High Blood Pressure Medication (cont.)
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Calcium channel blockers (CCBs)
Calcium is needed by all muscle cells, including those of the heart and surrounding arteries, in order for the cells to contract. Calcium channel blockers (CCBs) inhibit the movement of calcium into muscle cells. The reduction in calcium reduces the force of the heart's muscular pumping action (cardiac contraction) and thereby reduces blood pressure. CCBs also relax the muscle cells surrounding the arteries to further reduce blood pressure.
Three major types of calcium channel blockers are available. One type is the dihydropyridines, which do not slow the heart rate or cause other abnormal heart rates or rhythms (cardiac arrhythmias). Examples of these drugs include:
The other two types of calcium channel blockers are referred to as the non-dihydropyridine agents. One type is verapamil (Calan, Covera, Isoptin, Verelan) and the other is diltiazem (Cardizem, Tiazac, Dilacor, and Diltia).
Diuretics are among the oldest known medications for treating high blood pressure. They work in the tiny tubes (tubules) of the kidneys to remove salt from the body. Water (fluid) also is removed along with the salt; however, the exact mechanism whereby diuretics lower blood pressure is not clearly known. The leading theory is that they directly cause the muscles surrounding blood vessels to relax. Diuretics may be used alone for high blood pressure. More frequently, however, low doses of diuretics are used in combination with other medications for high blood pressure to enhance the effect of the other medications.
The most commonly used diuretics to treat hypertension include:
The thiazide drugs are related to sulpha drugs. For those individuals who are allergic to sulfa drugs, ethacrynic acid, a loop diuretic, is a good option. Note that diuretics probably should not be used in pregnant women.
Alpha receptors on the muscles surrounding arteries, like beta receptors, cause the muscles surrounding the arteries to contract and narrow the arteries. By blocking the alpha receptor, alpha-blockers relax the muscles and lower blood pressure.
Examples of alpha-blockers include:
Alpha-beta-blockers work the same way as alpha-blockers but also slow the heartbeat as beta-blockers do. As a result, less blood is pumped through the vessels, vessels dilate and blood pressure is lowered. Examples of alpha-beta blockers include:
Clonidine (Catapres) is an inhibitor of the nervous system in the brain. These inhibitors of the nervous system act by binding to receptors on nerves in the brain to reduce the transmission of messages from the nerves in the brain to nerves in other areas of the body. By inhibiting transmission to nerves outside of the brain that innervate muscle cells of the heart and blood vessels, heart rate and blood pressure are reduced.
Minoxidil is a vasodilator. Vasodilators are muscle relaxants that work directly on the smooth muscle of the peripheral arteries throughout the body. The peripheral arteries then dilate and blood pressure is reduced.
REFERENCE: Food and Drug Administration Prescribing Information.
Last Editorial Review: 4/8/2010
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