Development and Evaluation of Swellable Elementary Osmotic Pump Tablets of Metoprolol Succinate and Ramipril

Swellable elementary osmotic pump (SEOP)utilizes the osmotic pressure and polymer-swelling force to deliver drugs to the GI tract in a reliable and reproducible manner.Metoprolol and ramipril are one of the combinationsindicated in the management of hypertension in patients with heart failure and post myocardial infarction. This combination was selected to develop SEOP to release the drugs continuously for a period of 24hrs and the release is controlled by swellable polymer and the osmogen.SEOP tablets of Metoprolol and Ramipril were preparedusing additives likeMannitol MCC, talc, magnesium stearate, aerosol with varying concentrations ofswellable polymers(PEO,Carbopol) coating of cellulose acetate as semi permeable membrane, Dibutyl phthalate as plasticizer. An orifice was made on one face of the tablet mechanically. Effects of differentconcentrations of PEO (MRSE1-MRSE3) and carbopol (MRSE4-MRSE6)and various orifice size (MRSE7-MRSE10) on the in vitro release were studied. On comparing in vitro release of formulations (MRSE1MRSE6), the release rate decreased with the increasedconcentrations of polymers and directly proportional to the orifice size. Thedecreased release rate was due to solubility-modulating properties of the polymer. Among the formulations, MRSE3 shown optimum drug release rate 97.54% and 89.6% for Metoprolol and Ramipril respectivelyat the end of 24 hours. The optimized formulations was independent of the agitation intensity, pH of the medium, stable and deliverMetoprolol and Ramipril at a zero order rate for 24 hrs.