ANTI-ARRHYTHMIC
DRUGS
Ma. Janetth B. Serrano, M.D.,DPBA
ANTI – ARRHYTHMIC DRUGS
Cardiac Arrhythmias:
- 25% treated with digitalis
- 50% anesthetized patients
- 80% patients with AMI
 reduced cardiac output
 drugs or nonpharmacologic:
- pacemaker, cardioversion, catheter
ablation, surgery
ANTI – ARRHYTHMIC DRUGS
ELECTROPHYSIOLOGY
SA node
OF
ATRIA
NORMAL
AV node
CARDIAC
His-Purkinje System
RHYTHM
VENTRICLES
ANTI – ARRHYTHMIC DRUGS
IONIC BASIS OF MEMBRANE ELECTRICAL ACTIVITY


Transmembrane potential of cardiac cells
is determined by the concentrations of
the ff. ions:
– Sodium, Potassium, Calcium
The movement of these ions produces
currents that form the basis of the cardiac
action potential
ANTI – ARRHYTHMIC DRUGS
PHASES OF ACTION POTENTIAL
Phase 1
>Limited depolarization
>Inactivation of fast
Na+ channels→ Na+
ion conc equalizes
>↑ K+ efflux & Cl- influx
Phase 0
>Rapid depolarization
>Opening fast Na+
channels→ Na+ rushes
in →depolarization
Phase 2
>Plateau Stage
>Cell less permeable to Na+
>Ca++ influx through slow
Ca++ channels
>K+ begins to leave cell
Phase 3
>Rapid repolarization
>Na+ gates closed
>K+ efflux
>Inactivation of slow
Ca++ channels
Phase 4
>Resting Membrane Potential
>High K+ efflux
>Ca++ influx
ANTI – ARRHYTHMIC DRUGS
MECHANISMS OF ARRHYTHMIA
ARRHYTHMIA
DYSRRHYTHMIA
– absence of rhythm
– abnormal rhythm
ARRHYTHMIAS result from:
1.
Disturbance in Impulse Formation
2. Disturbance in Impulse Conduction

Block results from severely depressed conduction

Re-entry or circus movement / daughter impulse
ANTI – ARRHYTHMIC DRUGS
FACTORS PRECIPITATING CARDIAC ARRHYTHMIAS:
1. Ischemia


pH & electrolyte abnormalities
80% – 90% asstd with MI
2. Excessive myocardial fiber stretch/ scarred/
diseased cardiac tissue
3. Excessive discharge or sensitivity to autonomic
transmitters
4. Excessive exposure to foreign chemicals & toxic
substances


20% - 50% asstd with General Anesthesia
10% - 20% asstd with Digitalis toxicity
ANTI – ARHYTHMIC DRUGS
ARRHYTHMIAS:
 Ventricular:
 Supraventricular:
- Wolff-Parkinson- Atrial Tachycardia
White (preexcitation
- Paroxysmal
Tachycardia
- Multifocal Atrial
Tachycardia
- Atrial Fibrillation
- Atrial Flutter
syndrome)
-
-
Ventricular
Tachycardia
Ventricular Fibrillation
Premature Ventricular
Contraction
ANTI – ARRHYTHMIC DRUGS
CLASS I: Sodium Channel Blocking Drugs

IA

IB

IC
-
lengthen AP duration
Intermediate interaction with Na+ channels
Quinidine, Procainamide, Disopyramide
shorten AP duration
rapid interaction with Na+ channels
Lidocaine, Mexiletene, Tocainide, Phenytoin
no effect or minimal  AP duration
slow interaction with Na+ channels
Flecainide, Propafenone, Moricizine
ANTI – ARRHYTHMIC DRUGS
CLASS II: BETA-BLOCKING AGENTS





Increase AV nodal conduction
Increase PR interval
Prolong AV refractoriness
Reduce adrenergic activity
Propranolol, Esmolol, Metoprolol,
Sotalol
ANTI – ARRHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS

