Benztropine
Benztropine is a generic medication for the drug :
Benztropine medication comes in several different strengths; click on the strength you need to view prices from pharmacies competing to earn your business.
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Benztropine 0.500 mg
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Benztropine 1 mg
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Benztropine 2 mg
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Pharmacology
Pharmacokinetics
When given orally, benztropine has an onset of action of between 1 and 2 hours. When given by im or iv injection, the onset of action is within minutes. Benztropine binds extensively, approximately 95%, with serum proteins. Benztropine crosses the blood-brain barrier.
Indications
The symptomatic treatment of all etiologic groups of parkinsonism and drug-induced extrapyramidal reactions.
Precautions
Geriatrics
Geriatric patients are frequently more sensitive to the adverse effects of anticholinergic medications, including benztropine. These patients may require lower doses, especially at the onset of therapy, and slower dose titration than younger adults.
Drug Interactions
Amantadine: Benztropine and other anticholinergic drugs may potentiate CNS side effects of amantadine. Monitor patients for this effect and reduce the dose of one or both drugs as necessary.
Anticholinergics: Additive anticholinergic effects may occur when benztropine is used concurrently with drugs such as amantadine, atropine, MAO inhibitors, tricyclic antidepressants and phenothiazines. Paralytic ileus (sometimes fatal), hyperthermia and heat stroke may occur. Patients should be advised to report gastrointestinal problems, fever or heat intolerance promptly.
Cholinesterase Inhibitors: Benztropine and other anticholinergic drugs that readily penetrate the blood-brain barrier may, theoretically, interfere with the action of donepezil and other centrally-acting cholinesterase inhibitors. Conversely, cholinesterase inhibitors have the potential to interfere with the activity of anticholinergic medications.
CNS depressants: Benztropine may enhance the CNS depressant effects of drugs including alcohol, antiepileptics, barbiturates, MAO inhibitors, opioid analgesics, phenothiazines and tricyclic antidepressants.
Occupational Hazards
Benztropine may impair mental and/or physical abilities required for performance of hazardous tasks such as operating machinery or driving a motor vehicle.
Lactation
It is not known if benztropine is excreted into breast milk.
Children
Benztropine is not recommended in children under 3 years of age (see Contraindications).
Pregnancy
The safe use of this drug in pregnancy has not been established.
Supplied
Not currently available for this CPhA monograph. Please consult individual product monographs.
Contraindications
Benztropine is contraindicated in patients with a known hypersensitivity to benztropine or to any of its excipients, in patients with angle-closure glaucoma or severe ulcerative colitis. Because of its adverse anticholinergic effects, this drug is contraindicated in children under 3 years of age and should be used with caution in older children.
Warnings
Benztropine, alone or in combination with antipsychotics or anticholinergics, may cause anhidrosis and/or hyperthermia, which may be fatal. Patients should avoid becoming overheated from prolonged exposure to high environmental temperatures and/or from sustained heavy exercise. The elderly, the chronically ill, alcoholics and those with CNS disease may be particularly vulnerable. If there is evidence of anhidrosis, the dosage should be decreased so that the ability to maintain body temperature equilibrium by perspiration is not impaired. Benztropine should also be used with caution in patients with fever.
Adverse Effects
Genitourinary
urinary retention and/or dysuria.
Endocrine
hyperthermia, anhidrosis, heat stroke.
Gastrointestinal
dry mouth, constipation, nausea, vomiting, rarely paralytic ileus. Dry mouth may be relieved by the use of a saliva substitute or sugarless gum.
Central Nervous System
nervousness, impaired memory, numbness of fingers, listlessness, depression. Mental confusion, excitement and visual hallucinations with high doses.
Hypersensitivity
skin rash may occur occasionally.
Skeletomuscular
weakness and inability to move particular muscle groups.
Ophthalmic
blurred vision, mydriasis.
Cardiovascular
tachycardia, arrhythmias.
