Percutaneous absorption of clioquinol (Vioform)

The percutaneous absorption of clioquinol from three different preparations for skin treatment (Vioform cream, Locacorten-Vioform cream and Vioform-Hydrocortisone cream) was evaluated. After topical dosages corresponding to 30 mg clioquinol, concentrations in the blood were below the detection limit of the analytical procedure, i.e., smaller than 0.02 micrograms/ml; therefore the percutaneous absorption was evaluated by measuring cumulative urinary excretion of clioquinol and was compared to that found after an equivalent oral dose. The study was carried out in 4 healthy volunteers. The topical preparations were applied under occlusive dressings. Following epicutaneous application of the three topicals in quantities containing 30 mg clioquinol each, the urinary excretion of the drug was between 1.2 and 3.6% of the applied dose. When the same dose of clioquinol was administered orally to two volunteers, 52.4 and 92.9% of the dose was excreted in the urine. Taking the urinary elimination as the minimal amount of drug absorbed, the extent of percutaneous absorption from the three dermatological preparations amounted to 1.2-3.6% of the applied dose. There was no difference in the pattern of urinary excretion products among the three topicals and the oral formulation. The bulk of clioquinol was excreted as glucuronide (mean: 96 +/- 3%) and only a small fraction was excreted as sulfate (mean: 3.8 +/- 3%). A small amount of free clioquinol (1.1%) was measured in 1 subject only after the oral dose.