Validated LC-MS/MS methods for the determination of risperidone and the enantiomers of 9-hydroxyrisperidone in human plasma and urine.

Two liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) methods are described, one for the quantitative determination of risperidone and the enantiomers of its active metabolite 9-hydroxyrisperidone (paliperidone) in human plasma and the other for the determination of the enantiomers of 9-hydroxyrisperidone in human urine. The plasma method is based on solid-phase extraction of 200 microl of sample on a mixed-mode sorbent, followed by separation on a cellulose-based LC column with a 13.5-min mobile phase gradient of hexane, isopropanol and ethanol. After post-column addition of 10 mM ammonium acetate in ethanol/water, detection takes place by ion-spray tandem mass spectrometry in the positive ion mode. Method validation results show that the method is sufficiently selective towards the enantiomers of 7-hydroxyrisperidone and capable of quantifying the analytes with good precision and accuracy in the concentration range of 0.2-100 ng/ml. An accelerated (run time of 4.3 min) and equally valid method for the enantiomers of 9-hydroxyrisperidone alone in plasma is obtained by increasing the mobile phase flow-rate from 1.0 to 2.0 ml/min and slightly adapting the gradient conditions. The urine method is based on the same solid-phase extraction and chromatographic approach as the accelerated plasma method. Using 100 microl of sample, (+)- and (-)-9-hydroxyrisperidone can be quantified in the concentration range 1-2000 ng/ml. The accelerated method for plasma and the method for urine can be used only when paliperidone is administered instead of risperidone, as there is insufficient separation of the 9-hydroxy enantiomers from the 7-hydroxy enantiomers, the latter ones being present only after risperidone administration.

Pharmacokinetic comparison of fast-disintegrating and conventional tablet formulations of risperidone in healthy volunteers.

BACKGROUND: Difficulties with and resistance to tablet-taking are common in all patient groups and can exacerbate compliance problems and undermine treatment efficacy. In recent years, rapidly dissolving oral drug formulations have been developed to overcome problems related to swallowing difficulties. OBJECTIVE: The goal of this study was to evaluate the bioequivalence of a fast-disintegrating oral tablet of risperidone and the conventional oral tablet. METHODS: This was a randomized, open-label, 2-way crossover trial in which healthy volunteers received two 0.5-mg tablets of a fast-disintegrating oral risperidone formulation and two 0.5-mg tablets of conventional oral risperidone, each in a single administration. Blood samples for pharmacokinetic analysis of the active moiety (risperidone + 9-hydroxy-risperidone), risperidone, and its active metabolite 9-hydroxy-risperidone were obtained during a 96-hour period after dosing. Safety assessments included monitoring of adverse events, hematology and biochemistry tests of the sampled blood, urinalysis, blood pressure measurements, and electrocardiography. RESULTS: The bioequivalence assessment was based on pharmacokinetic and statistical analysis of data from 37 subjects who completed both treatment periods. The plasma concentration-time profiles of the active moiety, risperidone, and 9-hydroxy-risperidone were similar after intake of the 2 formulations. The fast-disintegrating tablet and the conventional tablet showed bioequivalence with respect to the active moiety, risperidone, and 9-hydroxy-risperidone. The 90% CIs for the mean treatment ratios of the log-transformed peak plasma concentration, area under the plasma concentration-time curve (AUC) to the last quantifiable time point, and AUC extrapolated to infinity were all within the predefined equivalence range from 80% to 125%. Twenty-eight of 50 (56%) subjects originally randomized reported adverse events, with a similar incidence for both treatments. All adverse events were mild, with somnolence and headache being the most frequently reported. No clinically relevant changes were observed in physical, biochemical, hematologic, or urinalysis variables during the study. CONCLUSION: In this study in healthy subjects, a single administration of two 0.5-mg fast-disintegrating risperidone tablets was bioequivalent to a single administration of two 0.5-mg conventional risperidone tablets.

Efficacy and safety of paliperidone palmitate in adult patients with acutely symptomatic schizophrenia: a randomized, double-blind, placebo-controlled, dose-response study.

This 13-week, double-blind study evaluated the efficacy and safety of the atypical antipsychotic paliperidone palmitate (recently approved in the United States) versus placebo administered as monthly gluteal injections (after two initial doses given 1 week apart) in acutely symptomatic patients with schizophrenia. Patients (N=388) were randomly assigned (1 : 1 : 1 : 1) to paliperidone palmitate 50, 100, or 150 mg eq. or placebo. As the 150 mg eq. dose was administered to fewer patients (n=30) than planned, meaningful and definitive conclusions cannot be drawn from the results of this group. The change from baseline in Positive and Negative Syndrome Scale total score at endpoint showed improvement in both paliperidone palmitate 50 and 100 mg eq. groups but was significant only in the 100 mg eq. group (P=0.019). The paliperidone palmitate 50 (P=0.004) and 100 mg eq. (P<0.001) groups showed significant improvement in the Personal and Social Performance score from baseline to endpoint versus placebo. Common adverse events (in >or=2% of patients in any group) more frequent with paliperidone palmitate 50 or 100 mg eq. than placebo (>or=5% difference) were headache, vomiting, extremity pain, and injection site pain. Treatment with paliperidone palmitate (100 mg eq.) was efficacious and all doses tested were tolerable.