A 69-year-old woman with advanced rheumatoid arthritis (RA) suffered two episodes of hyperkalemic hyperchloremic metabolic acidosis (HCMA), Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were markedly suppressed in the first episode occurring in paralell with the administration of metoprolol during piroxicam and lobenzarit (CCA) therapy. Rechallenge with diclofenac sodium and CCA lead to the second hyper-kalemia, but no significant suppression of the renin-aldosterone axis was seen at that time. This suggests that the different mechanisms contribute to the development of these episodes, including the tubulo-interstitial injury which is not uncommon in RA. The combined use of nonsteroidal anti-inflammatory drugs (NSAIDs) and β-adrenergic blockers may increase the risk of life-threatening hyperkalemia through their suppressive effect on the renin-aldosterone system, whereas the concomitant administration of CCA with NSAIDs through the impairment in the renal tubular function. These drugs should be most carefully given to patients with a latent defect in renal potassium excretion.
