Millions of people taking common medications such as ramipril and bisoprolol have been issued essential advice by the UK government, particularly relevant as temperatures are expected to reach 34°C this week. The Medicines and Healthcare products Regulatory Agency (MHRA) warns that extreme heat can compromise the effectiveness of many drugs.
MHRA Warning on Heat and Medicines
On June 26, the MHRA issued guidance on protecting medicines during extreme heat, following a heatwave that peaked at a record 37.7°C and caused school closures. This week, temperatures are forecast to top 30°C, reaching up to 34°C by Wednesday and Thursday. Alison Cave, chief safety officer at the MHRA, stated: “It’s easy to forget that medicines left in the heat – in cars, bags, or on sunny windowsills – might not work properly when you need them. Some medicines can also make you more likely to burn in the sun, feel dizzy, or get dehydrated.”
Why Heat Affects Medicines
Most medicines must be stored below 25°C. Heat breaks down active ingredients, and medicines requiring refrigeration are especially vulnerable. If affected, they may not work properly. Additionally, some medicines impair the body’s ability to cope with heat. Blood pressure drugs like ACE inhibitors (e.g., ramipril, captopril, enalapril) and beta-blockers (e.g., bisoprolol, atenolol, propranolol) can hinder temperature regulation and suppress thirst. Diabetes medications such as insulin and metformin increase dehydration risk. Antipsychotics like olanzapine or quetiapine, and stimulants for attention disorders, can raise body temperature. Diuretics like furosemide cause fluid loss. Some antibiotics, diuretics, antidepressants, and acne treatments increase sunburn susceptibility.
Signs of Dehydration
Dehydration symptoms include dizziness, headaches, tiredness, confusion, and dark urine. Older adults, young children, and those with heart or kidney conditions are particularly at risk. If feeling unwell, move to a cooler place, sip water slowly, and seek medical advice if symptoms persist.
How to Keep Medicines Safe
The MHRA advises: store medicines in a cool, dry place out of sunlight; avoid leaving them in cars or bags in the sun; know heat-related illness signs; stay hydrated; take extra sun care if your medicine increases burn risk; read the leaflet; and consult a healthcare professional with questions.
