Other Effects

b Receptor antagonists block catecholamine-induced tremor and inhibit mast-cell degranulation by catecholamines.


Propranolol interacts with b1 and b2 receptors with equal affinity, lacks intrinsic sympathomimetic activity, and does not block a receptors.


Propranolol is highly lipophilic, almost completely absorbed after oral administration, and subject to a prominent first-pass effect (hepatic metabolism during the drug's first passage through the portal circulation), such that only ~25% reaches the systemic circulation. Individual variation in hepatic clearance of propranolol contributes to variability in plasma concentrations (~20x) after oral administration. Hepatic extraction of propranolol is saturable, thus the extracted fraction declines as the dose is increased; one hepatic metabolite, 4-hydroxypropranolol, has some b antagonist activity. The bioavailability of propranolol may be increased by the concomitant ingestion of food and during long-term administration of the drug. Propranolol readily enters the CNS. A sustained-release formulation of propranolol (inderal la) maintains therapeutic plasma concentrations over a 24-hour period.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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