benztropine mesylate

Action

Inhibits cholinergic excitatory pathways and restores balance of dopamine and acetylcholine in CNS, thereby decreasing excess salivation, rigidity, and tremors (parkinsonian symptoms)

Availability

Injection: 1 mg/ml in 2-ml ampules

Tablets: 0.5 mg, 1 mg, 2 mg

Indications and dosages

➣ Parkinsonism

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

Dosage adjustment

• Elderly patients

Off-label uses

• Excessive salivation

Contraindications

• Hypersensitivity to drug

• Angle-closure glaucoma

• Tardive dyskinesia

• Children younger than age 3

Precautions

Use cautiously in:

• seizure disorders, arrhythmias, tachycardia, hypertension, hypotension, hepatic or renal dysfunction, alcoholism, prostatic hypertrophy

• elderly patients

• pregnant or breastfeeding patients.

Administration

• 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.)

Adverse reactions

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

Interactions

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

Patient monitoring

• 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.

Patient teaching

• Advise patient to use caution during activities that require physical or mental alertness, because drug causes sedation.

• Tell patient to avoid increased heat exposure.

See 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.