Research Article
Apparent resistance to hypotensive effect of clonidine.
Br Med J 1977; 1 doi: https://doi.org/10.1136/bmj.1.6054.136 (Published 15 January 1977) Cite this as: Br Med J 1977;1:136
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- L M Wing,
- J L Reid,
- D S Davies,
- H J Dargie,
- C T Dollery
Abstract
Clonidine failed to reduce the blood pressures of two patients with essential hypertension. On was given 5-4 mg/day and the other 6 mg/day, and their respective peak plasma clonidine concentrations were 26-2 ng/ml and 14-4 ng/ml. Several months after the end of clonidine treatment a single oral dose of 0-3 mg of clonidine produced maximum falls in blood pressure of 30/22 mm Hg and 88/41 mm Hg with peak plasma clonidine concentrations of 1-4 ng/ml and 0-9 ng/ml. Resistance to the hypotensive effect of high doses of clonidine may be due to stimulation of peripheral alpha-adrenoceptors causing vasoconstriction, which maintains a raised blood pressure.