John Vincent A. Yangco
ANTI-ARRHYTHMIC DRUGS

Drugs used for Tachyarrhythmias
1. Class IA
a.
b.
c.
Quinidine
Procainamide
Disopyramide
a.
b.
c.
d.
2. Class IB
Lidocaine
Phenytoin
Tocainide
Mexiletine
3.
a.
b.
c.
Class IC
Flecainide
Encainide
Propaferone
a.
b.
c.
d.
e.
f.


4. Class II
Propanolol
Atenolol
Esmolo
Metoprolol
Nadolol
Pindolol
5.
Class III
a.
Bretylium
b.
Amiodarone
c.
Sotalol
6.
Class IV
a.
Verapamil
b.
Diltiazem
Drugs used for Bradyarrhytmias
7.
Atropine
8.
Glycopyrrolate
9.
Propantheline bromide
Procainamide
-Brand name: Pronestyl®
-Action: A class IA antiarrhythmic agent, exhibits cardiac action similar to that of
quinidine. It is considered both a supraventricular and ventricular antidysrhythmic. It
prolongs the refractory times in both the atria and ventricles, decreases myocardial
excitability, and depresses automaticity and conduction velocity. It has anticholinergic
properties.
-Clinical uses: Useful for the treatment of ventricular premature complexes (VPC’s),
ventricular tachycardia, or supraventricular tachycardia associated with Wolff-ParkinsonWhite (WPW) syndrome with wide QRS complexes.
-Adverse effect: Gastrointestinal effects may include anorexia, vomiting, or diarrhea.
Effects related to the cardiovascular system can include weakness, hypotension, negative
inotropism, widened QRS complex and QT intervals, AV block, multiform ventricular
tachycardias. There is also a possibility of fever and leukopenias.
-Contraindication: Contraindicated in patients with myasthenia gravis. Also in patients
hypersensitive to it, procaine or other chemically related drugs. In humans, it is
contraindicated in patients with systemic lupus erythematous (SLE). It should not be used
in patients with torsade de pointes, or with 2 or 3 degree heart block.
nd
rd
-Drug Interaction: Use with
 Amiodarone
 Anticholinesterase agents
 Cimetidine
 Hypotensive drugs
 Lidocaine
 Neuromuscular blocking agents
 Quinidine
 Phenytoin
 Propanolol
 Ranitidine
 Trimethoprim
-Dosage:



Dogs - 10-30 mg/kg q6h PO, to a maximum dose of 40 mg/kg
 8-20 mg/kg IV or IM
 Constant rate infusion (CRI): Initial loading dose of 10 mg/kg,
followed by 20 mcg/kg/min IV CRI; the CRI rate can be increased
to 25-50 mcg/kg/min if needed for refractory arrhythmias
Cats – 3-8 mg/kg q6-8h IM or PO
 CRI: 1-2 mg/kg IV slowly, then 10-20 mcg/kg/min IV
Horses – 25-35 mg/kg q8h PO
 Up to 20 mcg/kg IV
-Formulation: Available in 250-, 375-, and 500-mg tablets or capsules and a 100- and 500mg/ml injection.

Lidocaine
-Brand name: Xylocaine®
-Action: A class IB antidysrhythmic agent. At therapeutic levels, lidocaine causes phase 4
diastolic depolarization attenuation, decreased automaticity, and either a decrease or no
change in membrane responsiveness and excitability.
-Clinical uses: Use as a local and topical anesthetic agent. It is also used to treat ventricular
arrhythmias, principally ventricular tachycardia and ventricular premature complexes in
all species.
-Adverse effect: CNS signs include drowsiness, depression, ataxia, muscle tremors, etc.
Nausea and vomiting may occur, but are usually transient.
-Contraindication: Cats tend to be more sensitive to the CNS effects of lidocaine.
Contraindicated in patients with known hypersensitivity to the amide-class local
anesthetics, a severe degree of SA, AV or intraventricular heart block, or Adams-Stokes
syndrome. Used with caution in patients with liver disease, congestive heart failure,
shock, hypovolemia, severe respiratory depression, or marked hypoxia.
-Drug interaction: Use with





Antiarrhythmics
Cimetidine
Phenytoin
Propranolol
Succinylcholine
-Dosage:



