Isolation and identification of paracetamol metabolites

A comparison has been made of the urinary metabolites of volunteers who had taken therapeutic doses of paracetamol with those of persons who had taken an overdose in an attempt to highlight the metabolic changes associated with massive doses. The main technique for examining urine samples was two-dimensional thin layer chromatography. Other chromatographic techniques were used for the isolation and purification of metabolites. The urinary metabolites after a therapeutic dose of paracetamol were identified as free paracetamol, paracetamol sulphate, 3-hydroxy-paracetamol-3-sulphate, 3-methoxy-paracetamol sulphate, paracetamol glucuronide, 3-methoxy-paracetamol glucuronide, paracetamol 3-cysteine conjugate and paracetamol 3-mercapturate. The same metabolites were also present in urine following overdosage but the proportions were quite different. There was particularly a big increase in the relative amounts of cysteine and mercapturic acid conjugates excreted. No new metabolites were found. The significance of these findings is briefly discussed in relation to the metabolism and toxicology of paracetamol.