MHRA issues warning on contraception use alongside weight-loss injections

The medicines regulator has issued new guidance warning women taking weight-loss injections to ensure they are also using effective contraception.

While the information is already contained in patient information leaflets, the alert raises concerns that with many women purchasing the drugs online, they may not be aware of the risks.

In particular, women taking tirzepatide (Mounjaro), should also use condoms if they are on oral contraception because the weight-loss drug may reduce its effectiveness, the Medicines and Healthcare products Regulatory Agency (MHRA) said.

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) must not be taken during pregnancy, while trying to get pregnant, or during breastfeeding and anyone who gets pregnant should stop using them immediately, the MHRA added.

This is because there is not enough safety data to know whether taking the medicine could cause harm to the baby, the regulator added.

In some cases, women are also advised to continue using contraception for up to two months between stopping the medicine and trying to get pregnant.

The pregnancy warning is part of wider guidance on safe use of the drugs which reiterates they must be prescribed by a healthcare professional.

It also contains a reminder over the dangers of purchasing weight-loss injections from unregulated sellers such as beauty salons or via social media.

The MHRA has received more than 40 reports relating to pregnancy among women on the drugs. Of those, 26 were related to tirzepatide, with one reported as unintentional, and eight reports were for people taking semaglutide.

A further nine have been recorded for liraglutide, of which one recorded the pregnancy was unintentional – although women do not have to disclose this information.

The MHRA stressed that Yellow Card data is not representative of the whole population and that a reported reaction does not necessarily mean it has been caused by the medicine, only that the reporter had a suspicion it may have.

The alert also highlights adverse effects to look out for when using the medicines including the symptoms of acute pancreatitis.

Dr Alison Cave, MHRA 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.

‘This guidance should not be used as a substitute to reading the patient information leaflet or having a conversation with a healthcare professional as part of the prescribing process.’

Professor Rebecca Reynolds, professor of metabolic medicine at the University of Edinburgh, said: ‘It is very important to raise awareness about this MHRA advice among women and clinicians around potential issues with GLP-1 drugs affecting the effectiveness of oral contraceptives in those who are overweight.

‘There is hardly any available data from human studies to be able to advise if these weight-loss drugs are safe in pregnancy.

‘The data from animal studies suggests the potential for harm with low birthweight and skeletal abnormalities, though more evidence is needed to assess if there are risks of taking these drugs in pregnant humans.’

Professor Ying Cheong, consultant in reproductive medicine at the University of Southampton, said the MHRA reminder was both timely and necessary.

‘Gastrointestinal side effects such as vomiting and diarrhoea can impair oral contraceptive absorption, increasing the risk of unintended pregnancy.

‘Although direct evidence linking GLP-1 drugs to contraceptive failure is limited, the widespread uptake of these medications means even that small risks could translate into public health concerns, if confirmed in further studies.

‘Patients must be supported with clear, evidence-based guidance to prevent potential avoidable reproductive consequences.’

She added: ‘The unregulated use of GLP-1 receptor agonists from black-market sources is a serious clinical concern.

‘These are not harmless lifestyle drugs. The public urgently needs to understand that these medications require proper medical supervision to avoid unintended harm, particularly to reproductive health.’