Cutaneous Adverse Drug Reaction

Any drug, drug vehicle, or food product can cause an adverse reaction in the skin (toxiderma) (Figure 12-6). Most authors agree that toxiderma can mimic any skin disease. Some specific drugs preferentially induce pinna lesions.

Self-induced mutilation of the head and neck has been reported in hyperthyroid cats treated with carbimazole. The same symptoms have been observed less

Figure 12-6

A, Sudden onset of ear and neck excoriation in an 8-year-old male domestic short-hair cat associated with treatment. No other lesions could be seen on the body. B, The same cat 2 months later.

commonly in cats treated with the carbimazole metabolite, methimazole.^14,15 Facial pruritus has also been associated with propylthiouracil and clavulanic acid and amox­icillin.¹⁶ Cephalexin-induced pemphigus foliaceus lesions on the whole ear pinna and extending to the face have been observed in one cat.¹⁶ Vasculitis, causing necrotic pinnal lesions and onychomadesis, was associated with penicillin injections.¹⁶