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

Heat, mugginess? Even medicines 'suffer'. But what really happens to medicines when temperatures soar as they do these days? Carelessness such as leaving a medicine in the car or taking it before exposing oneself to the sun can in fact have serious consequences. Similarly, those undergoing therapy may be more prone to dehydration or heat-related drops in blood pressure, 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, affecting their mechanism of action. Warnings are issued by the Italian Drug Agency, which, with a vademecum on social networks and an in-depth study on its website, suggests useful indications for those taking therapies.

Some active ingredients may in fact impair 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 the doctor, a remodulation of therapy may be considered,' Aifa clarifies, then goes on to list individual cases. Antihistamines, for example, can hinder sweating. Antipsychotics and antidepressants, as well as antiparkinsonian drugs, can lower blood pressure. Anxiolytics and muscle relaxants may worsen the feeling of exhaustion, cause dizziness or aggravate respiratory problems. Beta-blockers and vasodilators may affect the body's ability to dissipate heat, increasing the risk of hypotension and dehydration. Diuretics may contribute to excessive fluid and electrolyte loss. Another recommendation concerns skin reactions from photosensitisation: antibiotics, topical anti-inflammatories and cortisone can cause skin rash or erythema when combined with exposure to UV radiation. "If you take these medications, you should protect yourself with sunscreen and light clothing".

In addition to therapy management, another important aspect concerns proper storage. High temperatures can, in fact, change the chemical and physical stability of many molecules, rendering 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 medication in a car or in the sun. When travelling, cool bags or thermal containers should be used. On aeroplanes, essential medicines should be kept in hand luggage, together with a prescription. If a medicine changes colour, smell or consistency, it is important not to take it. Whenever possible, it is better 'to prefer tablets or capsules over liquid solutions' as they are more stable at high temperatures. Finally, it is a good idea to 'always keep medicines in their original packaging, which offers protection from light and moisture, and includes all useful information'.

Aifa also identifies the categories of drugs that, based on their mechanisms of interference with the effects of heat, can aggravate the effects of high temperatures on health. Here is the list: Anticolinergics: may interfere with thermoregulation, reduce the state of vigilance, hinder sweating Antipsychotics: may inhibit the sweating mechanism, decrease blood pressure and thermoregulation centrally and reduce the state of vigilance, making the subject unable to adopt defensive strategies Antihistamines may inhibit the sweating mechanism and reduce blood pressure Antiparkinsonians: may inhibit the sweating mechanism and reduce blood pressure, cause dizziness and state of confusion Antidepressants: may reduce sweating, interfere with central thermoregulation and reduce state of alertness Anxiolytics and muscle relaxants: may reduce sweating and cause dizziness, decrease cardiac output and influence cooling by vasodilation, may cause exacerbation of respiratory symptomsAnti-adrenergics and beta-blockers: may influence dilation of skin blood vessels, reducing ability to dissipate heat by convention Simpatomimetics vasodilators, including nitrates and calcium channel regulators, may worsen hypotension in vulnerable individuals Antihypertensives and diuretics: may lead to dehydration and reduce blood pressure; a common side effect is hyponatremia, which may be exacerbated by excessive fluid intakeAntiepileptics: may reduce alertness and increase confusion