[Use of the new hypotensive agent Minipress (prazosin hydrochloride]

Efficacy of minipress in patients with hypertension stage II and its haemodynamic effects were studied after a single administration and during a course of treatment. It is shown that its main mechanism is in vasodilatation caused by relaxation of the muscular component of arterioles. The authors suggest that minipress can produce redistribution of the blood through peripheral venoconstriction. Decrease of the index of the external work of the heart points indirectly to decreased oxygen utilization by the myocardium which may reflect changes in haemodynamics under the influence of minipress or through direct action of the drug on the heart. Hypotensive effect of minipress is recorded already by the 5th day of its administration (p less than 0.001), however, its further effect is unstable. Increase of the circadian dose becomes necessary and also its combined use with thiazide diuretics. Positive chronotropic effect of Minipress has been recorded, with maximum towards the end of the 2nd week of treatment and seen as increased rate of cardiac contractions by 13.2% (p less than 0.01). To decrease this effect authors advise to use minipress in combination with beta-adrenoblockers.