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These Medications Can Be Dangerous to Take During the Summer

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Medically reviewed by Jonathan Pascucci, PharmD. 

When temperatures increase, it’s important to protect yourself from the heat. And while most people know to do things like drink more water and stay in air conditioning or shade, it’s easy to forget that your medications can also be dangerously affected by summer. Excessive heat mixed with medications can lead to decreased sweating, increased risk of dehydration and other side effects, so it’s important to talk with your doctor about potential risks of your own medications and how to use them carefully as summer heats up.

We’ve compiled a list of medications that may lead to heat-induced side effects. While not everyone experiences medication or its side effects the same way, there are some general risks that may be helpful to keep in mind. Even if you don’t see any of your medications listed here, it’s still a good idea to check with your doctor about any potential risks. Your doctor can also help you limit your risk of heat-induced side effects through strategies like drinking more water, staying out of the sun and using sunscreen.


Anticholinergics block acetylcholine, a neurotransmitter, to inhibit the nerve impulses that control involuntary muscle movement. These drugs are used to treat conditions including overactive bladder and incontinence, chronic obstructive pulmonary disease (COPD), asthma and Parkinson’s disease.

However, these drugs can also make you sweat less, which increases your body temperature and can be dangerous in high heat.

A few anticholinergic drugs include:

  • Benztropine mesylate (Cogentin)
  • Dicyclomine (Bentyl)


Doxycycline is used to treat bacterial infections, most famously Lyme disease. One side effect is that it can cause sun sensitivity, resulting in sunburns or an itchy, red rash.

Fentanyl Transdermal Patch

Fentanyl is a powerful opioid that can be administered through a sticky patch placed on the skin. In prolonged heat exposure, however, too much medication may be released at once. In addition to excessively hot weather, users should be careful while using a sauna, hot tub or electric heating pad over the patch.


Antidepressants create changes in the brain’s chemistry and impact the neurotransmitters in the brain, which can interfere with temperature regulation and cause excessive sweating. Some antidepressants can also cause photosensitivity, resulting in an itchy, inflamed reaction on your skin. Antidepressants are often used to treat other illnesses besides depression. For example, the selective serotonin and norepinephrine reuptake inhibitor (SSNRI) Cymbalta (generic name: duloxetine) is an antidepressant also commonly used to treat fibromyalgia.

A few antidepressants include:

  • Amitriptyline (Elavil)
  • Doxepin (Sinequan)
  • Nortriptyline (Pamelor)
  • Duloxetine (Cymbalta) — may cause hyperhidrosis specifically
  • Fluoxetine (Prozac) –may cause hyperhidrosis specifically


Antihistamines are used to treat allergies by blocking histamine produced during an allergic reaction, and may decrease sweating.

A few antihistamines include:

  • Diphenhydramine (Benadryl)
  • Cyproheptadine (Periactin)
  • Promethazine (Phenergan)


Diuretics, also known as “water pills,” are typically used to treat high blood pressure. They work by increasing the amount of water and salt expelled through urine and decreasing the amount of fluid in your blood vessels.  By decreasing the fluids in your body, they can lead to dehydration, making it important that you stay hydrated on those sweltering summer days.


Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat pain and inflammation and have been known to make a very small percentage of users more sensitive to the sun. Users are advised to wear sunscreen and protective clothing.

A few NSAIDs include:

  • Ibuprofen (Advil, Motrin)
  • Diclofenac (Voltaren)
  • Naproxen (Aleve)


Methotrexate can be used to treat autoimmune diseases like rheumatoid arthritis, Crohn’s disease and psoriasis. It can make your skin more sensitive to UV light, and can also make psoriasis sores worse. Patients are encouraged to wear protective clothing and sunscreen.

And one last note: Drugs’ potency may also be affected when stored in particularly high temperatures, so make sure to keep them in a cool, dry place.

Jonathan Pascucci, PharmD, is the pharmacy manager at a major national pharmacy and a professor at Touro College of Pharmacy.

Getty photo by diego_cervo

Originally published: July 6, 2018
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