Drugs That Can Increase the Risk of Heat-Related Illness

Intense heat can not only affect mental health and well-being, but heat waves may also cause life-threatening conditions or other injuries (for example, accidental falls) and lead to increased emergency-room visits or hospitalizations.[1] Dangerous heat waves are likely to become more frequent, extreme and longer due to climate change.[2] For example, several regions in the United States experienced record-breaking high temperatures in 2023, and the summer months were the hottest ever recorded. During this period, heat-related emergency-room visits also were higher than in prior years.

Although intense heat poses health risks for everyone, some people are at a particularly high risk, including those who work outdoors or who cannot adequately protect themselves from heat (for example, because they do not have access to air conditioning).[3] Older adults and patients with chronic conditions, such as cardiovascular disease, respiratory disease, chronic kidney disease, diabetes, dementia or mental health disorders, also are at a higher risk of heat-related adverse events.[4]

Additionally, heat can interact with certain prescription or over-the-counter medications.[5] For instance, heat can affect the efficacy of drugs or may cause medication-delivery devices, such as inhalers, to malfunction. Even if ambient temperatures are only mildly increased, higher temperatures in delivery trucks, cars or mailboxes can degrade or damage medications.[6]

Some drugs also may impair cognitive function or are very sedating, such as opiates (for example, hydrocodone [HYSINGLA ER and generics]) or benzodiazepines (including alprazolam [XANAX and generics]). People taking such medicines may not realize that they need to drink water or seek cool surroundings.

Moreover, as discussed in the June 2023 issue of Worst Pills, Best Pills News,[7] some drugs can cause sensitivity to sunlight.

This article discusses drugs that are associated with an increased risk of heat injuries because they may interfere with the body’s ability to regulate its core temperature or to tolerate heat exposure.[8]

Regulation of body temperature

People usually maintain a stable temperature of 97 to 99 degrees Fahrenheit, regardless of the ambient temperature.[9] A structure in the brain called the hypothalamus regulates several processes that stabilize the body’s internal temperature and fluid balance. For example, it helps the body dissipate heat by dilating blood vessels on the skin, feet, face or arms. Increased sweating helps to cool the body or leads to sufficient discomfort for a person to seek out water and shade.[10]

If the body overheats (internal temperature above 104 degrees), there is a risk of heat injury or heatstroke, a life-threatening condition that can rapidly damage the brain, kidneys, heart and muscles.[11] Symptoms of heat injury and heatstroke include changes in sweating patterns, flushed skin, muscle cramps or pain, dizziness, tiredness or weakness, rapid breathing, nausea and vomiting, changes in behavior or mental state, headache, rapid heart rate, and fainting.[12]

Examples of medications that increase the risk of heat injury

Medications that can increase the risk of heat-related injury by affecting the body’s ability to regulate its internal temperature include antidepressants, antihistamines, antipsychotics, antiseizure medications and cardiovascular drugs.[13]

For example, cardiovascular drugs such as beta blockers (including metoprolol [KAPSPARGO SPRINKLE, LOPRESSOR, TOPROL-XL and generics]) and antiplatelet medications (including clopidogrel [PLAVIX and generics]) can impair the body’s ability to dilate skin blood vessels, which decreases the body’s ability to dissipate heat.

Other cardiovascular medications can reduce the sensation of thirst. Examples of such drugs include angiotensin-converting enzyme inhibitors such as enalapril (VASOTEC and generics), angiotensin receptor blockers such as valsartan (DIOVAN and generics), and diuretics such as furosemide (LASIX and generics). Reduced thirst also can lead to dehydration, which in turn may increase the risk of adverse effects because drugs are cleared from the body more slowly.[14]

Diuretics can not only reduce the sensation of thirst but also reduce blood pressure and blood volume, affecting the amount of blood flowing to the skin.[15]

Table 1, below, provides additional examples of drugs that can reduce the sensation of thirst and affect blood volume.
 

Table 1. Examples of Oral Drugs That Can Reduce the Sensation of Thirst and Affect Blood Volume[16],[17]

†Brand-name combination products that contain other active ingredients are not included.
*Designated as Limited Use by Public Citizen’s Health Research Group

Other drugs can impair temperature regulation by affecting the body’s ability to sweat.[18] For instance, antidepressants such as the selective serotonin reuptake inhibitors, including fluoxetine (PROZAC and generics), and serotonin and norepinephrine reuptake inhibitors, such as duloxetine (CYMBALTA, DRIZALMA SPRINKLE and generics), as well as the antiseizure medication oxcarbazepine (OXTELLAR XR, TRILEPTAL and generics), can increase sweating.

