Studies on hydralazine. III. Bioavailability of hydralazine in man.
The bioavailability of orally administered hydralazine was assessed in 4 healthy subjects after separate administration of a single oral or intravenous dose (0.3 mg-kg-1). Comparison of the areas under the serum concentration-time curves showed that 26-55% of the oral dose was available to the systemic circulation as unchanged drug. The 0-24 h excretion of the drug in urine was rapid: 11.4-14.1% of the dose after intravenous administration, and 2.0-3.6% after an oral dose. Acetylation of hydralazine leads to formation of 3-methyl-s-triazolo-3,4, aphthalazine (MTP) and a gas-liquid-chromatographic method for its measurement in urine was developed. After oral and intravenous administration, 0.8-1.2% and 1.4-2.3% of the dose, respectively, were recovered within 24 hours from urine as MTP. After oral administration there was a relative increase in the amount of MTP in every subject, which indicates route-dependent metabolism. The lower bioavailability of oral hydralazine could be explained in terms of first-pass metabolism.
D000107:Acetylation; D000284:Administration, Oral; D000328:Adult; D001682:Biological Availability; D002849:Chromatography, Gas; D004231:Diuresis / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006830:Hydralazine / Q000009:adverse effects / Q000378:metabolism* / Q000494:pharmacology; D007275:Injections, Intravenous; D008297:Male; D008954:Models, Biological; D010641:Phenotype; D013997:Time Factors
D006830:Hydralazine