The Medicines and Healthcare products Regulatory Agency (MHRA) has issued a warning regarding certain medications that may worsen heat-related effects, including dehydration, sunburn, and dizziness. Additionally, hot conditions can affect the efficacy of some medications if they are not stored properly.
Professor Azeem Majeed, head of primary care and public health at Imperial College London, explained that high temperatures can increase the risk of dehydration, which may alter how some medicines work and increase the likelihood of side effects. He noted that heat can also change how the body absorbs, distributes, and eliminates medications, and some medicines interfere with the body's natural temperature regulation or increase sun sensitivity.
Commonly prescribed medicines that may increase vulnerability to hot weather include diuretics and SGLT2 inhibitors, which can increase dehydration risk. Medicines with anticholinergic properties, such as some antidepressants and antipsychotics, can reduce the body's ability to sweat. Certain medications, including tetracycline antibiotics and retinoids, can cause photosensitivity, making individuals more sensitive to the sun. Beta blockers, diuretics, and nitrates for angina may increase dizziness.
Professor Majeed advises checking medication patient information leaflets for advice on sun exposure and hydration. He also recommends drinking enough fluids, staying out of direct sunlight during the hottest parts of the day, keeping homes cool, wearing lightweight clothing, using broad-spectrum sunscreen, and following storage instructions carefully. Most medicines should be stored below 25°C, though some can be stored below 30°C. It is crucial not to stop prescribed medication without medical advice, and pharmacists can offer guidance on heat-related effects.