European Journal of Clinical Pharmacology

, Volume 10, Issue 6, pp 395–401 | Cite as

Studies on hydralazine

III. Bioavailability of hydralazine in man
  • T. Talseth


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 O - 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,a-phthalazine (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.

Key words

Hydralazine bioavailability polymorphic acetylation first-pass metabolism oral and intravenous dosing 


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Copyright information

© Springer-Verlag 1976

Authors and Affiliations

  • T. Talseth
    • 1
  1. 1.Medical Department B, RikshospitaletUniversity HospitalOsloNorway

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