Prolong effective refractory period by
prolonging Action Potential
– Amiodarone
- Ibutilide
– Bretylium
- Dofetilide
– Sotalol
ANTI – ARRHYTHMIC DRUGS
CLASS IV: CALCIUM CHANNEL BLOCKERS

Blocks cardiac calcium currents
→ slow conduction
→ increase refractory period
*esp. in Ca++ dependent tissues (i.e. AV node)

Verapamil, Diltiazem, Bepridil
ANTI – ARRHYTHMIC DRUGS
Miscellaneous:

ADENOSINE
→ inhibits AV conduction &
increases AV refractory period

MAGNESIUM
→ Na+/K+ ATPase, Na+, K+,
Ca++ channels

POTASSIUM
→ normalize K+ gradients
ANTI – ARRHYTHMIC DRUGS
CLASS I: Sodium Channel Blocking Drugs
CLASS IA:




QUINIDINE
Depress pacemaker rate
Depress conduction & excitability
Slows repolarization & lengthens AP duration
→ due to K+ channel blockade with reduction of
repolarizing outward current → reduce maximum
reentry frequency → slows tachycardia
(+) alpha adrenergic blocking properties →
vasodilatation & reflex ↑ SA node rate
ANTI – ARRHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: QUINIDINE

Pharmacokinetics:
– Oral → rapid GI absorption
– 80% plasma protein binding
– 20% excreted unchanged in the urine →
enhanced by acidity
– t½ = 6 hours
– Parenteral → hypotension

Dosage: 0.2 to 0.6 gm 2-4X a day
ANTI – ARRHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: QUINIDINE

Therapeutic Uses:
– Atrial flutter & fibrillation
– Ventricular tachycardia
– IV treatment of malaria

Drug Interaction:
– Increases digoxin plasma levels
ANTI – ARRHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: QUINIDINE

Toxicity:
– Antimuscarinic actions → inh. vagal effects
– Quinidine syncope (lightheadedness, fainting)
– Ppt. arrhythmia or asystole
– Depress contractility & ↓ BP
– Widening QRS duration
– Diarrhea, nausea, vomiting
– Cinchonism (HA, dizziness, tinnitus)
– Rare: rashes, fever, hepatitis, thrombocytopenia,etc
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: PROCAINAMIDE

Less effective in suppressing abnormal ectopic
pacemaker activity

More effective Na+ channel blockers in
depolarized cells

Less prominent antimuscarinic action

(+) ganglionic blocking properties → ↓PVR →
hypotension (severe if rapid IV or with severe LV
dysfunction)
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: PROCAINAMIDE
PHARMACOKINETICS:





Oral, IV, IM
N-acetylprocainamide (NAPA) → major
metabolite
Metabolism: hepatic
Elimination: renal
t½ = 3 to 4 hrs.
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: PROCAINAMIDE

Dosage:
Loading IV – 12 mg/kg at 0.3 mg/kg/min or less
rapidly
Maintenance – 2 to 5 mg/min

Therapeutic Use:
2nd DOC in most CCU for the treatment of
sustained ventricular arrhythmias asstd. with MI
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: PROCAINAMIDE

Toxicity:
- ppt. new arrhythmias
- LE-like syndrome
- pleuritis, pericarditis, parenchymal
pulmonary disease
- ↑ ANA
- nausea, DHA, rash, fever, hepatitis,
agranulocytosis
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: DISOPYRAMIDE

More marked cardiac antimuscarinic effects
than quinidine → slows AV conduction

Pharmacokinetics:
- oral administration
- extensive protein binding
- t½ = 6 to 8 hrs
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: DISOPYRAMIDE



Dosage: 150 mg TID up to 1 gm/day
Therapeutic Use: Ventricular arrhythmias
Toxicity:
- negative inotropic action (HF without
prior myocardial dysfunction)
- Urinary retention, dry mouth, blurred
vision, constipation, worsening glaucoma
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: AMIODARONE







