Truth or myth of minimum effective dose for patients with remitted psychosis: Implications from a guided dose reduction trial

Objective

Optimizing antipsychotic dosage is crucial for patients to resume functioning without increased risk of relapse. The reported antipsychotic minimum effective dose (MED) for treatment of either acute phase or stable patients is a chlorpromazine equivalent (CPZE) dose of 200 mg/d. A cohort of remitted patients undergoing prospective dose reduction were evaluated to determine if a dose less than the designated MED could still provide adequate prophylactic effects.

Methods

Ninety-six individuals with schizophrenia-related psychotic disorders whose symptoms were stable with their current medication were eligible for a 2-year dose tapering trial. Divided into two groups according to antipsychotic doses (CPZE > 200 vs. CPZE ≤ 200 mg/d), we evaluated if there were differences in clinical severities, personal social performance, quality of life, medication satisfaction, and employment status between baseline and the end of 2-year follow-up.

Results

At baseline, 59 participants received CPZE ≤ 200 mg/d and 37 participants received CPZE > 200 mg/d. At the 2-year follow-up, 42 patients had successfully reduced their doses. Among subgroups, 13 participants whose doses were reduced from > 200 mg/d to ≤ 200 mg/d had clinical outcomes comparable to their baseline levels; while 45 patients who received ≤ 200 mg/d throughout the 2 years showed significantly better outcomes, such improvements were mainly contributed by 25 of them further reducing antipsychotics at such a low dose level.

Conclusion

Maintenance dose CPZE ≤ 200 mg/d was common in this small sample-sized cohort. Careful dose tapering allowed some patients to reduce antipsychotics further with no increased risk of relapse and were able to improve their functioning.