126 Investigation of the Systemic Bioavailability of 5% Minoxidil Topical Solution in Young Males with Early Androgenetic Alopecia

R.J. Trancik1, J.R. Spindler1, J.J. Ferry1, R.V. Cuddihy1, R.D. Gilbert2, M. Casser2. Pharmacia Consumer Healthcare, Peapack, NJ, USA1 and TKL Research Inc., Paramus, NJ2.

There are no pharmacokinetic data on minoxidil topical solution (MTS) in adolescents with androgenetic alopecia (AGA). The objective of this investigation was to establish the steady-state percutaneous absorption and systemic bioavailability characteristics of 5% MTS in young male subjects (age 17 years and younger) with early AGA. This study was designed as a single-arm, single-center, open-label clinical investigation. Thirteen male subjects, age 17 or younger, with evidence of thinning hair at the frontal or vertex area of the scalp, self-administered 5% MTS 1.0 mL twice daily for a total of 11 doses to the balding area of the scalp. Serum and urine minoxidil levels were measured. AUC estimation and Cmax calculations were performed. Thirteen subjects who met entry criteria completed the study and were evaluable for analysis. Steady-state levels of minoxidil were achieved rapidly in these subjects. Mean Cmax was 1.58 ng/mL and mean AUC (0-24) was 25.4 ng-hr/mL. Mean total minoxidil excretion over the initial 12 hours after the application of the last dose was 537 mcg. There were no reports of scalp irritation with the use of 5% MTS. Fourteen adverse events were reported including abnormal liver function test findings. One subject had 2 adverse events (increased total bilirubin and increased ALT) that the investigator attributed to the study medication; none were serious. No one discontinued study participation because of an adverse event. Based on the results of this study, and in comparison to previous studies in older male subjects, it appears that younger subjects (<18 years of age) are not at risk for increased absorption of minoxidil when 5% MTS is applied BID for multiple days.