Acute and short-term effects of clonidine in heart failure

The authors performed a randomized, double-blind, placebo-controlled trial to assess the tolerance and effects of chronic oral clonidine administration on the clinical status, exercise tolerance, and ventricular function of 10 male patients with chronic heart failure. Patients were given either oral clonidine (400 micrograms/day) or matching placebo for twelve weeks and then tapered off medication over a two-week period. Results are summarized as follows: Profiles over time between groups were significantly different for resting heart rate (p = 0.0005), were different for arterial pressure (p = 0.04), were different for left ventricular ejection fraction (p less than 0.006), and were different for mean accumulated workload (p = 0.076). Exercise double product at 25 watts changed little in three patients and showed a decrease in 2 patients following six weeks of oral clonidine; after twelve weeks, it decreased in three patients, increased in 1, and changed little in another. After washout, double product returned toward baseline values. In the placebo groups, double product showed little change. Resting of the heart by decreasing heart rate, systemic arterial blood pressure, and venous tone are thought by the authors to be major contributing factors to the observed beneficial effect of chronic oral clonidine in chronic heart failure.