Your medications can make it harder for you to beat the heat

For some, chronic health conditions can add an extra kick or two when it comes to regulating body temperature. Not only do some conditions affect physiological cooling, but the medications that treat those conditions can also interfere with body air. Older people are especially vulnerable to these effects, both because they face higher rates of certain chronic diseases and because the body’s ability to relax decreases with age.

Cardiovascular drugs, antipsychotics, and other medications have been associated with an increased risk of hospitalization during hot flashes. But researchers don’t have a firm understanding of which drugs pose the greatest threat or the mechanisms behind the potential risks. Some drugs can interfere with sweat and blood flow. Others can affect the body’s fluid levels, which ensure that we continue to produce sweat and pump blood safely.

Determining which medications can dangerously alter physiology is difficult, says Soko Setoguchi, an epidemiologist at Rutgers University in New Brunswick, NJ. This is because people usually get prescriptions to treat an illness, so “it becomes important to tease if [vulnerability to the heat comes from] disease or medicine”. Ethical considerations, such as weaning people off life-sustaining drugs, make it difficult to conduct randomized studies among patients.

But the risks are growing. For people who depend on medication to manage illness, “hotter weather caused by climate change represents a serious health risk,” says Jericho Wee, a thermal physiologist at the National University of Singapore’s Yong Loo Lin School of Medicine. Additionally, the World Health Organization estimates that the share of adults older than 60 in the global population is expected to roughly double by 2050 compared to 2015. There is a sense of urgency to understand how drugs interact with heat, says Wee.

Some heart and brain drugs interfere with the body’s cooling system

To begin to understand how medications and illnesses are affected by heat, Setoguchi and colleagues dug into the records of nearly 10,000 Medicare patients age 65 and older and found that antipsychotics and cardiovascular medications were among those associated with hospitalization. related to heat. Even in the absence of heat waves, certain medications, such as diuretics, were associated with a higher risk of patients being hospitalized for heat-related illnesses, the team reported in PLUS One in 2020.

Chlorpromazine, an antipsychotic used to treat psychiatric conditions, including schizophrenia, is an example of a drug that can make colds difficult. The drug can suppress sweating and divert blood flow away from the skin, Wee says. It can also damage the body’s internal thermostat, leading to an increase in body temperature.

Other antipsychotic drugs can have similar effects. A 2021 case report of a 47-year-old man taking risperidone and fluphenazine for schizophrenia and hospitalized for heat illness suggested that the drugs changed the man’s brain chemistry in ways that may have made his body less inclined to understand that he was thirsty and overheated. . He was successfully treated to lower his body temperature and sent home.

Heart disease treatments can also make patients more vulnerable to heat, Wee says. Beta-blockers used to treat high blood pressure and antiplatelet drugs that prevent blood clotting can reduce the amount of blood that rushes to the skin to release heat to the surrounding air. And taking diuretics, common heart failure medications that help the body flush out excess fluid that would otherwise accumulate in the lungs and joints, can lead to dehydration if people don’t replace that fluid loss in extreme heat, says Wee. Dehydration also causes less blood to flow to the skin.

There is no strong evidence to suggest that people should stop taking or reduce doses of medication in extreme heat, Setoguchi says. “People are taking medications because they need them.” Instead, people should talk to their doctors about ways to avoid the heat and learn what to do in cases of heat stress.

What are the challenges to studying heat, health issues and medicines?

While studies are beginning to reveal how brain and heart drugs may affect temperature regulation, there are a host of other drugs with unknown effects in extreme heat, says Jason Lee, a physical and thermal physiologist at the Yong Loo School of Medicine. Lin. This includes treatments for diabetes and cancer.

Researchers can make assumptions about how a drug might affect the body’s response to heat based on what is known about how the drug works. But how these processes interact with our complex physiology in heat is still relatively unknown, says Nicole Vargas, a thermal physiologist at the Australian National University in Canberra. “It’s one thing for clinicians and pharmacists to say, ‘Hey, this drug works on the hypothalamus. We know that the hypothalamus is really important in many of our thermoregulatory functions. It should act for thermal regulation.’ But what does that mean?”

Part of the difficulty in finding answers is that there are ethical and practical challenges, Lee says. For one, it is unethical to conduct randomized clinical trials that withhold treatment for a group of patients who are dependent on medications to treat their disease. For another, “you can’t randomize heat [waves]”, says Setoguchi.

Some researchers have tried giving drugs to otherwise healthy people and comparing their heat tolerance to that of those not taking the drug. For example, researchers at the University of Sydney’s Heat and Health Research Incubator are exploring whether antidepressants affect the way the body handles heat in people without depression, Vargas says.

But such work leaves out underlying conditions that can confound the way heat interacts with a drug. Case studies can help, Setoguchi says, especially those that follow many patients, comparing when each patient takes the drug versus when they don’t. So can studies involving people taking a different medication for the same condition. However, the severity of the disease varies between people. Someone with worse symptoms may be more vulnerable to heat than someone with milder disease who is not taking medication, confounding how researchers can interpret the results.

It’s important to consider everything together, from the disease to the specific medication a patient is taking, Setoguchi says. This can help doctors predict who may face the greatest risk in extreme heat. For now, however, the race is on to better understand which drugs researchers should focus on.