Plan B with antibiotics: interactions and safety
Antibiotic courses are common, short-term and often combined with chronic medications such as Plan B (Levonorgestrel). Most antibiotics do not interfere meaningfully with Levonorgestrel at 1.5mg, but a few classes do, and a small number of combinations are best avoided.
Common antibiotic interactions
Macrolides (clarithromycin, erythromycin) and certain antifungals can inhibit hepatic metabolism (CYP3A4) and raise plasma levels of many medications including some Hormones and Birth Control agents. Rifampicin has the opposite effect, accelerating metabolism. Most penicillins, cephalosporins, fluoroquinolones and tetracyclines have no clinically meaningful interaction with Levonorgestrel at 1.5mg.
Practical guidance
According to the prescribing information for Levonorgestrel, an antibiotic course should be reviewed by the prescriber or pharmacist for known interactions before Plan B is co-administered. Adjusted 1.5mg dosing or temporary substitution is sometimes preferred for the duration of the antibiotic course.
Frequently asked questions
Can I take Plan B during an antibiotic course? ▾
For most common antibiotics, yes. A few classes — notably macrolides and azole antifungals — alter how Levonorgestrel is metabolised and may need a temporary 1.5mg adjustment. The prescribing pharmacist should review any new antibiotic against the existing Plan B regimen.
Will antibiotics make Plan B stop working? ▾
Most antibiotics do not affect Plan B efficacy. Rifampicin and a few others can lower Levonorgestrel levels and reduce effect; in those cases the prescriber may adjust the dose during and shortly after the antibiotic course.
More on Plan B
- With alcoholPlan B and alcohol — is it safe to drink?
- With foodShould Plan B be taken with food?
- Side effectsPlan B side effects: common, rare and warning signs
- Dosage guidePlan B dosage guide: how much to take and when
- OnsetHow fast does Plan B start working?
- DurationHow long does Plan B last?
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.