Some of the most common medications, including those used to treat depression, attention-deficit hyperactivity disorder, and high blood pressure medications, can increase the risk of dehydration and other conditions associated with hyperthermia.
At the height of the heat wave that swept Europe in June this year, Ileana Okumos could not understand why she was suffering more from the heat than others.
The 28-year-old, who lives in a top-floor apartment in Brussels without air conditioning, describes what happened to her as saying that her face began “sweating, as soon as I left my apartment.”
She was looking for comfort anywhere, in the office or in the local café, but that was not enough.
“It used to take half an hour, or an hour, for my body to feel cold,” Iliana says. “One day, the temperature inside the apartment reached 34 degrees Celsius. I think I slept for about 18 hours.”
She was already having difficulty waking up, and feared her blood pressure would drop.
Extreme heat waves were no stranger to Ileana Okumos, as she had previously lived in temperatures reaching 40 degrees Celsius elsewhere in the world. However, this was the first time she had experienced such a high body temperature.
It was only after she saw posts on social media of people with similar symptoms that she thought of making the connection between the heat and the medications she started taking two years ago to treat depression and anxiety.
But as heat waves become more frequent and intense as a result of climate change, doctors and health organizations are warning that some of the most common medications, including psychiatric, blood pressure, and heart medications, may affect the body's ability to regulate its temperature, putting people at risk of developing heat-related illnesses.
Many medications used to treat mental health conditions, such as depression, anxiety, and bipolar disorder, are known to increase susceptibility to heat symptoms due to their interaction with the hypothalamus, the brain's temperature-regulating center.
“This area of the brain causes us to be less active, sweat more, and reduce our metabolic rate, all of which help with temperature adaptation,” says Robert Feder, a retired psychiatrist in New Hampshire and a member of the FMA Steering Committee on Climate and Health.
The most prominent medications that affect this area are the most widely used antidepressants, which are selective serotonin reuptake inhibitors (SSRIs) and serotonin noradrenaline reuptake inhibitors (SNRIs). These medications include sertraline, fluoxetine, escitalopram, and venlafaxine.
These medications work by preventing the reabsorption of serotonin in the brain, a natural chemical that regulates mood and other body functions.
The high level of serotonin in the hypothalamus disrupts the regulation of body temperature and causes excessive sweating. This affects about one in five people who take antidepressants, and may lead to dehydration and loss of electrolytes (minerals and salts found in body fluids such as blood, sweat and urine).
“This problem is exacerbated when you are already dehydrated due to high temperatures,” Feder says.
Tricyclic antidepressants, an older type of antidepressant, can also stimulate or inhibit sweating, which is also a problem because not sweating reduces heat loss and raises body temperature.
These antidepressants have an “anticholinergic” effect, meaning they block the activity of a neurotransmitter called acetylcholine, which is involved in many different body functions including sweat secretion.
Caroline Friesinet, a 36-year-old career coach in Los Angeles, struggled this summer with the side effects of taking three different psychiatric medications: an antidepressant, a mood stabilizer and a medication for attention-deficit/hyperactivity disorder.
Caroline found herself losing focus, feeling extra nervous, and sweating more than usual, in the middle of an unusually long and humid July heatwave.
At first, Caroline thought these symptoms were due to poor nutrition and not drinking enough water, until her friend from a mental health support group sent her articles linking heat to medications, and others in the group said they faced the same challenges.
“Even though I knew very well about my psychological state and the side effects (of my medications), this was strange to me,” Carolyn says.
Other types of psychiatric medications can also have an effect. Antipsychotics, used to treat schizophrenia and bipolar disorder, inhibit dopamine in the hypothalamus, preventing natural responses that help cool the body.
Previous heatwave studies have linked the use of antipsychotics to an increased likelihood of death during heatwaves, and stimulants used to treat ADHD, such as the drug Ritalin, increase heat production and cause blood vessels to constrict, disrupting the body's natural cooling process.
What is also interesting about these medications, according to Robert Feder, is that they may also mask the effects of heat stress, which means that people may not realize that their body temperature has increased in the first place.
Of course, psychiatric medications are not the only ones responsible for increasing the impact of heat waves on our bodies. There are also blood pressure and heart medications that affect the body's sensitivity to heat.
Common medications to treat high blood pressure, such as diuretics, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers, may increase the risk of electrolyte imbalance. The last two medications can also interfere with the hormone responsible for the feeling of thirst.
“Because of this overlapping effect of the drugs, a person may become so dehydrated that they increase their risk of kidney failure, heart attack, or other serious organ complications,” says Logan Harper, MD, a family physician and associate director of the Climate and Health Fellowship Program at the University of Colorado Anschutz.
Meanwhile, beta blockers, a common heart drug that slows the heartbeat by blocking the effect of the hormone adrenaline, reduce blood flow to the skin, which means the body cannot get rid of internal heat efficiently.
Besides tricyclic antidepressants, other types of anticholinergic medications, used to treat a wide range of conditions such as Parkinson's, overactive bladder, respiratory disorders, and allergies, can affect the body's sweating and cooling mechanisms.
“Patients are often taking multiple medications that can hamper their ability to cool their bodies and increase the likelihood of organ damage,” Harper adds. He explains that this is especially true for older people, who are also more susceptible to heat illness in general.
Also, moderate temperatures may become a bigger problem due to some medications: This was confirmed by a study of elderly patients in the United States who take medications, including diuretics, antipsychotics, beta blockers, stimulants, and antihypertensives.
But older people may be more at risk of being hospitalized due to heat in the summer, even without significant temperature increases. People over the age of 65 also take multiple medications to treat various health problems.
“It's a medical axiom that combining these medications increases the risk compared to taking one medication at a time,” Harper says. He explains that it is not yet understood which drug combinations pose the greatest risk.
Social and economic factors also influence the increase in risk.
According to Harper, those in manual professions may be exposed to a lot of heat, and there are those who live outdoors without sun protection, and even in urban areas there may be a significant thermal effect, and those who live there cannot afford the cost of air conditioning. (Urban heat islands refer to densely populated areas with few trees and large expanses of dark concrete that absorb heat.)
Cecilia Ahanono, MD, a physician assistant in emergency medicine and an assistant professor at Touro University of Southern Nevada, witnessed one such case firsthand recently.
While participating in a community health awareness event in Las Vegas, when temperatures reached around 43 degrees Celsius, she saw a man in his 60s sleeping in a park. “He was pale, sweating profusely, and had a rapid heartbeat,” she says.
The man, who was taking diuretics and SSRIs, did not realize how high his body temperature was.
Ahanono describes the situation as "he did what most of us do, and thought his symptoms were due to the extreme heat." But after further questioning him, she discovered another possible reason: his medications.
Ahanono quickly advised the man to follow basic heat safety rules, drink more water, and avoid exposure to the sun during peak hours, and provided him with a list of nearby cooling centers. She also warned him of more serious symptoms to watch out for that could indicate heat stroke, a potential medical emergency.
“If there is any change in mental status or confusion, or if the person is not behaving normally, he or she should be taken immediately to the nearest emergency department,” she says.
Harper advises that there is a need for better training and greater awareness among doctors themselves about the relationship between temperature and medications.
As for Caroline Freycinet, she did not think about stopping taking her medication, and she says: “The medication is very effective for me.”
She confirmed that she felt reassured after knowing that what happened to her was a side effect of her medications, and not another health problem.
She adds: "This confirms to me that the matter is real, and not just a passing symptom. This in itself helped me a lot."
IMPORTANT NOTICE: All information in this article is for general informational purposes only and is not a substitute for advice from healthcare professionals.
