Paper II
2017 February (2010 Scheme) · 40 marks · 120 min

Question

Comment on the interactions produced by oral contraceptive pills and rifampicin.

Q91 marksShort Answers

Answer

Rifampicin is a potent inducer of hepatic microsomal (CYP450) enzymes. It significantly increases the metabolism of the oestrogen and progestin components of oral contraceptive pills, lowering their plasma levels below the threshold needed for reliable contraceptive efficacy — leading to breakthrough bleeding and risk of contraceptive failure/unwanted pregnancy. Patients on rifampicin should be advised to use an alternative/additional non-hormonal method of contraception.

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