Topically applied verapamil hydrochloride inhibits tuberculin-induced delayed-type hypersensitivity reactions in human skin.

Calcium channel antagonists have been reported to possess inhibitory effects on lymphocyte migration and activation in vitro, and on cell-mediated immune reactions in the skin of experimental animals. We have therefore studied the effects of topically applied 8% (w/v) verapamil hydrochloride in propylene glycol on tuberculin-induced delayed-type hypersensitivity reactions in the skin of normal human volunteers. There was significant inhibition of the tuberculin reactions by the verapamil preparation compared to vehicle controls, as determined by forearm skin fold thickness measurement and assessment of the density of mononuclear cell infiltrates in skin biopsies. The precise mechanism of action of verapamil hydrochloride remains unclear, but could include effects on T-cell migration and activation, on antigen-presenting cells, and/or on other cells. The potential for the use of topical calcium channel antagonist preparations in inflammatory skin diseases warrants further study.