The UK government has reissued essential advice on safeguarding medicines during hot weather, with particular caution for methotrexate users. The Medicines and Healthcare products Regulatory Agency (MHRA) updated its guidance on 26 June as temperatures peaked at a record 37.7C, and now warns again as forecasts predict highs in the high 20s Celsius this week.
Methotrexate requires particular care
The MHRA highlights that some common medicines can increase skin sensitivity to the sun, including certain antibiotics, diuretics, antidepressants, and skin treatments for acne or eczema. Painkillers like ibuprofen or naproxen may also cause mild sun sensitivity, though less commonly.
One medicine singled out is methotrexate, used for rheumatoid arthritis, psoriasis, Crohn’s disease, and cancer. It can cause extreme skin sensitivity even at low doses, leading to painful rashes, blistering, or swelling resembling severe sunburn. In rare cases, these reactions have resulted in serious infections.
Why heat affects medications
Heat can break down active ingredients in medicines, making them less effective. This includes tablets, inhalers, hormone patches, insulin, and EpiPens. Medicines requiring refrigeration, such as insulin or certain liquid antibiotics, are especially vulnerable.
Signs of heat damage include changes in colour, smell, texture, or appearance. The MHRA advises consulting a pharmacist if such changes are noticed. Even without visible changes, heat can affect absorption, so the agency recommends speaking to a pharmacist or doctor if you feel unwell or your medicine seems less effective.
Keeping medicines safe
The MHRA advises storing medicines in a cool, dry place away from direct sunlight, avoiding leaving them in cars or bags in the sun, knowing the signs of heat-related illness, staying hydrated, and taking extra sun precautions if your medicine increases sensitivity. Always read the leaflet and ask a healthcare professional if uncertain.
