Percutaneous penetration of dipyrithione in man: effect of skin color (race).

A single chemical dose of dipyrithione (2,2'-dithiobispyridine-1,1'-dioxide), 4 or 12 micrograms/cm(2) (containing 1 micro Ci of 2-6-14C material), was applied to the ventral forearm (intact skin, methyl alcohol vehicle [MeOH]), forehead (intact and stripped skin; cosmetic cream and MeOH vehicle), and scalp (intact and stripped skin; shampoo and MeOH vehicle) of human (white and black) volunteers. The urinary excretion of 14C was measured over the 7-day study period. Percutaneous penetration data were corrected for incomplete urinary recovery using data from intravenous studies (Wedig et al). The results obtained in this study suggested: (1) means from the complete analysis indicated 34% less (p less than 0.02) absorbed by blacks; (2) less was absorbed by blacks than whites when seven out of seven means were compared within groups (p less than 0.02); (3) a difference (p less than 0.03) in penetration, blacks 47% lower than whites, between a cosmetic cream vehicle vs MeOH on the forehead; (4) on the scalp (MeOH vs shampoo vehicle) more was absorbed using MeOH (p less than 0.02); (5) no evidence of a significant difference in penetration was noted when (a) the various anatomic sites were compared or (b) intact skin was compared with stripped skin.