Successful transdermal administration of therapeutic doses of a polypeptide to normal human volunteers
The human stratum corneum constitutes a relatively impermeable barrier to the transdermal absorption of most substances, including polypeptides and proteins. This double-blind, randomized, crossover study in 13 normal men evaluated whether a low level of electrical current could induce changes in cutaneous permeability sufficient to produce absorption of a polypeptide. We compared cutaneous absorption of 5 mg of leuprolide (a 9 amino acid luteinizing hormone releasing hormone analogue) in transdermal patches containing 0.2 mA electrical current (active) and in patches containing no electrical current (passive). Serum luteinizing hormone (LH) concentration was measured 12 times during an 8-hour period as a measure of drug effect. Similar baseline LH levels were seen in each group: active = 11.3 +/- 3.1 mIU/ml and passive = 13.7 +/- 4.7 mIU/ml (p not significant). Significant elevations of LH were seen in active compared with passive patches (p = 0.0084). As predicted, passive patches produced no elevation of LH concentration (LH = 11.8 +/- 7.1 mIU/ml at 4 hours). However, active patches produced elevations comparable to those achieved with subcutaneous administration of the drug (LH = 56.4 +/- 49.6 mIU/ml at 4 hours and p = 0.003 compared with passive). The patches were well tolerated without significant cutaneous toxicity. It is concluded that the use of low levels of electrical current can induce changes in the permeability of the stratum corneum. These changes are sufficient to promote the transdermal absorption of therapeutically relevant amounts of a polypeptide. This has major importance for our understanding of skin permeability and for the development of new techniques for drug administration.