Tetrazepam drug sensitivity -- usefulness of the patch test

The muscle relaxant tetrazepam may cause severe cutaneous adverse effects. We report 4 cases of varying intensity: Stevens-Johnson syndrome, erythema-multiforme-like exanthema, maculopapular and maculo-urticarial exanthema. Patch testing with tetrazepam (10% in petrolatum) was strongly positive in the 2 patients with severe skin eruptions and weakly positive in the other 2. Oral rechallenge with tetrazepam was positive in 3 patients (1 not done). Diazepam, with a similar chemical structure to tetrazepam, was negative on patch testing and on oral challenge testing in 2 patients. Although the optimal patch test concentration of tetrazepam has still to be determined, it is a useful diagnostic tool to confirm sensitization, particularly in patients with severe bullous eruptions.