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Ag 412 Cardiac Drugs


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What causes increased force of contraction of the heart, disturbance of rhythm and reduced beat frequency.
Digitalis is derived from?
foxglove plant
What is digitalis used for?
control of congestive heart failure
What are the types of digitalis?
digoxin & digitoxin
What type of digitalis is only used for emergency? Why?
>more toxic than digoxin
What are the side effects of digitalis?
>muscle weakness
>visual disturbances
What are severe signs of toxicity?
What are some considerations that should be taken with digitalis?
>always anticipate toxicity
>digitalis is toxic to people
>metabolized in liver & excreted by kidneys
>keep in hospital if critical
>start on low dose if non-critical
What drugs reduce the effectiveness of digitalis by enhancing its excretion?
>barbiturates and its derivatives
>bute (horses)
What drugs increase the likelihood of digitalis toxicity by slowing down the excretion of digitalis?
>certain antibiotics
>>some sulfa
What are the Class 1A anti-arrhythmic drugs?
What are the Class 1A anti-arrhythmic drugs used for?
>depress myocardial excitability
>ventricular and premature ventricular contractions
>wide bizarre QRS complexes
What are the Class 1B anti-arrhytmic drugs?
What are the Class 1B anti-arrhythmic drugs used for>
>depress myocardial activity
>tx ventricular arrhythmias
>decreas cell automaticity (prevents depolarization)
How is lidocaine used as an anti-arrythmic drug?
>single bolus under cardiac arrest
>given IV than put in fluids for continuous rate infusion
Propanolol (Indarol) is what type of drug?
Class II beta blocker
How does lidocaine decrease cell automaticity?
blocks the inflow of sodium into the cell which prevents depolarization
What are Class II beta blockers used for?
>Tx heart disease
>slow heart rate
>lowers blood pressure
How does a Class II beta blocker work?
reduces the cell automaticity
How does Propanolol reduce cell automaticity?
blocks the receptor sites for electrical impulses
What are the Class IV calcium channel blockers?
Cardazen (dilatazen)
How does the Class IV calcium channel blockers work?
blocks entry of calcium into myocardial cells - depressing contractility and reducing automaticity
What are the Class IV calcium channel blockers used for?
Atrial fibrillation
What are the adverse effects of the anti-arryhthmic drugs?
>increased lethargy & anorexia
>muscle weakness
>dry mouth
>incoordination & other CNS abnormalities
>articular or ventricular standstill
What is the clinical use of Catecholamines?
short term managment of severe heart failure or anaphylaxis
What are the types of Catecholamines?
Dopamine & Dobutamine
Epinephrine is used for?
cardiac arrest
How does epinephrine work?
promotes movement of the heart muscle
Dopamine and Dobutamine are used for?
respiratory drug/stimulant
How doe dopamine and dobutamine work?
>increases rate & force of contraction
>increases blood pressure
What is diuretics?
agents that promote excretion of urine through their effects on kidney function
What are the diuretic drugs?
Furosemide (Lasix)
Thiazides (Diuril, Naturetin)
What type of diuretic is Furosemide (Lasix)?
loop diuretics
How does Furosemide (Laxis) work?
>inhibits reabsorption of sodium and water in the loop of Henle, leads to increased urine excretion
>increases renal blood flow - increases filtration rate & urine output
What is Furosemide(Lasix) used for?
relief of cardiac and pulmonary edema
What is the duration of Furosemide (lasix)?
2-3 hours
Which diuretic is seldom used in veterinary medicine?
What is the duration of Thiazides?
12-24 hours
What type of diuretic is Mannitol?
osmotic diuretic
What is the action of Mannitol?
limits tubular reabsorption of water by exerting a high osmotic pressure in the kidney tubules

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