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Introduction

  1. Pharmacology. Benztropine is an antimuscarinic agent, pharmacologically similar to atropine, but with additional antihistaminic properties. Benztropine is used to treat parkinsonism as well as extrapyramidal side effects associated with neuroleptic drug use.
  2. Indications. Benztropine is an alternative to diphenhydramine for the treatment of acute dystonic reactions in adults (diphenhydramine is preferred in children). It has a longer duration of action compared to diphenhydramine and is administered twice daily. Note: It is not effective for tardive dyskinesia or neuroleptic malignant syndrome.
  3. Contraindications
    1. Angle-closure glaucoma.
    2. Obstructive uropathy (prostatic hypertrophy).
    3. Myasthenia gravis.
    4. Per manufacturer, not recommended for children under 3 years; preferentially use diphenhydramine. Consider benztropine only if the child is unresponsive or hypersensitive to diphenhydramine and is experiencing a severe or life-threatening situation (eg, dystonic laryngeal or pharyngeal spasms).
    5. Tardive dyskinesia.
    6. Known hypersensitivity.
  4. Adverse effects
    1. Adverse effects include sedation, confusion, blurred vision, tachycardia, urinary hesitancy or retention, intestinal ileus, flushing, dry mouth, and hyperpyrexia. Adverse effects are minimal after a single dose.
    2. Use in pregnancy. Not categorized by FDA. Safe use not established. However, this does not preclude its acute, short-term use for a seriously symptomatic patient (Introduction).
  5. Drug or laboratory interactions
    1. Benztropine has additive effects with other antimuscarinic drugs (eg, antihistamines, cyclic antidepressants).
    2. Slowing of GI motility may delay or inhibit absorption of certain drugs.
  6. Dosage and method of administration
    1. Parenteral. Give 1-2 mg IV or IM (children 3 years of age: 0.02 mg/kg and 1 mg maximum). May repeat dose in 15 minutes if the patient does not improve.
    2. Oral. Give 1-2 mg PO every 12 hours (children 3 years old: 0.02 mg/kg and 1 mg maximum) for 2-3 days to prevent recurrence of symptoms. Maximum recommended dose for adults is 6 mg/d.