High-pressure liquid chromatographic analysis of cimetidine, a histamine H2-receptor antagonist, in blood and urine.

A method is described for extraction of cimetidine, a histamine H2-receptor antagonist, from whole blood and urine with subsequent analysis by high-pressure liquid chromatography (HPLC). The drug is extracted from biological fluids with 1-octanol and back-extracted into dilute acid and then into a small volume of ethanol by saturation with potassium carbonate. HPLC analysis is performed on a column of 5-micrometer silica with a mixed mobile phase consisting primarily of acetonitrile. The method measures concentrations of cimetidine as low as 0.05 microgram/ml and is reproducible. Blood levels and urinary excretion data obtained with the analytical procedure are given for a group of human subjects who received 200-mg oral doses of cimetidine.