indication

For use as an adjunct in the therapy of all forms of parkinsonism and also for use in the control of extrapyramidal disorders due to neuroleptic drugs.

pharmacology

Benztropine is an anticholinergic used in the symptomatic treatment of all etiologic groups of parkinsonism and drug-induced extrapyramidal reactions (except tardive dyskinesia). Benztropine possesses both anticholinergic and antihistaminic effects, although only the former has been established as therapeutically significant in the management of parkinsonism. Benztropine's anticholinergic activity is about equal to that of atropine. Benztropine also inhibits dopamine reuptake via the dopamine transporter at nerve terminals.

mechanism of action

Benztropine is a selective M1 muscarinic acetylcholine receptor antagonist. It is able to discriminate between the M1 (cortical or neuronal) and the peripheral muscarinic subtypes (cardiac and glandular). Benztropine partially blocks cholinergic activity in the CNS, which is responsible for the symptoms of Parkinson's disease. It is also thought to increase the availability of dopamine, a brain chemical that is critical in the initiation and smooth control of voluntary muscle movement.

toxicity

Signs of overdose include confusion, nervousness, listlessness, hallucinations, dizziness; muscle weakness, ataxia, dry mouth, mydriasis, blurred vision, palpitations, tachycardia, elevated blood pressure, nausea, vomiting, dysuria, numbness of fingers, headache, delirium, coma, shock, convulsions, respiratory arrest, anhidrosis, hyperthermia, glaucoma, and constipation.

absorption

Onset of action is 1-2 hours following oral administration. The onset of action is within minutes when administered by IM or IV injection.

drug interactions

Donepezil: Possible antagonism of action

Galantamine: Possible antagonism of action

Haloperidol: The anticholinergic increases the risk of psychosis and tardive dyskinesia

Rivastigmine: Possible antagonism of action

Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Benztropine, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.

Trimethobenzamide: Trimethobenzamide and Benztropine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Triprolidine: Triprolidine and Benztropine, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.

Trospium: Trospium and Benztropine, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.