Heart Drugs Flashcards
Loop diuretics
Furosemide- most common
Act on the ascending loop of Henle.
Decreases the re-absorption of sodium and chloride and increases excretion of potassium.
Increase the renal excretion of water, sodium, chloride, calcium, magnesium, hydrogen, ammonium, and bicarbonate.
Furosemide
2-4mg/kg Q1-8hrs CRI: 0.1mg/kg/hr Watch for: Electrolyte disturbances (K, Ca, Na). Severe dehydration Decline in renal functions Hypotension due to hypovolemia
Spironolactone
Potassium-sparing diuretic Aldosterone receptor blocker Slow onset (2-3 days)- long term treatment 2-4mg/kg/day PO Hyperkalemia - watch kidney functions
What are examples of Thiazide diuretics and what do they do?
Hydrochlorothiazide
Chlorothiazide
Inhibit sodium reabsorption and promote potassium excretion
Decreases renal blood flow - do not administer to azotemic animals
Positive inotropes
Increases strength of contraction of the myocardial muscle=increases cardiac output 4 groups: Sympathomimetic amines Phosphodiesterase inhibitors Calcium sensitiser Digitalis glycosides
Name two sympathomimetic amines used for heart failure
Dopamine
Dobutamine
Stimulates beta-adrenergic receptor sites and increases calcium availability
Short half lives and must be CRIs
Dobutamine
Increases myocardial contractility and stroke volume = increased cardiac output
5-20mcg/kg/min
Counteracts effects of beta blockers
Dopamine
Precursor of norepinephrine
Dose related:
*Low dose (1-5mcg/kg/min)common
- vasodilation do renal, mesentric, cerebrovasucular and coronary
arteries by acting on dopamine receptors
High dose (6-10mcg/kg/min)
- generalized systemic arteriolar vasoconstriction
-increases afterload
-decrease cardiac output
-acting on beta receptors
Higher than 10mcg/kg/min
-acting on the alpha cells that stimulate catecholamines and leads to
vasoconstriction
*Watch for: nausea, anorexia, tachycardia and arrhythmias
: phlebitis and tissue necrosis if extravasated
Give examples of phosphodiesterase inhibitors
*Milrinone
: 50mcg/kg/min and then 0.375-0.75mcg/kg/min CRI
*Amrinone
: 1-3mcg/kg/min and then 10-100mcg/kg/min
Short half-life = CRI
*Sildenafil
:5 phosphodiesterase
: potentially be able to reduces left ventricular afterload (seen in
humans)
* Pimobendan
: phosphodiesterase inhibitors
: calcium sensitization
= positive inotropic effects and vasodilation
: long term medication PO for CHF
: potent inhibitor of platelet aggregation (watch for bleeding)
Digitalis glycosides
Improves cardiac performance Normalizing neurohormonal aberrations Reduce fluid retention Abolishing supraventricular tachyarrhythmias Lowers heart rate
Name two types of digitalis glycosides
1)Digoxin
-more prevalent
-only form that can be used in cats
-used in dogs with renal dysfunction
: <20kg. 0.005-0.008mg/kg PO q12
-cats
: 0.006-0.007 mg/kg PO Q48
2)Digitoxin
-dogs. 0.01-0.03mg/kg Q8
- Must monitor for digitalis toxicity
- cardiac arrhythmias = worsening heart disease
- gastro upset
- anorexia
- weight loss
- diarrhea
- Drug interactions
- antacids
- cimetidine
- Metoclopramide
- oral neomycin
- chemotherapeutic agents will decrease amount of digitalis absorbed from the GIT
- Drugs that enhances toxic effects of digitalis:
- diazepam
- quinidine
- anticholinergics
- succinylcholine
- verapamil
- tetracycline
- erythromycin
- Diuretics or other drugs that deplete body of potassium may predispose to toxicity
Vasodilators
Classified as:
1) Arteriolar dilators
- decrease afterload (resistance of left ventricle ejection of blood)
- used in dilated cardiomyopathy, mitral valve regurge, intracardiac or vascular shunts
- Hydralazine : must watch for sodium and water retention and GI signs
2) Venodilators
- reduces preload (vol of blood in the left ventricle just before it contracts)
