Abstract
The transdermal delivery of theophylline was evaluated using various ethanol (EtOH)/water (60/40)-hydroxypropylmethylcellulose (HPMC) systems with or without lauric acid as a permeation enhancer. The in vitro skin permeability of theophylline across the excised hairless mouse skin and the in vivo skin absorption of the drug using abdominal rat skin were remarkably enhanced by the addition of lauric acid to the EtOH/water (60/40) binary vehicle or EtOH/water(60/40)-HPMC systems. The limited concentration of lauric acid for the maximal permeability of the drug was 4% (w/w). The in vivo skin absorptions of theophylline from EtOH/water (60/40)-HPMC systems with 4% (w/w) lauric acid and with various concentrations of three HPMCs(65SH-400, -1500, -4000) showed essentially same patterns as that from EtOH/water (60/40) binary vehicle with 4% (w/w) lauric acid. Furthermore, EtOH/water (60/40) -3% (w/w) HPMC 65SH-4000 system with 4% (w/w) lauric acid indicated the greatest bioavailability (92.7%) in the systems investigated and was considered as the most useful recipe for delivery of theophylline applicable to the skin.
