The UK’s Medicines and Healthcare products Regulatory Agency (MHRA) has warned that women using weight loss jabs must use effective contraception to avoid pregnancy while on the medication.
The regulator says there is not enough safety data to say whether popular glucagon like peptide-1 receptor agonist (GLP-1RA) medicines such as Novo Nordisk’s Wegovy (semaglutide) and Eli Lilly’s Mounjaro (tirzepatide) do not harm the developing foetus.
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The MHRA said it has received 40 reports relating to pregnancy among women taking the jabs via the Yellow Card scheme. This scheme is the MHRA’s framework for collecting and monitoring suspected safety concerns of medicines.
An MHRA spokesperson told Pharmaceutical Technology that this includes “two reports of unintentional pregnancies”.
“While they do not raise any safety signals this is being carefully monitored. People should continue to avoid using these products in pregnancy,” the spokesperson added.
It also warned that Mounjaro specifically could reduce the effectiveness of oral contraceptives, such as the birth control pill, in those who are overweight. This is because Mounjaro can slow or impair the absorption of oral medications via its affects on gastric emptying, along with side effects of vomiting.
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By GlobalDataWomen taking Mounjaro are therefore recommended to also use a non-oral form of contraception, such as condoms and intra-uterine devices (IUDs). The MHRA said this is especially important in the first month after starting the weight loss jab and after any dose increase.
Patient leaflets for Wegovy and Mounjaro both highlight pregnancy as a reason to not use the drugs. Women seeking to become pregnant are recommended to stop taking the medications at least two months in advance. The GLP-1RAs are also not licensed to be taken during breastfeeding. The drug leaflets also contain information on contraception usage.
The MHRA alert comes as the usage of Wegovy and Mounjaro soar, with fears that patients are not receiving the information, especially those who obtain them through unregulated channels.
Global sales for Wegovy reached around $8bn in 2024, while Mounjaro generated $11.5bn. While most patients have prescriptions from a doctor to collect the jabs from a legitimate pharmacy, some have gone to unregulated sellers to acquire the medication.
This is because on the UK National Health Service (NHS), GLP-1RAs are only available to people with a body mass index (BMI) above 30 kg/m2 or those with high BMI and accompanying weight-related comorbidities.
Unregulated sellers have much lower requirements, meaning patients can sometimes gain access to the medication without seeing a doctor in-person. Those who buy medication in this way are often not fully informed about safety information.
In its alert, the MHRA took the opportunity to remind patients that these medicines should not be bought from this category of sellers, which include beauty salons and social media vendors. Over in the US, the US Food and Drug Administration (FDA) has been cracking down on online retailers selling unapproved GLP-1RA products.
The UK’s National Pharmacy Association (NPA) has previously called for tougher rules on GLP-1RAs, explaining that it was aware of patients whose body weight was already low being wrongly prescribed the drugs. The association said that a two-way consultation is needed, rather than filling out online forms.
Dr Alison Cave, the MHRA’s chief safety officer, said: “Skinny jabs are medicines licensed to treat specific medical conditions and should not be used as aesthetic or cosmetic treatments. They are not a quick fix to lose weight and have not been assessed to be safe when used in this way.”
