Bacterial degradation of risperidone and paliperidone in decomposing blood.

The stability of two benzisoxazole antipsychotics was determined in vitro in decomposing porcine blood inoculated with bacteria, utilizing a high-performance liquid chromatography with ultraviolet and fluorescence detection method for drug quantitation. Stability experiments for risperidone and paliperidone were conducted at 7, 20 and 37°C for 4 days using sterile and bacterially inoculated porcine blood. The drugs were stable in sterile blood at each temperature and in inoculated blood at 7°C, but degraded significantly in inoculated blood at 20 and 37°C. Complete loss occurred within 2 days when incubated at 37°C. The benzisoxazole-cleaved degradation products for both drugs were identified as 2-hydroxybenzoyl-risperidone and 2-hydroxybenzoyl-paliperidone utilizing liquid chromatography quadrupole-time-of-flight mass spectrometry and accurate mass measurements. The degradation products have been found in postmortem case studies, including one case where risperidone and paliperidone were not detected, indicating complete conversion can occur in situ.

Enantioselective fungal biotransformation of risperidone in liquid culture medium by capillary electrophoresis and hollow fiber liquid-phase microextraction.

Knowing that microbial transformations of compounds play vital roles in the preparation of new derivatives with biological activities, risperidone and its chiral metabolites were determined by capillary electrophoresis and hollow fiber liquid-phase microextraction after a fungal biotransformation study in liquid culture medium. The analytes were extracted from 1 mL liquid culture medium into 1-octanol impregnated in the pores of the hollow fiber, and into an acid acceptor solution inside the polypropylene hollow fiber. The electrophoretic separations were carried out in 100 mmol/L sodium phosphate buffer pH 3.0 containing 2.0% w/v sulfated-α-CD and carboxymethyl-ß-CD 0.5% w/v with a constant voltage of -10 kV. The method was linear over the concentration range of 100-5000 ng/mL for risperidone and 50-5000 ng/mL for each metabolite enantiomer. Within-day and between-day assay precisions and accuracies for all the analytes were studied at three concentration levels, and the values of relative standard deviation and relative error were lower than 15%. The developed method was applied in a pilot biotransformation study employing risperidone as the substrate and the filamentous fungus Mucor rouxii. This study showed that the filamentous fungus was able to metabolize risperidone enantioselectively into its chiral active metabolite, (-)-9-hydroxyrisperidone.

Physicochemical characterization of neuroleptics. Relative stability of 7- and 9-hydroxyrisperidones and their protonated forms in gas phase and in solution.

Conventional ab initio and DFT-B3LYP calculations have been used to investigate on molecular conformation, dipole moments, intramolecular hydrogen bond and relative energies of 9-hydroxy and 7-hydroxyrisperidone metabolites of risperidone, in their neutral and mono-protonated forms in the gas phase and in solution. Three minimum energy conformations characterize the potential energy surface of 7-hydroxyrisperidone, while 9-hydroxyrisperidone is dominated by a strong intramolecular OH...N hydrogen bond of ca. 8 kcal/mol, which drastically reduces in water solution. In the gas phase, 9-hydroxyrisperidone is the most stable isomer both in the neutral and in the protonated forms. Solvent effects favour 7-hydroxyrisperidone rotamers owing to their higher dipole moment values. Under the physiological pH of 7.4, the protonated forms of both isomers in water coexist in almost equivalent amount, in qualitative agreement with the experiment. It is suggested that to stabilize the pharmacologically active 9-hydroxyrisperidone over the 7-OH isomer one has to increase its molecular dipole moment and the intramolecular OH...N hydrogen bond energy.

Paliperidone for schizophrenia.

