Effect of oral dose size on hydralazine kinetics and vasodepressor response

Clin Pharmacol Ther. 1984 Nov;36(5):595-600. doi: 10.1038/clpt.1984.227.


Levels of hydralazine in blood are log-linearly related to its vasodepressor effect. We examined the effect of oral dose size on the proportion of hydralazine that reaches systemic circulation. Nine subjects with hypertension were given hydralazine in oral doses in the therapeutic range. Blood hydralazine levels, effective liver blood flow, blood pressure, and heart rate were measured. As the hydralazine dose increased, the ratios of the AUC of hydralazine to hydralazine dose and of peak blood hydralazine concentration to hydralazine dose increased, indicating an increase in the proportion of the dose in blood. Liver blood flow tended to increase (maximum 40%) as dose increased above 0.5 mg/kg. Vasodepressor response and degree of tachycardia increased disproportionately with increasing hydralazine dose. There were strong log-linear relationships between peak hydralazine levels and both vasodepressor response and tachycardia that did not change with increasing hydralazine dose. Thus blood hydralazine and vasodepressor response increase disproportionately with increasing hydralazine doses in hypertension.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylation
  • Administration, Oral
  • Adult
  • Aged
  • Blood Pressure / drug effects
  • Dose-Response Relationship, Drug
  • Heart Rate / drug effects
  • Humans
  • Hydralazine / blood
  • Hydralazine / metabolism*
  • Hydralazine / therapeutic use
  • Hypertension / drug therapy
  • Liver / blood supply
  • Male
  • Middle Aged


  • Hydralazine