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Caution: Some Drugs Might Make You More Sensitive to Heat

Huong Le, PharmD Candidate Class of 2011
Consumer Health Information Corporation and
Bernard J, Dunn School of Pharmacy, Shenandoah University

and

Dorothy L. Smith, Pharm.D.

CEO and President

Consumer Health Information Corporation

McLean, Virginia

 

Did you know that some medicines can make your body more sensitive to heat? These medicines can affect your body’s ability to regulate its temperature. This is why you should take extra care if you plan on spending time outdoors in hot weather or when using a hot tub or sauna. This can be dangerous and could even lead to heat stroke.

 

How does the body regulate its temperature?

Your body regulates its own temperature by continuously producing and getting rid of heat. For example, in a hot car when your skin feels hot, your body needs to cool off to lower its temperature to normal. It does this by increasing blood flow to the skin and sweating. Some drugs may interfere with these normal processes and cause the body to overheat. This can lead to heart and multiple organ failure and even death.

 

What drugs can interfere with your body’s temperature?

Heat illness, especially during a heat wave, has been linked to certain drugs known to affect body temperature.

Drugs that may make you more heat-sensitive

How they increase body temperature

  • Allergy drugs (loratadine, promethazine)
  • Muscle spasm drugs (atropine, scopolamine)
  • Belladonna alkaloids
  • Mental illness drugs  (thioridazine, chlorpromazine, prochlorperazine)
  • Major tranquilizers (phenothiazines, butyrophenones, thioxanthenes)
  • High blood pressure drugs (mecamylamine )

They  prevent sweating so the body cannot cool itself.

  • High blood pressure drugs (beta blockers)
  • Migraine drugs (triptanes)

These drugs decrease blood flow to the skin and the body cannot cool down.

  • Ephedrine/pseudoephedrine (OTC decongestant, Sudafed)
  • Cocaine
  • Attention-Deficit Hyperactivity Disorder (ADHD) drugs (amphetamines)

These drugs decrease blood flow to the skin and the body cannot cool down. They also increase muscle movement (seizures) and raise body temperature.


What are the warning signs?

Early warning signs that your body is more sensitive to heat and having trouble regulating your temperature are:

  • Weakness
  • Dizziness
  • Headache
  • Muscle cramps
  • Nausea
  • Vomiting
  • Body temperature between 100.4°F-104.9°F
  • Low blood pressure
  • Fast heartbeats


Mild heat illness may lead to heat stroke if left untreated. Heat stroke is an emergency situation where you need to go to the emergency room. Signs include:

  • All the early warning signs
  • Body temperature of at least 104.9°F
  • Confusion and coma
  • Throbbing headache
  • Unconsciousness
  • Red, hot and dry skin without sweating
 

 

Patient Information Tips to preventing heat illness

  • Be very careful with certain drugs that are known to cause heat- related illness. If you are not sure, ask your doctor what to do if you become overheated.
  • Limit time in saunas or spas (5 - 10 minutes at a time).
    Wear loose fitting, lightweight clothing that will allow sweating to help keep you cool.
  • Drink cool water on schedule to keep your body hydrated. Warning: Check with your doctor if he/she has limited your fluid intake before drinking more than allowed.
  • Do not drink alcohol or caffeinated beverages. They will make you lose more fluids. Too much fluid loss causes you to stop sweating. Then you are unable to cool yourself.
  • Avoid staying inside a hot car. When a car is parked in the sun, its original temperature can rise by 20°F (e.g. 100°F to 120°F) in just 10 minutes.
  • Take frequent cooling breaks, staying in shaded areas or air-conditioned places.
  • Avoid heavy outdoor activity when the sun is hottest (10AM to 6PM).

 

If you feel you have heat exhaustion or a heat stroke

  • Take off as much clothing as possible.
  • Shower, bathe or apply wet towels with cool water often.
  • Drink plenty of fluids like water (do not drink caffeinated or alcoholic beverages). Do not drink fluids if you have difficulty swallowing!
  • Stay in shaded or air conditioned places.
  • Call 911 for help.
  • Go to the emergency room if you become confused, lose consciousness, vomit frequently or are unable to sweat or urinate.

 

Do not stop taking your drugs without talking to your doctor or pharmacist first! There are simple patient education steps you can take to prevent heat illness.

Certain drugs can cause you to become more sensitive to heat. This is especially true for young children and the elderly. Know which drugs these are and ask your doctor or pharmacist about any precautions you should take. By taking simple steps such as not staying inside a hot car, exercising when the sun is at its hottest or forgetting to keep yourself cool, you can prevent your drugs from causing heat related illness.  Always ask your doctor for patient information materials you can take home so that you don't have to try to remember everything from the office visit.

 

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