Introduction
Benztropine mesylate is a synthetic anticholinergic agent used primarily for the treatment of Parkinson's disease and drug-induced extrapyramidal symptoms. As a centrally acting antimuscarinic agent, it represents an important therapeutic option in neurological and psychiatric practice, particularly for managing medication-induced movement disorders.
Mechanism of Action
Benztropine exerts its therapeutic effects through competitive inhibition of acetylcholine at muscarinic receptors in the central nervous system. It functions by restoring the balance between dopamine and acetylcholine in the basal ganglia, which is disrupted in Parkinsonian syndromes. The drug also possesses antihistaminic properties due to its structural similarity to diphenhydramine, contributing to its anti-Parkinsonian effects.
Indications
- Treatment of Parkinson's disease (all forms)
- Drug-induced extrapyramidal symptoms (except tardive dyskinesia)
- Acute dystonic reactions
Dosage and Administration
Adults:- Parkinsonism: 0.5-6 mg daily in divided doses (start with 0.5-1 mg daily)
- Drug-induced EPS: 1-4 mg once or twice daily
Pharmacokinetics
Absorption: Well absorbed from GI tract Distribution: Crosses blood-brain barrier; protein binding: Moderate Metabolism: Hepatic metabolism via oxidation Elimination: Renal excretion (50% unchanged); half-life: 6-48 hours Onset of action: Within 1-2 hours orally; minutes parenterallyContraindications
- Hypersensitivity to benztropine or related compounds
- Angle-closure glaucoma
- Myasthenia gravis
- Gastrointestinal obstruction
- Megacolon
- Tachycardia
- Prostatic hypertrophy with urinary retention
Warnings and Precautions
- Elderly patients: Increased sensitivity to anticholinergic effects
- Mental impairment: May cause confusion, memory disturbances
- Heat prostration: Risk of heat stroke in hot environments
- Abrupt withdrawal: May exacerbate Parkinsonian symptoms
- Pregnancy: Category C (use only if benefit justifies risk)
- Breastfeeding: Excreted in milk; not recommended
Drug Interactions
- Other anticholinergics: Additive effects (antihistamines, TCAs)
- Alcohol: Enhanced CNS depression
- Dopamine agonists: Potential synergistic effects
- Haloperidol: May decrease haloperidol levels
- Digoxin: Increased digoxin absorption
- Ketoconazole: May increase benztropine levels
Adverse Effects
Common (≥1%):- Dry mouth
- Blurred vision
- Constipation
- Urinary retention
- Drowsiness
- Dizziness
- Confusion/disorientation
- Hallucinations
- Tachycardia
- Hyperthermia
- Angle-closure glaucoma
- Neuroleptic malignant syndrome (with withdrawal)
Monitoring Parameters
- Therapeutic response and symptom control
- Mental status changes
- Intraocular pressure (baseline and periodic)
- Renal function
- Signs of urinary retention
- Bowel function
- Heart rate and rhythm
- Temperature regulation in hot environments
Patient Education
- Take with food if GI upset occurs
- Avoid alcohol and other CNS depressants
- Use caution when driving or operating machinery
- Maintain adequate hydration, especially in warm weather
- Report any vision changes, urinary difficulties, or constipation
- Do not stop abruptly without medical supervision
- Use sugar-free lozenges or gum for dry mouth
- Rise slowly from sitting/lying position to prevent dizziness
References
1. National Institutes of Health. LiverTox: Benztropine. 2020 2. American Society of Health-System Pharmacists. AHFS Drug Information. 2023 3. Factor SA, et al. Parkinson's Disease: Therapeutic Options. Neurol Clin. 2020 4. Pharmaceutical Press. Martindale: The Complete Drug Reference. 2022 5. FDA Prescribing Information: Cogentin (benztropine mesylate) 6. Jankovic J. Parkinson's disease: clinical features and diagnosis. J Neurol Neurosurg Psychiatry. 2008 7. Miller LG. Herbal medicinals: selected clinical considerations. Arch Intern Med. 1998