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Studies on hydralazine

III. Bioavailability of hydralazine in man

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Summary

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.

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Authors and Affiliations

  1. Medical Department B, Rikshospitalet, University Hospital, Oslo, Norway

    T. Talseth

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  1. T. Talseth
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Talseth, T. Studies on hydralazine. Eur J Clin Pharmacol 10, 395–401 (1976). https://doi.org/10.1007/BF00563075

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  • DOI: https://doi.org/10.1007/BF00563075

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