Verapamil sustained release: new formulation and convolution

A novel bead formulation of verapamil hydrochloride was developed comprising a combination of extrusion and spheronization to produce a relatively high drug load, followed by coating of the bead with an insoluble polymer (ethylcellulose) that contains a water soluble channeling agent (lactose), thus allowing the application of a sufficiently thick outer coating that is uniform and robust without 'shutting down' release of the relatively insoluble drug. The new formulation provided the unexpected benefit that by adjusting both coating thickness and ethylcellulose/lactose ratio, it is possible to obtain essentially non-agitation sensitive and approximately zero-order drug release up to 14 hours in either KCl or two pH media, at stirring speeds of either 75 or 200 rpm with either the USP basket or USP paddle stirring method.