reverse transcriptase inhibitors can raise or lower progestin levels unpredictably. If you’re on HIV treatment, your provider needs to check each specific drug for interactions before relying on Nexplanon alone.
St. John’s Wort and Herbal Supplements
St. John’s wort, a widely available herbal supplement used for mild depression and anxiety, is one of the most overlooked risks for Nexplanon users. It triggers the same liver enzyme pathway as the prescription drugs listed above, lowering the hormone levels your implant maintains. This isn’t a theoretical concern. The UK’s drug safety agency reported two cases of women with etonogestrel implants who started taking St. John’s wort and became pregnant.
Because St. John’s wort is sold over the counter and often perceived as harmless, many people don’t think to mention it to their provider. If you’re using Nexplanon, avoid St. John’s wort entirely. If you’re looking for support with mood symptoms, talk to your provider about options that won’t interfere with your contraception.
Health Conditions That Rule Out Nexplanon
Certain medical conditions make Nexplanon unsafe to use at all. The FDA lists these as strict contraindications:
- Blood clots: a current or past history of blood clots or clotting disorders
- Breast cancer: known, suspected, or a personal history of breast cancer or other hormone-sensitive cancers
- Liver disease: active liver disease or liver tumors of any kind, whether benign or malignant
- Unexplained vaginal bleeding: any abnormal genital bleeding that hasn’t been evaluated
- Pregnancy: known or suspected
- Allergy: a reaction to any component of the implant
These aren’t precautions or relative risks. They’re conditions where Nexplanon should not be placed or should be removed if already in use.
Smoking and Nexplanon
If you smoke, you’ve likely heard warnings about birth control and cardiovascular risk. The good news is that Nexplanon is considered a safer option for smokers compared to any contraceptive containing estrogen. Estrogen raises the risk of blood clots on its own, and smoking compounds that risk by damaging blood vessels and lowering oxygen in the blood. Because Nexplanon contains only progestin (no estrogen), it doesn’t carry that same compounded clot risk. Johns Hopkins Medicine lists the progestin arm implant among the recommended options for smokers who don’t plan to quit.
That said, smoking still damages your cardiovascular system regardless of which birth control you use. Nexplanon doesn’t make smoking safer; it simply avoids adding estrogen-related clot risk on top of it.
What About Body Weight?
You may have heard that Nexplanon works less well at higher body weights. A systematic review published in BMJ Sexual & Reproductive Health found no meaningful reduction in effectiveness for people with overweight or obesity through the approved duration of use. Among women with a BMI of 25 to 30, zero pregnancies were reported across all nine studies reviewed. Among women with a BMI of 30 or higher, seven of nine studies also reported no pregnancies, and the two that did reported rates of 0.02 and 0.23 per 100 woman-years, still extremely low.
While one pharmacokinetic study did find numerically lower hormone levels in women with obesity, this didn’t translate into reduced real-world effectiveness. You don’t need to avoid Nexplanon or seek additional contraception based on your weight.
After Insertion: What to Skip
The first few days after getting Nexplanon placed require basic wound care. Keep the pressure bandage on for 24 hours. After removing it, leave a smaller adhesive bandage over the insertion site for 3 to 5 days. Keep the area dry during that time, which means avoiding submerging your arm in water (baths, swimming pools) until the site has healed.
You should be able to feel the implant under your skin as a small, thin rod. If at any point you can no longer feel it, contact your provider. Migration of the implant away from the insertion site is rare, but a non-palpable implant needs imaging to locate. As long as you can feel it in place, it’s working where it should be.
How Long Nexplanon Lasts
Nexplanon is now FDA-approved for up to five years of use, extended from the original three-year approval. The approval was based on a clinical trial that tracked women using the implant during years four and five. Zero pregnancies occurred during that period, giving it a pregnancy rate of 0.0 per 100 woman-years. Avoid leaving the implant in beyond five years, as there isn’t data to support effectiveness past that point. If you want to continue using Nexplanon after five years, your provider can remove the current one and place a new implant during the same visit.