Heart rate responses during treatment of hypertension with propranolol. The clinical usefulness of the nitroglycerin test.

Increments in heart rate during the TNG test (sublingual nitroglycerin with assumption of upright posture), passive head-up tilt, and postrecumbency standing were compared to the effects of intravenous isoproterenol in 15 mild hypertensives during administration of placebo and two dosage levels of propranolol. TNG test results correlated with responsiveness to isoproterenol, but nitroglycerin tachycardia was reduced only about 50% during propranolol treatment. The TNG response was almost maximally inhibited by 160 mg/day of propranolol while the response to postrecumbency standing was inhibited only by a dose of 320 mg/day. The results indicate that: (1) the TNG test is of limited value in the assessment of beta adrenergic blockade in hypertensive patients, and (2) propranolol in a dose of 160 mg/day induces near-maximal cardiac blockade.