PDE5 inhibitors beyond erectile dysfunction.
The 90% confidence intervals for Test/Reference ratios of the pharmacokinetic parameters (Cmax, AUC0-t and AUC0-∞) of both risperidone and its active metabolite (9-hydroxyrisperidone) fell within the acceptable bioequivalence range (80 - 125%) according to ASEAN guideline.
The preparation and investigation of sustained-release risperidone-encapsulated microspheres using erodible poly(D, L-lactide-co-glycolide) (PLGA) of lower molecular weight were performed and compared to that of commercial Risperdal Consta™ for the treatment of schizophrenia. The research included screening and optimizing of suitable commercial polymers of lower molecular weight PLGA50/50 or the blends of these PLGA polymers to prepare microspheres with zero-order release kinetics properties. Solvent evaporation method was applied here while studies of the risperidone loaded microsphere were carried out on its drug encapsulation capacity, morphology, particle size, as well as in vitro release profiles. Results showed that microspheres prepared using 50504A PLGA or blends of 5050-type PLGAs exerted spherical and smooth morphology, with a higher encapsulation efficiency and nearly zero-order release kinetics. These optimized microspheres showed great potential for a better depot preparation than the marketed Risperdal Consta™, which could further improve the patient compliance.
Eleven olanzapine ODT examples and orodispersible risperidone strengths were evaluated in vitro for formulation composition, manufacturing method, disintegration and dissolution characteristics, and formulation differences in comparison with freeze dried Zydis(®) ODT. Automated dissolution test equipment captured ODT dissolution rates by measuring real-time release of active ingredient. A high-speed video camera was used to capture tablet disintegration times in warm simulated saliva.
The ODT manufacturing method was associated with time to disintegrate; the fastest were freeze dried tablets, followed by soft compressed tablets and then hard/dense tablets. Olanzapine Zydis(®) was the only ODT that completely disintegrated in less than 4 s for all strengths (5, 10, 15, and 20 mg), followed by 5-mg Prolanz FAST(®) (12 s) and then risperidone ODT 4 mg (40 s). Reasons for slow dissolution of the olanzapine generics may include low product potency, excipient binding, excipient solubility, active ingredient particle size and incomplete disintegration.
Six trials (1343 participants) of risperidone as monotherapy or as adjunctive treatment to lithium, or an anticonvulsant, were identified. Permitted doses were consistent with those recommended by the manufacturers of Haldol (haloperidol) and Risperdal (risperidone) for treatment of mania and trials involving haloperidol allowed antiparkinsonian treatment. Risperidone monotherapy was more effective than placebo in reducing manic symptoms, using the Young Mania Rating Scale (YMRS) (weighted mean difference (WMD) -5.75, 95% confidence interval (CI) -7.46 to -4.04, P<0.00001; 2 trials) and in leading to response, remission and sustained remission. Effect sizes for monotherapy and adjunctive treatment comparisons were similar. Low levels of baseline depression precluded reliable assessment of efficacy for treatment of depressive symptoms. Risperidone as monotherapy and as adjunctive treatment was more acceptable than placebo, with lower incidence of failure to complete treatment (RR 0.66, 95% CI 0.52 to 0.82, P = 0.0003; 5 trials). Overall risperidone caused more weight gain, extrapyramidal disorder, sedation and increase in prolactin level than placebo. There was no evidence of a difference in efficacy between risperidone and haloperidol either as monotherapy or as adjunctive treatment. The acceptability of risperidone and haloperidol in incidence of failure to complete treatment was comparable. Overall risperidone caused more weight gain than haloperidol but less extrapyramidal disorder and comparable sedation.
The pharmacological choices for the treatment of schizophrenia have been greatly expanded with the availability of the atypical compounds clozapine (Clozaril, Novartis), risperidone (Risperdal, Janssen-Cilag), olanzapine (Zyprexa, Eli Lilly & Co.), quetiapine (Seroquel, AstraZeneca), ziprasidone (Geodon, Pfizer Inc.) and aripiprazole (Abilify, Otsuka Pharmaceutical Co. Ltd). In this article, the effects of the newer antipsychotics and their side effects are reviewed. Key issues in acute and maintenance treatment, often lifelong, will be reviewed. Side-effect management to ensure adherence to an optimal treatment regimen will be discussed. Coexisting syndromes must be treated in concordance with the patient's clinical presentation. For treatment-resistant patients, atypical compounds are generally more effective than their typical counterparts but medication augmentation strategies are frequently recommended. Finally, the results of recent meta-analyses comparing the effects of atypical versus typical compounds will be critically reviewed and remaining gaps in the current pharmacotherapy of schizophrenia will be explored.