MHRA Urges Contraception With GLP-1 Weight-Loss Drugs

The Medicines and Healthcare products Regulatory Agency (MHRA) has reiterated that women using weight-loss drugs must use effective contraception, as the risks of these drugs to a foetus remain unclear.

The warning follows concerns that some users in the UK may not be taking GLP-1s safely. To date, the MHRA has received more than 40 reports relating to pregnancies in women taking these medications.

“These medicines must not be taken during pregnancy, while trying to get pregnant, or during breastfeeding,” the MHRA stated. 

Women who become pregnant while using these drugs should stop treatment immediately and consult a healthcare professional. There is not enough safety data to determine if the drugs could harm a developing baby, the agency said.

Avoid Unregulated Sellers, MHRA Warns

The MHRA also warned against buying these drugs from unregulated sources such as beauty salons or via social media.

“Not only does this expose people wanting to lose weight to serious health risks, it is also against the law to sell these medicines in this way,” said Dr Alison Cave, the MHRA’s chief safety officer.

The agency emphasised that weight-loss drugs should not be taken without first consulting a healthcare professional.

“The only way to guarantee receiving a genuine GLP-1 medicine is to obtain it from a legitimate pharmacy,” Cave said.

Pharmacies Seeing High Demand 

“Community pharmacies have been experiencing unprecedented levels of interest for weight loss injections,” said Jasmine Shah, medication safety officer at the National Pharmacy Association. 

“It is therefore important that regulations and guidance keep pace with this demand.”

Mounjaro May Lower Effectiveness of Oral Contraceptives

The MHRA noted that Mounjaro (tirzepatide) may reduce the effectiveness of oral contraceptives in people with overweight or obesity. 

Women taking Mounjaro should use a non-oral contraceptive method for 4 weeks after starting the drug and for 4 weeks after any dose increase. This advice applies only to Mounjaro users.

Patients are also advised to be alert for signs of acute pancreatitis.

Risks in Pregnancy Remain Unclear

“There is hardly any available data from human studies to be able to advise if these weight loss drugs are safe in pregnancy,” said Rebecca Reynolds, professor of metabolic medicine at the University of Edinburgh. “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 humans,” she told the Science Media Centre (SMC).

Dr Bassel Wattar, consultant obstetrician and gynaecologist at Epsom and St Helier University Hospitals, supported the MHRA’s warning. 

“There is some data from animal studies suggesting there is a risk of malformation to the foetus — in animals falling pregnant while taking GLP-1 agonists — but data remains limited in humans,” he said. 

However, Dr Caroline Ovadia, senior clinical lecturer in obstetrics at the University of Edinburgh, noted to the SMC that existing human cohort studies had not shown clear evidence of harm.

Online Buyers May Miss Safety Guidance

Although direct evidence linking GLP-1 drugs to contraceptive failure is limited, the high number of users means even a small risk could have public health implications, experts warned.

Professor Ying Cheong, consultant in reproductive medicine at the University of Southampton, speaking to the SMC, said that gastrointestinal side effects, such as vomiting and diarrhoea, could impair oral contraceptive absorption, increasing the risk of unintended pregnancy. 

“Many people are buying weight loss drugs online and so may not receive this important advice about contraception,” Reynolds pointed out.

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

Rob Hicks is a retired National Health Service doctor. A well-known TV and radio broadcaster, he has written several books and has regularly contributed to national newspapers, magazines, and online publications. He is based in the United Kingdom.