Measurement of tafenoquine (WR 238605) in human plasma and venous and capillary blood by high-pressure liquid chromatography

A simple, rapid, and accurate high-pressure liquid chromatographic method w ith fluorescence detection is described for the measurement of tafenoquine (TQ) (also known as WR 238605) from human plasma and venous and capillary b lood. Tafenoquine was measured in plasma and venous blood following protein precipitation. Chromatographic separation was achieved using a Waters S5P Spherisorb phenyl analytical cartridge (150 mm x 4.6 mm ID., 5 mu m particl e size) (Waters, Milford, MA, USA) and a mobile phase of 22 mM ammonium ace tate, pH 4:acetonitrile (45:55, vol/vol). The flow rate was 1.5 mL/min and the retention times were similar to 3.5 min far WR VIIIAc (internal standar d) and similar to 7.8 min for TQ. The interday and intraday coefficients of variation of TQ over a concentration range of 20-1000 ng/mL in plasma were less than or equal to 8.4% and in venous blood were less than or equal to 9.6%. The mean percent difference between added concentration and obtained concentration was 7.3% in plasma and 8.5% in venous blood over the correspo nding concentration range. The limit of quantitation for both fluids was 10 ng/mL, Tafenoquine concentrations were comparable between capillary and ve nous blood with no significant difference between measurement in both biolo gical fluids. The clinical application of the method was demonstrated by me asuring plasma and whole blood concentrations of TQ from participants in a chemosuppression trial of the drug against malaria infections in Thailand.