Impact of clozapine once-daily versus multiple-daily dosing regimen on relapse in patients with treatment-resistant schizophrenia: A 1-year retrospective cohort study.

RATIONALE

Clozapine, the standard treatment for treatment-resistant schizophrenia (TRS), is generally recommended in a multiple-daily dosing regimen. However, it is commonly administered once daily in clinical practice. Few studies have compared the longitudinal clinical outcomes of these two dosing regimens.

OBJECTIVE

To investigate the effect of once-daily versus multiple-daily dosing regimens of clozapine on relapse in patients with TRS.

METHODS

This retrospective cohort study included patients with TRS who commenced treatment with clozapine during hospitalization and were discharged between April 2012 and January 2022 from a tertiary psychiatric hospital in Japan. Relapse, defined as a psychiatric exacerbation requiring re-hospitalization within the first-year post-discharge, was analyzed. Multivariable Cox proportional hazards regression analysis compared the relapse risk between once-daily and multiple-daily dosing regimens. A subgroup analysis was conducted to examine the potential interactions between dosing regimen and dose category (low versus high dose).

RESULTS

Among 179 patients, 107 (59.8%) received clozapine once daily. No significant difference in the relapse risk was observed between once-daily and multiple-daily dosing regimens (adjusted hazard ratio [aHR]: 1.16; 95% confidence interval [CI]: 0.68-1.99; p = 0.58). However, in patients receiving high doses of clozapine (> 300 mg/day), multiple-daily dosing increased the relapse risk compared to once-daily dosing (aHR: 2.23; 95% CI: 1.00-4.97; p = 0.049).

CONCLUSIONS

Once-daily clozapine dosing may not be associated with an increased relapse risk. The increased relapse risk in high-dose multiple-daily dosing may be confounded by unmeasured non-adherence. Further randomized controlled trials are required to validate these findings.