title: Sensitive high-performance liquid chromatographic assay for endralazine and two of its metabolites in human plasma.
abstract: Endralazine (I) is a new antihypertensive which is chemically and pharmacologically related to hydralazine and dihydralazine. A sensitive high-performance liquid chromatographic-fluorescence assay for the drug and two of its metabolites [methyltriazoloendralazine (VII) and hydroxymethyltriazoloendralazine (VIII)] in human plasma was developed. After conversion of I and its internal standard to triazolopyridopyridazine derivatives the latter and metabolites were separated by high-performance liquid chromatography and detected using their fluorescence. The limits of detection of the assay were 1 nmol/l for I and VII and 0.1 nmol/l for VIII. Intra-assay coefficients of variation were 2.5-5.1% for I (range 1000-10 nmol/l), 4.2-4.5% for VII (range 100-5 nmol/l) and 3.4-5.7% for VIII (range 100-1 nmol/l). Following oral administration of 5 and 10 mg of I to two normal volunteers (slow acetylators) peak plasma levels of I occurred between 0.75 and 1 h after the dose, and declined in a biexponential fashion. The terminal half-life ranged from 2.8-3.7 h. These results contrast with those obtained for hydralazine in plasma where in vitro and in vivo half-lives were less than 30 min.
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods; D006801:Humans; D006830:Hydralazine / Q000097:blood; D011724:Pyridazines / Q000008:administration & dosage / Q000097:blood* / Q000378:metabolism; D013997:Time Factors
chemical_list: D011724:Pyridazines; D006830:Hydralazine; C014926:BQ 22-708