Drugs used in the treatment of CHF Flashcards Preview

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Flashcards in Drugs used in the treatment of CHF Deck (24):
1

Positive inotropic drugs

Digitalis Glycosides
Beta-1 agonists

2

Types of Digitalis Glycosides

Digitoxin
Ouabain
Digoxin

3

MOA of Digoxin

Inhibition of Na+-K+ ATPase in the myocardial cell membrane increases Na+ available for exchange with Ca2+
The result is increase inintracellular Ca2+ which results in a positive inotropic effect

4

Cardiovascular effects of Digoxin

Positive inotrope
Reduction in sinus rate and slowing AV conduction
Prolonged PR intervals in ECG
Increased mechanical efficiency of the failing heart
Normalization of BP and peripheral resistance

5

Digoxin kidney and GI effects

Kidney = Diuretic effect mainly secondary to increased cardiac output
GI = GI irritation, vomiting

6

Digoxin Pharmacokinetics

Administered orally and can be given by slow IV in an emergency
Oral bioavailability is more for the elixir than for the tablet
Half life depends on the species
Small amount metabolized by the liver
Undergoes hepatic recycling
Excretion is mainly renal in dogs and horses, and renal and hepatic in cats

7

Therapeutic uses of Digoxin

CHF
Atrial arrhythmias in dogs

8

Adverse effects of Digitalis Glycosides

Digitalis has a narrow safety margin
Cats are more sensitive than dogs
Tachyarrhythmias
Bradyarrhythmias
GI

9

Adverse effect of Digitalis Glycosides
-Tachyarrhythmias

Predisposing Factors - hypokalemia, hypomagnesemia, hypercalcemia, hypernatrmia, hypothyroidism, hypoxemia
Treatment - drug withdrawal, K+ IV, antiarrhythmic drugs, cholestgramine, Digoxine immuen Fab

10

Adverse effect of Digitalis Glycosides
-Bradyarrhythmias

Treatment - drug withdrawal, Atropine (drug of choice)

11

Adverse effect of Digitalis Glycosides
-GI

Clinical signs - anorexia, vomiting, diarrhea
Treatment - drug withdrawal, fluid therapy

12

Beta-1 agonist drugs and uses

Positive Inotropes
Only used in emergencies
Dopamine
Dobutamine

13

Inodilator drugs

Inamrinone
Milrinone
Pimobendan

14

MOA of Inodilators

In the failing heart, Pinobendanacts by sensitization of the cardiac contractile apparatus to Ca2+ by enhancing the interaction between Ca2+ and troponin C complex
Inhibits phosphodiesterase III and IV = potential to increase intracellular Ca2+ and increased myocardial O2 consumption; minimal effect at therapeutic doses in dogs with CHF
Inhibition of phosphodiesterase III and IV results in vasodilation in arteries and veins = reduction in both cardiac preload and afterload

15

Uses of Inodilators

Approved to treat CHF in dogs
Adjunctive therapy in improving the quality and length of life in dogs with heart failure due to both dilated cardiomyopathy and chronic degenerative valvular disease
Used with furosemide, spironolactone, or ACE in heart failure patients

16

Side effects of Inodilators

Less arrhythmogenic than digitalis but may cause diarrhea, vomiting, inappetence, seizures, and polyuria/polydipsia

17

Contraindications of Inodilators

Should not be used in hypertrophic cardiomyopathy
Clinical conditions where an increase in cardiac output is not physically possible

18

Pharmacokinetics of Inodilators

Absorbed readily upon oral ingestion and around 60% bioavailability
Metabolically activated in the liver
Metabolites are excreted in feces
Bound to plasma proteins

19

Vasodilator drugs

ACE inhibitors
Hydralazine
Nitrates - Sodium nitroprusside, Nitroglycerin, Isosorbide dinitrate
Prazosin

20

Vasodilators
-ACE inhibitors

Captopril, Enalapril, Lisinopril, Benazepril
Angiotensin converting enzyme inhibitors
Vasodilators that also block the RAAS
Blocks conversion of Angiotensin I to Angiotensin II which is a vasoconstrictor

21

Diuretics
-types and drugs

Loop diuretics - Furosemide
Thiazide diuretics - Hydrochlorothiazide, Chlorothiazide
Potassium-sparing diuretics - spironolactone, Triamterene, Amiloride

22

Beta-blocker drugs

Carvedilol
Metoprolol or Atenolol

23

MOA of Carvedilol

Nonselective Beta-blocker and alpha-1 blocker
Antioxidant
Inhibits endothelin (ET) release
(peptides that constrict blood vessels and raise BP)

24

Use of Carvedilol

Beta-blocker
In early treatment of CHF due to dilated cardiomyopathy to blunt the harmful effects of the sympathetic nervous system to the heart