Mounjaro’s NHS Launch: New Warning for Women
A new advisory concerns women prescribed Mounjaro, a weight-loss drug soon available on the NHS. The Medicines and Healthcare products Regulatory Agency (MHRA) has issued guidance on contraception, pregnancy, and breastfeeding for those using the medication, which has gained popularity for its impact on weight loss.
Contraception and Pregnancy Concerns
The MHRA warns against using Mounjaro during pregnancy, while trying to conceive, or when breastfeeding. Women who become pregnant while taking it should stop using the drug and consult their doctors. The agency highlights the lack of safety data regarding the drug’s effect on the baby.
The guidelines also address contraception. Women using oral contraceptives, who are also overweight, are advised to use additional non-oral birth control methods, such as implants or condoms. This precaution is particularly important in the initial four weeks of Mounjaro use and after dose increases.
“These medicines must not be taken during pregnancy, while trying to get pregnant, or during breastfeeding. Anyone who gets pregnant while using them should speak to their healthcare professional and stop the medicine as soon as possible. This is because there is not enough safety data to know whether taking the medicine could cause harm to the baby.”
—MHRA Statement
According to the National Institutes of Health, the use of GLP-1 receptor agonists such as Mounjaro can affect the absorption rate of medications. This can impact how oral contraceptives work, as the drug delays gastric emptying (NIH, 2024).
What is Mounjaro?
Mounjaro, containing tirzepatide, mimics hormones released after eating, aiding weight loss and managing Type-2 diabetes. It is set to be available through the NHS, but a limited supply may be offered to around 220,000 people over the next three years.
Previously, the medication was available via private prescription within the UK. It functions by mimicking GLP-1 and GIP hormones to help individuals feel full for longer, which decreases appetite. Other drugs, like Wegovy and Ozempic, operate in a similar way.
Oliver Picard, the chair of the National Pharmacy Association, has stated that demand will initially outstrip NHS supply. He predicts many patients will continue to seek prescriptions privately.
Manufacturer’s Response
The drug’s manufacturer, Eli Lilly and Company, emphasized its commitment to patient safety. They stated that the medicine’s summary of product characteristics highlights that it may affect how quickly other oral medicines are absorbed. This impact is most noticeable when beginning treatment.
The guidance emphasizes that patients should only use GLP-1 medicines under a healthcare professional’s supervision. The patient information leaflet includes detailed advice on pregnancy and contraception.
