Determination of Blood and Other Tissue Concentrations of Paracetamol in Dog and Man

The even distribution of non-conjugated paracetamol in the tissue waters of the dog has been confirmed. The mean tissue water: plasma water concentration is 1·1. A technique for the determination of non-conjugated paracetamol in man has been devised from existing methods. It has increased sensitivity and is applicable to the routine determination of a large number of samples. This method determines only non-conjugated paracetamol, the sulphated and glucuronated conjugates do not interfere with its accuracy, and it gives results comparable with previous methods. In man, 45 min. after oral administration of paracetamol, the whole blood: plasma concentration ratio is virtually constant at 1·1, indicating that the determination of non-conjugated paracetamol in whole blood should give a satisfactory indication of tissue level.