The aim of the current study was to design controlled porosity osmotic pump tablets of Rabeprazole sodium. The porous osmotic pump contains pore forming water-insoluble additive (Synthetic Hydrotalcite) in the coating membrane which after coming in contact with water is removed from membrane, resulting in an in situ formation of micro porous structure. The dosage regimen of Rabeprazole sodium is a 50-mg tablet once in a day. The plasma half-life ranges from 1 to 2 hours. Hence, Rabeprazole sodium was chosen with an aim to develop a controlled release system for 5 hours. The effect of different formulation variables, namely, ratio of drug to osmogent, membrane weight gain and level of pore former on the in vitro release was studied using 23 factorial designs. Ethyl cellulose was used as the semi permeable membrane. The effects of pH and agitation on drug release were also studied. Drug excipients compatibility was studied by FT-IR. The optimized formulation was subjected to stability study for one month period. It was found that drug release rate increased with the amount of osmogent because of increased water uptake, and hence, increased the driving force for drug release. Drug release was inversely proportional to membrane weight gain, however, directly related to the level of pore former in the membrane. Optimized formulation was found to deliver above 98% of drug (Rabeprazole sodium) at a zero order rate for 5 hours.
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