Dogs – Antiarrhythmic: 2-4 mg/kg IV (to a maximum dose of 8 mg/kg over 10minute period)
 Antiarrhythmic: 25-75 mcg/kg/min IV, CRI
 Antiarrhythmic: 6 mg/kg q1.5h IM
 Epidural: 4.4 mg/kg of 2% solution
Cats – Antiarrhythmic: Start with 0.1 to 0.4 mg/kg initially, and then increase to
0.25-0.75 mg/kg IV slowly if there has been no response
 Antiarrhythmic: Loading dose of 0.5-1 mg/kg IV, followed by 1020 mcg/kg/min, (0.6-1.2 mg/kg/hr), IV, CRI
 Epidural: 4.4 mg/kg of 2% solution
Horses – Antiarrhythmic: 0.25-0.5 mg/kg q5-15 min IV, for a total of 1.5 mg/kg,
then as a CRI of 0.05 mg/kg/min (50 mcg/kg/min)
 Postoperative ileus: 1.3 mg/kg IV bolus administered over 15
min, followed by 0.05 mg/kg/min (50 mcg/kg/min) CRI
 Analgesia: 2 mg/kg IV, followed by 50 mcg/kg/min, CRI
-Formulation: Available in 5-, 10-, 15-, and 20-mg/ml injection.

Diltiazem
-Brand name: Cardizem®, Dilacor XR®
-Action: A calcium-channel blocker similar in action to drugs such as verapamil or
nifedipine. It inhibits the transmembrane influx of extracellular calcium ions in myocardial
cells and vascular smooth muscle, but does not alter serum calcium concentrations. It also
slows AV node conduction and prolongs refractory time.
-Clinical uses: Useful in treatment of hypertension, atrial fibrillation, and supraventricular
tachycardias.
-Adverse effects: Bradycardia is the most prominent side effect reported in dogs. In cats,
vomiting is reported as the most common side effect. Potentially, lethargy, GI distress
(anorexia), hypotension, heart block or other rhythm disturbances, CNS effects, rashes,
or elevations in liver function tests could occur in other species.
-Contraindication: Contraindicated in patients with severe hypotension (<90 mm Hg
systolic), sick sinus syndrome or 2 or 3 degree AV block (unless a functioning pacemaker
is in place), acute MI, radiographically documented pulmonary congestion, or when the
patient is hypersensitive to it.
nd
rd
-Drug interaction: Use with

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





Anesthetics
Benzodiapines
Beta-blockers
Buspirone
Digoxin
Cimetidine/ranitidine
Cyclosporine
Rifampin
Quinidine
-Dosage:



Dogs – 0.5-1.5 mg/kg q8h PO. For atrial fibrillation 5 mg/kg q12h, PO and a
combination of diltiazem (3 mg/kg q12h PO) plus digoxin (0.005 mg/kg q12h, PO)
has been used
 Atrial fibrillation: 0.05-0.25 mg/kg IV administered q5min to
effect
 Supraventricular tachycardia: 0.25 mg/kg over 2 min IV
 Acute renal failure: 0.2 mg/kg IV, followed by 3-5 mcg/kg/min
constant rate infusion
Cats – 1.75-2.4 mg/kg q8h PO
Horses – 0.125 mg/kg IV over at least 2 minutes
-Formulations: Available in 30-, 60-, 90- and 120-mg tablets; 60-, 90-, 120-, 180-, 240-, and
300-mg extended release capsules; and in a 5-mg/ml injection solution.

Glycopyrrolate
-Brand name: Robinul-V®
-Action: Anticholinergic agent parasympatholytic. It produces atropine-like effects
systemically. It has less effect on CNS compared to atropine because of lower penetration
to CNS. It may produce a longer duration of action than atropine.
-Clinical uses: Used to inhibit vagal effects and increase heart rate in animals. It also will
decrease respiratory, salivary, and GI secretions. It may be used as an adjunct to
anesthesia when it is necessary to override vagal stimulus.
-Adverse effects: Antimuscarinic (anticholinergic) effects. Side effects of therapy include
xerostomia, ileus, constipation, tachycardia, and urine retention.
-Contraindication: Do not use in patients with glaucoma, intestinal ileus, gastroparesis, or
tachycardia.
-Drug interaction: No specific drug interactions. However, it is expected that
glycopyrrolate will antagonize drugs that stimulate respiratory and GI secretions and GI
motility.
-Dosage:


Dogs and cats: 0.005-0.01 mg/kg IV, IM or SQ
Cattle and horses: use during anesthesia: 0.005-0.01 mg/kg IM or SQ or 0.00250.005 mg/kg IV
-Formulation: Available as a 0.2-mg/ml injection.