Absorption and disposition of econazole nitrate after application to the skins and vaginas of rabbits.

1. The absorption and tissue distribution of radioactivity has been studied in rabbits after application of a cream containing 10 mg of the 3H-labelled 1-(2,4-dichloro-beta-[(p-chlorobenzyl)oxy]phenethyl) imidazole nitrate (econazole nitrate, Pevaryl) to the normal or abraded skins of rabbits. 2. Approximately one-third of the dose was absorbed through the occluded normal skins of rabbits during 8 days, mainly during 7 to 24 h. In the same time interval, slightly more of the dose was absorbed through the occluded abraded skins of rabbits at slightly greater rates. Co-formulation of triamcinolone acetonide in the cream reduced and delayed the peak rates of absorption through normal and abraded skin, but the extent of absorption during 8 days was similar in the presence or absence of triamcinolone acetonide. 3. After application to normal skin or abraded skin, the peak of mean concentrations in the plasma of 220 ng/ml (range 132-276 ng/ml) or 307 ng/ml (range 270-321 ng/ml), respectively, occurred at 24 h. Tissue distribution of radioactivity was similar after application to normal or abraded skin, and concentrations were highest in the liver, kidneys and gastrointestinal tract (which are the organs of biotransformation and excretion) and also in the adrenals and to a lesser extent in the uterus, ovaries and untreated skin. 4. After application of a cream containing 5 mg of 3H-econazole nitrate to the vaginas of rabbits, approximately one-third of the dose was absorbed during 8-24 h, and rates of excretion were higher through the more permeable vaginal membrane. 5. After vaginal doses of 5 mg, a peak concentration of 209 ng/ml occurred at 6 h in the plasma. Tissue concentrations of radioactivity after vaginal doses were highest in liver, kidneys, gastrointestinal tract, adrenals and ovaries, and the tissue distribution was similar to that observed after cutaneous doses.