seen in exercise tolerance and left ventricular size. ACE inhibitors are well tolerated
and have been shown to decrease hospitalizations and deaths. For these reasons,
agents in this class are first line pharmacologic treatment for congestive heart failure.
b. ACE Inhibitors are often initiated immediately after a heart attack or when a
patient still has mild symptoms of heart failure. The starting dose is low and titrated
(gradually increased) up to the maximum tolerated dose (based on heart rate and blood
pressure). The most bothersome side effect is a dry cough which develops in some
patients. Other side effects include angioedema (facial swelling) and elevated
potassium levels.
c. Agents included in this class include captopril (Capoten), enalapril
(Vasotec), lisinopril (Prinivil, Zestril), and ramipril (Altace)
3-5. DIGITALIS AND THE RELATED GLYCOSIDES
a. The mechanisms of action of digitalis and related cardiac glycosides in the
treatment of congestive heart failure are not fully understood. The main
pharmacological property of these drugs is their ability to increase the force of
myocardial contraction (the heart muscle's contraction) by a direct action on the
ventricular heart muscles. Conduction is also slowed somehow between the SA node
and the AV node, resulting in a decrease in heart rate. Because of the slower heart rate
and increase in the force of the myocardial contraction, the heart has more time to
adequately fill with venous blood. The secondary changes seen as a result of the first
three mechanisms of action will be a decrease in heart size and a decrease in heart rate
due to more efficient pumping of the heart. Because of the slower heart rate, cardiac
glycosides are also used in the treatment of atrial flutter or atrial fibrillation.
b. Because of improved circulation to the kidneys, an increase in urinary output
(diuresis) within 24 to 48 hours following administration of cardiac glycosides will also
be seen. Digitalis toxicity is enhanced in patients who have low serum potassium
(hypokalemia), so potassium supplements may be given based upon periodic blood test
analysis.
c. Digitalis and related glycosides have very narrow therapeutic indices (the
treatment dose is very close to the toxic dose) and many drug-drug interactions. The
dose must also be adjusted in renal failure, which is common in CHF patients. For
these reasons digitalis is reserved for acute symptomatic heart failure or in those
patients with CHF and atrial fibrillation.
3-6. DIGITALIZING DOSE
a. The digitalizing dose of a cardiac glycoside is the initial large dose of the drug
that is given to the patient in order to relieve the symptoms of congestive heart failure or
to render the patient asymptomatic as it is commonly referred to. Often the digitalization
is accomplished by administering relatively large doses of digitalis preparations within a
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