Posted by Sunnely on August 2, 2001, at 22:22:09
In reply to Hyperthermia with Lithium and Chlorpromazine, posted by annettehunt52 on August 2, 2001, at 15:40:42
HEAT-RELATED SIDE EFFECTS OF PSYCHOTROPIC MEDICATIONS
Two main properties of medications are responsible for the majority of heat-related adverse events reported during the summer months. The first, dopaminergic blockade as seen with antipsychotics, has long been known to interfere with central thermoregulation in mammals. Body temperature is controlled in the hypothalamus by regulation of various factors, such as metabolism (via control of thyroid activity), peripheral vasoconstriction or dilation, and rate of perspiration. Dopamine receptor blockers directly interfere with the ability of the hypothalamus to maintain a stable body temperature that tends to follow ambient air temperature much more than is usually allowed by the hypothalamus. In addition, once body temperature begins to rise, there is an increase in cellular metabolism (13% for every degree centrigrade rise in core temperature). These factors can lead to a vicious cycle of ever increasing body temperature, heatstroke, and finally death. In the hot summer months, the susceptibility to heaststroke is dramatically increased in patients taking antipsychotic drugs. Other risk factors for hyperthermia include advanced age, a history of central nervous system injury, and the concomitant ingestion of anticholinergic agents.
Muscarinic blockade or anticholinergic potency is the second property of drugs that contributes to heat-related clinical adverse events. The mechanism by which these various agents cause problems is straightforward. They simply interfere with the ability to perspire in a dose-related manner. One needs to remember that peripheral vasodilation and perspiration are the two main mechanisms by which the body dissipates heat. In anticholinergic toxicity, the patient usually present febrile, flushed, with cessation of sweating.
One of the challenges for physicians is keeping track of all the antipsychotic and anticholinergic medications available. All antipsychotic drugs, even clozapine, block dopamine. All antipsychotics, especially clozapine have anticholinergic properties. Reglan (metoclopramide), Compazine (prochlorperazine), and Asendin (amoxapine) are often overlooked dopamine blocking agents. All tricyclic antidepressants and all antihistamines also have anticholinergic properties. Most over-the-counter sleep aids and some cold preparations contain antihistamines. At higher doses even the SSRIs show some anticholinergic acitivity.
What then can be done to avoid the episodes of hyperthermia associated with hot summer temperature? First, minimize the anticholinergic load prescribed to the patient as much as possible. Consider prescription hypnotics for patients using the over-the-counter sleep aids. For the high-risk population (i.e., the elderly) requiring antipsychotics, consider amantadine, if necessary, rather than an anticholinergic. Warn patients that they are at risk for developing heatstroke and that they should dress appropriately in summer and avoid strenuous activity during hot spells. Those without air conditioning should at least attempt to sleep with windows open. Lastly, patients and their families need to understand that if someone begins to develop symptoms of hyperthermia (headache, nausea, lethargy, flushed facies, and confusion), immediate attention could be life-saving.
HEATSTROKE is a medical emergency that occurs when the body's temperature-regulating mechanism breaks down - the person can't sweat. Internal body temperature can rise as high as 108 which can cause irreversible brain damage and death.
HEATSTROKE FACTS:
More likely when outside temperature is very hot
More likely when taking the following medications:
Antipsychotics like chlorpromazine, thioridazine, mesoridazine, clozapine, risperidone, olanzapine, quetiapine, and ziprasidone; Antiparkinsonian medications like benztropine, trihexyphenidyl, procyclidine, bidperiden; Antihistamines such as diphenhydramine and chlorpheniramine; Antidepressants especially tricyclics like imipramine, amitriptyline, nortriptyline, doxepin, desipramine, and protriptyline;
Drugs for diabetes, thyroid condition, allergies, heart or circulatory problems.
PEOPLE AT HIGHER RISK FOR HEAT-RELATED ILLNESS:
1. Users of some medications especially certain psychotropic drugs, drugs for movement disorders, allergies, heart or circulatory problems.
2. Older adults
3. Infants and young children
4. People with disabilities
5. Chronic heart or lung problems
6. Overweight persons
7. Those who work outdoors or in hot settings
8. Isolated persons who won't know when or how to cool off or call for help
THINGS YOU CAN DO TO PREVENT HEAT-RELATED ILLNESS:
1. Keep your living space cool. Cover windows to keep direct sun out. If you don't have air conditioner, open windows to let air circulate. When it's hotter than 95 degrees, use fans to blow hot air out of the window, rather than to blow hot air on your body. Basements or ground floors are often cooler than upper floors.
2. Drink plenty! Eat lightly!. Your body needs plenty of water or juice. Avoid alcohol or caffeinated beverages - they can cause the body to lose more fluids than they replace. Don't wait for thirst - drink frequently through the day. Avoid hot or heavy meals.
3. Spend time in cool places - shopping malls, the movies or a friend or family's house if your house if too hot.
4. Slow down! Limit physical activity. Plan any outings or exertion for the coolest parts of the day (early morning or after dark).
5. Wear lightweight, loose-fitting, ligtht-colored clothes, and add a hat or umbrella to keep your head cool. Don't forget sun-screen!
6. If you feel warm, easy ways to cool off include a cool (not cold) bath or shower (works faster than an air conditioner); a trip to an air conditioned lobby or the basement; or cold wet rags applied to neck, head and limbs.
7. Remain with other people.
8. Never leave children, disabled persons or pets in a car-even briefly! Temperatures in a car can become life-threatening within minutes.
9. Check on elderly relatives and neighbors and those taking medications.
10. Infants should drink breast milk or formula to get the right balance of water, salts and energy. Don't dilute formula beyond what the instructions say unless instructed by your doctor. You may supplement your infant's fluids with an additional 4 to 8 ounces of water per day.
11. Be aware that the medications listed above may not only keep a person from sweating, but may affect their heat perception, preventing them from feeling overheated even if they are.
12. Don't stop medicines unless your doctor says so! Take extra care to stay cool, and ask your doctor or pharmacist for any special heat advice.
WARNING SIGNS OF HEATSTROKE:
1. Nausea
2. Headache
3. Feeling poorly
4. Weakness
5. Irritability
6. Fast pulse
7. Rapid breathing
8. Dizziness
9. Hot OR dry skin
10. Confusion
11. Vomiting
12. Diarrhea
Get cool or get help NOW if you feel: Dizziness, headache, muscle cramps, nausea or vomiting, weakness.
Call 911 for these symptoms: Hot, dry skin, confusion, unconsciousness, chest pain, shortness of breath.
*********************************> I understand Lithium and Chlorpromazine can have a problematic effect on the heat regulatory system.
> I personally had a problem with heatstroke recently ...severe vertigo, nausea and headache lasting 36 hours... during a strenuous walking holiday at which time i was taking both Lithium and Chlorpromazine.
> I am trying to find some articles about this problem and would be grateful if anyone can help with urls or articles.
> Thank you
> Annette
poster:Sunnely
thread:73141
URL: http://www.dr-bob.org/babble/20010731/msgs/73189.html