Plasma amisulpride in relation to prescribed dose, clozapine augmentation, and other factors: data from a therapeutic drug monitoring service, 2002-2010

Objective This study aimed to investigate the effect of dose and other factors on plasma amisulpride concentrations in clinical practice. Method Amisulpride therapeutic drug monitoring data 2002–2010 have been studied. Results There were 296 samples (196 adult patients). Amisulpride was not detected in 10% of samples. In the remainder, the mean plasma amisulpride in relation to the prescribed dose (mg/day) was as follows: 100–200 (111 µg/L), 201–400 (254 µg/L), 400–800 (421 µg/L), and 800–1200 (494 µg/L). For prescribed doses up to 800 mg/day, only 51% of results were within 100–319 µg/L. There were no significant sex differences in mean plasma amisulpride or mean dose. The mean plasma amisulpride, but not the dose, was significantly higher in smokers. Linear regression analysis showed that dose explained only 42% of the variation in plasma amisulpride after log10 transformation of both variables. There was no significant difference in the mean dose or mean plasma amisulpride in patients co‐prescribed clozapine as compared with the remaining samples. Conclusion In practice, dose is a poor predictor of plasma amisulpride concentration. Therapeutic drug monitoring may not only help assess adherence, but also guide dosage. Copyright © 2012 John Wiley & Sons, Ltd.