Approved only in serious ventricular arrhythmias
Broad spectrum of action on the
Very effective Na+ channel blocker but low affinity
for activated channels
Markedly lengthens AP by blocking also K+
channels
Weak Ca++ channel blocker
Noncompetetive inhibitor of beta adrenoceptors
Powerful inhibitor of abnormal automaticity
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: AMIODARONE






Slows sinus rate & AV conduction
Markedly prolongs the QT interval
Prolongs QRS duration
↑ atrial, AV nodal & ventricular refractory
periods
Antianginal effects – due to noncompetetive α
& β blocking property and block Ca++
influx in vascular sm.m.
Perivascular dilatation - α blocking property
and Ca++ channel-inhibiting effects
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: AMIODARONE




Pharmacokinetics:
> t½ = 13 to 103 days
> effective plasma conc: 1-2 μg/ml
Dosage: - Loading – 0.8 to 1.2 g daily
- Maintenance – 200 to 400 mg daily
Drug Interaction: reduce clearance of warfarin,
theophylline, quinidine, procainamide, flecainide
Therapeutic Use: Supraventricular & Ventricular
arrhythmias
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IA: AMIODARONE

Toxicity:
- fatal pulmonary fibrosis
- yellowish-brown microcrystals corneal deposits
- photodermatitis
- grayish blue discoloration
- paresthesias, tremor, ataxia & headaches
- hypo - / hyperthyroidism
- Symptomatic bradycardia or heart block
- Ppt. heart failure
- Constipation, hepatocellular necrosis, inflam’n, fibrosis,
hypotension
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IB: LIDOCAINE






Intravenous route only
Arrhythmias asstd with MI
Potent abnormal cardiac activity suppressor
Rapidly act exclusively on Na+ channels
Shorten AP, prolonged diastole → extends time
available for recovery
Suppresses electrical activity of DEPOLARIZED,
ARRHYTHMOGENIC tissues only
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IB: LIDOCAINE




Pharmacokinetics:
- Extensive first-pass hepatic metabolism
- t½ = 1 to 2 hrs
Dosages: loading- 150 to 200 mg
maintenance- 2-4 mg
Drug Interaction:
propranolol, cimetidine – reduce clearance
Therapeutic Use:
DOC for suppression of recurrences of
ventricular tachycardia & fibrillation in the first
few days after AMI.
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IB: LIDOCAINE

Toxicity:
–
–
–
–
Ppt. SA nodal standstill or worsen impaired
conduction
Exacerbates ventricular arrhythmias
Hypotension in HF
Neurologic: paresthesias, tremor, nausea,
lightheadedness, hearing disturbances,
slurred speech, convulsions
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IB: TOCAINIDE & MEXILETENE






Congeners of lidocaine
Oral route - resistant to first-pass hepatic
metabolism
Tptic use: ventricular arrhythmias
Elimination t½ = 8 to 20 hrs
Dosage: Mexiletene – 600 to 1200 mg/day
Tocainide – 800 to 2400 mg/day
S/E: tremors, blurred vision, lethargy, nausea,
rash, fever, agranulocytosis
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IB: PHENYTOIN







Anti-convulsant with anti-arrhythmic properties
Suppresses ectopic pacemaker activity
Useful in digitalis-induced arrhythmia
Extensive, saturable first-pass hepatic metabolism
Highly protein bound
Toxicity: ataxia, nystagmus, mental confusion,
serious dermatological & BM reactions,
hypotension, gingival hyperplasia
D/I: Quinidine, Mexiletene, Digitoxin, Estrogen,
Theophyllin, Vitamin D
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IC: FLECAINIDE






Potent blocker of Na+ & K+ channels
No antimuscarinic effects
Used in patients with supraventricular
arrhythmias
Effective in PVC’s
Hepatic metabolism & renal elimination
Dosage: 100 to 200 mg bid
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IC: PROPAFENONE






