ABSTRACT
Clonidine was found to have such as low allergenicity that it impeded studies of sensitization mechanisms in guinea pig models. Indeed, using Draize repeat insult patch test assays in men, clonidine 9% pet. did not induce contact allergy, whereas 4 of 74 volunteers having undergone the procedure with the clonidine-TTS became sensitized. Another possible explanation given was that the small amount of acetaldehyde present in the device is critical and may induce a clonidine derivative, a reactive condensation product of acetaldehyde and two molecules of clonidine, which is the actual sensitizing hapten in a number of the patients. Sensitization rates to clonidine have been cited to be highest in white women followed by white men, black women and black men. Oral administration of clonidine in patients sensitized to the TTS are in most cases well tolerated. In a prospective study, 29 patients with hypertension were treated with clonidine-TTS.
