Determination of Amrinone in Human Plasma by High-Performance Liquid Chromatography with Ultraviolet Detection

A specific, rapid and sensitive high pressure liquid chromatographic method is described for the determination of amrinone in human plasma. The method involves the use of a commercially available 4 ^m particle size reverse phase Waters Nova pak Cyano Column, guard pak Cyano cartridges and a UV/VIS detector. The extraction was based on liquid - liquid single step method. Extraction is carried out with ethyl acetate on a 100 μ plasma sample. The residue is reconstituted with 100 ^1 of the solution 50:50 (Acetonitrile and 3.2 pH phosphate buffer) and 20 fi of the final solution is injected into the column. Elution is carried out at ambient temperature using acetonitrile and 3.2 pH phosphate buffer (70:30 by volume) as mobile phase at a flow rate of 2.0 ml/min at 1200 PSI. Detection is at 210 nm. Mean retention time (+- SEM) was 4.18 ± 0.26 minutes. Separation requires 5 minutes and the sensitivity limit is 0.25 μg/ml - 10 μg/ml. This technique was used in 19 newborn and young infants receiving amrinone. Their plasma concentrations of amrinone were 1.48 ± 2.13 mg/L during a constant infusion of amrinone 5 to 10 micrograms/kg/minute indicating applicability of this technique in therapeutic drug monitoring.