Comparison of haloperidol plasma concentrations between twice-a-day and once-a-day dosing in Chinese schizophrenic...

There is a trend in clinical psychiatric practice to make the dosing schedules of psychotropic medications as simple as possible. In this study, the authors measured the steady state haloperidol plasma levels in patients on different dosing schedules. Twenty-three schizophrenic in-patients were placed on haloperidol with a twice-a-day (10 mg bid) schedule for 14 days; the patients were then changed to a once-a-day (20 mg qd) schedule for another 14 days. Plasma haloperidol (HAL) and reduced haloperidol concentrations were measured at the end of each two-week period. The mean HAL plasma concentrations obtained from the bid and qd dosing schedules were 16.6 +/- 4.9 ng/mL and 12.7 +/- 5.3 ng/mL, respectively. These results are reasonable as the elimination half-life of HAL, as reported by most investigators, is about 24 hours. The present study suggests that a once-a-day dosing schedule in HAL treatment is adequate for most chronic patients.