New aspects of the clinical pharmacology of clonidine.

Using a newly developed radioimmunoassay, we observed the pharmacokinetics and the pharmacologic effects of clonidine simultaneously (mean arterial pressure, plasma catecholamines) in normotensive subjects following single and multiple administration of infusions, tablets, and Perlongets given in varying doses. The following findings were established: (1) The terminal elimination half-life of clonidine was 20 to 25 hours. (2) The pharmacokinetics were modified by an enterohepatic circulation. (3) The pharmacokinetics of clonidine were linear. (4) Clonidine was 100 percent bioavailable in tablets and Perlongets. (5) The pharmacokinetic and pharmacodynamic properties of the drug remained stable during multiple dosing. (6) Following cessation of clonidine medication, no overshooting was observed.