Medicines and heat: unexpected effects, reactions and how to store them if you travel. Here is the list

Hot, muggy? Even medicines “suffer”. But what really happens to medicines when temperatures soar like these days? Oversights such as leaving medicine in the car or taking a medicine before exposing yourself to the sun can in fact have serious consequences. Similarly, those following a therapy could be more exposed to dehydration or drops in blood pressure related to the heat, but also to skin rashes. High temperatures, in fact, can alter the efficacy and safety of many medicines, such as those for anxiety, hypertension, Parkinson's and antibiotics, influencing their mechanism of action. The Italian Medicines Agency is warning, with a handbook on social media and an in-depth article on the portal, suggesting useful indications for those taking therapies.

Some active ingredients can in fact compromise the body's ability to regulate body temperature or increase the risk of dehydration, causing even serious side effects. "In extreme cases, and only on the advice of a doctor, a remodulation of the therapy can be considered", clarifies Aifa, which then goes on to list the individual cases. Antihistamines, for example, can hinder sweating. Antipsychotics and antidepressants, as well as antiparkinsonian drugs, can lower blood pressure. Anxiolytics and muscle relaxants can worsen the feeling of exhaustion, cause dizziness or aggravate breathing problems. Beta-blockers and vasodilators can affect the body's ability to dissipate heat, increasing the risk of hypotension and dehydration. Diuretics can contribute to the excessive loss of fluids and electrolytes. Another recommendation concerns skin reactions from photosensitivity: antibiotics, topical anti-inflammatories and cortisone can cause skin rashes or erythema when combined with exposure to UV rays. "If you take these medicines you must protect yourself with sunscreen and light clothing".

In addition to therapy management, another important aspect concerns correct storage. High temperatures can, in fact, modify the chemical-physical stability of many molecules, making them ineffective or even dangerous. In particular, insulin, hormones or vaccines must be stored at controlled temperatures, often between 2 and 8 °C. In summer, never leave medicines in the car or under the sun. When traveling, it is advisable to use cooler bags or thermal containers. On the plane, essential medicines must be kept in hand luggage, together with the medical prescription. If a medicine changes color, smell or consistency, it is important not to take it. When possible, it is better to "prefer tablets or capsules over liquid solutions", because they are more stable at high temperatures. Finally, it is good practice to "always keep medicines in their original packaging, which offers protection from light and humidity, and includes all useful information".

AIFA also identifies the categories of drugs that, based on the mechanisms of interference with the effects of heat, can aggravate the effects of high temperatures on health. Here is the list: Anticholinergics : can interfere with thermoregulation, reduce the state of alertness, hinder sweating Antipsychotics : can inhibit the sweating mechanism, decrease blood pressure and central thermoregulation and reduce the state of alertness, making the subject unable to adopt defensive strategies Antihistamines: can inhibit the sweating mechanism and reduce blood pressure Antiparkinsonians : can inhibit the sweating mechanism and reduce blood pressure, cause dizziness and confusion Antidepressants: can reduce sweating, interfere with central thermoregulation and reduce the state of alertness. Anxiolytics and muscle relaxants : may reduce sweating and cause dizziness, decrease cardiac output and influence cooling by vasodilation, may cause worsening of respiratory symptoms Antiadrenergics and beta-blockers : may influence the dilation of blood vessels in the skin, reducing the ability to dissipate heat by convection Sympathomimetics: vasodilators, including nitrates and calcium channel blockers, may worsen hypotension in vulnerable subjects Antihypertensives and diuretics : may lead to dehydration and reduce blood pressure; a common side effect is hyponatremia which may be worsened by excess fluid intake Antiepileptics: may reduce alertness and increase confusion