enzyme activity does not return to normal for several weeks after stopping an enzyme-inducing drug - therefore appropriate contraceptive measures are required for 4 weeks for the liver enzymes to return to normal functionality (1)
therefore higher doses of the COC, with or without additional contraceptive protection, should be continued for 4 weeks after stopping the AED (2)
this period should be increased to 8 weeks after more prolonged used of enzyme inducers. In all cases, the PFI should be omitted when switching back to a standard or low-dose COC (2)
Reference:
Faculty of Sexual & Reproductive Healthcare Clinical Guidance.Clinical Guidance: Drug Interactions with Hormonal Contraception January 2018.
NHS Specialist Pharmacy Service (May 2019). Which combined oral contraceptive pill is suitable in a patient who is taking hepatic enzyme-inducing drugs, such as carbamazepine, phenytoin, rifampicin or rifabutin?
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