Salicylates and renal function in rheumatoid arthritis.

The effect of salicylate treatment on the kidney, particularly medullary function, was investigated. In a retrospective analysis patients with rheumatoid arthritis (RA) treated with high doses of salicylates were shown to have inferior urinary concentrating power and increased excretion of N-acetyl-beta-D-glucosaminidase (NAG) when compared with patients who had not received salicylate treatment. A prospective study of renal funcition in healthy people and patients with RA starting salicylate in therapeutic doses showed that while epithelial cell excretion was only transiently raised in both groups the excretion of NAG was increased in all cases at three days and this increase was sustained at 10 days, all values being much higher in the patients than in the healthy subjects. Thus salicylate treatment does cause renal tubular damage but this damage results in only minimal impairment of function and does not constitute a reason for withholding salicylate treatment.