Pharmacokinetics and concentration-effect relationships of intervenous and oral clonidine

Clin Pharmacol Ther. 1977 May;21(5):593-601. doi: 10.1002/cpt1977215593.


The kinetics of the disposition of intravenous and oral clonidine in five normotensive subjects have been determined. It is proposed that a two-compartment model adequately describes the disposition of the drug. The drug is rapidly distributed (t1/2alpha = 10.8 +/- 4.7 min) but slowly elimainated (t1/2beta = 8.5 +/- 0.9 hr). The bioavailability of oral clonidine in the tablets tested averaged 75.2% and 40 to 50% of the bioavailable dose is excreted unchanged in urine. Renal clearance of the drug showed considerable intersubject variation (1.82 +/- 0.34 ml/min/kg) and exceed the calculated glomerular filtration rate in some subjects. Oral and intravenous clonidine induced significant falls in blood pressure (greater than 20/15 mm Hg) in our normotensive subjects and consistently caused marked sedation and dryness of the mouth. Sedation and salivary flow correlated with plasma clonidine concentration over the range 0 to 4 ng/ml. Falls in blood pressure were related to plasma concentration to 1.5 to 2 ng/ml but at higher concentrations the hypotensive effect was attenuated.

Publication types

  • Comparative Study

MeSH terms

  • Administration, Oral
  • Adult
  • Biological Availability
  • Blood Pressure / drug effects
  • Clonidine / administration & dosage
  • Clonidine / metabolism*
  • Clonidine / pharmacology
  • Computers
  • Half-Life
  • Humans
  • Hypnotics and Sedatives
  • Infusions, Parenteral
  • Kinetics
  • Male
  • Models, Biological
  • Salivation / drug effects
  • Xerostomia / chemically induced


  • Hypnotics and Sedatives
  • Clonidine