Dr Charytan points out that our case is "typical of the effects seen with tetracyclines in azotemic patients" but doubts that it documents direct nephrotoxicity. We would agree. As we pointed out in our comments, tetracycline nephropathy may be multifactorial in origin. It is difficult in the analysis of a single case to specifically incriminate or exclude any of these factors. However, since this drug has been widely promoted as a "safe" tetracycline to administer to renal patients, we feel that it is important for physicians to recognize that doxycycline may produce side effects typical of those seen with other tetracyclines in azotemic patients.