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Contraception - emergency - Management
What drug interactions can occur with oral levonorgestrel emergency contraception?
Interactions with liver enzyme-inducing drugs
- The most important drug interactions with oral levonorgestrel are those caused by drugs that induce the liver enzymes which metabolize levonorgestrel. These drugs are listed in Table 1.
- Management is discussed in Women on a liver enzyme-inducing drug.
Interactions with warfarin
- One case involving a possible interaction between warfarin and oral levonorgestrel emergency contraception has been reported. The international normalized ratio increased, but there was no bleeding, and values returned to normal 2 days after warfarin treatment was stopped [Ellison et al, 2000].
Table 1. Drugs that induce liver enzymes.
Drug class | Drug |
|---|
Anti-epileptics | Carbamazepine Oxcarbazepine Phenytoin Phenobarbital Primadone Topiramate |
Antibiotics | Rifampicin Rifabutin |
Antifungals | Griseofulvin |
Antiretrovirals | Protease inhibitors Ritonavir Amprenavir Atazanavir Nelfinavir Pinavir Saquinavir Non-nucleoside reverse transcriptase inhibitors Efavirenz Nevirapine |
Gastrointestinal drugs | Lansoprazole |
Immunosuppressants | Tacrolimus |
Respiratory drugs | Bosentan |
Central nervous system drugs | Modafinil |
Herbal preparations | St John's wort |
|
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