- used in the same situation as diuretics
- Nitroglycerin ointment
- Monitor for hypotension
3) both
- Nitroprusside is both
- must be CRI
- 0.5-10 mcg/kg/min
- Closely monitor HR and BP due to dilation effects
ACE I
Blocks the conversion of angiotensin I to II (vasoconstrictor)
- Promotes renal sodium and water excretion
- Slow or every reverse the progression of pump dysfunction and pathological remodeling of heart failure
- Used in hypertension, CHF secondary to valvular disease and dilated cardiomyopathy dogs and hypertrophic cardiomyopathy in cats
Examples of ACE I drugs
- Enalapril
- Imidapril
- Ramipril
- Benazepril
- Adverse side effects: vomiting, diarrhea, hypotension, renal dysfunction and hyperkalemia
Calcium channel blockers
Another type of vasodilator
2 types:
1) Dihydripyridine
-arteriolar vasodilator
-Amlodipine:
-prevents cardiac output
-used in hypotension
-0.2mg/kg PO Q24
2) Non-dihydripyridine
-negative inotropic drugs
-less potent vasodilators
-negative chronotropic drugs (slows conduction through AV node)
-Dilitiazem
:controls supraventricular tachycardia or artrial fibrillation and hyperthrophic cardiomyopathy
: 0.5-2.0mg/kg PO q8
*Adverse effects: GIT disturbances, hypotension, conduction block, CNS effects, peripheral or pulmonary edema, rashes or altered liver functionAmlodipine
- Primary dihydropyridine calcium channel blocker
- minimal myocardial depression
- preserves cardiac output
- used for systemic hypertension
- monitor for renal insufficiency, hypotension and vomiting
Non-dihydropyridine calcium channel blockers
- negative inotropic drugs
- depresses cardiac contractility allowing myocardial relaxation
- less potent vasodilators
Negative chronotropic drugs
Slows conduction through AV node
Diltiazem
- Most common non-dihydropyridine calcium channel blocker
* controls or terminates supraventricular tachycardia or atrial fibrillation and hypertrophic cardiomyopathy
What are the adverse side effects of non-dihydropyridine calcium channel block Dilitiazem?
Gastrointestinal disturbances, hypotension, conduction block or other rhythm disturbances, CNS effects, peripheral or pulmonary edema, rashes, altered liver function
Beta-adrenergic blockers
- Binds to beta receptors of sympathetic nervous system (fight or flight) located in vascular system, heart and bronchioles
- 2 types: beta-1 and beta-2
What does the stimulation of beta-1 receptors cause?
*Increase in HR, AV nodal conduction velocity, increase in strength of myocardial contraction
What does the stimulation of beta-2 receptors cause?
*vasodilation of skeletal muscle and bronchodilation in the airways
What are the most common beta-blockers?
Propranolol, Atenolol, Metoprolol, and Esmolol
Propranolol
- Beta-1 and 2 blocker
- Decrease HR, slower conduction through AV node, decreased myocardial contractility = decrease cardiac output
- Bronchial constriction
Atenolol and metoprolol
- Selectively blocks beta-1 receptor sites
- Blocks beta-2 receptor sites at very high doses
- Act as negative inotropic and negative chronotropic drug
- Causes: decreased myocardial oxygen demands, and reduces blood pressure
- No respiratory effects
Why are atenolol and metoprolol better than Proponolol for respiratory compromised patients?
They do not cause bronchoconstriction
What beta blockers causes prolongation of hypoglycemic effects of insulin?
Atenolol and propranolol
Esmolol
- Ultrashort acting beta-1 blocker
- only injectable
- similar to atenolol
- used as test drug
- infusion for short term Tx of supraventricular tachyarrhythmias
What are the adverse effects of esmolol?
Hypotension and bradycardia
- *Increase serum digoxin levels
- Morhpine Patients need to have lower doses of esmolol
Angiotensin II
Potent vasodilator
