Radioimmunoassay for colchicine in plasma and urine

A radioimmunoassay for the measurement of colchicine (in quantities as small as 0.05 nanogram) in plasma and urine was developed with the use of an antibody from immunized rabbits. After the intravenous injection of 2 milligrams of colchicine in seven subjects, the calculated zero-time concentration in the plasma was 2.9 +/- 1.5 micrograms per deciliter, and the mean half-time in the plasma was 58 +/- 20 minutes. Declining, but measurable, amounts of colchicine could be detected in urine up to day 9 after the drug was administered.