(+) weak β-blocking activity
Potency ≈ flecainide
Average elim. t½ = 5 to 7 hrs.
Dosage: 450 – 900 mg TID
Tptic use: supraventricular arrhythmias
Adv. effects: metallic taste, constipation,
arrhythmia exacerbation
ANTI – ARHYTHMIC DRUGS
CLASS I: SODIUM CHANNEL BLOCKERS
CLASS IC: MORICIZINE






Antiarrhythmic phenothiazine derivative
Used in ventricular arrhythmias
Potent Na+ channel blocker
Donot prolong AP duration
Dosage: 200 to 300 mg orally tid
Adv. effects: dizziness, nausea
ANTI – ARHYTHMIC DRUGS
CLASS II: BETA ADRENOCEPTOR BLOCKERS





↑ AV nodal conduction time (↑ PR interval)
Prolong AV nodal refractoriness
– Useful in terminating reentrant arrhythmias that
involve the AV node & in controlling ventricular
response in AF & A.fib.
Depresses phase 4 → slows recovery of cells, slows
conduction & decrease automaticity
Reduces HR, decrease IC Ca2+ overload & inhibit after
depolarization automaticity
Prevent recurrent infarction & sudden death in
patients recovering from AMI
ANTI – ARHYTHMIC DRUGS
CLASS II: BETA ADRENOCEPTOR BLOCKERS

“membrane stabilizing effect”



“intrinsic sympathetic activity”



Exert Na+ channel blocking effect at high doses
Acebutolol, metoprolol, propranolol, labetalol,
pindolol
Less antiarrhythmic effect
Acebutolol, celiprolol, carteolol, labetalol, pindolol
Therapeutic indications:


Supraventricular & ventricular arrhythmias
hypertension
ANTI – ARHYTHMIC DRUGS
CLASS II: BETA ADRENOCEPTOR BLOCKERS
Specific agents:

Propranolol
Acebutolol

Esmolol

Sotalol

– (+) MSA
– as effective as quinidine in
suppressing ventricular ectopic
beats
- short acting hence used
primarily for intra-operative &
other acute arrhythmias
– has K+ channel blocking
actions (class III)
ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS


Drugs that prolong effective refractory period
by prolonging action potential
Prolong AP by blocking K+ channels in
cardiac muscle (↑ inward current through
Na+ & Ca++ channels)

Quinidine & Amiodarone → prolong AP duration
Bretylium & Sotalol → prolong AP duration &
refractory period
Ibutilide & Dofetilide → “pure” class III agents

Reverse use-dependence


ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS
BRETYLIUM
 Antihypertensive
 Interferes with neuronal release of
catecholamines
 With direct antiarrhythmic properties
 Lengthens ventricular AP duration & effective
refractory period
 Markedly ↑ strength of electrical stimulation
needed to induce V.fib. & delays onset of
fibrillation after acute coronary ligation
 (+) inotropic action
ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS
BRETYLIUM
 Intravenous administration
 Dosage: 5 mg/kg
 Tptic Use: ventricular fibrillation
 In emergency setting, during attempted
resuscitation from ventricular fibrillation when
lidocaine & cardioversion have failed
 S/E:
postural hypotension***
ppt. ventricular arrhythmia
nausea & vomiting
ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS
SOTALOL






Nonselective beta-blocker that also slows
repolarization & prolongs AP duration
Effective antiarrhythmic agent
Used in supraventricular & ventricular
arrhythmias in pediatric age group
Renal excretion
Dosage: 80 – 320 mg bid
Toxicity: torsades de pointes
beta-blockade symptoms
ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS
IBUTILIDE






Slows repolarization
Prolong cardiac action potentials
MOA:
> enhance inward Na+ current
> by blocking Ikr> both
routes: Oral, IV (1 mg over 10min)
Clin. Uses: atrial flutter, atrial fibrillation
Toxicity: Torsades de pointes
ANTI – ARHYTHMIC DRUGS
CLASS III: POTASSIUM CHANNEL BLOCKERS
DOFETILIDE





