FUNDAMENTAL INVESTIGATION OF A NOVEL DRUG-DELIVERY SYSTEM, A TRANSDERMAL DELIVERY SYSTEM WITH JET INJECTION

A new drug delivery system simultaneously using jet injection and a tr ansdermal delivery system was proposed. After pretreatment of hairless rat skin by a jet injector containing physiological saline without an y drug to make a pore in the skin, aqueous solution containing gentamy cin sulfate, nicardipine hydrochloride or theophylline was applied on the pore. Absorption clearance (volume flow rate) through the skin (th e product of permeability coefficient and application area) was almost the same (0.4 mu l/h) with any type of drug and regardless of propert ies and concentrations. Plasma concentration of gentamycin when the di stance between the injector and skin surface was 5 mm was twice that w hen there was no space between the two. It was found by morphological observation that injection from 5 mm away made a larger pore in the st ratum corneum (about 0.3 mm(2)) and a clear saline reservoir in the vi able epidermis and dermis. Mathematical analysis showed that this larg er pore greatly increased the skin delivery (absorption) rate, whereas the saline reservoir increased it little. This high delivery rate con tinued for over 1 week with theophylline.