Effects of oral propranolol in normal subjects

The effects of oral propranolol were evaluated in 10 normal volunteers. The resting heart rate decreased from the mean control value of 68 plus or minus 3.3 (SE) to 56 plus or minus 2.8 beats per minute (bpm) on propranolol (p smaller than 0.001, paired test). Mean systolic blood pressur also decreased from 125 plus or minus 5.0 to 114 plus or minus 4.2 mm Hg (p smaller than 0.03). Resting systolic time intervals were unaffected by propranolol. Mean maximal treadmill exercise tolerance time was not significantly altered by propranolol although the mean heart rate systolic blood pressure product a maximal exertion was markedly decreased (1.91 plus or minus 0.17 vs 2.62 plus or minus 0.17 times 10-4, p smaller than 0.004) . The nonsignificant effect of oral propranolol on resting systolic time intervals and maximum exercise tolerance despite significant changes in heart rate and blood pressure at rest and duringexercise stand in contrast to the reported effects of intravenous propranolol. Explantations for this difference between the effects of oral and intravenous propranolol in normal subjects are examined.