Liquid chromatography/tandem mass spectrometry method for simultaneous determination of risperidone and its active metabolite 9-hydroxyrisperidone in human plasma

A rapid and sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for simultaneous quantification of risperidone (RSP) and its active metabolite 9-hydroxyrisperidone (9-OH-RSP) in human plasma. The analytes were extracted from human plasma by using the protein precipitation extraction technique. Methyl risperidone was used as internal standard for RSP and 9-OH-RSP. A Betasil C18 column provided chromatographic separation of analytes followed by detection with mass spectrometry. The mass transition ion-pair was followed as m/z 411.28 --> 191.15 for RSP and m/z 427.30 --> 207.10 for 9-OH-RSP. The method involves a simple extraction, isocratic chromatography conditions and mass spectrometric detection that enable detection at sub-nanogram levels. The proposed method has been validated with a linear range of 0.10-15.0 ng/mL for RSP and 9-OH-RSP. The intrarun and interrun precision and accuracy values were within 15%. The overall recoveries for RSP and 9-OH-RSP were 82.1% and 83.2%, respectively. The total analysis time was as low as 3.0 min only. The developed method was applied for the determination of the pharmacokinetic parameters of RSP and 9-OH-RSP following a single oral administration of a 1 mg RSP tablet in 24 healthy male volunteers.