Briefly, a solution of drug and polymer (10–20% polymer concentration) in dichloromethane was injected into an aqueous continuous phase at a ratio between 250 and 350 parts of polymer phase:aqueous phase, under stirring with a Silverson

L4R mixer (Silverson machines, MA, USA) at 5000rpm. Subsequently, #Camptothecin in vivo randurls[1|1|,|CHEM1|]# the solvents were removed by stirring after which the microspheres were recovered by filtration, suspended in a suitable vehicle, filled into vials, and freeze-dried. The microspheres were characterized as described Inhibitors,research,lifescience,medical in Section 2.3. 2.3. Characterization of Microspheres 2.3.1. Particle Size Particle size distribution of the microspheres prior to vialing was determined using a laser Inhibitors,research,lifescience,medical diffraction technique (Malvern 2600c Particle Sizer, Malvern, UK). The particles were suspended in 0.05% Tween 80 and counted using a laser sensor [41]. The average particle size was expressed as volume mean diameter in microns (μm). 2.3.2. Surface Morphology The surface morphology was examined by scanning electron microscopy (SEM) (Hitachi S800, Japan) at an appropriate magnification, after Inhibitors,research,lifescience,medical palladium/gold coating of the microsphere sample on an aluminum stub. 2.3.3. Bulk Density Bulk density of the microspheres was determined by transferring a weighed amount of microspheres to a graduated cylinder. The cylinder was subsequently tapped 50 times from

a vertical distance of approximately Inhibitors,research,lifescience,medical 0.5 inches and the occupied volume recorded. The tapping process was repeated until the volume occupied by particles remained unchanged. The final volume was recorded as bulk volume,

Vb, and the tapped bulk density (g/cc) was calculated as M/Vb, where “M” was the weight of microspheres employed. 2.3.4. Drug Content Risperidone content in the microspheres was analyzed by a reverse phase HPLC method using a Nucleosil C-18 column (Phenomenex, Torrance, CA) at a flow rate of 1 mL/min. The mobile phase consisted of 30% v/v acetonitrile and 0.1% (v/v) trifluoroacetic acid in water. Drug content (%) was expressed as the “weight of drug in microspheres/weight of microspheres × 100.” 2.3.5. In Vivo Studies In accordance Inhibitors,research,lifescience,medical with Institutional Guidelines and an in-house Methisazone developed and an approved protocol, four groups of male Sprague-Dawley rats (Harlan Inc., Indianapolis, IN) weighing approximately 300gm were used in the in vivo study. Group 1 received Formulation A, Group 2 received Formulation B, Group 3 received Formulation C, and Group 4 received Formulation D. Briefly, vials containing freeze dried microspheres along with diluent were reconstituted with WFI (water for injection) and injected subcutaneously at the base of the rat neck at a dose of 20 or 40mg/kg Risperidone (Table 1). Blood was sampled from the rat tail vein at predetermined intervals, after which the samples were centrifuged in Microtainer tubes (Becton Dickinson & Co., Franklin Lakes, NJ) and serum was collected.