DISPOSITION OF CLONIDINE IN RATS AS DETERMINED BY RADIOIMMUNOASSAY

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 207  (1) , 195-202
Abstract
A radioimmunoassay for the antihypertensive clonidine was developed and is capable of detecting as little as 10 pg of clonidine. 2,6-Dichlorophenylguanidine, a known metabolite of clonidine, did not cross-react with the antiserum, but another metabolite, 4-hydroxyclonidine, was as potent as clonidine in displacing labeled clonidine from the antibody. A simple solvent extraction step before the radioimmunoassay selectively extracted clonidine from a mixture of clonidine and 4-hydroxyclonidine in alkaline plasma and this procedure permitted a specific assay for clonidine. The plasma levels of clonidine in rats after the administration of a hypotensive dose (100 .mu.g/kg, i.v.) were determined by radioimmunoassay. These data indicated that the disposition of clonidine conforms to an open 2-compartment, pharmacokinetic model. Clonidine rapidly accumulated in the brain as shown by the attainment of peak concentrations within 2 min of i.v. injection.