Heat and Medications – Guidance for Clinicians

Heat and Medications

Medications and heat can interact, leading to potentially severe side effects. The information presented here is intended to 1) alert clinicians and patients that certain medications can increase the risk of heat-related illness, 2) review how medications and heat interact with examples of specific medications that may do this, and 3) facilitate the development of a medication plan for hot days. This guidance reflects expert opinion and any actions should reflect careful review of risks and benefits with your patients.

Commonly prescribed medications that increase risk from heat include diuretics, anticholinergic agents, and some psychotropic medications. Over the counter medications can also interact with heat. Certain combinations of medications, such as an angiotensin converting enzyme (ACE) inhibitor or an angiotensin II receptor blocker (ARB) with a diuretic, may significantly increase risk of harm from heat exposure. Angiotensin Receptor-Neprilysin Inhibitors (ARNIs) may carry the same additive risk. For children and adolescents, medications that may increase risk of heat related illnesses include non-selective antihistamines (e.g., diphenhydramine), stimulants like methylphenidate for attention-deficit/hyperactivity disorder (ADHD), tricyclic antidepressants, selective serotonin reuptake inhibitors (SSRIs), and diuretics.

Medications can contribute to heat sensitivity in the following ways:

• Reduced thirst sensation (e.g., diuretics, ACE inhibitors, ARBS)
• Interference with central thermoregulation (e.g., antipsychotics, anticholinergics, stimulants)
• Impaired sweating and therefore impaired cooling (increased with Selective Serotonin Reuptake Inhibitors (SSRIs), Serotonin and Norepinephrine Reuptake Inhibitors (SNRIs), decreased with Tricyclic Antidepressants (TCAs), typical and atypical antipsychotics, anticholinergic agents)
• Volume depletion, hypotension, or reduced cardiac output with increased risk of fainting and falls, as a result of reduced renal blood flow and/or kidney injury from nephrotoxic drugs (non-steroidal anti-inflammatory drugs [NSAIDs], diuretics, beta blockers, TCAs, laxatives)
• Reduced dilation of superficial blood vessels with impaired ability to dissipate heat (e.g., aspirin, beta-blockers, and clopidogrel)
• Drug toxicity from reduced clearance of medications in people who are dehydrated, especially for medications with a narrow therapeutic index (e.g., apixaban, carbamazepine, and lithium)
• Electrolyte imbalance (e.g., diuretics, beta blockers, calcium channel blockers, antacids, laxatives, lithium, and trimethoprim-sulfamethoxazole)
• Sedation or cognitive impairment with increased risk of falls and reduced thirst sensation (e.g., opiates, benzodiazepines, typical and atypical antipsychotic medications, antidepressants, anticonvulsants)

In addition, heat exposure may damage medication delivery devices or degrade medications. Inhalers, for example, can burst in hot environments, such as car trunks on hot days. EpiPens may malfunction or deliver less epinephrine when exposed to heat. Insulin, which should be stored in a refrigerator, may become less effective if left in the heat for prolonged periods.

Some medications can increase the sensitivity of the skin to the sun. Antifungal medications like flucytosine, griseofulvin, and voriconazole and antibiotics like metronidazole, tetracyclines and fluoroquinolones can increase sun sensitivity and lead to a sunburn-like rash. For patients on these medications, sun avoidance, protective clothing and hats, and broad-spectrum sunscreen that filters out UVA and UVB rays, with an SPF of 30 or higher, are recommended.

See the table at the end of this section that lists medications, including over the counter medications, that can increase health harms from heat and the associated mechanism of action. This list is not comprehensive but includes many commonly used medications.

What Clinicians Can Do

Attention to heat exposure as a component of medication management may prevent harm. Medication regimens can be reviewed with your patients, with consideration to their risk profiles related to heat. Consider making a plan with your patients for medication management on HeatRisk orange, red, and magenta days and for when to seek medical care.

Review the information in this section to familiarize yourself with how medications interact with heat and which medications may do so. Consider these action steps.

• Review your patient's medication list with them, highlighting medications that may need to be adjusted because of interactions with heat. This is especially important for patients, including older patients, who take multiple medications that may amplify risks of harm from heat via different mechanisms.
• Remind patients to avoid abruptly stopping any medications without having a plan in place.
• Consider adjusting medication dose or frequency during hot weather months based on potential medication interactions with heat and an assessment of symptom severity. Any changes in medication dose or schedule should be individualized, will be drug-class dependent, and should consider risks and benefits for your patient.
• Consider adjusting fluid restrictions on hot days, especially for patients who take medications that may lead to dehydration or affect electrolytes.
• Talk to your patients about signs and symptoms that heat may be interacting with their medications, when to seek medical care, which symptoms are an emergency, and what to do in an emergency.
• Provide guidance on proper storage of medications. Remind patients that insulin can be degraded by heat and should be refrigerated. Counsel patients not to leave medications in a car or other places that can get excessively hot. Remind patients that inhalers can malfunction or burst from extreme heat.
• Help your patients develop a power outage plan, including how they will manage medications that require refrigeration, like insulin, or medical devices that require electricity, like nebulizer machines, ventilators, and oxygen concentrators during a power outage.
• Counsel patients taking medications that increase sun sensitivity to limit sun exposure and apply sunscreen when they need to be outside in the sun.
• Document any medication or fluid adjustments to be made on hot days and when to resume normal medication schedule. Encourage your patients to reflect information discussed with you related to heat and medications in the medication section of their Health Action Plan.
• Encourage your patients to seek a cool environment.
• Ask your patient to identify a point of contact to check on them if they take medications that may increase the risk of harm from heat, especially for older patients and patients with altered cognition.