Preparation of monolithic osmotic pump system by coating the indented core tablet

A method for the preparation of monolithic osmotic pump tablet was obtained by coating the indented core tablet compressed by the punch with a needle. Atenolol was used as the model drug, sodium chloride as osmotic agent and polyethylene oxide as suspending agent. Ethyl cellulose was employed as semipermeable membrane containing polyethylene glycol 400 as plasticizer for controlling membrane permeability. The formulation of atenolol osmotic pump tablet was optimized by orthogonal design and evaluated by similarity factor (f2). The optimal formulation was evaluated in various release media and agitation rates. Indentation size of core tablet hardly affected drug release in the range of (1.00–1.14) mm. The optimal osmotic tablet was found to be able to deliver atenolol at an approximately constant rate up to 24 h, independent of both release media and agitation rate. The method that is simplified by coating the indented core tablet with the elimination of laser drilling may be promising in the field of the preparation of osmotic pump tablet.