Pathophysiologic and pharmacokinetic determinants of the antihypertensive response to propranolol

The tendency for patients with essential hypertension to differ markedly in antihypertensive response to propranolol could arise from pathophysiologic or pharmacokinetic differences between them. This possibility was investigated in 23 men with mild to moderately severe essential hypertension. At each of three propranolol doses, 40 mg, 80 mg, and 320 mg daily, approximately a 20-fold range in steady-state plasma propranolol concentrations was observed. Clinical response however was unrelated to plasma propranolol: oral dose ratio, since patients with higher plasma levels were less sensitive to the existing plasma drug concentration. When falls in blood pressure and plasma propranolol concentration were compared overall, a biphasic dose-response relationship was noted, with a first component at plasma propranolol concentrations of 3 to 30 ng/ml and a second at concentrations above 30 ng/ml. Only patients with increased sympathetic nervous system activity and high plasma renin activity (PRA) had substantial falls in pressure at propranolol levels of 3 to 30 ng/ml. Cardiac beta adrenergic receptor blockade, not suppression of PRA, seemed to be the antihypertensive mechanism. This relation of pretreatment sympathetic nervous activity and PRA to antihypertensive response existed only at lower plasma propranolol concentrations. With a propranolol dose of 320 mg daily, both plasma norepinephrine concentration and PRA were unrelated to the clinical response.