The main objective of pre-formulation testing is to generate information useful in developing the formulation, which is stable, and bioavailability. Further, the use of pre-formulation parameters maximizes the chances in formulating an acceptable, safe, efficacious and stable product. Respiridone is a selective serotonin reuptake inhibitor, chemically unrelated to tricyclic, tetracyclic, or other antidepressants, presumably, the inhibition of serotonin reuptake from brain synapse stimulated

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... tonin activity in the brain. The drug & excipient Compatibility studies no interaction between polymer and drug. The angles of repose of different formulations were found between 23.91± 0.4 to 28.45± 0.47. The bulk density of blend of Respiridone and excipients were found between 0.57 g/ml to 0.66 g/ml. True density were found between 0.54 g/ml to 0.65/ml. The Carr's index for all the formulations was found to be 17.2-19.7. The thickness of the tablets was found out using Vernier Caliper and the thickness found to be in the range of 4.02-4.12 mm for the uncoated tablets (F1-F6), hardness studies and results showed they were in between 6.1-8.0 Kg/cm 2 in all batches. The dissolution rate was found to be increased in the first two hours and the drug release was found to be 53.5%, 44.1%, 38.4% at the end of 2 hrs. Formulation F4 containing HPMCK4M and HPMCK100M showed much prolonged drug release when compared to formulation F5 containing HPMCK4M and ethyl cellulose. Formulation F6 was carried out using three rate controlling polymers HPMCK4M, HPMCK100M and ethyl cellulose.. In the formulations F9, F10 and F11 HPMCKM concentration was decreased and ethyl cellulose was increased. The similarity factor (f 2) of all the formulations ranged from 30 to 68.7. The similarity factor of F10 is high when comparing to other formulations so, it is more similar to that of marketed formulation.