Nonsteroidal antiinflammatory drugs can adversely affect the kidney. They may induce sodium retention and antagonize the action of diuretics, impair free-water clearance and cause hyponatremia, and prevent aldosterone production and cause hyperkalemic hyperchloremic acidosis. If patients taking these drugs are exposed to a renal insult, acute renal failure becomes more likely. Similarly, patients with chronic renal disease who are taking them appear to be at greater risk of chronic renal failure. However, not all renal effects of nonsteroidal antiinflammatory drugs are adverse. Beneficial effects have been reported in patients with Bartter's syndrome and in those with severe orthostatic hypotension.