Simultaneous Determination of Efavirenz, Rifampicin and Its Metabolite Desacetyl Rifampicin Levels in Human Plasma

A simple and rapid isocratic, high performance liquid chromatography (HPLC) assay employing solid phase extraction (SPE) for the simultaneous determination of the anti HIV drug, efavirenz, the anti-tuberculosis drug, rifampicin and the desacetyl metabolite of rifampicin in plasma from HIV/tuberculosis infected patients has been developed. Using a Zorbax SB-Phenyl reverse-phase analytical column with UV detection, good separation and detection of the drugs was attained within a 10min run time. Intra- and inter-assay precision RSD values were found to be less than 15% at the concentrations examined (0.1-20μg/mL). The LOQ was found to be 0.1μg/mL for each agent and the assay was found to generate a linear response up to 20μg/mL. This low cost assay can accurately detect efavirenz and rifampicin concentrations within a clinically relevant concentration range using standard chromatography equipment, making it particularly applicable to resource-limited settings.