Action of Beta Blockers
Nadolol, marketed under the brand name Corgard, belongs to a class of drugs called beta blockers. Beta blockers work by preventing the uptake of the hormone adrenaline (epinephrine) by cells at points of entry on the surface of the cells called beta-adrenergic receptor sites.
Beta-adrenergic receptor sites are located in the cells of the heart, kidneys, lungs, blood vessels and other tissues.
When adrenaline is blocked at these receptor sites, the overall effect is to reduce the amount of adrenaline available to prepare the body for "fight or flight."
Fight or Flight Mechanism
The body's "fight or flight" mechanism is a function of the part of the nervous system that is activated in times of stress. In times of stress, the adrenal glands secrete adrenaline, which stimulates the heart to beat harder and faster, and causes blood to be diverted from the gastrointestinal tract to the muscles to prepare the body to fight or run. Adrenaline also stimulates the kidneys to produce an enzyme called renin, which sets off a cascade of events, including fluid retention and blood vessel constriction.
Reduced Cardiac Output
Nadolol, which blocks the uptake of circulating adrenaline, causes a decrease in adrenaline in body cells, particularly the heart and kidneys. A decrease in the amount of adrenaline in the cells of the heart causes impulses to travel more slowly through the heart's conduction system, resulting in a decreased heart rate. It also causes the heart to pump less forcefully, resulting in a reduction in the amount of blood ejected with each heart beat. The amount of blood ejected from the beating heart is referred to as cardiac output.
A decreased cardiac output results in a reduction of circulating blood volume contained in the body's blood vessels. This reduction in blood volume reduces the pressure exerted on the walls of arteries carrying blood away from the heart, resulting in lowered blood pressure.
Decreased Renin Production
Additionally, a decreased amount of renin produced by the kidneys contributes to a reduction in blood pressure.
