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Toxicology. 1975 Nov;5(2):209-20.

Comparative percutaneous absorption of pyrithiones.


The percutaneous absorption of 3H or 35S labelled pyridine-2-thione-N-oxide (PT) through the skin of rat, rabbit and guinea pigs in vivo is reported. The sodium (Na) zinc (Zn) and zirconium (Zr) derivatives of PT were studied and the effects of duration of contact and concentration of the NaPT and ZnPT in test solutions were examined. Shampoo test solutions containing the isotopically labelled PT were applied to the skin of the animals. The skins were then rinsed, the treated areas of skin protected and excreta were monitored for the isotope for 2 days after treatment. Penetration was calculated from the amounts of isotope in the excreta. Further groups of animals were treated with test solutions applied under occlusive patches for 6 h before rinsing the skin. The turnover of Na and ZnPT in the three species after intraperitoneal and subcutaneous injection was measured. All three species rapidly excreted the injected isotope principally via the urine. The comparative penetration of the three PT samples was Na greater than Zr greater than Zn from all treatments. The comparative permeability of the animals' skins to these PTs was rabbit greater than rat greater than guinea pig. NaPT penetration was found to be dependent upon duration of contact and concentration in the test solution whereas the penetration of ZnPT was found to be proportional to concentration but independent of duration of contact of the test solution. Extrapolation of these findings to the use of shampoos containing up to 1% (w/v) ZnPT by man indicated an adequate margin of safety for use of this type of product.

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