Contact sensitivity to quinidine sulfate from occupational exposure.

Three workers exposed to quinidine sulfate became sensitized after short exposure times (2-3 months). They were patch test positive to quinidine in different vehicles, but negative to the diastereoisomer quinine. Guinea pig maximization tests demonstrated quinidine and quinine to be grade V allergens according to the classification of Magnusson & Kligman. When challenged for cross reactivity, the animals sensitive to quinine did not react to quinidine. Among the quinidine-sensitive guinea pigs, three of 20 (P greater than 0.05) reacted when challenged with quinine.