An acute intravenous injection of clonidine may produce a transient pressor response that apparently is due to stimulation of peripheral vascular a-receptors. The pressor response does not occur after oral administration, because the drug's centrally mediated depressor action overrides it.
The decrease in blood pressure produced by cloni-dine correlates better with a decreased cardiac output than with a reduction in peripheral vascular resistance. The reduction in cardiac output is the result of both a decreased heart rate and reduced stroke work; the latter effect is probably caused by a diminished venous return.
Renal blood flow and glomerular filtration are not decreased, although renal resistance is diminished. Like a-methyldopa, it is a useful agent for hypertension complicated by renal disease. Plasma renin activity is reduced by clonidine, presumably as a result of a centrally mediated decrease in sympathetic stimulation of the juxtaglomerular cells of the kidney.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...