Benztropine mesylate tablets for treatment of parkinsonism and drug-induced movement disorders

Benztropine mesylate tablets are a medication used primarily as an adjunct treatment for various forms of parkinsonism. They are also helpful in managing extrapyramidal symptoms caused by neuroleptic drugs, such as phenothiazines. The tablets come in 0.5 mg, 1 mg, and 2 mg strengths for oral administration.

Benztropine mesylate tablets are indicated for:

• Adjunctive therapy for all forms of parkinsonism, including idiopathic and postencephalitic parkinsonism.
• Control of extrapyramidal disorders caused by neuroleptic (antipsychotic) drugs, except tardive dyskinesia.

The medicine should be used with caution in pediatric patients over three years of age and is contraindicated in children under three years due to atropine-like side effects.

Benztropine mesylate

Benztropine mesylate acts primarily through its anticholinergic properties, which help restore the balance between acetylcholine and dopamine in the brain, alleviating motor symptoms of parkinsonism. It also has antihistaminic activity, though this is not considered therapeutically important for its use in parkinsonism and extrapyramidal disorders.

General dosing guidelines

Dosage must be individualized based on patient age, weight, and condition treated. Because of cumulative action, therapy begins with a low dose, gradually increasing at five- or six-day intervals by 0.5 mg increments, up to a maximum of 6 mg daily or until optimal relief is achieved without excessive side effects.

Parkinsonism

• Usual dose: 1 to 2 mg per day (range 0.5 to 6 mg orally).
• Idiopathic parkinsonism: Start with 0.5 to 1 mg at bedtime; some may need up to 4 to 6 mg daily.
• Postencephalitic parkinsonism: Start typically with 2 mg daily in one or more doses; sensitive patients may begin at 0.5 mg at bedtime.
• Doses may be taken once daily, often at bedtime, or divided into two to four doses depending on patient response.

Drug-induced extrapyramidal disorders

• Recommended dose is 1 to 4 mg once or twice daily orally.
• For acute symptoms shortly after neuroleptic initiation, 1 to 2 mg two or three times daily often relieves symptoms within 1 to 2 days.
• After 1 to 2 weeks of treatment, withdrawal should be attempted to assess ongoing need; rechallenge if symptoms recur.

Important administration notes

• Do not abruptly stop other antiparkinsonian drugs when starting benztropine; taper those drugs gradually.
• May be used concomitantly with carbidopa-levodopa or levodopa, with dose adjustments as needed.
• Choose dose timing (bedtime vs divided doses) based on symptom relief and tolerance.

• Hypersensitivity to benztropine mesylate tablets.
• Children under three years due to risk of severe atropine-like side effects.

• Safety during pregnancy has not been established.
• May impair mental and physical abilities needed for hazardous tasks such as driving.
• When used with phenothiazines, haloperidol, or other anticholinergic/antidopaminergic drugs, promptly report gastrointestinal symptoms, fever, or heat intolerance due to risk of paralytic ileus, hyperthermia, or heat stroke—these may be fatal.
• Caution during hot weather because benztropine may cause decreased sweating (anhidrosis) leading to hyperthermia.
• Use caution in populations at risk for impaired heat regulation: chronically ill, alcoholics, CNS disease, or those performing manual labor in heat.

Common side effects (mostly anticholinergic)

• Tachycardia
• Dry mouth (reduce dose or temporarily discontinue if severe)
• Constipation, nausea, vomiting
• Blurred vision, dilated pupils
• Mild urinary retention or dysuria

Serious or less common effects

• Paralytic ileus
• Toxic psychosis, confusion, disorientation, memory impairment, hallucinations
• Exacerbation of psychotic symptoms in patients with mental illness
• Heat stroke and hyperthermia
• Allergic skin reactions

Concurrent use with antipsychotics such as phenothiazines or haloperidol, and tricyclic antidepressants increases the risk of serious side effects like paralytic ileus, hyperthermia, and heat stroke. Close monitoring is advised.

The safety of benztropine mesylate in pregnancy has not been established. No specific breastfeeding information is provided.

Signs of overdose mirror atropine poisoning and antihistamine toxicity, including CNS depression or stimulation, confusion, hallucinations, muscle weakness, dry mouth, mydriasis, tachycardia, elevated blood pressure, nausea, vomiting, urinary retention, skin rash, delirium, coma, convulsions, respiratory arrest, anhidrosis, hyperthermia, glaucoma, and constipation.

Treatment includes administration of physostigmine salicylate 1 to 2 mg SC or IV to reverse anticholinergic symptoms, repeated after 2 hours if needed. Supportive care involves respiratory support, CNS symptom management, gastric decontamination (except if contraindicated), cooling measures for hyperpyrexia, and circulatory support.

Store tablets at controlled room temperature between 20° to 25°C (68° to 77°F). Dispense in a well-closed container as defined by USP requirements.