Allopurinol-Caused Toxic Epidermal Necrolysis

To the Editor.—  It is risky to imply that allopurinol was more likely to have caused toxic epidermal necrolysis than ampicillin or cephalothin in cases 1 and 3 in the report by Ellman et al in the Archives (111:986-990,1975) titled "Toxic Epidermal Necrolysis Associated With Allopurinol Administration." In fact, it is as likely that the eruption was caused by ampicillin as allopurinol in two of their three patients. In the third patient, case 2, the patient was also taking methyldopa and indomethacin. It is well known that one drug may have a propensity to produce different eruptions and many different drugs may produce the same eruption. When a patient is taking several drugs, it becomes critical to identify the offensive drug when (1) continuous treatment is indicated as in subacute bacterial endocarditis or (2) the eruption is life-threatening.The argument that allopurinol alone produced these eruptions is less convincing to