The recent bank holiday weekend saw record-breaking temperatures across the UK, with the mercury hitting 30C for the first time this year. While many welcomed the sunny weather, health officials are warning that certain medications can affect how the body handles heat, increasing the risk of dehydration and other complications.
The Medicines and Healthcare products Regulatory Agency (MHRA) has issued an alert highlighting medications that may be disrupted by hot weather. One common culprit is methotrexate, used for conditions such as rheumatoid arthritis, psoriasis, Crohn's disease, and cancer. It can make skin extremely sensitive to the sun, even at low doses, causing painful rashes or blistering. The MHRA noted that even a short walk at lunchtime could trigger a reaction.
Diuretics, or 'water tablets' like furosemide, are prescribed for heart conditions to remove excess fluid and control blood pressure. However, they increase the risk of dehydration and mineral imbalances during a heatwave. Similarly, ACE inhibitors, beta-blockers, and calcium channel blockers can make it harder for the body to regulate temperature or suppress the natural thirst response.
Diabetes medications, including insulin and metformin, can increase dehydration risk and make early symptoms harder to spot. Insulin may be absorbed more quickly from injection sites in warm weather, raising the risk of hypoglycaemia, according to Diabetes UK. Antipsychotics like olanzapine or quetiapine, and stimulants for attention disorders, can raise body temperature, making overheating more likely.
The MHRA urged patients to read their medication's patient information leaflet or consult their pharmacist about potential sun sensitivity. With more hot weather expected, those on affected medications are advised to take extra precautions, such as staying hydrated and avoiding direct sun exposure during peak hours.
