Aellte reuI ran." _II ......... -COD"' •• " kl..." ..... : flrst ,.rt Due to patient misunderstanding and noncompliance a man had been taki~ 25-30 magnesium trisilicatt;(SOOmg) + aluminium hydroxide (2S0mg) tablets daily for several years to relieve gastritis. He presentt;d at the emergency room with oedema, vomiting and difficulty in passing urine or several days duration. During the previous 2 weeks he had been treated with diphenoxylate hydrochloride-atropine sulphate for diarrhoea and had continued taki~ diazepam which he had been usina for some time. Serum sodium and chloride were normal but potassium (6. 3mEq/ D. blood urea nitroaen (72mg/dO. and creatinine ( 13.1 JrII,I dJ) were all elevated. Acute renal failure Was diagnosed and he was admitted. Elevated magnesium levels were found (8. 4mg/ dJ) and subsequent questioning revealed his excessive antacid use (up to 200 tablets/week). No urine was returned when a Foley catheter was inserted so peritoneal dialysis was carried out with 40 eJlcbanges over the next four days. A retrograde pyelogram revealed many kidney stones. which were tben surgically removed. The ureteral catheters remained in place. and over the next four days the patient experienced a massive diuresis with a 14.Skg weight loss. He was discharged on the 15th day and 4 weeks later there was no apparent residual kidney damll8e. On analysis the kidney stones were found to contain crystals of mqnesium-ammonium phosphate. High amounts of magnesium were present but no calcium was fwoo. S~pensions of magnesium and aluminium hydroxide have been shown to increase urinary pH which promotes the formation of magnesium-ammonium phosphate crystals. This could bave been a contributing factor in this catient. On discharge the patient was counselled on the proper use of antacids and was given a different preparation which. although magnesium-containing, was a more effective antacid. Millette. C. H. and Snodanss. G . L : American Journal of Hospilal Pharmacy J8 : 1 JS2(Sep 1981)

Re8Ct1oos 15 Jan 1982 3