Some medicines, called antipsychotic drugs, that are used to treat schizophrenia and other mental disorders can cause side effects that are similar to the symptoms of Parkinson's disease. The patient does not have Parkinson's disease, but he or she may experience shaking in muscles while at rest, difficulty with voluntary movements, and poor muscle tone. These symptoms are similar to the symptoms of Parkinson's disease.
One way to eliminate these undesirable side effects is to stop taking the antipsychotic medicine. Unfortunately, the symptoms of the original mental disorder usually come back, so in most cases simply stopping the antipsychotic medication is not a reasonable option. Some drugs such as biperiden that control the symptoms of Parkinson's disease also control the parkinsonian side effects of antipsychotic medicines.
Biperiden works by restoring the chemical balance between dopamine and acetylcholine, two neurotransmit-ter chemicals in the brain. Taking biperiden along with the antipsychotic medicine helps to control symptoms of the mental disorder, while reducing parkinsonian side effects. Biperiden is in the same family of drugs (commonly known as anticholinergic drugs) as benztropine, amantadine, and trihexyphenidyl.
Biperiden is available in 2-mg tablets. For the treatment of tremor, poor muscle tone, and similar parkinsonian side effects, the dose of biperiden is 2 mg orally one to three times daily. Parkinson-like side effects caused by antipsy-chotic drugs may come and go, so biperiden may not be needed on a regular basis. Biperiden may also be prescribed to prevent these side effects before they actually occur. This is called as prophylactic (preventative) therapy.
Biperiden should never be used in children under age three. It should be used cautiously and with close physician supervision in older children and in the elderly. Biperiden, like all anticholinergic drugs, decreases sweating and the body's ability to cool itself. People who are unaccustomed to being outside in hot weather should take care to stay as cool as possible and drink extra fluids. People who are chronically ill, have a central nervous system disease, or who work outside during hot weather may need to avoid taking biperiden.
People who have the following medical problems may experience increased negative side effects when taking biperiden. Anyone with these problems should discuss their condition with their physician before starting the drug:
• glaucoma, especially closed-angle glaucoma
• intestinal obstruction
• urinary bladder obstruction
Although rare, some patients experience euphoria while taking biperiden and may abuse it for this reason. Euphoria can occur at doses only two to four times the normal daily dose. Patients with a history of drug abuse should be observed carefully for biperiden abuse.
Although biperiden helps control the side effects of antipsychotic drugs, it can produce side effects of its own. A person taking biperiden may have some of the following side effects, which may vary in intensity:
• blurred vision
• nausea or vomiting
• increased heart rate
• urinary retention
Dry mouth, if severe to the point of causing difficulty in speaking or swallowing, may be managed by dosage reduction or temporary discontinuation of the drug. Chewing sugarless gum or sucking on sugarless candy may also help to increase the flow of saliva. Some artificial saliva products may give temporary relief.
Men with prostate enlargement may be especially prone to urinary retention. Symptoms of this problem include having difficulty starting a urine flow and more difficulty passing urine than usual. This side effect may be severe and require discontinuation of the drug. Urinary retention may require catheterization. People who think they may be experiencing any side effects from this or any other medication should tell their physicians.
Patients who take an overdose of biperiden are treated with forced vomiting, removal of stomach contents and stomach washing, activated charcoal, and respiratory support if needed. They are also given physostigmine, an antidote for anticholinergic drug poisoning.
When drugs such as biperiden are taken with antide-pressants such as amitriptyline, imipramine, trim-ipramine, desipramine, nortriptyline, protriptyline, amoxapine, and doxepin, as well as with many antihis-tamines that also have anticholinergic properties, the effects of biperiden are usually intensified.
Drugs such as biperiden decrease the speed with which food moves through the stomach and intestines. Because of this, it is possible that the absorption of some drugs may be enhanced by biperiden. Patients receiving biperiden should be observed for unusual responses to other drugs they might be taking.
American Society of Health-System Pharmacists. AHFS Drug Information 2002. Bethesda: American Society of Health-System Pharmacists, 2002. DeVane, C. Lindsay, Pharm.D. "Drug Therapy for Psychoses " In Fundamentals of Monitoring Psychoactive Drug Therapy. Baltimore: Williams and Wilkins, 1990.
Jack Raber, Pharm.D.
Biphetamine see Amphetamines
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