INVITRO RELEASE AND PERMEATION OF LEVOBUNOLOL FROM VARIOUS TRANSDERMAL FORMULATIONS

Levobunolol (LB) is a potent beta-blocker with proven antihypertensive activity. However, it has a short biological half-life and requires frequent dosing. To overcome these problems, the feasibility of systemic delivery of LB via the transdermal route was explored. A series of in vitro skin permeation studies of the drug were conducted at 37-degrees-C across hairless mouse skin. It was found that the skin permeation potential of LB free base was much higher than that of its hydrochloride salt. Release of LB from different systems showed a characteristic matrix diffusion-controlled Q vs t1/2 linear relationship, whereas skin permeation profiles from all those systems showed a membrane permeation-controlled Q vs t linear relationship. The in vitro skin permeation flux values ranged from 1.09 to 60.92-mu-g/cm2 per h depending upon the system at a 5% (w/w) loading dose of LB base. Azone showed a skin permeation enhancing effect on LB at a 10% (w/w) concentration. The flux value obtained from an indirect in vivo method using a polyacrylate patch showed an excellent in vitro/in vivo correlation.