Drug Information for Plan B One-Step (levonorgestrel) tablet, 1.5 mg, for oral use (Duramed Pharmaceuticals, Inc.): 7 DRUG INTERACTIONS

  • Drugs or herbal products that induce enzymes, including CYP3A4, that metabolize progestins may decrease the plasma concentrations of progestins, and may decrease the effectiveness of progestin-only pills. Some drugs or herbal products that may decrease the effectiveness of progestin-only pills include:

    • barbiturates
    • bosentan
    • carbamazepine
    • felbamate
    • griseofulvin
    • oxcarbazepine
    • phenytoin
    • rifampin
    • St. John’s wort
    • topiramate

    Significant changes (increase or decrease) in the plasma levels of the progestin have been noted in some cases of co-administration with HIV protease inhibitors or with non-nucleoside reverse transcriptase inhibitors.

    Consult the labeling of all concurrently used drugs to obtain further information about interactions with progestin-only pills or the potential for enzyme alterations.

  • Drug Information Provided by National Library of Medicine (NLM).