Effect of acute paracetamol overdose on changes in serum and urine electrolytes

Abstract

What is already known about this subject • Paracetamol causes renal failure in overdose. Experimental studies have shown that paracetamol can inhibit COX II systemically in a manner similar to selective COX‐II inhibitors. • In overdose nonsteroidal anti‐inflammatory drugs such as ibuprofen, cause dose‐dependent increase in urinary potassium excretion (FeK) and sodium retention, probably due to vasoconstriction. What this study adds • Paracetamol overdose is associated with dose‐related hypokalaemia and kaliuresis of short duration (<24 h), suggesting a specific renal effect of paracetamol in overdose. • This effect seems likely to be via cyclo‐oxygenase inhibition and may be separate from the nephrotoxic effects of paracetamol. Aims To investigate the effects of acute paracetamol overdose on renal function, serum and urine electrolyte excretion in man. Methods Two studies were performed in patients admitted with paracetamol overdose: a retrospective study examining changes in serum electrolytes, and a prospective study evaluating changes in serum and urine electrolytes. A control group with SSRI overdose was included in the prospective study. Results There was a significant dose‐dependent relationship between admission (4 h) paracetamol concentration and fall in serum potassium in the retrospective study ( P < 0.01) and a significant positive relationship between serum paracetamol at 4 h and fractional excretion of potassium at 12 h postingestion ( P < 0.01) in the prospective study. No changes were seen in the control group. No cases developed renal failure. Conclusions Paracetamol overdose is associated with dose‐related hypokalaemia, and kaliuresis of short duration (<24 h), suggesting a specific renal effect of paracetamol in overdose perhaps via cyclo‐oxygenase inhibition. This effect seems distinct from any nephrotoxic effect of paracetamol.