Overdose
Symptoms
Symptoms of benztropine overdose are primarily extensions of its anticholinergic actions. Tachycardia, flushed/hot/dry skin, dry mucous membranes, mydriasis and blurred vision are common. Drowsiness, nervousness and lightheadedness may progress to, or alternate with, agitation, confusion, delirium and hallucinations, especially in children or the elderly. Urinary retention, hyperthermia, thirst and decreased gastrointestinal motility are also seen. Susceptible patients may experience angle-closure glaucoma. In severely poisoned patients coma or seizures may occur. Psychosis, rash, dystonic reactions, ataxia, weakness, respiratory depression, cardiac arrhythmia and rhabdomyolysis have been reported.
Treatment
Treatment is symptomatic and supportive. Consider administration of a single dose of activated charcoal to patients who present within 4 hours, since gastric emptying may be delayed. Monitor vital signs, urine output and ECG in severely poisoned patients. Maintain respiration and fluid and electrolyte balance. Hyperthermia can be managed with physical measures and control of agitation. Seizures may be treated with iv benzodiazepines. Physostigmine, a reversible cholinesterase inhibitor available through Health Canada's Special Access Programme, may be considered for management of delirium upon consultation with a regional poison control centre, and is preferable to benzodiazepines in many patients. Avoid antipsychotics and other anticholinergic drugs. If rhabdomyolysis does occur, hydration with crystalloid is the mainstay of treatment. Peritoneal dialysis and hemodialysis are of no value in the management of benztropine overdose.
Dosage
Benztropine should be used orally in all cases when patients are able to take oral medication. When patients are unable to do so, or when more rapid response is desired, benztropine mesylate may be administered iv or im.
Since there is no significant difference in onset of effect after iv and im injection, there is usually no need to give benztropine iv. It is quickly effective by either route, with improvement sometimes noticeable a few minutes after injection.
Because benztropine has cumulative action, therapy should be initiated with a low dose, which is increased gradually by 0.5 mg increments at 5- or 6-day intervals, to the smallest amount necessary for optimal relief without excessive adverse effects. The maximum adult dose is 6 mg. Generally, older patients, thin patients and those with vascular parkinsonism cannot tolerate large doses. Most patients with postencephalitic parkinsonism need larger doses and tolerate them well. Patients with dementia or mental confusion are usually poor candidates for therapy.
Vascular (Arteriosclerotic), Idiopathic and Postencephalitic Parkinsonism: Therapy may be initiated with a single daily dose of 0.5 to 1 mg at bedtime. In some patients, this will be adequate; in others, 4 to 6 mg daily may be required.
Some patients experience optimal relief by taking the entire daily dose at bedtime; others respond more favorably to divided doses 2 to 4 times daily.
Therapy with other agents should not be terminated abruptly when therapy with benztropine is initiated, but may be reduced or discontinued gradually. Benztropine may be administered concomitantly with levodopa or a levodopa/carbidopa combination, in which case the dose of each may need adjustment.
Drug-induced Extrapyramidal Symptoms: Benztropine mesylate should not be used beyond the period necessary to counteract the extrapyramidal manifestations. In the majority of patients, the use of anticholinergic agents is not required after 3 months of antipsychotic therapy. Although therapy with the drug causing parkinsonism can frequently be continued without change of dosage when adjunctive therapy with benztropine is used, a reduction in dosage of the psychotropic drug might be indicated.
Patients must be closely observed for severe reactions and benztropine discontinued temporarily if they appear (see Precautions and Adverse Effects).
Adults: In treating extrapyramidal disorders caused by antipsychotics, the recommended dosage is 1 to 4 mg once or twice daily, orally or parenterally. Dosage must be individualized.
In acute dystonic reactions, 2 mg of benztropine given im or iv relieves the condition quickly. After that, 1 to 2 mg given orally twice daily for 2 to 3 days usually prevents recurrence.
When extrapyramidal disorders develop soon after initiation of treatment with antipsychotics, they are likely to be transient. One to 2 mg given orally 2 or 3 times daily usually provides relief within 1 or 2 days. After 1 or 2 weeks, the need for continued therapy with benztropine should be re-evaluated.
Children ≥ 3 years of age: 0.02 to 0.05 mg/kg/dose po/im/iv once or twice daily.
