In a GOV.UK campaign notice, the Medicines and Healthcare products Regulatory Agency has reminded people taking prescription or over-the-counter medicines to take extra care in warm weather. The regulator says some treatments can affect hydration, temperature control or tolerance of sun exposure, creating added risk during hot periods even where the medicine is being used correctly. The message forms part of the MHRA’s 'Summer-proof your health' campaign, which is intended to support the safe use of medicines and medical devices during warmer months. For a policy audience, the notice is notable because it links seasonal self-care advice to the regulator’s wider medicine safety function, including post-market reporting through the Yellow Card scheme.
Dr Alison Cave, the MHRA’s Chief Safety Officer, said several widely used medicines can make it harder for the body to cope with heat. Diuretics, often prescribed for blood pressure or heart conditions, can increase fluid loss and make dehydration more likely. The regulator also says some antidepressants and antipsychotics can affect temperature regulation, while beta blockers may reduce the body’s response to heat stress. That matters because the relevant symptoms are not always easy to distinguish from ordinary effects of hot weather. Dizziness, tiredness or reduced urination may be dismissed as a routine response to heat, when a medicine may also be contributing to lower heat tolerance or a greater risk of dehydration.
The notice also sets out a separate group of risks linked to sun exposure. According to the MHRA, certain antibiotics including doxycycline and tetracycline, acne treatments such as isotretinoin and topical retinoids, and the antifungal medicine voriconazole can all increase photosensitivity, meaning skin may burn faster or more severely than expected. The regulator extends that warning to disease-modifying antirheumatic drugs including methotrexate and azathioprine, which are used in conditions such as rheumatoid arthritis, psoriatic arthritis and lupus. It also notes a very low risk that proton pump inhibitors, used for reflux and heartburn, may be associated with a lupus-like skin reaction triggered by sunlight, and says common painkillers including ibuprofen and naproxen may increase sun sensitivity.
The operational advice is practical rather than complex. The MHRA says patients should check the patient information leaflet supplied with their medicine, where advice on hydration, heat exposure and sunlight may already be set out. The same information can also be accessed through the agency’s online medicines product pages, and the regulator says routine precautions such as drinking enough fluid, avoiding the strongest midday sun, and using protective clothing and sunscreen can reduce risk. The campaign also asks patients and carers to watch for signs that the body is struggling in hot conditions. The symptoms highlighted in the GOV.UK notice include dizziness, headaches, unusual fatigue, confusion and reduced urination, alongside skin that becomes red, sore, blistered or reacts more strongly than expected after time in the sun.
The MHRA is equally clear on what patients should not do. Prescribed medicines should not be stopped during hot weather without clinical advice, even where there are concerns about side effects or sun sensitivity. Instead, the regulator directs people to pharmacists or GPs if they are unsure how a medicine may be affected by heat or sunlight. For the health system, that places community pharmacy and primary care at the centre of first-contact risk management. It also reduces the chance that patients respond to seasonal safety messages by discontinuing treatment without supervision, which can create separate clinical risks and avoidable pressure elsewhere in the system.
Alongside the prevention message, the campaign reinforces reporting. Anyone who suspects a side effect is encouraged to discuss it with a doctor, pharmacist or nurse and may also submit a report directly through the MHRA Yellow Card scheme. The agency says NHS login can now be used to create a new Yellow Card account or access an existing one, making the reporting route more straightforward for people already using NHS digital services. As an executive agency of the Department of Health and Social Care, the MHRA is using the summer campaign to connect public advice, medicine safety and surveillance in a single communication. The practical effect is to frame hot weather not simply as a general public health issue, but as a medicines safety issue requiring vigilance from patients, carers, clinicians and regulators.