Are “copycat” compounded weight loss drugs safe?

Abstract

Growing demand for weight loss drugs means that gaps are being filled by compounded versions. Katharine Lang asks if these can safely make up the shortfall In the UK more than 3 in every 1000 people are taking glucagon-like peptide-1 (GLP-1) agonist drugs, says Kevin McCarroll, consultant physician and geriatrician at St James Hospital, Dublin.1 Depending on the region, 77-179 in 100 000 people are using the leading GLP-1 drug semaglutide (Ozempic for type 2 diabetes, Wegovy for obesity), he says.1 And these are just the official prescribing figures—anecdotal evidence suggests many are purchasing the drugs from unofficial sources. Growing evidence of the drugs’ efficacy for weight loss2 is fuelling demand worldwide. The number of patients in the US approved for GLP-1 agonist treatment for obesity rose from 190 000 a month in 2021 to 1.8 million in 2024.3 Analysis of the US market shows that 5.2% of women and 4.2% of men with obesity are being prescribed the drugs, although access varies. “The global supply shortage seen in 2024 was at least partly because of a surge in off-label prescriptions for semaglutide for weight loss,” says Eamon Laird, assistant lecturer in nutritional science at ATU Sligo in Ireland. He added that use of the drug for weight loss by people without obesity and those who do not have any weight related health problems is exacerbating the situation. “Manufacturers are trying to upscale production, but it’s taking time. This is a global shortage with global demand. Similar shortages are reported in Ireland, the UK, the EU, and the US.” To try to increase availability the US Food and Drug Administration (FDA) has allowed pharmacies to manufacture and sell “compounded” versions of the drugs—these are copies of approved drugs or drugs under patent, allowed when licensed drugs are …