The aim of the present investigation was to prepare a hydrophobic matrix, investigate the drug release kinetics and statistically optimize the formulation for sustained release drug delivery of venlafaxine hydrochloride. A novel combination of carnauba wax and Eudragit E 100 was used to prepare the hydrophobic matrix. A simplex centroid design was constructed using the amount of carnauba wax, Eudragit E 100 and lactose as formulation variables. Drug release after 12 hrs and time required for 50% release of the drug were evaluated as response parameters. It was observed that EudragitL 100 had more pronounced effect on retarding the release at the end of 12 hrs whereas carnauba wax was more effective in prolonging the time required for 50% release of the drug. Lactose had least effect on both of these parameters. It was also observed that a combination of all these factors resulted in optimum results for both response parameters. Statistical models and response surface technologies were used to optimize the formulations and these models were found to be valid for predicting the values of response parameters.
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