Singapore—With dangerously high temperatures and humidity popping up around the United States this summer, pharmacists might want to caution patients that their medications might affect their ability to manage heat.

“Pharmacological agents used to treat or manage diseases can modify the level of heat strain experienced by chronically ill and elderly patients via different mechanistic pathways,” wrote researchers from the National University of Singapore. “Human thermoregulation is a crucial homeostatic process that maintains body temperature within a narrow range during heat stress through dry (i.e., increasing skin blood flow) and evaporative (i.e., sweating) heat loss, as well as active inhibition of thermogenesis, which is crucial to avoid overheating. Medications can independently and synergistically interact with aging and chronic disease to alter homeostatic responses to rising body temperature during heat stress.”

The report in Pharmacological Reviews pointed out that medications to treat various chronic diseases can hamper the body’s ability to shed heat and regulate its core temperature to optimal levels. The authors emphasized that the loss of effective thermoregulation especially has implications for older adults receiving treatment for illnesses like cancer, cardiovascular, Parkinson’s disease/dementia, and diabetes, especially during hot weather.

The study team identified and reviewed relevant research papers using keyword searches on the associations and effects of medications on thermoregulation. The results indicated that medications used to treat common chronic conditions, such as blood thinners, blood pressure medications, Parkinson’s/Alzheimer’s disease medications, and some chemotherapy drugs, can make it more difficult for the human body to cope with hot weather by reducing its ability to sweat or increase blood flow to the skin.

“Long-term medications modulate thermoregulatory function, resulting in excess physiological strain and predisposing patients to adverse health outcomes during prolonged exposures to extreme heat during rest and physical work (e.g., exercise),” the researchers pointed out. “Understanding the medication-specific mechanisms of altered thermoregulation has importance to both clinical and research fraternities, paving the way for work towards refining current medication prescription recommendations and formulating mitigation strategies for adverse drug effects in the heat in chronically ill patients.”

It might be important for pharmacists to take a lead role on the issue, with coauthor Melvin Leow, MD, senior consultant endocrinologist at Tan Tock Seng Hospital, explaining that “physicians are often unaware of the potential harms certain drugs may cause by compromising the body’s thermoregulatory control mechanisms. This is an especially important area to delve into as those with chronic diseases and older adults are susceptible to adverse health outcomes in the heat, due to their reduced thermoregulatory capacity. It is timely and prudent that scientists and doctors collaborate even closer in this important field that cuts across a wide range of medical disciplines.”

The study noted the following:

• Patients on certain cancer medications have reported symptoms of hot flushes, such as inappropriate sweat responses and an increase in core temperature, which affects quality of life
• Patients who have cardiovascular diseases, such as coronary heart disease, stroke, and heart failure, are more vulnerable to high-heat exposure because their hearts will be working harder to deliver blood to the skin and working muscles to maintain core temperature at an optimal level while maintaining work output. Antiplatelet medications, such as aspirin and clopidogrel, also may increase core temperature, whether at rest or during exercise
• Used for multiple cardiovascular conditions, such as ischemic heart disease, high blood pressure, and heart failure, beta-blockers can reduce skin blood flow during heat stress by reducing blood pressure and facilitating additional constriction of skin blood vessels
• Insulin, which is typically used to reduce high blood sugar, or hyperglycemia, in patients with type 1 diabetes, has been shown to impair the ability of the body to regulate heat properly
• Due to an internal imbalance in dopamine and acetylcholine levels, patients with neuropsychiatric diseases such as Parkinson’s and Alzheimer’s disease experience thermoregulatory dysfunction when their body is unable to control its temperature
• Anticholinergics and cholinesterase inhibitors are prescribed to improve motor and cognitive symptoms in the brain for Parkinson’s disease patients, but those agents also alter the dopamine and acetylcholine levels, likely inducing changes in the central thermoregulatory drive
• Dopamine replacement agents and dopamine agonists are usually prescribed to those with Parkinson’s disease to increase dopamine levels to help in movement and coordination. While highly effective, these agents have been observed to significantly influence thermoregulation and impair sweat responses which are crucial for heat dissipation.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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