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Pharmacologic class: Anticholinergic
Therapeutic class: Antiparkinsonian
Pregnancy risk category C
Inhibits cholinergic excitatory pathways and restores balance of dopamine and acetylcholine in CNS, thereby decreasing excess salivation, rigidity, and tremors (parkinsonian symptoms)
Injection: 1 mg/ml in 2-ml ampules
Tablets: 0.5 mg, 1 mg, 2 mg
Indications and dosages
Adults: Initially, 1 to 2 mg/day P.O. or I.M. at bedtime or in two or four divided doses. Dosage range is 0.5 to 6 mg/day.
➣ Acute dystonic reactions
Adults: Initially, 1 to 2 mg I.M. or I.V., then 1 to 2 mg P.O. b.i.d.
➣ Drug-induced extrapyramidal reactions (except tardive dyskinesia)
Adults: 1 to 4 mg P.O. or I.M. once or twice daily
• Elderly patients
• Excessive salivation
• Hypersensitivity to drug
• Angle-closure glaucoma
• Tardive dyskinesia
• Children younger than age 3
Use cautiously in:
• seizure disorders, arrhythmias, tachycardia, hypertension, hypotension, hepatic or renal dysfunction, alcoholism, prostatic hypertrophy
• elderly patients
• pregnant or breastfeeding patients.
• Give after meals to prevent GI upset.
• Crush tablets if patient has difficulty swallowing them.
• Know that I.V. route is seldom used.
• Be aware that entire dose may be given at bedtime. (Drug has long duration of action.)
CNS: confusion, depression, dizziness, hallucinations, headache, weakness, memory impairment, nervousness, delusions, euphoria, paresthesia, sensation of heaviness in limbs, toxic psychosis
CV: hypotension, palpitations, tachycardia, arrhythmias
EENT: blurred vision, diplopia, mydriasis, angle-closure glaucoma
GI: nausea, constipation, dry mouth, ileus
GU: urinary hesitancy or retention, dysuria, difficulty maintaining erection
Musculoskeletal: paratonia, muscle weakness and cramps
Skin: rash, urticaria, decreased sweating, dermatoses
Drug-drug. Antacids, antidiarrheals: decreased benztropine absorption
Antihistamines, bethanechol, disopyramide, phenothiazines, quinidine, tricyclic antidepressants: additive anticholinergic effects
Drug-herbs. Angel's trumpet, jimsonweed, scopolia: increased anticholinergic effects
Drug-behaviors. Alcohol use: increased sedation
• Monitor blood pressure closely, especially in elderly patients.
• Monitor fluid intake and output; check for urinary retention.
• Assess for signs and symptoms of ileus, including constipation and abdominal distention.
• Advise patient to use caution during activities that require physical or mental alertness, because drug causes sedation.
• Tell patient to avoid increased heat exposure.
☞ Caution patient not to stop therapy abruptly.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, herbs, and behaviors mentioned above.