Inappropriate methods for the emergency determination of plasma paracetamol.

Methods for the estimation of plasma paracetamol which depend on acid hydrolysis to p-aminophenol without a prior extraction step also measure inactive metabolites which are present in high concentrations. The extent of the overestimate obtained with such methods was determined using 24 samples from patents after paracetamol overdosage. There was a positive error of between 40 and 700% compared with a high-performance liquid chromatography reference method which measured only unchanged paracetamol. These non-specific methods should not be used to determine the need for specific therapy in patients with paracetamol poisoning.