Anti-Arrhythmics Flashcards
Aims of antiarrythmic therapy (2)
- Reduce ectopic pacemaker activity
- Regularize impulse of conduction pathway
What do class 1 anti-arrythmics do
Membrane stabilizers
- Increase threshold of excitability
- Decrease conduction velocity
- Prolong effective refractory period
- Reduce phase zero of AP
Who are class 1a antiarrythmics? What do they do
- Quinidine sulphate
- Procainamide
Which anti-arrythmic is good for ventricular premature complexes and supra-ventricular tachycardia in large breeds
Quinidine sulphate
Which drug is good for atrial flutter in horses
Quinidine sulphate
What are A/E of quinidine sulphate in horses
- Wheals
- Laminitis
- GI upset
- Nasal mucosa damage
Which Class 1a is best for atrial arrythmias
Quinidine sulphate
Which class 1a is best for ventricular arrythmias
Procainamide
Which class 1a is less vagolytic
Procainamide
Which class 1a has long half-life in dogs
Procainamide
Toxicity of procainamide
Wide QRS
Arrythmias
Hypotension
What do Class-1b drugs do
Reduce conduction velocity in injured cardiac cells
What effects do Class-1b drugs have on AP/RP
minimal effects
Which Class-1b drug is a broad antiarrythmic
Aprindine, Indecainide (more potent)
- Good for dogs that are resistant to others*
- Lots of A/E! –> give as last resort*
Which class-1B is used for cardiac emergencies
Lidocaine - give IV (rapid effect, short half-life)
Class-1b drugs mainly target what kind of arrythmias
Ventricular arrythmias
(except Aprindine/Indecainide which are broad spectrum)
Adverse effects of Aprindine.
- Leukopenia
- Hepatotoxicosis
- Hypotension
- Seizures
- etc…
Whats the difference between Indecainide and Aprindine
Indecainide is more potent and has fewer A/E
Which Class-1b is given for digitalis arrythmias (along with ventricular arrythmias)
Phenytoin
Toxicity occurs with Phenytoin if you give it with what….
Chloramphenicol (potent inhibit for CP450 – phenytoin tox)
Postural ataxia, hypermetric gait
Which class-1b has good oral absorption (no 1st pass effect) and long duration
Tocainide
Compare/contrast Lidocaine and Tocainide for administration and duration
Lidocaine: inefficient oral administration. Short half-life
Tocainide: efficient oral administration (no 1st pass). Long duration
Which class-1b is similar to Tocainide (good for oral admin, long duration, ventricular arrythmias)
Mexiletine
What are class-1c drugs used for? Name them (3)
- Ventricular tachycardia
- Premature beats (ventricular or atrial)
‘FEL’
1. Flecainide
2. Encainide
3. Lorcainide
What are Class 2 drugs
Beta blockers!
What do class 2 drugs do
Treat arrythmias caused by high catecholamines
- Reduce HR
- Reduce CO
- Reduce automaticity
- Prolong AV
- Reduce AP
Selective cardio beta blockers (4)
‘MACE’
1. Metoprolol
2. Atenolol
3. Carvedilol
4. Esmolol
Which class-2 can be used with COPD
Selective cardio B1 blockers
Metoprolol
Atenolol
Carvdiolol
Esmolol
3 uses of propanolol
- Catecholamine induced supraventricular arrythmias
- Tachyarrythmias associated with Digitalis tox
- Arrythmias due to halogenated hydrocarbon anesthesia
Your dog is in sugery under halogenated hydrocarbon anesthesia. He develops an arrythmia. What do you give? What do you definitely NOT give
Give: Propanolol (non-selective Class-2)
DONT GIVE: Bretylium (increased arrythmia)
Can you give Propanolol to patients with COPD
No! Causes airway obstruction due to anatgonizes B2 receptors in lungs (b2 = bronchodilation)
What do Class-3 antiarrythmics do? What are they?
Prolong AP
Extend RP
1. Amiodarone
2. Bretylium
What does Amiodarone do?
Class III anti-arrythmic
- Blocks K+ channels
- Inhibits B-receptor
Which species is Amiodarone preferred for
Dogs with ventricular arrythmias
An adverse effect of Amiodarone is it can increase concentration of…
- Digoxin
- Quinidine (1**a)
- Procainamide (1a
- Phenytoin (1b)
- Warfarin
- Diltiazem (4)
Which drug is contraindicated with halogenated hydrocarbon anesthetics
Bretylium
What do class 4 antiarrythmics do
Ca++ channel blockers
What are class-4 drugs used for? What are they?
Superventricular arrythmias
Ventricular hypertrophy
- Diltiazem
- Verpamil
Which class-4 is good for atrial arrythmias and supraventricular tachycardia
Verpamil
Can you give Class-2 drugs with Class-4 drugs?
No! AV shock
Adverse effects of class 4 drugs
(Diltiazem, Verpamil)
- Hypotension (due to vascular dilation —> reduced Ca)
- Bradycardia (reduced Ca)
- Reduced CO
What effect does Epinephrine have on the heart
Very potent vasodilator**
- B1 (heart): pos. inotrope, pos. chromotrope
- A1 (vessels): vasoconstriction
- B2 (vessels in skeletal m.): vasodilation
Which drug is Epinephrine often used with
Lidocaine
Adverse effects of Epinephrine
- Allergic reactions
- Cardiac arrest
What beta-agonist is used for cardiac arrest
Isoproterenol
What are effects of Isoproterenol (3)
Non-selective B agonist
- Pos. inotrope, pos. chromotrope (B1)
- Dilation of skeletal m vessels (B2)
- Bronchial relaxation (B2)
Which receptors does Dopamine act on and what does it do
- D1 receptor: vasodilation of spleen, kidneys
- B1 receptor: increased CO
What are two conditions Dopamine is preferred for
- Oliguric renal failure (increased CO, increased renal blood flow) —> with Furosemide
- Cardiogenic shock/ Severe Hypotension (IV)
- A1 receptors: vasoconstriction
- B1 receptor: increased contractility
Your patient is in oliguric renal failure. Which two drugs do you give and how do they work?
- Dopamine: increased CO (B1 receptor), increased renal blood flow (D1 receptor)
- Furosemide (diuretic)
