As heat wave warnings go into effect in many areas across the globe, especially deadly heat in the US, you likely know that precautions are warranted to limit the risk of dehydration or heat stroke. But did you know that certain medications can influence the risk of heat illness? This can happen in a variety of ways.

Medications, such as cardiovascular drugs (e.g., diuretics, ACE inhibitors or ARBs) can alter volume status. Cardiovascular drugs, as well as select antibiotics and NSAIDs can also adjust electrolyte balances and influence volume status. This can result in an increased potential for fainting and falls. Furthermore, patients on these medications may have a reduced desire to drink (thirst impairment), and should be encouraged to monitor their fluid intake to avoid dehydration. Select cardiovascular medications, including aspirin and clopidogrel, can also influence capillary bed dilation, reducing heat that is dissipated.

Neuroactive drugs may also influence thermoregulation. Anticholinergics and stimulants disrupt central thermoregulation signals, while psychotropics (including most antidepressants and antipsychotics) impair sweating. Sedatives (including opiates and anticonvulsants) can also reduce thirst sensation. All of these classes of medications could put individuals at an increased risk of harm from severe heat.

Medications, such as antifungals and antibiotics, can increase a patient’s sensitivity to sun exposure. These patients should be counseled on the photosensitivity risk, and encouraged to practice extra precautions in the sun. This includes limiting overall sun exposure, in particular during the peak times of the day. It also includes wearing sun protective clothing and applying sunscreen liberally, with re-application every 2-4 hours. Patients that see early signs of a sun rash developing should seek shelter and avoid the further sun exposure if possible.

An increased risk of side effects can occur in medications that depend on renal clearance and have a narrow therapeutic window, if the patient becomes dehydrated. For instance, this has been seen in patients that became dehydrated and are chronically taking apixaban, carbamazepine, and lithium.

Thyroid replacement medications, such as levothyroxine, may contribute to an elevated temperature and excessive sweating, which could increase the risk of dehydration developing.

Heat can also degrade some medications, influencing their effectiveness. Particular medications at risk of this include inhalers, epinephrine, and insulin. Whenever possible, when recreating outside in the heat, these items should be carefully stored in the central part of the bags or backpacks to protect these from direct sun exposure, yet still be readily accessible if potentially needed in an emergency.  

Clinicians can help patients prepare for exposure in the heat by reviewing their chronic medications for any potential risks that could exacerbate heat sensitivity. In addition to providing general recommendations for keeping safe in extreme heat (including prescription drug use), the CDC provides a comprehensive list of medications that are influenced by heat, with additional resources to guide care in select chronic conditions (e.g., cardiovascular disease or asthma).

A primary care provider may be able to adjust medication doses or frequency after an assessment of heat risk. This may be particular helpful in elderly patients that have several medications that are influenced by heat, especially if they have compounding mechanisms for increased heat sensitivity. For instance, it may be useful to temporarily reduce NSAID dosing, if tolerated. Though if no plan is made in advance, then it is critical that patients do not abruptly stop taking their medications. Instead they should focus on ways to recreate safely in heat: wear loose-fitting clothing that ideally covers the arms and legs, yet breathes well, in addition to a wide-brimmed hat, seek out shade, consider caring a portable fan, and take frequent breaks.

In addition to the medications themselves, the primary care provider may be able to assess a patient’s fluid restriction goals on days excessive heat exposure is expected. Finally, it may be helpful for patients to identify a primary patient advocate that can check in on individuals that may be at increased risk of harm from heat exposure, in case of any altered mental status that may present.

Like other chronic conditions controlled with medications, it helps to have an action plan in place in advance. It is also helpful to educate patients to be aware of any early signs the body is showing to take a break, and to have a low threshold to take steps to cool down, in particular if they are taking a medication that may impair an early sign of dehydration such as thirst.

And don’t forget alcohol! While some may not consider it a drug per se, it is certainly consumed, especially on hot days. Alcohol can lead to increased sweating and urination, and decreased perception of heat. As well, alcohol can interact with many prescription drugs, contributing more to the risk of heat illness. Better to enjoy a cold refreshing alcohol-free beverage on those sweltering summer days.

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