The Medicines and Healthcare products Regulatory Agency (MHRA) has issued a Drug Safety Update after identifying falsified Mounjaro (tirzepatide) KwikPen 15mg pre filled injection pens circulating in the UK supply chain.
The affected products were supplied through a single online pharmacy and have been identified with batch number D873576. Healthcare professionals have been advised that all 15mg pens carrying this batch number are falsified and must not be supplied or used.According to the MHRA, the batch number is legitimate for a Mounjaro KwikPen 7.5mg product, but has been incorrectly applied to packaging labelled as the 15mg strength. To date, five falsified pens have been identified, with investigations ongoing.
The issue first came to light after reports of faulty pen mechanisms, with several devices experiencing problems such as the dose knob detaching during use.Testing carried out on recovered pens confirmed that they contained tirzepatide, the active ingredient used in Mounjaro. However, regulators warn that because the products were not manufactured through approved processes, they cannot be guaranteed to meet required quality or sterility standards. This means patients may face potential risks including infection or allergic reactions if the pens are used.
Advice for pharmacy teams
The MHRA has advised pharmacy teams to:
• Stop supplying Mounjaro KwikPen 15mg pens with batch number D873576 immediately
• Quarantine any remaining stock and return it to the supplier
• Advise patients who report a faulty pen to check the batch number and discontinue use if it matches the affected batch
• Report suspected adverse reactions or defective products through the MHRA Yellow Card Scheme
Advice for patients
Patients who have been supplied with a Mounjaro KwikPen 15mg pen are being asked to check the batch number on the packaging. If the pen carries batch D873576, they should not use the product and contact their pharmacist or healthcare professional for advice.
The MHRA continues to investigate the source of the falsified products and is working with the manufacturer and relevant authorities to ensure patient safety. Pharmacy teams are encouraged to remain vigilant and report any suspected counterfeit medicines through the established reporting channels.
For full details of the Drug Safety Update visit:
https://www.gov.uk/drug-safety-update/falsified-mounjaro-kwikpen-15mg-pre-filled-pens?utm_source=e-shot&utm_medium=email&utm_campaign=DSU(February2026)-FalsifiedMounjaroKwikPenmain1