Development and Validation of an Hplc Method with Post-column Derivatisation for Assay of N-acetylcysteine in Plasma

A quantitative reversed-phase HPLC method has been developed that enables determination of both low endogenous and high therapeutic concentrations of N-acetylcysteine (NAC) in plasma. The compound is detected fluorimetrically after derivatisation with ortho-phthalaldehyde in the presence of a primary amine. Validation of the method revealed injection and method repeatability were good. The linear range was adequate and the limit of quantification was between 0.4 and 0.6 μM. Recovery of N-acetylcysteine from plasma samples was also acceptable. This method was applied to plasma samples from patients with a clinical septic shock who had received very high doses of N-acetylcysteine. Six samples were taken at different times after administration of Nacetylcysteine. The blood-concentration profiles obtained indicate the method is suitable for following the evolution of NAC in plasma under these conditions and can therefore be used for pharmacokinetic profiling.