Ch 22 - Drugs Used to Treat Congestive Heart Failure - DONE Flashcards
Define congestive heart failure (CHF):
CHF results when CO is inadequate for the metabolic demands of the body
What are some of the most common cause of CHF?
- Myocardial infarction (MI)
- Hypertention (HTN)
- Arrythmia
- Valvular disease
- Arteriosclerotic heart disease
- these conditions either impair the ability of cardiac muscle to contract (MI, arrythmia) or increase the workload imposed upon the heart (HTN).
Name some of the physical signs of CHF:
- left-sided heart fialure results in pulmonary edema and dyspnea
- right-sided heart failure results in liver congestion and peripheral edema
Describe the compensatory physiological mechanisms that occur in heart failure:
- increased sympathetic tone, which results in tachycardia and greater peripheral vascular resistance
- reduced renal blood flow, which stimulate aldosterone and increases salt and water retention
- myocardial hypertrophy
Name three pharmacological approaches for the treatment of CHF:
- improve myocardial contractility
- reduce preload (which decreases myocardial oxygen demands)
- reduce afterload.
- Remember that cardiac output = heart rate x stroke volume.
- Stroke volume is dependent on preload, afterload, and contractility.
What are the pharmacological options of treating people who have CHF?
- cardiac glycosides
- bipyridine derivatives
- β-adrenergic agonists
- vasodilators
- diuretics
- Angiotensin-converting enzyme (ACE) inhibitors
- β-adrenergic blockers
Name three Cardiac glycosides:
- Digoxin
- Digitoxin
- Ouabain (no longer in use)
- Digoxin is by far the most widely used form because of its favorable pharmacokinetics
Where do Cardiac glycosides originate?
they are extracts of the foxglove plant, Digitalis lanata
Describe how glycosides work? ALOT
READ ON PAGE 188+ difference between digoxin and digitoxin
What are the clinical indications for the administration of Digoxin?
- Congestiv eheart failure
- Atrial flutter and fibrillation- Digoxin slows the conduction velocity and increases the refractory period at the AV node
State the contraindications of using Digoxin and Digitoxin?
bradycardia and ventricular fibrillation
What major electrolyte imbalances can predispose to Digoxin toxicity?
- Hypokalemia (most important)
- Hypercalcemia
- Hypomagnesemia
Describe the potential ECG findings that occur with Digoxin toxicity?
- AV nodal block
- Prolongation of PR interval, shortening of QT interval, and inversion of the t wave
- Ventricular fibrillation
- Complete heart block
- Premature ventricular contraction
In addition to arrythmias, patients with Digoxin toxicitiy have what symptoms?
- Nausea and vomiting
- Diarrhea
- Headache
- Fatigue
- Blurred vision
- Hallucination
- Altered color perception (yellow-green hue)
- Rarely, gynecomastia
How do you treat Digoxin toxicity?
- By discounting the use of the drug
- By correcting any electrolyte imbalances
- Antiarrythmics (Lidocaine)!!
- If necessary. by using Digoxin antibodies that bind to and inactivate the drug
- Cardiac pacer: last resort
Are there any drug interactions to be aware of when using Digoxin?
- Quinidine, and amiodarone, and verapamil all reduce plasma clearance of Digoxin and can precipitate Digoxin toxicity.
- Loop and Thiazide diuretics can deplete K+ and cause Digoxin toxicity.
Has Digoxin been shown to reduce mortality?
No. Unlike ACE inhibitors or β-blockers Digoxin reduces only symptoms, not mortality
Name two Bipyridine derivatives:
- Amrinone
- Milrinone
Bipyridine derivatives mechanism of action:
- They inhibit phosphodiesterase, which leads to increased levels of cyclic adenosine monophosphate and intracellular calcium.
- This subsequently results in increased contractility.
- They also cause vasodilation
What is the clinical role of Bipyridine derivatives?
Bipyridine are rarely used today because of their AE. In the past they were used to treat acute heart failure.
Describe the route of administration of Amrinone and Milrinone (Bipyridine derivatives):
IV
What are the major toxicities of Amrinone and Milrinone (Bipyridine derivatives)?
- Arrythmias
- GI distrurbances
- Hepatotoxicity
- Thrombocytopenia - Amrinone only
Name two β-adrenergic agonists used in the treatment of CHF:
- Dobutamine
- Dopamine
What is the mechanism of action of β-adrenergic agonists?
By stimulating β-adrenergic receptors, they increase cardiac contractility
