BIOAVAILABILITY FOLLOWING TRANSDERMAL POWDERED DELIVERY (TPD) OF RADIOLABELED INULIN TO HAIRLESS GUINEA-PIGS

Transdermal powdered delivery (TPD) is a novel method for needle-free administration of drugs, vaccines, and other therapeutic compounds. In this study, the efficiency of the TPD method has been evaluated follo wing delivery of radiolabeled inulin to hairless guinea pigs. The quan tity of radioactive inulin excreted in the urine, as a percentage of t he total amount delivered, has been used as a measure of bioavailabili ty. Maximum urine recoveries of radiolabeled inulin (mean+/-SE) for TP D were 32.8+/-3.7% when the site was unwashed following injection and when large inulin particles (39-52 mu m) were used. Washing the inject ion site immediately following inulin administration resulted in decre ased recovery levels (12.2+/-1.3%) for the same sized particles. Deliv ery of smaller inulin particles (21-24 mu m) with no post-injection wa shing of the site resulted in a reduced urine recovery levels (10.8+/- 4.1%) over that obtained with the larger particles. For comparison, su bcutaneous injection of a similar dose resulted in recovery levels of 88.9+/-3.6%. Inulin residue within the prototype PowderJect(R) device used for these experiments was shown to be approximately 17% of the st arting dose. A small but acceptable degree of skin damage (erythema) a t the injection site was seen following administration of the compound .