Enhanced Skin Permeation of Sex Hormones with Novel Topical Spray Vehicles

The feasibility of using some novel topical spray vehicles for enhanced transdermal delivery of the sex hormones, testosterone (Tes), estradiol (E2), progesterone (Prog), and norethindrone acetate (NA) has been investigated. The new penetration enhancers, padimate O (PadO) and octyl salicylate (OSal) were used and compared with laurocapram (AZ) and oleic acid (OA). A finite dose (5 µL/cm2) of each vehicle was applied to either shed snake skin or swine skin in vitro, and the amount penetrated was measured with flow‐through diffusion cells. Partitioning into swine skin was determined after an exposure time of 1min. Rapid partitioning of Tes and PadO into swine skin occurred after 1min with 70% and 60% of the applied dose, respectively, remaining in the skin after the unabsorbed dose was removed by rinsing with absolute ethanol. The cumulative amount at 24h (Q24h) of Tes penetrating across the snake skin was significantly enhanced (p < 0.05) up to 6‐fold for OSal, 3‐fold for OA and AZ, and 2‐fold for PadO compared to control. Using PadO or AZ, the Q24 h ranged from three‐ to thirteen‐fold over control (p < 0.05) for E2, Prog, and NA. Extrapolation of these data to predict what would happen in humans suggests that it should be possible to deliver clinically relevant amounts of sex hormones in this manner with once daily dosing.