Ex vivo absorption of promestriene from oil-in-water emulsion into infant foreskin

Hypospadias is a birth defect in which the urinary tract opening is not at the tip of the penis. Hypospadias surgery is frequently complicated by healing deficiencies. Topical treatments with oestrogens were reported to improve healing. In the present study, ex vivo percutaneous absorption of promestriene, a synthetic oestrogen resulting of the double esterification of estradiol was conducted as a pre-requisite for further clinical trial in infants. Penetration of promestriene into infant foreskin treated with commercial oil in water emulsion (10 μg mg⁻¹) for 24 h was characterized showing controlled release properties enabling epidermal concentration more than six times higher than dermal concentration (4.13 ± 2.46 mg g⁻¹ versus 0.62 ± 0.84 mg g⁻¹, respectively). Furthermore, apparent promestriene fluxes into and through the skin (i.e., 1.5 μg cm⁻² h⁻¹ and < 0.89 μg cm⁻² h⁻¹, respectively) were calculated from (i) drug amount retained into epidermis and dermis, or (ii) the limit of detection into the receptor fluid. In conclusion, less than 2% of initial dose were absorbed within 24 h which compared well with others steroids applied topically in colloidal systems.