A novel metabolic pathway in the metabolism of 5-(4'-chloro-n-butyl)picolinic acid.

The metabolism of 5-(4'-chloro-n-butyl)picolinic acid, which inhibits dopamine beta-hydroxylase and exhibits an antihypertensive effect, has been studied by gas chromatography mass spectrometry, utilising characteristic reaction products after derivatization. In rat urine five metabolities were identified by mass spectral analysis. It is found that four were elongated by a C2 unit in the carboxyl group at the 2-position on the pyridine ring and accounted for approximately 50% of the radioactivity in the 24 hour urine. The facts show that the metabolic pathway corresponding to the chain elongation of fatty acids is the major route of metabolism for this drug in the rat. Furthermore, this pathway would be confirmed in man, rabbit, guinea pig and mouse.