Is it safe to prescribe Benztropine (anticholinergic medication) to a patient already taking Lorazepam (Ativan, benzodiazepine)?

Benztropine and Lorazepam Co-Prescription

Yes, benztropine can be prescribed to a patient already taking lorazepam, but this combination requires careful consideration of additive anticholinergic and sedative effects, particularly in elderly or debilitated patients.

Clinical Context and Safety Considerations

The combination of benztropine (an anticholinergic agent) with lorazepam (a benzodiazepine) is not contraindicated, but requires awareness of potential additive effects:

Additive Sedation and Cognitive Effects

• Both medications can cause sedation, confusion, and psychomotor impairment, which may be compounded when used together 1
• Benztropine has been shown to induce deficits in attention and concentration in patients receiving chronic therapy 2
• Lorazepam carries risks of drowsiness, dizziness, and paradoxical agitation, particularly when combined with other CNS depressants 1

Anticholinergic Burden

• Benztropine is a potent antimuscarinic agent that can cause significant anticholinergic toxicity including delirium 3
• When antipsychotics with anticholinergic properties are combined with anticholinergics like benztropine, there is increased risk of serious complications including ischemic colitis 4
• The anticholinergic effects of benztropine may be particularly problematic in elderly patients who are already at higher risk for delirium 1

Dosing Adjustments When Co-Prescribing

If prescribing both medications together, use reduced doses of lorazepam:

• Standard lorazepam dosing is 0.5-1 mg PRN (maximum 4 mg/24 hours) 1, 5
• When co-administered with anticholinergics or in elderly/debilitated patients, reduce lorazepam to 0.25-0.5 mg 1
• For elderly patients specifically, maximum daily lorazepam should not exceed 2 mg when combined with other CNS-active medications 1

Clinical Indications Where This Combination May Be Appropriate

• Acute dystonic reactions: Benztropine is indicated for neuroleptic-induced acute dystonias, and lorazepam may be used concurrently for anxiety or agitation 1, 6
• Delirium with agitation: Guidelines support adding benzodiazepines like lorazepam to antipsychotic regimens when patients remain agitated, though benztropine would typically only be added if extrapyramidal symptoms develop 1
• Parkinson's disease with anxiety: Benztropine may be used for parkinsonian symptoms while lorazepam addresses anxiety, though this requires careful monitoring 7

Key Monitoring Parameters

• Watch for excessive sedation, particularly in the first few days of combined therapy 1
• Monitor for anticholinergic toxicity: dry mouth, urinary retention, constipation, confusion, and delirium 4, 3
• Assess fall risk, especially in elderly patients, as both medications increase this risk 1, 5
• Evaluate for paradoxical agitation, which can occur with either medication 1, 6

Important Caveats

• Benztropine should only be prescribed if extrapyramidal symptoms are actually present, not prophylactically, as only 14.2% of patients develop symptoms severe enough to require treatment 2
• Lorazepam should be prescribed for short-term use only (ideally maximum 4 weeks) to prevent tolerance and dependence 7
• The combination should be avoided or used with extreme caution in patients with severe pulmonary insufficiency, severe liver disease, or myasthenia gravis 1
• Consider diphenhydramine instead of benztropine for dystonic reactions if the patient is already on lorazepam and you want to minimize additive effects 1