Abstract
Three groups of hypertensive patients were studied after they had received one of the three pharmacologically different beta blockers for at least 1 month: pindolol, 10 mg twice a day (n = 7), propranolol median dose, 80 mg three times a day (n = 9), or metoprolol, 150 mg (twice a day (n = 8). After abrupt withdrawal of drug and replacement with placebo, we mwasured the following on day 0 and approximately every 2 days up to 3 weeks; beta-adrenergic sensitivity (BAS) by the chronotropic dose of isoproterenol to increase heart rate by 25 bpm (CD 25), resting heart rate and blood pressure, and symptoms. All values are medians. On day 0, beta blockade was evident by increased CD 25 values of 618 μg for pindolol, 57 μg for propranolol, and 10 μg for metoprolol as compared to 2.8, 2.4, and 3.0 μg, respectively, at days 14 to 21, which were considered the ultimate baseline. After pindolol on day 0, the CD 25 slowly decreased to, but never below, baseline by days 8 to 21. In contrast, after propranolol on day 0, the CD 25 decreased significantly two- to fivefold below baseline from days 4 to 14 (↑BAS) and after metoprolol two- to threefold below baseline from days 2 to 8. After pindolol, heart rate and blood pressure gradually returned to, but not above, ultimate baseline. In contrast, during the period of ↑BAS there was a significant overshoot of heart rate in eight of eight patients after metoprolol (day 0 = 61, peak = 88, baseline = 74) but not after propranolol, while a significant overshoot of blood pressure occurred in six of nine patients after propranolol ( day 0 = 140 87 , peak = 157 95 , baseline = 140 89 ) but not after metoprolol. Withdrawal symptoms of headache, palpitations, and tremor occurred in one of seven patients after pindolol, six of nine after propranolol, and three of eight after metoprolol. The degree and duration of beta blockade appeared related to drug potency. Withdrawal phenomena occurred after propranolol and metoprolol but not after pindolol.
Published Version
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