Clonidine: irritant and allergic contact dermatitis assays.

Clonidine in petrolatum, clonidine transdermal device, and its placebo device were assayed for relative irritancy potential (21-day cumulative irritancy assay) and allergic contact dermatitis potential (Draize repeat insult patch test assay). Both clonidine in petrolatum and the clonidine transdermal device appear to be of minimal irritancy potential. Only the clonidine device demonstrated, in the Draize assay (and in clinical trials), allergic contact dermatitis potential. Its relatively delayed onset of demonstration of allergic contact sensitization in clinical trials requires investigation as to mechanism.