Heat and Medications: What Pharmacists Need to Know

Are you experiencing heatwaves in your state? If that’s the case, you are not alone. Over the last couple of years, summers have been ranked amongst the hottest on record in the United States.¹ Extreme heat is defined as a period of abnormally high temperatures, often accompanied by high humidity, that lasts for at least 2 to 3 days and exceeds the average maximum temperature for a specific location.² Although extreme heat can significantly impact our environment, there can be great impacts on the efficacy, safety, and accessibility of various medications and dosage forms used by patients.

Extreme heat can be harmful to healthy individuals and result in several heat-related illnesses like dehydration, hyperthermia, cramps, heat exhaustion, and heat stroke.³ Although extreme heat can impact the health of all patients, certain populations (eg, infants, children, pregnant women, and older adults) are at increased risk of heat-related illnesses.^4,5 Extreme heat can also worsen the health of patients, especially those suffering from chronic disease states like diabetes, cardiovascular diseases, renal impairment, pulmonary disorders, and mental health disorders.^5-8 In fact, a study involving Medicare beneficiaries reported that elderly patients with chronic disease states described above were more likely to experience hospitalizations due to heat-related illnesses.⁹ Extreme heat can also increase growth of parasites and microorganisms, promote antibiotic resistance, and increase risk of certain infections (eg, fungal infections) in both healthy individuals and patients with chronic diseases.^10-12

Importantly, certain medications being taken by patients to manage their health can make them more vulnerable to heat-related illnesses.¹³ These include medications that can impact the body’s ability to cool itself and regulate body temperature. One of the primary mechanisms used by the body to cool itself includes sweating.^3,4 Sweating is regulated by the parasympathetic neurotransmitter acetylcholine; thus, medications that impede the action of the neurotransmitter acetylcholine by blocking cholinergic receptors (ie, medications with anticholinergic activity) can worsen the impact of heat. Several classes of medications have anticholinergic activity. Some of these classes of medications include anticholinergic medications, antipsychotics, antihistamines/antiallergy, and antidepressants.¹⁴

The hypothalamus plays an important role in maintaining body temperature and regulates various thermoregulatory responses, which allow the body to adapt to extreme heat.⁴ Antidepressants like selective serotonin reuptake inhibitors can increase susceptibility to heat-related illnesses by impairing the thermoregulatory function of the hypothalamus.^15,16 In addition, medications that increase cellular metabolism and increase body temperature, such as those used for attention deficit hyperactivity disorder (eg, amphetamines, methylphenidates) and thyroid hormones, can also increase the occurrence of heat-related illnesses in individuals taking such medications.^13,15

Medications that decrease thirst, like angiotensin-converting enzyme inhibitors and glucagon-like peptide-1 agonists, can also increase vulnerability to extreme heat by diminishing thirst and water intake in individuals taking these medications.^16,17 Another class of medications that increase vulnerability to heat-related illnesses include medications that can cause loss of water and/or electrolytes (eg, diuretics). Medications such as beta blockers can also increase the vulnerability to heat-related illnesses by slowing heart rate and impairing cutaneous vasodilation.¹⁶ In doing so, these medications can impair the ability of the body to circulate blood efficiently for cooling. A detailed list of medications that can increase susceptibility of patients to heat-related illnesses is available via the CDC.¹⁸

In addition to increasing vulnerability to heat-related illnesses, extreme heat can damage exposed organs like the skin. Extreme heat exposure can result in several skin conditions such as sunburn, photosensitivity, skin cancer, and/or worsening of existing skin diseases.¹⁹ Several classes of medications such as antibiotics (eg, doxycycline, sulfonamides, and ciprofloxacin), nonsteroidal anti-inflammatory drugs (eg, ibuprofen and naproxen), diuretics (eg, thiazide diuretics), antidepressants (eg, tricyclic antidepressants), antifungals (eg, flucytosine & griseofulvin), and retinoids can make the skin more vulnerable to extreme heat.^18,20

Heat-related rise in body temperature and dehydration can impact the pharmacokinetics of medications. For example, dehydration can affect blood volume and renal function and thus impact volume of distribution and elimination of medications by the kidneys.¹³ This in turn may increase levels of medications, resulting in greater toxicity. Narrow therapeutic index medications used in the treatment of bipolar disorder (eg, lithium) and epilepsy (eg, carbamazepine) may produce more toxicity during extreme heat due to elevated blood levels.^13,15,18

