SMALL ANIMALS DRUGS FOR TREATING CARDIAC DISEASE Flashcards
drugs for treating heart failure
-decrease preload
-decrease afterload
-enhance inotropic function
drugs that decrease preload, indication; excessive preload-signs of
congestion: pulmonary edema, pleural effusion, ascites
>diuretics
>venodilators
drugs that decrease preload: diuretics - increase excretion of
sodium > reduction in extracellular fluid volume > lower circulating fluid volume > reduction in preload
classes of diuretics
3 classes:
1. loop
2. thiazide
3. potassium sparing
diuretics side effects
-polyuria
-polydipsia
diuretics complications
-hypotension
-azotemia
-hypokalemia(loop), hyponatremia
furosemide, torsemide
=loop diuretics
>blockade of Na+/K+/2Cl-
>loop of Henle
(most potent 25%)
hydrochlorothiazide
-thiazide
>blockade of Na+/Cl- carrier
>distal tubule and connecting segment
furosemide drug that decrease preload-diuretics: first line therapy for patients with signs of
congestion
furosemide: patients can become refractory to drugs to drug with chronic treatment
-higher doses
-coadministration of diuretics that act at different sites in nephron
-substitute for torsemide
spironolactone-drugs that decrease preload: diuretics: aldosterone receptor
antagonist
-insufficient natriuretic potency to be used as sole diuretic
-benefits well regocnized
>cats: cutaneous adverse drug reactions
drugs decrease preload: ventilators: nitroglycerin: treatment of
acute heart failure ( with loop diuretic)
-transdermal
-adverse effects: rashes at application site, hypotension, headache
drugs that decrease AFTERLOAD: vasodilators: left ventricular afterload reduction:
systemic vasodilation
>nitroprusside
-ACEI-angiotensin converting enzyme inhibitors
>pimobendan: Ca channel blockers
-complications: hypotension
drugs that decrease AFTERLOAD: vasodilators: right ventricular afterload reduction:
pulmonary vasodilation
-indication: pulmonary hypertension
>slidenafil: phosphodiesterase V inhibitor
>pimobendan can have pulmonary vasodilatory properties
drugs that decrease AFTERLOAD: vasodilators: 1. nitroprusside and 2. ACEI and 3. Ca channel blockers
- balanced effect: preload reduction via ventilation and afterload reduction via arteriodilation, CRI, only in ICU setting (Intensive Care Unit), indications: acute/severe hypertension, acute heart failure, combo with dobutamine
- ACEI: enalapril, benazepril, inhibition of angiotensin converting enzyme : vasodilation, inhibit fluid retention, part of chronic therapy for heart failure
- Ca channel blockers: amlodipine: systemic hypertension, in dogs also as afterload reducer for refractory heart failure
drugs that enhance inotropic function: myocardial contractility is frequently
impaired in patients with heart failure
> increased cardiac contractility > increased cardiac output, indirectly decreased preload
enhance inotropic function: dobutamine used in
acute treatment of heart failure
enhance inotropic function: pimobendan used in
chronic treatment of heart failure
enhance inotropic function: digoxin treatment for
atrial fibrillation
enhance inotropic function: dobutamine indications
-acute signs if heart failure + hypotension / primary failure of myocardial contractility
enhance inotropic function: dopamine
adrenergic /dopaminergic inotropic agent
dopamine indications
in ICU setting severe hypontension/shock due poor cardiac contractility and / or vasodilation, hypotension during general anesthesia
(dobutamine preferred)
drugs enhance inotropic function: Pimobendan
=INODILATOR
-phosphidiesterase inhibiton and calcium sensitization: inotropic and casodilatory properties = INODILATOR
pimobendan indications
-most dogs, some cats with heart failure
-dogs with preclinical heart disease
anti arrhythmic therapies : Vaughan williams system classes 1-4
-class 1: block Na channels, depress depolarization ; Class 1a-1c
-class 2: antiadrenergic drugs: mainly beta adrenergic receptor blockers: indications : atrial tachyarrhythmias AF
-class 3: prolong repolarization,indications: ventricular arrhythmias, supra ventricular arrhythmias
-class 4: Ca channel blockers, indications: atrial tachyarrhythmias
adverse effects of antiarrthythmic therapy
-arrhythmias
-cardiac systolic and diastolic function
-many class 1 drugs have CNS and GI effects
mexiletine: class 1b: similar to lidocaine but less rapid
hepatic metabolism and longer elimination half life
-indicaiton: chronic therapy of ventricular tachyarrhythmias in dogs
-class 1b neurotoxic to cats
lidocaine: class 1b: first choice for treatment of
ventricular tachyarrhythmias
-hypokalaemia : poor response to lidocaine
-adverse effects: cats prone neurotoxicity>lower dose , GI effects
beta adrenergic blockers: class 2: action
reduced heart rate and excitability
-indications : supraventricular and ventricular tachuarrhythmias
-adverse effects: lethargy, collapse, bradycardia, hypotension
most used: atenolol, metoprolol
sotalol: class 3 (+class 2 action)- prolong
repolarization + beta 1 and 2 blocker
-indication: ventricular and supraventricular tachyarrhythmias: most often used in boxers with arrhythmogenic cardiomyopathy
-dogs ventricular tachycardia use lidocaine and procainamide
>adverse effects: negative inotropy
diltiazem: class 4
Ca channel blockers
>actions: slow sinus rate and AV node conduction, arteriodilator
>indication: supraventricular tachyarrhythmias
>adverse effects: bradycardia (dogs), vomiting (cats)
digoxin: digitalis glycoside DG : actions with
heart failure > increased myocardial contractility and cardiac output, diuresis, reduction of edema, reduction heart size, HR
>indication: dogs with atrial fibrillation + CHF
>adverse effect: arrhythmias, worsening HF
antithrombotic drugs: prevention of
arterial thromboembolism
antiplatelet drugs: inhibition of platelet aggregation
-aspirin NSAID
-clopidogrel
sedative/analgetic agents
-butorphanol: opioid agonist/antagonist > decrease stress (acute CHF)
-mu agonist (fentanyl)-severe pain (FATE)
drugs used in CPR
-reversals: opioids-naloxone
-vasopressors: maintain perfusion to vital organs
