'Miracle' weight loss drugs may interfere with contraception

Popular new drugs used to treat type 2 diabetes and obesity may reduce the effectiveness of contraceptive pills, the UK's Medicines and Healthcare products Regulatory Agency has warned.

The UK’s Yellow Card scheme allows members of the public to report side effects of medication. The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has issued a warning to UK residents on its website about the potential failure of contraceptives. It did so after receiving 40 reports of pregnancies while taking medicines such as Ozempic, Wegovy and Mounjaro.

Ozempic and Wegovy, which contain semaglutide, mimic the action of a hormone called GLP-1 to increase insulin production, slow down how quickly food is digested in the stomach and reduce appetite.

The active substance in Mounjaro is tirzepatid, which also acts on another hormone involved in appetite and blood sugar control, GIP.

The MHRA said Mounjaro could reduce the effectiveness of oral contraceptives such as the pill in overweight people, and women taking the medicine should use barrier contraception such as condoms. There have been 26 pregnancy reports for Mounjaro, the Guardian reported.

Eight of the reports involved pregnancies in people taking semaglutide, while nine involved liraglutide, which is found in another weight-loss drug, Saxenda. Although the reports don’t ask women whether the pregnancies were planned, two of the reports indicated that they were unintended.

The medicines must not be taken during pregnancy, trying to get pregnant or breastfeeding, the regulator said, as "there is not enough safety data to say whether taking the medicine could harm your baby".

In some cases, experts say women should continue using contraception for up to two months after stopping the medication to try to get pregnant.

"GLP-1 drugs mimic the natural hormones produced in the gut that make you feel full. This makes them an effective treatment for women to lose weight. Obesity reduces fertility in women. So obese women taking GLP-1 drugs are more likely to get pregnant than they were before they lost weight. We also think that the absorption of oral contraceptive pills may be reduced by GLP-1 drugs that slow stomach emptying, although more research is needed to confirm this," said Dr Channa Jayasena, consultant in reproductive endocrinology and andrology at Imperial College Healthcare NHS Trust, as quoted by the Guardian.

"The MHRA guidance is sensible because it highlights that women can accidentally become pregnant while taking GLP-1 medicines. We don't know how harmful GLP-1 medicines are during pregnancy; however, we do know that other forms of weight loss, such as weight-loss surgery, can increase the risk of miscarriage. Therefore, women are advised to do everything they can to avoid pregnancy while taking GLP-1 medicines," the researcher said, as quoted by the newspaper.

"These are medicines licensed to treat specific conditions and should not be used as aesthetic or cosmetic treatments. They are not a quick fix for weight loss and have not been assessed as safe when used in this way," said Dr Alison Cave, the agency's director of safety, on the MHRA's official website.

Experts say the pill may not be absorbed properly because of common side effects of new weight-loss drugs, such as vomiting and diarrhea, and because they slow stomach emptying.

The MHRA says women should use contraception while taking GLP-1 medicines and for a period after that before they start trying to get pregnant - two months for Wegova and Ozempic and one month for Mounjaro. It also recommends that people taking Mounjaro who are also taking oral contraceptives should also use a condom for four weeks after starting the medicine, or switch to another method such as a coil or implant.

The MHRA advises patients to talk to their doctor about the risks and benefits of taking weight-loss medicines and to be aware of their potential side effects. These medicines should not be bought from unregulated sellers, such as beauty salons or via social media, or taken without first consulting a healthcare professional. Not only does this expose people trying to lose weight to serious health risks, it is also illegal. The only way to guarantee that you will receive a genuine GLP-1 medicine is to buy it from a legitimate pharmacy.

The guidelines also remind patients of the symptoms to look out for in the case of acute pancreatitis, which, although rare, can be serious. The main symptom is severe stomach pain that radiates to the back and does not go away. Anyone experiencing this symptom should seek immediate medical attention. (PAP)

Paul Wernicki

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