benztropine
Brand: Cogentin
Beers Criteria Prototype: atropine
Drug Class: anticholinergic antiparkinson agent
Drug Family: antiparkinsonian
Subclass: muscarinic receptor antagonist
Organ Systems: cns
Mechanism of Action
Blocks muscarinic receptors in the striatum, restoring the dopamine-acetylcholine balance disrupted by dopaminergic neuron loss in Parkinson's disease. Also blocks histamine H1 receptors (contributing to sedation) and inhibits dopamine reuptake slightly. Used primarily for drug-induced EPS where dopaminergic therapy is not appropriate.
muscarinic acetylcholine receptors (M1)
Indications
- drug-induced extrapyramidal symptoms (particularly acute dystonia and parkinsonism)
- Parkinson's disease (mild cases or adjunct)
- off-label: hypersalivation in antipsychotic-treated patients
Contraindications
- narrow-angle glaucoma
- obstructive uropathy
- myasthenia gravis
- elderly patients with cognitive impairment (Beers Criteria)
Adverse Effects
Common
- dry mouth
- blurred vision
- constipation
- urinary retention
- tachycardia
- sedation
- confusion
Serious
- anticholinergic toxidrome (fever, delirium, ileus, urinary retention)
- hyperthermia in hot weather (impaired sweating)
Pharmacokinetics (ADME)
| Absorption | well absorbed orally and via IM/IV |
| Distribution | highly lipophilic; crosses BBB readily; protein binding not well characterized |
| Metabolism | hepatic; minimal CYP involvement |
| Excretion | renal |
| Half-life | ~36 hours |
| Onset | IM/IV: 15 minutes; oral: 1-2 hours |
| Peak | IM: 2-3 hours |
| Duration | 6-12 hours (oral); 12-24 hours (IM) |
| Protein Binding | not well characterized |
| Vd | not well characterized |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| anticholinergic drugs (including TCAs, antihistamines, bladder drugs) | additive anticholinergic toxidrome | major |
| antipsychotics | may mask EPS while additive anticholinergic effects occur | moderate |
| clozapine | potentiated anticholinergic ileus risk | major |
Nursing Considerations
- For acute dystonic reaction (emergency): administer benztropine 1-2 mg IM or IV; relief within 15 minutes; oral maintenance may follow.
- Elderly patients are at highest risk for anticholinergic complications (delirium, urinary retention, constipation) — Beers Criteria recommends against use in patients ≥65; avoid if possible.
- Warn about reduced sweating in hot weather; patients cannot thermoregulate effectively — advise to stay cool, hydrated, and avoid excessive heat exposure.
- Avoid concurrent use with clozapine or other anticholinergics; the combination can cause fatal anticholinergic ileus.
Clinical Pearls
- Benztropine 1-2 mg IM or IV is the first-line treatment for acute dystonic reactions from antipsychotics or metoclopramide; it provides rapid relief within 15 minutes and should be available in every nursing unit that uses antipsychotics.
- The concept of 'prophylactic anticholinergic prescribing' with every antipsychotic initiation is controversial and no longer recommended routinely; it is reserved for patients at high EPS risk.
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.