Medication use in a warmer world

Author(s):  Dr Sherilyn Houle

Moderate to strong El Niño conditions are being fueled by warm ocean waters, leading to predictions of increasing global temperatures and more extreme weather and rainfall patterns.¹ Above average temperatures are forecast worldwide from June to August 2026, with 90% or higher probabilities for this to continue until at least November.¹

High temperatures can be especially risky for those who are very young or old and for those with diabetes, renal disease, high body mass index, or acute infection, or who are pregnant.^2,3 Medication use can also predispose individuals to heat-related illness by impacting sweating, hydration status, susceptibility to falls, or contributing to the development or worsening of renal impairment.^4,5

A freely available online resource from the Canadian Pharmacists Association summarizes some of these higher-risk medications. The BADCLAP mnemonic stands for Beta blockers, ACE inhibitors (and ARBs), Diuretics, antiCholinergics, Lithium, Antidepressants, and antiPsychotics. The anticholinergics class includes all drugs with sedating or anticholinergic properties, including anticonvulsants, benzodiazepines, first-generation antihistamines, and opiates.⁵ Other drugs that may cause hypotension (e.g., calcium channel blockers, nitrates), that have a narrow therapeutic index which can be impacted by hydration and electrolyte status, or that may be nephrotoxic should also warrant a discussion with patients about protecting themselves during high heat.^4,5

Seeking air conditioning or shade, hydration, avoidance of alcohol, and minimizing physical exertion should be recommended, and all travellers to warm climates should be aware of the signs and symptoms of heat-related illness such as heat cramps, heat exhaustion, or heat stroke and their management.

An infographic on the BADCLAP mnemonic is available at https://www.pharmacists.ca/cpha-ca/assets/File/education-practice-resources/Medications_Affected_By_Heat-3.pdf

References

[1].  WMO: Prepare for El Nino.  World Meteorological Organization [link]
[2].  Heat and cold illness in travellers.  Backer HD, Freer L ‐ CDC Yellow Book 2026 [link]
[3].  Treatment and prevention of heat-related illness.  Sorensen C, Hess J ‐ N Engl J Med 2022;387(15):1404-13 [link]
[4].  Heat and medications – Guidance for clinicians.  Centers for Disease Control and Prevention [link]
[5].  Heat and medication.  Canadian Pharmacists Association [link]