BACKGROUND: Paliperidone, risperidone's active metabolite, is now available in an oral formulation for daily use, and an intramuscular formulation for monthly administration may follow shortly. OBJECTIVES: To compare effects of oral paliperidone with any other treatment for people with schizophrenia and schizophrenia-like illnesses. SEARCH STRATEGY: We searched the Cochrane Schizophrenia Group's Register (December 2006), and inspected references of identified studies for further trials. We contacted the manufacturers of paliperidone, the Food and Drug Administration, and authors of relevant trials for additional material. SELECTION CRITERIA: We included all relevant randomised trials. DATA COLLECTION AND ANALYSIS: We independently selected and critically appraised studies, extracted data and analysed on an intention-to-treat basis. Where possible and appropriate, we calculated risk ratios (RR) and their 95% confidence intervals (CI) with the number needed to treat (NNT). We calculated Weighted Mean Differences (WMD) for continuous data. MAIN RESULTS: Five studies compared paliperidone with placebo. Fewer people left the studies early if they were randomized to paliperidone (n=1647, 5 RCTs, RR 0.68 CI 0.61 to 0.76, NNT 7 CI 6 to 9) and those receiving any dose of paliperidone were significantly more likely to have an improvement in global state (n=1420, 4RCTs, RR 0.69 CI 0.63 to 0.75, NNT 5 CI 4 to 6). People randomised to paliperidone were less likely to experience a recurrence of psychosis (n=1638, 5 RCTs, RR 0.45 CI 0.31 to 0.66, NNT 16 CI 13 to 26) than those allocated to placebo. Adverse effect data were not well reported but paliperidone does seem to produce a greater incidence of tachycardia than placebo (n=1638, 5 RCTs, RR1.88 CI 1.28 to 2.76, NNH 21 CI 11 to 90) and a consistent, significant elevation in serum prolactin was found for both men (n=413, 3 RCTs, WMD 27.68 CI 23.66 to 31.69) and women (n=252, 3 RCTs, WMD 87.39 CI 74.27 to 100.51). People receiving paliperidone were more likely to experience extrapyramidal disorders (n=1638, 5 RCTs, RR 2.21 CI 1.26 to 3.88, NNH 28 CI 12 to 129) and weight gain (n=769, 4 RCTs, WMD 1.07 CI 0.65 to 1.49, I-squared 78%) compared with those allocated to placebo. When compared with 10 mg/day olanzapine we found no differences between paliperidone and olanzapine for leaving in the short term (n=1332, 3 RCTs, RR 1.04 CI 0.89 to 1.21; 40% in both groups left by six weeks). Those receiving any dose of paliperidone were no more likely to have a recurrence of psychotic symptoms than those receiving 10 mg/day olanzapine (n=1327, 3 RCTs, RR 0.1.07 CI 0.64 to 1.76). Data from all three studies found paliperidone was less likely to produce a weight change than olanzapine (n=660, 3 RCTs, WMD -0.88 CI -1.38 to -0.37). Results for various movement disorders all favoured olanzapine. There are no clear data relating to social functioning, services use, quality of life, satisfaction and cost. AUTHORS' CONCLUSIONS: In short-term studies, oral paliperidone is an antipsychotic that is more efficacious than placebo. We found its adverse effects to be similar to those of its parent compound, risperidone, with movement disorders, weight gain, and tachycardia all more common with paliperidone than placebo. In addition, paliperidone is associated with substantial increases in serum prolactin that may be associated with sexual dysfunction, although sexual functioning outcomes were not reported. At doses greater than 3 mg per day, oral paliperidone appears comparable in efficacy to oral olanzapine 10 mg per day. Regarding the critical comparison of oral paliperidone to risperidone, we have no information and are thus unable to determine if paliperidone has any advantages or disadvantages compared to its well-known parent compound.

Identification, isolation and characterization of potential degradation product in risperidone tablets.

One unknown impurity (degradation product) present at a level below 0.1% in the initial samples increased to a level of 0.5% in 6M/40 degrees C/75% RH stability samples of risperidone tablets was detected by gradient reverse-phase high-performance liquid chromatography (HPLC). This impurity was isolated using reverse-phase preparative liquid chromatography. Based on the spectral data the structure of this impurity is characterized as 3-[2-[4-[6-fluoro-1,3-benzoxazol-2-yl]piperidin-1-yl]ethyl]-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidin-4-one. Structural elucidation of this impurity by spectral data ((1)H NMR, (13)C NMR, DEPT, MS and IR), formation and mechanism has been discussed in detail.

Structural studies of impurities of risperidone by hyphenated techniques.

During the impurity profile of risperidone (RSP), a more polar impurity (RSP-1) and a more non-polar impurity (RSP-2) were detected in LC-MS with respect to risperidone. These impurities were isolated, enriched and were subjected to mass and NMR spectral studies. Based on the spectral data, RSP-1 and RSP-2 were characterized as risperidone N-oxide and 9-methylene risperidone, respectively. The formation of these impurities is rationalized. The structures of both the impurities were unambiguously confirmed by single crystal XRD Studies.

El uso de los nuevos antipsicóticos atípicos en el síndrome de Gilles de la Tourette / Use of atypical antipsychotics in Tourette´s syndrome

El síndrome de GiIles de la Tourette (SGT) es un trastorno neuropsiquiátrico con tics motores y vocales crónicos y una elevada comorbilidad y síntomas secundarios. Se han venido usando agonistas alfa-2 (clonidina) o antipsicóticos clásicos (haloperidol, pimocida) con buena eficacia pero mala tolerancia (Efectos adversos). Revisamos la literatura existente sobre eficacia y tolerancia de los nuevos antipsicóticos (clozapina, risperidona, olanzapina, quetiapina, amisulpride, ziprasidona) en esta patología

Tourette's syndrome is a neuropsychiatric disorder characterized by chronic motor and vocal tics and a high comorbidity and associated symptoms. Usually, alpha-2 agonists (clonidine) or typical antipsychotics (haloperidol, pimozide) have been used with a good efficacy but they are poorly tolerated (adverse effects). We review here the existing evidences on efficacy and tolerance for the new antipsychotics (clozapine, risperidone, olanzapine, quetiapine, amisulpride, ziprasidoné) on this disorder