Can I add benztropine (1 mg as needed daily) to a regimen of Abilify (aripiprazole, 5mg) and lithium (300mg twice a day, bid)?

Adding Benztropine to Aripiprazole and Lithium Regimen

Yes, benztropine 1 mg PRN daily can be safely added to your current regimen of Abilify 5mg and lithium 300mg twice daily to manage potential extrapyramidal symptoms.

Rationale for Adding Benztropine

Benztropine is commonly used to manage extrapyramidal symptoms (EPS) that can occur with antipsychotic medications like aripiprazole (Abilify). The NCCN guidelines specifically recommend benztropine for managing dystonic reactions that can occur with antipsychotics, stating:

• If allergic to diphenhydramine, "use benztropine at 1-2 mg IV or IM x 1 dose, followed by oral dose of 1-2 mg daily or BID if needed to control the reaction" 1

Medication Compatibility

The FDA drug label for aripiprazole specifically addresses this combination:

• "No dosage adjustment is necessary for valproate, lithium, lamotrigine, lorazepam, or sertraline when co-administered with aripiprazole" 2
• There is no contraindication listed for benztropine with aripiprazole

Dosing Considerations

The recommended dosing of benztropine for managing EPS is appropriate:

• 1-2 mg daily or BID as needed is the standard dosing range for managing dystonic reactions 1
• Using it on an "as needed" (PRN) basis is a reasonable approach to minimize anticholinergic side effects

Monitoring Requirements

When using this combination, monitor for:

1. Anticholinergic side effects: Dry mouth, constipation, urinary retention, blurred vision
2. Sedation: The combination may increase sedation
3. Orthostatic hypotension: Monitor blood pressure, especially when starting the medication

Potential Concerns and Precautions

While this combination is generally safe, be aware of these potential issues:

• Constipation risk: Anticholinergic medications like benztropine can cause severe constipation, which in rare cases has been associated with ischemic colitis when combined with antipsychotics 3
• Sedation: Benztropine may add to any sedative effects of your current medications

Alternative Approaches

If benztropine causes problematic side effects, consider:

1. Diphenhydramine 25-50 mg PO or IV every 4-6 hours for dystonic reactions 1
2. Adjusting the aripiprazole dose (though your current 5mg dose is already relatively low)
3. Discussing with your provider about switching to an antipsychotic with lower EPS risk if EPS becomes a persistent issue

Conclusion

Adding benztropine 1 mg PRN daily to your current regimen of aripiprazole 5mg and lithium 300mg BID is appropriate for managing potential EPS. Use it only when needed to minimize anticholinergic side effects, and report any concerns about excessive sedation, constipation, or other side effects to your healthcare provider.