Other drug classes, such as antihistamines, antipsychotics, some antiseizure medications, some cardiovascular medications, and older (tricyclic) antidepressants can decrease sweating. Table 2, below, provides examples of drugs that can decrease sweating.

Table 2. Examples of Oral Drugs That Can Decrease Sweating[19],[20]

†Brand-name combination products that contain other active ingredients are not included.
*Over-the-counter brand name
**Designated as Limited Use by Public Citizen’s Health Research Group
***Designated as Limited Use for epilepsy and as Do Not Use for migraine prevention by Public Citizen’s Health Research Group
****Designated as Do Not Use by Public Citizen’s Health Research Group

What You Can Do

To reduce your risk of heat-related illnesses and exacerbations of medical conditions during heat waves, make sure to stay hydrated and have a plan for how to stay cool, such as by seeking out shade or air-conditioned rooms, sipping cool water, carrying a fan or ice packs, wearing cool clothes, or taking cool baths. If you experience symptoms of heat injury or heatstroke, especially if you are vomiting, seek immediate medical help.

If you are taking medications that may increase heat-related adverse events, discuss with your clinician whether you can change medications or adjust doses to reduce your risk when it is hot or during heat waves.[21] Do not stop taking medications or adjust your dose without speaking with your clinician first.
 

References

[1] Vaidyanathan A, Gates A, Brown C, et al. Heat-related emergency department visits — United States, May–September 2023. MMWR Morb Mortal Wkly Rep. 2024;73:324–329.

[2] Gamboa L, Lafuente AS, Morera-Herreras T, et al. Analysis of heat stroke and heat exhaustion cases in EudraVigilance pharmacovigilance database. Eur J Clin Pharmacol. 2023 May;79(5):679-685.

[3] Ibid.

[4] Climate emergencies. UpToDate April 4, 2025.

[5] Centers for Disease Control and Prevention. Heat and medications – guidance for clinicians. June 18, 2024. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html. Accessed May 6, 2025.

[6] Climate emergencies. UpToDate April 4, 2025.

[7] Drugs that cause sensitivity to sunlight. Worst Pills, Best Pills News. June 2023. https://www.worstpills.org/newsletters/view/1538. Accessed May 6, 2025.

[8] Centers for Disease Control and Prevention. Clinical overview of heat. https://www.cdc.gov/heat-health/hcp/clinical-overview/index.html. Accessed May 6, 2025.

[9] Scientific American. How some common medications can make people more vulnerable to heat. May 1, 2024. https://www.scientificamerican.com/article/how-some-common-medications-can-make-people-more-vulnerable-to-heat/. Accessed May 6, 2025.

[10] Gamboa L, Lafuente AS, Morera-Herreras T, et al. Analysis of heat stroke and heat exhaustion cases in EudraVigilance pharmacovigilance database. Eur J Clin Pharmacol. 2023 May;79(5):679-685.

[11] Mayo Clinic. Heat stroke. September 12, 2024. https://www.mayoclinic.org/diseases-conditions/heat-stroke/symptoms-causes/syc-20353581. Accessed May 6, 2025.

[12] Substance Abuse and Mental Health Services Administration. Tips for people who take mediation: Coping with hot weather. https://library.samhsa.gov/sites/default/files/pep23-01-01-001.pdf. Accessed May 6, 2025.

[13] Centers for Disease Control and Prevention. Heat and medications – guidance for clinicians. June 18, 2024. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html. Accessed May 6, 2025.

[14] Climate emergencies. UpToDate April 4, 2025.

[15] Centers for Disease Control and Prevention. Heat and medications – guidance for clinicians. June 18, 2024. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html. Accessed May 6, 2025.

[16] Ibid.

[17] Climate emergencies. UpToDate April 4, 2025.

[18] Centers for Disease Control and Prevention. Heat and medications – guidance for clinicians. June 18, 2024. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html. Accessed May 6, 2025.

[19] Ibid.

[20] Climate emergencies. UpToDate April 4, 2025.

[21] Centers for Disease Control and Prevention. Heat and medications – guidance for clinicians. June 18, 2024. https://www.cdc.gov/heat-health/hcp/clinical-guidance/heat-and-medications-guidance-for-clinicians.html. Accessed May 6, 2025.