Hydralazine pyruvic acid hydrazone

Disposition in the Body. Readily absorbed after oral administration. It undergoes first-pass acetylation, the extent of which is genetically determined bioavailability 30 to 35% in slow acetylators, 10 to 16% in rapid acetylators. The major metabolites are 3-methyl-l,2,4-triazolo[3,4-a]phthalazine (MTP—the acetylation product) hydralazine pyruvic acid hydrazone (HPH) which is the major plasma metabolite 4-(2-acetylhydra-zino)phthalazin-l-one (A-AcHPZ) which is the major urinary metabolite 3-hydroxymethyl-1,2,4-triazolo[3,4-a]phthalazine (3-OHMTP). About 65% of a dose is excreted in the urine in 24 hours. In rapid acetylators, about 30% is excreted as A-AcHPZ and 10 to 30% as conjugated 3-OHMTP in slow acetylators, about 15 to 20% is excreted as A-AcHPZ and up to 10% as conjugated 3-OHMTP. Other metabolites include phthalazin-1-one (PZ), 1,2,4-triazolo[3,4-fl]phthalazine (TP), 9-hydroxy-MTP, phthalazine, tetrazolo[5,l-a]phthalazine, and hydrazones of hydralazine formed with acetone and a-ketoglutaric acid. About 10% of a dose is eliminated in the faeces. 

Interference in Assays for Hydra-lazin in Humans by a Major Plasma Metabolite, Hydralazine Pyruvic Acid Hydrazone... 

Hydralazine 219 is a good precursor for that ring system. Its reactions with pyruvic acid (75JOC2901), arylidene pyruvic acids (81AP1030), and 4-aryl-2-oxo-butanoic acids (87JHC63) gave the respective hydrazones... 

---