Preparation and evaluation of proliposomes containing propranolol hydrochloride

Proliposomes were prepared by the penetration of a methanol-chloroform solution of propranolol hydrochloride (PH) and lecithin into microporous sorbitol, with subsequent vacuum drying. They were characterized for surface morphology and flowability, and following the conversion to liposomes upon hydration, size distribution, drug content and in vitro drug release of the reconstituted liposomes were examined. The porous structure of sorbitol was maintained in the proliposomes, affording the proliposomes good flowability at lecithin-to-sorbitol ratios (w/w) of not more than 0.2. Multilamellar liposomes were reconstituted spontaneously from the proliposomes upon hydration. The mean diameter of the resultant liposomes was highly dependent on the PH-to-lecithin ratio, but less dependent on the lecithin-to-sorbitol ratio and sorbitol particle size (105-710 microns). Entrapment efficiency of PH in liposomes showed a maximum 10% at PH-to-lecithin ratio < 0.5 and a lecithin-to-sorbitol ratio > 0.1. Sustained release of propranolol from the proliposomes was achieved when the lecithin-to-PH ratio was > 2, and the lecithin-to-sorbitol ratio was in the range examined (0.067-0.2). In conclusion, granular proliposomes of PH with good flowability and sustained release characteristics could be prepared by controlling the drug/lecithin/sorbitol ratio and sorbitol particle size. PH proliposomes can be potential candidates for the sustained drug delivery of propranolol when applied directly onto the mucosal membranes.