Clonidine is well absorbed after oral administration, with bioavailability —100%. The peak concentration in plasma and the maximal hypotensive effect are observed 1—3 hours after an oral dose; plasma concentrations of clonidine and its pharmacological effects correlate well. The elimination t122 of the drug ranges from 6—24 hours (mean —12 hours). About half of an administered dose appears unchanged in the urine; the t122 of the drug may increase with renal failure. A transdermal delivery patch permits continuous administration of clonidine at a relatively constant rate for a week; 3-4 days are required to reach steady-state concentrations in plasma. When the patch is removed, plasma concentrations remain stable for ~8 hours and then decline gradually over a period of several days; this decrease is associated with a rise in blood pressure.
Was this article helpful?