The blood level of antipsychotics affects clinical responses to the drug; it can be influenced by race and several individual factors. This study analyzed the therapeutic plasma concentrations (Cps) of paliperidone for both oral and long-acting injectable (LAI) formulations in clinical samples from Taiwanese patients.

Patients diagnosed with schizophrenia and treated with either oral paliperidone for at least 4 weeks or LAI paliperidone for at least 6 months were enrolled. Blood samples were taken before the morning dose of oral paliperidone or the injection of LAI paliperidone to obtain the trough Cps.

Among the patients in this study, 51 were taking oral paliperidone, and 26 were receiving LAI paliperidone. In the oral group, the mean Cps were 40.2 ± 19.8 ng/mL in patients taking 9 mg/d and 44.2 ± 15.9 ng/mL in those taking 12 mg/d. In the LAI group, the mean Cps were 32.9 ± 12.7 ng/mL in patients receiving 100 mg per 28 days and 49.9 ± 25.9 ng/mL in those receiving 150 mg per 28 days. The mean Cps per daily dose (Cps/DD) were 4.11 ± 1.99 ng/mL/mg in the oral group and 9.24 ± 3.78 ng/mL/mg in the LAI group.

Under the suggested DD for oral and LAI paliperidone treatment, most Taiwanese patients with schizophrenia can reach the suggested therapeutic Cps range. Wide interindividual differences were observed in the Cps/DD for both the oral (7-fold) and LAI paliperidone (4-fold) groups. Compared with Western reports, no difference was observed in the body weight–adjusted Cps/DD.