A potential Ikr- blocker
Dosage: 250-500 ug bid
Clin. Uses: Atrial flutter & fibrillation
Renal excretion
Toxicity: Torsade de pointes
ANTI – ARHYTHMIC DRUGS
CLASS IV: CALCIUM CHANNEL BLOCKERS
VERAPAMIL
 Blocks both activated & inactivated calcium
channels
 Prolongs AV nodal conduction & effective
refractory period
 Suppress both early & delayed
afterdepolarizations
 May antagonize slow responses in severely
depolarized tissues
 Peripheral vasodilatation → HPN & vasospastic
disorders
ANTI – ARHYTHMIC DRUGS
CLASS IV: CALCIUM CHANNEL BLOCKERS
VERAPAMIL






Oral administration → 20% bioavailability
t½ = 7 hrs
Liver metabolism
Dosage:
IV: 5-10 mg every 4-6 hrs or infusion of 0.4 ug/kg/min
Oral: 120-640 mg daily, divided in 3-4 doses
Tptic use: SVT, AF, atrial fib, ventricular arrhythmias
Toxicity: AV block, can ppt. sinus arrest
constipation, lassitude, nervousness,
peripheral edema
ANTI – ARHYTHMIC DRUGS
CLASS IV: CALCIUM CHANNEL BLOCKERS
DILTIAZEM & BEPRIDIL


Similar efficacy to verapamil in
supraventricular arrhythmias & rate
control in atrial fibrillation
Bepridil


AP & QT prolonging action→ ventricular
arrhythmias but may ppt. torsade de pointes
Rarely used → primarily to control refractory
angina
ANTI – ARHYTHMIC DRUGS
MISCELLANEOUS ANTIARRHYTHMIC AGENTS:
DIGITALIS


Indirectly alters autonomic outflow by
increasing parasympathetic tone &
decreasing sympathetic tone
Results in decreased conduction time &
increased refractory period in the AV node
ANTI – ARHYTHMIC DRUGS
MISCELLANEOUS ANTIARRHYTHMIC AGENTS:
ADENOSINE




A nucleoside that occurs naturally in the body
t½ ≈ 10 seconds
MOA: enhances K+ conductance & inhibits
cAMP-induced Ca++ influx → results in marked
hyperpolarization & suppression of Ca++dependent AP
IV bolus: directly inhibits AV nodal conduction &
↑ AV nodal refractory period
ANTI – ARHYTHMIC DRUGS
MISCELLANEOUS ANTIARRHYTHMIC AGENTS:
ADENOSINE
 DOC for prompt conversion of paroxysmal SVT
to sinus rhythm due to its high efficacy & very
short duration of action
 Dosage: 6-12 mg IV bolus
 D/I:
 theophylline, caffeine – adenosine receptor
blockers
 Dipyridamole – adenosine uptake inhibitor
 Toxicity: flushing, SOB or chest burning, atrial
fibrillation, headache, hypotension, nausea,
paresthesia
ANTI – ARHYTHMIC DRUGS
MISCELLANEOUS ANTIARRHYTHMIC AGENTS:
MAGNESIUM


Effective in patients with recurrent
episodes of torsades de pointes (MgSO4 1
to 2 g IV) & in digitalis-induced arrhythmia
MOA: unknown → influence Na+/K+
ATPase, Na+ channels, certain K+ and
Ca++ channels
ANTI – ARHYTHMIC DRUGS
MISCELLANEOUS ANTIARRHYTHMIC AGENTS:
POTASSIUM




Therapy directed toward normalizing K+ gradients &
pools in the body
Effects of increasing serum K+:
1. resting potential depolarizing action
2. membrane potential stabilizing action
Hypokalemia:
 ↑ risk of early & delayed afterdepolarization
 ↑ ectopic pacemaker activity esp if (+) digitalis
Hyperkalemia:
 Depression of ectopic pacemakers
 Slowing of conduction