[The effect of prindolol on the blood-pressure profile of hypertensives (with special consideration of response to exercise and plasma-renin activity) (author's transl)]

Therapeutic trials of pindolol in hypertension: comparison and combination with other drugs

The antihypertensive effect of pindolol has been demonstrated in several hundred clinical trials performed in many countries. The results of several representative trials will be reviewed in this article. In a cooperative study of pindolol by Swiss internists, blood pressure (BP) normalization was achieved in 76% of the patients and a fair response in 9%. In a French trial, BP reduction was found to correlate with the initial pressure level. Pindolol was also found effective in treating renal hypertension (Germany) and was considered particularly useful in hypertensive patients with coexistent angina pectoris (South Africa). A favorable effect on the BP profile registered during the whole day was demonstrated by means of BP telemetry (Germany). A Swedish long-term study showed pindolol to have a sustained antihypertensive effect over 16 months associated with a progressive decrease in systemic vascular resistance. In a study conducted in New Zealand, pindolol compared favorably with drugs previously used for hypertension, (methyldopa, diuretics, rauwolfia, guanethidine, etc.). It proved slightly less effective than methyldopa in a Canadian trial but significantly more effective than this drug in a South African study. Danish investigators found pindolol equivalent to chlorthalidone in lowering the resting BP but more effective than the diuretic in reducing the pressure and pulse response to exercise. Of particular interest are comparisons of pindolol with other beta-blockers performed in Germany, Sweden, Australia, and New Zealand. BP reductions obtained with pindolol did not differ significantly from those obtained with the other beta-blockers, whether they were cardioselective (metoprolol, atenolol) or not (propranolol, timolol, nadolol); however, pindolol produced less slowing of resting heart rate than these five other drugs, which are devoid of intrinsic sympathomimetic activity (ISA). Pindolol proved somewhat more effective than other nonselective beta-blockers with ISA (i.e., oxprenolol), although both produced less bradycardia than propranolol (New Zealand). In resistant cases, the combination of pindolol with diuretics, methyldopa, or hydralazine was found to significantly increase the responder rate.

Decrease in plasma noradrenaline levels following long-term treatment with prindolol in patients with essential hypertension

15 patients (4 females, 11 males, 21 to 55-year old) with mild to moderate essential hypertension (EH) were treated with placebo for two weeks and thereafter with increasing doses of prindolol (15 to 38 mg/day in the mean) and kept on a mean maintenance dosage of 32 mg/day for an average of 16 weeks in all. Blood pressure (BP), heart rate und plasma noradrenaline (PNA) concentrations were measured under standardized conditions (supine, standing, walking) at the end of two weeks on placebo and after the experimental treatment period. The results were compared to those of a group of 15 normotensive untreated control subjects (NS): after an average of 16 weeks on prindolol BP fell from 163/113 mm Hg to 129/91 mm Hg in the mean. PNA levels in EH before prindolol were significantly higher than in NS (supine: 272 +/- 22.0 ng/l (mean +/- SEM) vs. 135 +/- 15.1 ng/l, standing: 448 +/- 31.9 ng/l vs. 359 +/- 18.4 ng/l, walking: 388 +/- 22.5 ng/l vs. 234 +/- 22.1 ng/l). In EH chronic administration of prindolol led to a significant decrease in PNA concentrations under all the three test conditions to levels which did not differ significantly any more from those derived from NS. The adrenergic response to upright posture reflected in the percentage increase in PNA was significantly less in EH before prindolol when compared to the percentage increase in NS. On prindolol the adrenergic response was not abolidhed, yet it tended to approach the values found in NS. Before prindolol under resting conditions diastolic BP correlated closely with the corresponding PNA levels (p less than 0.01, r = 0.66, n = 15). This correlation could not be reestablished after prindolol treatment. The decrease in PNA after long-term treatment with prindolol was not correlated to the fall in blood pressure. The decrease in PNA indicates a lower activity of the sympathetic nervous system which may contribute to the antihypertensive effect of prindolol.