The UK’s MHRA recently issued guidance reminding patients using the GLP-1 agonist tirzepatide, who are also on oral contraceptives, that a barrier form of contraception should also be used. This information is already included in the prescribing information in both the UK and the USA.

Tirzepatide affects the rate of gastric emptying, thereby influencing absorption of oral contraceptives. This is particularly significant in the first four weeks after starting treatment and after any dose increases when changes in gastric emptying are largest. This guidance is of particular importance as all GLP-1 agonists should be avoided in pregnancy, lactation and those trying to conceive, due to a lack of safety data.

Confusingly, the December 2024 South African package insert states the following: “This reduction in exposure after a single dose of MOUNJARO is not considered clinically relevant. No dose adjustment of oral contraceptives is required”. Until there is more clarity on this issue it might be wise to advise patients to use additional barrier methods when using oral contraceptives with tirzepatide.

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