Furthermore, rising temperatures and/or extreme heat can affect production of certain medications, which are dependent on nature. For example, the supply of medications that are dependent on natural products (eg, artemisinin from Artemisia annua L.). Growth of these plants can be affected by both rising temperatures and poor water supply due to extreme heat.¹¹ Power outages or inability to maintain cold chain access due to extreme heat or heat waves can also impact the stability of certain medications that are required to be maintained at certain temperatures for their stability (eg, insulin, blood products, and vaccines).^11,21

Extreme heat can either degrade medications or impact delivery of medications using other types of dosage forms such as Accuhalers, inhalers, and transdermal patches.^22,23 Further, stability of medications (eg, chemotherapy, analgesics, and antibiotics) administered at home parenterally using elastomeric infusion pumps can also be impacted by high weather temperatures, especially if manufacturer’s instructions regarding their storage are not closely followed.²⁴

High temperatures can affect the health of both healthy individuals and patients with chronic diseases. In addition, treatment of diseases can be impacted due to availability, stability, and/or delivery of medications, which can also be influenced by extreme heat and/or rising temperatures. Pharmacists can help patients prevent heat-related illnesses, improve management of disease states when heat waves are anticipated, and make recommendations regarding medications and heat.

The Centers for Disease Control and Prevention (CDC) advises using the HEAT questionnaire (Housing/indoor environment; Emergency preparedness; Awareness; Temperature/outdoor environment) to assess a patient’s risk for experiencing adverse events related to high temperatures. Three questions corresponding to the “A” in the mnemonic should be utilized to identify potential issues specifically related to medication use: 1) Does the patient have a plan to manage refrigerated medications and/or electric medical devices during a power outage? 2) Does the patient know if their medications can lead to complications in hot weather? 3) Does the patient have a heat and medication plan?²⁵

Based on the answers to these questions, pharmacists can take action as appropriate. This may involve educating patients about steps that may need to be taken to minimize or avoid potential harm. Patients should be encouraged to seek cool environments and to identify a contact who can check on them as needed on hot days. Pharmacists should counsel patients regarding signs and symptoms that may indicate that heat is interacting with their medications, including when emergency care may be needed. In addition, patients should be educated about medicines that alter electrolyte levels or may make them dehydrated or overheated, which may also involve adjustment of fluid intake. Pharmacists should remember that patients on polypharmacy may have risks of harm from heat for multiple medications, which may be compounded by other risk factors such as age. Pharmacists may need to collaborate with other members of the healthcare team to identify and adjust medications that interact with heat on HeatRisk orange, red, or magenta days. If changes are made, patients should be informed when to resume their normal medication schedule or fluid intake.¹⁸

Patients receiving medications that increase sun sensitivity should be counseled to limit sun exposure and, when outdoors, to wear protective clothing/hats and apply a broad-spectrum sunscreen of SPF 30 or higher. Pharmacists should also raise awareness that heat exposure may damage medication delivery devices or degrade medications. Patients should be educated on how to store medications properly, keeping in mind considerations regarding heat and humidity (for example, pharmacists should advise patients to avoid keeping medications in hot environments, such as their car).¹⁸

The CDC provides more detailed guidance for clinicians about the above considerations on its “Heat and Medications” page. In addition, the CDC has a patient-friendly resource, “Heat and Your Health,” that pharmacists can direct patients to for more information on the potential impact of heat on themselves, friends or family members, or even their pets. As the US continues to experience more extreme heat events, it is imperative that pharmacists understand the potential for heat-drug interactions. As the medication experts on the healthcare team and trusted community members, pharmacists should be at the forefront to lead appropriate actions and provide relevant patient education to mitigate potential harm.

Read the other installments:
Heat and Human Health: What Pharmacists Need to Know

Heat and Older Adults: What Pharmacists Need to Know

REFERENCES

1.Thompson A. Climate change fuels record summer heat, killing thousands. Scientific American. September 17, 2025. Accessed April 7, 2026. https://www.scientificamerican.com/article/climate-change-fuels-record-summer-heat-killing-thousands/

2. US Environmental Protection Agency. Climate change and extreme heat: What you can do to prepare. EPA; 2016. EPA 430-R-16-061.

3. Sorensen C, Hess J. Treatment and prevention of heat-related illness. N Engl J Med. 2022;387(15):1404- 1413. doi:10.1056/NEJMcp2210623

4. Xu J, Wang Q, Anikeeva O, et al. Effects of extreme heat on physiology, morbidity, and mortality under climate change: mechanisms and clinical implications. BMJ. 2025;391:e084675. doi:10.1136/bmj-2025-084675

5. Bell ML, Gasparrini A, Benjamin GC. Climate change, extreme heat, and health. N Engl J Med. 2024;390(19):1793-1801. doi:10.1056/NEJMra2210769

6. Liu J, Varghese BM, Hansen A, et al. Heat exposure and cardiovascular health outcomes: a systematic review and meta-analysis. Lancet Planet Health. 2022;6(6):e484-e495.

