Plasma concentration of paracetamol and its major metabolites after p.o. dosing with paracetamol or concurrent administration of paracetamol and its N-acetyl-DL-methionine ester in mice.

1. Single doses of paracetamol 400 (PAR 400) and 800 mg/kg (PAR 800), SUR 2647 combination (free paracetamol + paracetamol-N-acetyl-DL-methionate, paracetamol/methionine ratio 2:1) equivalent to PAR 400 (SURc 400) and PAR 800 (SURc 800) were given p.o. to male Bom:NMRI mice. 2. The objective was to compare the plasma concentrations of free paracetamol and the major metabolites paracetamol-sulphate and paracetamol-glucuronide for a 6 hr period after each test drug. 3. There was no significant difference between PAR 400 and SURc 400 with respect to plasma paracetamol, paracetamol-glucuronide and paracetamol-sulphate concentration with the exception of lower plasma paracetamol concentration (P less than 0.03) at 3 hr following PAR 400. 4. There was no significant difference between PAR 800 and SURc 800 with respect to plasma paracetamol, paracetamol-glucuronide and paracetamol-sulphate concentrations with the exception of lower plasma paracetamol-glucuronide concentration (P less than 0.03) at 4 hr after dosing following SURc 800. 5. Combining free paracetamol and its methionine ester does not seem to alter the pattern of plasma paracetamol, paracetamol-glucuronide and paracetamol-sulphate compared to equal doses of free paracetamol alone after p.o. administration of toxic doses to male Bom:NMRI mice.