Robotic analysis of 3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo [3,2-b]indole-2-carboxamide in human plasma.

An automated liquid chromatographic assay using unattended robotic sample preparation has been developed and validated to quantitate 3,7-dimethoxy-4-phenyl-N-1H-tetrazol-5-yl-4H-furo(3,2-b)indole-2- carboxamide (CI-922) in human plasma. The drug and internal standard 2 were isolated from plasma by solid-phase extraction onto Bond-Elut C-18 cartridges. Plasma interferences were selectively removed, and the compounds were eluted from the cartridge. Separation was achieved at ambient temperature using a C-18 column (5 microns, 4.0 X 150 mm) with an isocratic eluant consisting of acetonitrile:water:glacial acetic acid (45:55:1). The column effluent was monitored spectrophotometrically at 340 nm. Peak-height ratios were proportional to plasma concentrations of 1 over the range 0.025-5.0 micrograms/mL, and the recovery of 1 from plasma was 63.5%. Calibration curve precision was +/- 6.7%, based on relative standard deviations (RSD) of 1.9 to 6.7% for calibration standards. The accuracy of calibration curves was +/- 7.2%, with relative errors ranging from -7.2 to 3.6%. Assay precision was +/- 4.8%, based on RSD values of 3.9, 4.8, and 3.4% for spiked control samples of pooled human plasma containing 0.20, 1.50, and 2.50 micrograms/mL of 1, respectively. Assay accuracy was -0.7 to 2.0%. This method has been used to analyze 1 in clinical plasma samples.