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Your ‘Regular’ Medications Can Cause Hyperthermia

July 11, 2008

Q: You mentioned several types of medications that increase the risk of hyperthermia during hot weather. Would you provide a detailed list?

A: Hot weather can cause the body to overheat, called hyperthermia. The evaporation of sweat is the body’s primary way of cooling off.

Numerous medications impair the body’s ability to sweat and so boost the risk for heat exhaustion and heat stroke, conditions covered in a recent column.

The chief culprits are drugs with anticholinergic effects, including antihistamines, antidepressants, antipsychotics, anti-Parkinson’s disease agents, anti-nausea/motion sickness agents, anti-diarrheal agents, antispasmodic agents, anti-asthma drugs and antiarrhythmic heart drugs.

The following is the detailed list you requested, by generic name:

_Antihistamines: chlorpheniramine, clemastine, cyproheptadine, dexchlorpheniramine, diphenhydramine, hydroxyzine

_Antidepressants: amitriptyline, clomipramine, doxepin, imipramine, mirtazapine, nortriptyline, protriptyline

_Antipsychotics: chlorpromazine, clozapine, fluphenazine, haloperidol, mesoridazine, olanzapine, pimozide, prochlorperazine, promethazine, risperidone, thioridazine, thiothixene, quetiapine, ziprasidone

_Anti-Parkinson’s agents: amantadine, benztropine, biperiden, trihexyphenidyl

_Anti-nausea/motion sickness agents: dimenhydrinate, meclizine, prochlorperazine, promethazine, scopolamine (e.g., ear patch for motion sickness), trimethobenzamide

_Anti-diarrheal agents: diphenoxylate/atropine

_Antispasmodic agents: belladonna alkaloids, clidinium, darifenacin, dicyclomine, flavoxate, hyoscyamine, oxybutynin, propantheline, solifenacin, tolterodine, trospium

_Anti-asthma drugs: ipratropium bromide, tiotropium

_Antiarrhythmic heart drugs: disopyramide, quinidine, procainamide

If you’ve taken one these medications, you’ve likely experienced one or more of the following anticholinergic side effects: dry mouth, dry skin, blurred vision, rapid heartbeat, constipation and urinary retention. (The last-mentioned effect further worsens urination difficulties caused by an enlarged prostate.)

Anticholinergic drugs also tend to cause confusion and impaired memory, particularly in elderly persons. In fact, they directly oppose the effects of drugs prescribed to improve memory in those with Alzheimer’s disease.

Dehydration, or excessive loss of body water, boosts the risk of hyperthermia.

Drugs with potential to cause diarrhea or nausea/vomiting can lead to dehydration due to loss of body water. These include magnesium-containing antacids, laxatives, misoprostol and exenatide (Byetta injection for diabetes).

Aspirin and other salicylates can contribute to dehydration by increasing perspiration and the rate and depth of breathing. (Each exhalation takes a bit of body water with it).

Amphetamines, carbenicillin, dexmethylphenidate, methylphenidate, topiramate and zonisamide raise the risk for hyperthermia in other ways.

Use extra care not to overheat during hot weather if you take any of these medications.

If you need help sorting out whether any of your meds might put you at greater risk, check with your pharmacist.

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(Richard Harkness is a consultant pharmacist, natural medicines specialist and author of eight published books. Write him at 1224 King Henry Drive, Ocean Springs, MS 39564 or rharkn@aol.com.)

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(c) 2008, The Sun Herald (Biloxi, Miss.).

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