The authors studied the effects of oral propranolol administered in 2 low dose schedules (5 or 20 mg 8 hourly) and for a short term (30 to 36 hours) on heart rate, plasma renin activity, and arterial pressure, both at rest and after an isoprenaline challenge (8 mg i.v. over 2 min) in 6 normal subjects. Resting heart rate, plasma renin activity, and systolic pressure all fell significantly after the 5 mg dose and only small additional falls were observed when the dose was increased to 20 mg. The fall of diastolic pressure was not significant with 5 mg, but was significant with 20 mg. That beta blockade occurred with these low doses was confirmed by diminished responses to isoprenaline. The isoprenaline induced changes of heart rate, plasma renin activity, and diastolic pressure were reduced by 77, 80, and 65 percent, respectively, by the 5 mg dose of propranolol, and by 89, 94, and 87 per cent by the 20 mg dose, suggesting that cardiac and renal receptors are equally sensitive to propranolol. These data indicate a rapid blood pressure lowering action of low dose propranolol in normal subjects and suggest that this effect is in part at least a consequence of blockade of renal and/or cardiac beta receptors. The authors' results also raise the possibility that much lower doses of propranolol than generally used may be clinically effective.
|Number of pages||5|
|Journal||British Heart Journal|
|Publication status||Published - 1979|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine