Can some medications impact your ability to handle extreme heat? What to know

Canadians are sweltering under the heat wave in Ontario and parts of Quebec, and for those taking certain medications, precaution is needed as the thermometre soars.

The two provinces are seeing the humidex reach the low to mid-40s on Wednesday with the heat expected to stay to the end of the week, and medical experts like Dr. Samantha Green say those on some medications should be aware that what they’re taking could impact their ability to handle that extreme heat.

“Some of those medications directly interfere with the hypothalamus, which is the body’s thermostat, and the way that the body kind of co-ordinates normal thermo-regulation, and some of those medications interfere with some of the ways that our body is able to cool itself,” Green, a family physician, told Global News.

According to Green, that part of the brain tells the lungs to start breathing faster and the heart to start beating at a higher rate. It causes the blood to be closer to the surface of the skin and helps the body lose some of its heat through radiant cooling. In addition, the body will also sweat, which allows people to lose further body heat by evaporation.

According to Health Canada, medication that can impact the hypothalamus, heat perception, cardiac output, sweat rate, body hydration, renal function and electrolyte status can cause someone to be at a higher risk of heat illness.

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Some examples of medications that can have an impact on the body during heat are ACE inhibitors and beta blockers used to treat heart-related problems, diuretics, antidepressants, anti-seizure medication, and even antihistamines, which can reduce sweating.

Medications like antidepressants and anti-psychotics can also have an impact on the hypothalamus. Diuretics, which can be used to treat blood pressure, can interfere with normal sweating because the body can end up slightly dehydrated.

“You don’t get as thirsty or don’t feel the sensation of thirst as you would have if you weren’t on that medication, so you’re not necessarily making sure that you’re drinking as much because you’re not feeling that sensation of thirst,” Ontario pharmacist Kristen Watt told Global News.

She added that people with health conditions like heart failure can also impact this, as they’re not allowed to drink as many fluids.

The high temperatures can also affect how medications work, which is why experts say it’s important to store them properly.

Green and Watt say this means that while medications don’t need to be refrigerated unless stated on the label, they should still be stored in a cool, dark place, even in a home without central air.

Some medications, like insulin, can become no longer effective when exposed to extreme heat.

Both Green and Watt note that the issue can be compounded if someone is taking multiple medications, with the former suggesting taking a diuretic and beta blocker could cause dehydration and a slower heart rate.

Among those at high risk for illness in heat waves are children and older people, and also people with chronic mental and physical conditions. One example is schizophrenia, which Green says impacts the hypothalamus. Its symptoms can interfere with the ability to cope with the heat, and some being socially isolated can add to the risk. That’s then further compounded by the antipsychotic medications commonly used for the condition, which also impact thermoregulation.

Watt notes that as people get older, even without chronic conditions the ability to regulate heat changes.

“Then you add on a chronic condition and then you add on a medication, and you’ve got a perfect storm of potentially dangerous situations for our patients,” Watt said.

With Canada forecast to have above-average heat this summer, people are advised to know their risk factors.

“I think people do need to be aware when they’re on certain medications, that means that they are more at risk and need to pay attention,” Green said. “They don’t necessarily recognize that they are in particular at risk and so it’s just being aware.”