Therapeutic drug monitoring of haloperidol, perphenazine, and zuclopenthixol in serum by a fully automated sequential solid phase extraction followedby high-performance liquid chromatography

In Denmark, haloperidol, perphenazine, and zuclopenthixol are among the mos t frequently requested antipsychotics for therapeutic drug monitoring. With the number of requests made at the authors' laboratory, the only rational analysis is one that can measure all three drugs simultaneously. The author s therefore decided to develop an automated high-performance liquid chromat ography (HPLC) method. Two milliliters serum, 2.0 mL 10 mmol/L sodium phosp hate buffer (pH 5.5), and 150 muL internal standard (trifluoperazine) solut ion were pipetted into HPLC vials and extracted on an ASPEC XL equipped wit h I mt (50 mg) Isolute C2 (EC) extraction columns and acetonitrile-methanol -ammonium acetate buffer (60:34:6) as extracting solution. Three hundred fi fty microliters was analyzed by HPLC; a 150 x 4.6-mm S5CN Spherisorb column with a mobile phase of 10 mmol/L ammonium acetate buffer-methanol (1:9), a flow rate of 0.6-1.7 mL/min, and ultraviolet detection at 256 and 245 nm w ere used. Reproducibility was 5-12% and the lower limit of quantitation was 10, 1, and 5 nmol/L (4, 0.4, and 2 ng/mL) for haloperidol, perphenazine, a nd zuclopenthixol, respectively. The method was found to be sufficiently se lective and robust for routine analysis.