Unit 1 Description of a Pharmacy Grammar

Cardiovascular drugs.

These drugs may be divided into three groups: drugs that affect the heart; drugs that affect blood pressure; and drugs that prevent blood clotting.

Drugs That Affect the Heart. Drugs may affect the heart in two major ways: changing the rate and forcefulness of the heartbeat and altering the rhythm of the heartbeat.

The most common drugs used to change the rate and forcefulness of the heartbeat are the digitalis glycosides (cardiac glycosides). These drugs are used to treat patients with heart failure (when the heart is not contracting with sufficient force). Most of the digitalis glycosides are obtained from the leaf of the digitalis (foxglove) plant, either as a crude mixture or as the purified glycoside from the leaf of the plant.

The important effects of the digitalis glycosides are the strengthening of the myocardium (heart muscle) and the slowing of the rate of contraction of the heart. Examples of digitalis glycosides are: digitalis, digoxin, and digitoxin.

Other drugs, which belong to the general class of sympathomimetics, are used to increase heart rate and the force of contraction. These include isoproterenol and epinephrine.

Drugs used to correct abnormal heart rhythm are called antiarrhythmics. Examples of these drugs are quinidine, procainamide, lidocaine (Xylocaine), and propranolol. These drugs help restore the heart rhythm to a regular cycle by depressing ectopic (outside, unwanted) myocardial impulses. Quinidine comes from the bark of the cinchona tree and is the primary drug used to treat arrhythmias. Quinidine decreases the number of times the heart muscle can contract in a given period of time. The cocaine derivatives procainamide and lidocaine (Xylocaine) are also useful in controlling abnormal cardiac rhythms.