Rifampicin is a potent inducer of hepatic drug-metabolising enzymes. Starting it can lower levels of many co-prescribed drugs, including some antiretrovirals, anticoagulants, hormonal contraceptives, antiepileptics and immunosuppressants. When it stops, the induction fades over weeks and levels of those drugs can rise.
Make an interaction check part of starting treatment, and again at the end, particularly for warfarin and drugs with a narrow therapeutic window. For a woman using hormonal contraception, discuss a non-hormonal alternative.
- Review every co-prescribed drug when starting rifampicin.
- Monitor INR closely if the patient is on warfarin, both when starting and when stopping.
- Advise non-hormonal contraception during treatment.
- Check antiretroviral compatibility with the HIV service before co-treating TB and HIV.
Why it matters
Interactions with rifampicin cause avoidable treatment failure of other drugs and can reappear after stopping.
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