Investigation of the effect of solubility increase at the main absorption site on bioavailability of BCS class II drug (risperidone) using liquisolid technique.

BCS class II drugs usually suffer inadequate bioavailability as dissolution step is the absorption rate limiting step. In this work, the effect of solubility increase at the main absorption site for these drugs was investigated using risperidone as a drug model. Liquisolid technique was applied to prepare risperidone per-oral tablets of high dissolution rate at intestinal pH (6.8) using versatile nonionic surfactants of high solubilizing ability [Transcutol HP, Labrasol and Labrasol/Labrafil (1:1) mixture] as liquid vehicles at different drug concentrations (10-30%) and fixed (R). The prepared liquisolid tablets were fully evaluated and the dissolution rate at pH 6.8 was investigated. The formulae that showed significantly different release rate were selected and subjected to mathematical modeling using DE25, MDT and similarity factor (f2). Depending on mathematical modeling results, formula of higher dissolution rate was subjected to solid state characterization using differential scanning calorimetric (DSC), infrared spectroscopy (IR) and X-ray diffraction (XRD). Finally, the drug bioavailability was studied in comparison to conventional tablets in rabbits. Results showed that liquisolid tablet prepared using Labrasol/Labrafil (1:1) mixture as liquid vehicle containing 10% risperidone is a compatible formula with law drug crystallinity and higher dissolution rate (100% in 25 min). The drug bioavailability was significantly increased in comparison to the conventional tablets (1441.711 µg h/mL and 137.518 µg/mL in comparison to 321.011 µg h/mL and 38.673 µg/mL for AUC and Cpmax, respectively). This led to the conclusion that liquisolid technique was efficiently improved drug solubility and solubility increase of BCS class II drugs at their main absorption site significantly increases their bioavailability.

Formulation and characterization of clozapine and risperidone co-entrapped spray-dried PLGA nanoparticles.

In the current study, polylactide-co-glycolide (PLGA) nanoparticles entrapping both clozapine (CLZ) and risperidone (RIS) were formulated by spray-drying using Buchi Nano Spray Dryer B-90 (Flawil, Switzerland). Parameters such as inlet temperature, spray mesh diameter, sample flow rate, spray rate and applied pressure were optimized to produce nanoparticles having desired release profile using both low- and high-molecular weight PLGA polymer. Smallest size nanoparticle of size around 248 nm could be prepared using a 4.0 µm mesh diameter with low-molecular weight polymer. The load of CLZ and RIS was 126.3 and 58.2 µg/mg of polymer particles, respectively. Entrapment efficiency of drugs in PLGA nanoparticles was 94.74% for CLZ and 93.12% for RIS. Both the drugs released continuously from the nanoparticle formulations. PLGA nanoparticles formulated using low-molecular weight polymer released around 80% of the entrapped drug over 10 days of time. Nature of drug inside polymer particles was amorphous, and there was no chemical interaction of CLZ and RIS with polymer. Polymeric nanoparticles were found to be non-toxic in nature using PC12 cell line. This nanospray drying process proved to be suitable for developing polymeric nanoformulation delivering dual drugs for the treatment of Schizophrenia.

Preparation, release and pharmacokinetics of a risperidone elementary osmotic pump system.

Preparation and in vitro/in vivo evaluation of risperidone elementary osmotic pump (RIS-EOP) formulations were investigated. A method for the preparation of RIS-EOP tablets was developed by modulating RIS solubility with citric acid. The influence of osmotic agents and the compositions of semipermeable membrane on drug release profiles was evaluated. The formulation of RIS-EOP was optimized by orthogonal design. The in vitro release profile of the optimum formulation achieved to deliver RIS at an approximate zero-order up to 12 h. The pharmacokinetic profiles of RIS-EOP were evaluated compared with immediate release tablets in beagle dogs. The mean tmax and mean residence time of RIS-EOP for RIS and its active metabolite, 9-hydroxyrisperidone, were remarkably longer, compared with immediate release tablets. These results corroborated prolonged release of RIS from EOP formulations. Moreover, drug plasma levels with lower fluctuations could be achieved with RIS-EOP tablets. These results suggested that increasing drug solubility by adding or reacting with alkali/acid might be used for the preparation of EOP tablets of certain poorly water-soluble drugs.

Developing in vitro-in vivo correlation of risperidone immediate release tablet.

The present study was aimed to predict the absorption profile of a risperidone immediate release tablet (IR) and to develop the level A in vitro-in vivo correlation (IVIVC) of the drug using the gastrointestinal simulation based on the advanced compartmental absorption and transit model implemented in GastroPlus™. Plasma concentration data, physicochemical, and pharmacokinetic properties of the drug were used in building its absorption profile in the gastrointestinal tract. Since the fraction absorbed of risperidone in simulation was more than 90% with low water solubility, the drug met the criteria of class II of the Biopharmaceutics Classification System. The IVIVC was developed based on the model built using the plasma data and the in vitro dissolution data in several dissolution media based on the Japanese Guideline for Bioequivalence Studies of Generic Products. The gastrointestinal absorption profile of risperidone was successfully predicted. A level A IVIVC was also successfully developed in all dissolution media with percent prediction error for Cmax and the area under the curve less than 10% for both reference and test drug.

An efficient synthesis of risperidone via stille reaction: antipsychotic, 5-HT2, and dopamine-D2-antagonist.

Risperidone has been reported to have neuroleptic activity. In this study, risperidone was synthesized using a new method involving a stille reaction, in which 2-methyl-3-vinyl-6,7,8,9-tetrahydropyrido[1,2-a]pyrimidin-4-one was synthesized (5). The chemical synthesis process was found to be simple and produced risperidone in a high yield. In addition, can be easily scaled up for large scale synthesis.