7. Liu J, Varghese BM, Hansen A, et al. Hot weather as a risk factor for kidney disease outcomes: a systematic review and meta-analysis of epidemiological evidence. Sci Total Environ. 2021;801:149806.

8. Mascitelli A, Tumini S, Chiacchiaretta P, et al. Effect of atmospheric temperature variations on glycemic patterns of patients with type 1 diabetes: analysis as a function of different therapeutic treatments. Int J Environ Res Public Health. 2025;22:1850. doi:10.3390/ijerph2212185

9. Layton JB, Li W, Yuan J, Gilman JP, Horton DB, Setoguchi S. Heatwaves, medications, and heat-related hospitalization in older Medicare beneficiaries with chronic conditions. PLoS One. 2020;15(12):e0243665.. doi:10.1371/journal.pone.0243665

10. Dupke S, Buchholz U, Fastner J, et al. Impact of climate change on waterborne infections and intoxications. J Health Monit. 2023;8(suppl 3):62-77. doi:10.25646/11402

11. Kaplan WA, Hamer DH, Shioda K. The potential impact of climate change on medication access and quality deserves far more attention. One Health. 2024;20:100957. doi:10.1016/j.onehlt.2024.100957

12. Ni Y, Zhao J, Yuan Y, Feng B. Climate change and antimicrobial resistance: a global-scale analysis. BMC Infect Dis. 2025;25(1):1191. doi:10.1186/s12879-025-11616-9

13. Westaway K, Frank O, Husband A, et al. Medicines can affect thermoregulation and accentuate the risk of dehydration and heat-related illness during hot weather. J Clin Pharm Ther. 2015;40(4):363-367. doi:10.1111/jcpt.12294

14. Hanlon P, Quinn TJ, Gallacher KI, et al. Assessing risks of polypharmacy involving medications with anticholinergic properties. Ann Fam Med. 2020;18(2):148-155. doi:10.1370/afm.2501

15. Kalisch Ellett LM, Pratt NL, Le Blanc VT, et al. Increased risk of hospital admission for dehydration or heat-related illness after initiation of medicines: a sequence symmetry analysis. J Clin Pharm Ther. 2016;41(5):503-507. doi:10.1111/jcpt.12418

16. Stöllberger C, Lutz W, Finsterer J. Heat-related side effects of neurological and non-neurological medication may increase heatwave fatalities. Eur J Neurol. 2009;16(7):879-882. doi:10.1111/j.1468-1331.2009.02581.x

17. Santollo J, Daniels D. Fluid transitions. Neuropharmacology. 2024;256:110009. doi:10.1016/j.neuropharm.2024.110009

18. Centers for Disease Control and Prevention. Heat and medications: Guidance for clinicians. September 18, 2025. Accessed April 7, 2026. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html

19. Belzer A, Parker ER. Climate change, skin health, and dermatologic disease: a guide for the dermatologist. Am J Clin Dermatol. 2023;24(4):577-593. doi:10.1007/s40257-023-00770-y

20. Houston Methodist. Medications that don’t mix well with the sun or heat. June 2024. Accessed April 7, 2026. https://www.houstonmethodist.org/blog/articles/2024/jun/medications-that-dont-mix-well-with-the-sun-or-heat/

21. E. Baumgartner. Hot summer threatens efficacy of mail-order medications. August 2024. Accessed April 7, 2026. https://www.nytimes.com/2024/08/13/health/heat-mail-order-drugs.html

22. Hao J, Ghosh P, Li SK, Newman B, Kasting GB, Raney SG. Heat effects on drug delivery across human skin. Expert Opin Drug Deliv. 2016;13(5):755-768. doi:10.1517/17425247.2016.1136286

23. Hoye WL, Mogalian EM, Myrdal PB. Effects of extreme temperatures on drug delivery of albuterol sulfate hydrofluoroalkane inhalation aerosols. Am J Health Syst Pharm. 2005;62(21):2271-2277. doi:10.2146/ajhp050067

24. van der Merwe SM, Boyd N, Mavhunga S. Stability of intravenous medicines - evidence of maximum temperature reached in both summer and winter within soft shell elastomeric pumps. Eur J Hosp Pharm. 2025;32(6):550-556. doi:10.1136/ejhpharm-2024-004276

25. Centers for Disease Control and Prevention. HEAT: A heat and health risk factor screening questionnaire. June 18, 2024. Accessed April 7, 2026. https://www.cdc.gov/heat-health/hcp/clinical-guidance/HEAT-screening-questionnaire.html