MHRA warns common painkillers and other medicines can raise sunburn, heat risks

Britain’s medicines regulator has warned that a range of widely used drugs can make people more sensitive to the sun and raise the risk of heat-related harm as the country faces another intense spell of hot weather. The Medicines and Healthcare products Regulatory Agency (MHRA) said the public should take extra precautions if they are taking certain medicines.

Which drugs are implicated and how they act

The MHRA highlighted several categories of medicines that may increase the likelihood of sunburn or reduce the body’s ability to cope with heat. These include:

• Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen — commonly used for pain and inflammation — which can increase sensitivity to sunlight.
• Certain antibiotics including doxycycline and tetracycline, associated with heightened photosensitivity.
• Acne treatments such as isotretinoin and topical retinoids, which can thin or alter the skin and increase sun sensitivity.
• Antifungal medicines like voriconazole, known to raise the risk of phototoxic reactions.
• Other drug groups — for example, diuretics, some antidepressants and antipsychotics, and beta blockers — which can affect fluid balance, sweating or cardiovascular responses to heat.

These medicines can affect the body’s usual mechanisms for regulating temperature — sweating, skin blood flow and fluid balance — making it harder to keep cool in high temperatures. The MHRA emphasised that older adults and people with chronic conditions, especially heart or lung disease, or those on multiple medicines, are particularly vulnerable.

Practical precautions urged

The MHRA advised straightforward measures that can substantially reduce risk: staying well hydrated, avoiding the strongest sun during the middle of the day, using protective clothing and regularly applying sunscreen. The regulator also reminded people to check their medication leaflets and to talk to a healthcare professional if they are unsure how their drugs may interact with hot weather.

“Some commonly used medicines can affect the body’s ability to stay hydrated, regulate temperature, or protect itself from sun exposure. Simple precautions can make a significant difference,” said Dr Alison Cave, chief safety officer at the MHRA.

Heat and medication: who should be most careful

The MHRA singled out several groups who should be alert. These include:

• Older people, whose ability to thermoregulate is often reduced.
• People with long-term heart or lung conditions.
• Those taking multiple prescription medicines, which may have combined effects on hydration or heat responses.

Diuretics used for blood pressure and heart conditions can increase fluid loss and the risk of dehydration, while some mental health medicines may blunt the body’s ability to regulate temperature. Beta blockers may reduce the cardiovascular response to heat stress.

Context and wider public-health implications

The MHRA warning arrives as the UK prepares for a fifth heatwave this summer, with forecasts of temperatures reaching the mid-30s Celsius in parts of England. Public-health bodies have repeatedly highlighted that hot spells increase demand on healthcare services and can lead to serious illness or death, particularly among vulnerable populations.

Previous heatwaves this year have been linked to a marked rise in excess deaths and contributed to public concerns about the effects of prolonged high temperatures on health services and community wellbeing. The interaction between medicines and heat underlines the need for targeted advice to patients and clinicians alike.

What patients should do now

The MHRA’s practical steps for patients are concise and actionable:

• Check the patient information leaflet that came with your medicine for warnings about sun sensitivity or heat.
• Keep hydrated and avoid prolonged exposure to strong sunlight, particularly between late morning and mid-afternoon.
• Wear protective clothing and apply broad‑spectrum sunscreen when outdoors.
• Seek advice from a pharmacist or GP if you are worried about how your medicines might affect your response to heat.

People should not stop prescribed medicines without consulting a clinician. If someone develops symptoms of heat illness — dizziness, weakness, confusion, very high temperature or fainting — they should seek immediate medical help.

The MHRA’s advisory is a timely reminder that widely used medicines can interact with environmental hazards. Taking straightforward precautions and seeking professional advice where necessary will help reduce the risk of sunburn and heat-related illness during the present heatwave.