A heat wave can affect how your medications act.

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Hot weather can change the effectiveness of your medication and increase the risk of side effects. Getty Images

As the days get longer and the weather heats up, summer is nearly here — meaning it’s time for vacation, outdoor adventures, and occasionally a dip in the pool.

But the reasons why people enjoy the summer, the sun and the heat, are the exact reasons why some medications can have disastrous health complications.

The side effects of many prescription medications and even over-the-counter (OTC) medications could obscure the fun in the sun.

“Many types of medications may increase risk of harm from heat, including diuretics, beta blockers, certain antipsychotics, and antihistamines,” says Dr. Aaron Bernstein, co-director of the Center for Climate, Health and the Global Environment, Harvard T.H. Chan School of Public Health.

Here’s a look at how some common medications can be impacted by hot weather.

The popular antidepressant, amitriptyline (Elavil), and the overactive bladder medication, oxybutynin (Ditropan), can inhibit the body’s ability to regulate elevating body temperatures. Normally the body can open pores to release heat from the body in an effort to cool it. When taking these medications the body has less ability to sweat and cool down rising core temperatures, leading to increased internal body heat.

Even the commonly used Parkinson’s medication benztropine (Cogentin) inhibits the nerve impulses that allows the body to sweat. This inhibition raises body temperature and can be disastrous in high heat.

One of the most common effects of the summer months is dehydration. And although this is easily regulated with increased water consumption, several medications can make dehydration worse just by the way the medication works.

For example, diuretics such as furosemide (Lasix) can cause you to urinate more and even have less thirst. As a result, one’s risk of dehydration increases.

The body relies on its own regulatory mechanisms to control body temperature. However, there are some medications that can affect this regulatory system.

Medications that control behavior and mental health are also affected by rising internal body temperatures. Antipsychotic medications such as haloperidol (Haldol) and risperidone (Risperdal) block the signals to the brain letting it know that the body temperature is rising. When this occurs, the body has difficulty sweating and releasing excessive heat.

People who use antibiotics can also become victim to the effects of taking medications and heat exposure. Antibiotics like doxycycline, which is used to treat bacterial infections including Lyme disease, can increase one’s skin sensitivity leading to sunburns that are both itchy and painful.

Cipro and other fluoroquinolone antibiotics can also cause similar photosensitivity rashes.

In the summer, acne is on the rise as sweat glands begin to open more in warm months. As a result, medications to treat acne should be taken with caution. Retin-A or products that have salicylic acid can also cause an itchy and painful rash, which can dampen summer fun.

“One should be especially careful in the sun if taking doxycycline, Cipro, and Retin-A,” says Dr. Michele Green, a dermatologist in New York City. “These medications can potentially be photosensitive and cause burns of blisters or hyperpigmentation from the sun.”

Not all medications with heat sensitivity are prescription based. Over-the-counter antihistamines whose active ingredient is diphenhydramine (Benadryl) also decreases sweating, resulting in unintended increased body temperatures with harmful heat effects.

If you’re facing dehydration and you take nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen, you’re at an increased risk of renal failure and faster onset of heat stroke because of their damaging effects on the kidneys.

Heat-related illnesses and death are most commonly seen in newborns and the elderly, but everyone is susceptible.

According to the Centers for Disease Control and Prevention, between 1999 and 2010, more than 8,000 heat-related deaths were reported in the United States. Almost all these deaths were associated during the May through September months with the highest reported cases in Arizona, Texas, and California.

The Korey Stringer Institute at The University of Connecticut says prevention is key. They recommend avoiding being outdoors during the hottest parts of the day, many times in the early to mid-afternoon.

The institute also recommends drinking lots of water as hydration is an important aspect of heat stroke prevention. By wearing light-colored loose-fitting clothing and taking frequent breaks, people can help prevent the disastrous effects of heat.

It is important to check the side effect profile of medications of your loved ones because heat exhaustion and heat stroke can lead to confusion and they may not be able to take care of themselves if one of these complications were to arise.

“Special care to avoid the sun and use sunblock while taking medications during the summer is vital,” says Green.

While most people know to drink more water and to stay in air conditioning as often as they can during the summer months, it’s easy to forget that medications can also dangerously affect the body. Talking to your physician about potential risks associated with your own medication regimen is important to ensuring your safety as temperatures begin to rise.

Rajiv Bahl, MD, MBA, MS, is an emergency medicine physician and health writer. Learn more about him at his website.