The Effect of Dexamethasone on Urinary Acidification

Summary Although it is well recognized that mineralocorticoids enhance renal acid excretion, the effect of glucocorticoids on renal acidification is unclear. Oral administration of dexamethasone to six healthy volunteers for 1 week at a daily dose of 4.5 mg was associated with mild respiratory alkalosis and a small but statistically significant increase in baseline urine pH. However, neither the ability to lower urine pH nor to excrete titratable acid and ammonium after NH4Cl acid-loading was altered. Administration of a single intravenous dose of dexamethasone sodium phosphate (7.5 mg) was associated with a significant rise in urine pH and potassium excretion and decreased titratable acid, ammonium, and phosphorus excretion in the absence of changes in blood acid-base status, creatinine clearance, or urine flow. The authors wish to thank Drs. Lawrence Fishman and Ulrich Michael for their critical review of the manuscript and Kenneth Bailey, Olive Pappas, Raul Rodriguez, and Robert Rubin for their assistance.