Antarrhythmic drugs

Question 1

General class I
Na channel blocker

Answer 1

⬇️slope of phase 0 of depolarization
⬇️conduction in depolarized cell
Selectively depress tissues that are frequently depolarized

Question 2

Class IA
Quinidine
Procainamide
Disopyramide

Answer 2

AP⬆️
⬆️effective refractory period
⬆️QT
K channel block

Clinical use : atrial and ventricular arrhythmia, SVT, VT

Adverse : thrombocytopenia
Torsade de points due to ⬆️QT
Cinchonism (headache and nausea with quinidine)
Reversible 
SLE-like syndrome(procainamide)
HF (Disopyramide)

Question 3

Class I B
Lidocaine
Mexiltine
Phenytoin

Answer 3

⬇️AP
Preferentially affect ischemic tissue or depolarized purkinje and ventricular tissue

Clinical use : post MI, acute ventricular arrhythmia
Dig induced arrhythmia

Adverse : CNS stimulation or depression , cardiovascular depression

Question 4

Class I C
Flecainide
Propafenone

Answer 4

Strong Na channel blocker
⬆️effective refractory period in AV node and by pass tracts
No change in ERP of purkinje or ventricular tissue

Use: SVT, AF, refractory VT

ADVERSE: pro arrhythmic, specially after MI
CONTRADICTED after MI, structural snd ischemic heart disorders

Question 5

Class II

Beta blocker

Answer 5

Propranolol
Esmolol
Atenolol
Timolol
Carvedilol
Metoprolol

Question 6

Class II mechanism

Answer 6

⬇️cAMP&raquo_space; ⬇️ SA and AVnodal activity
Suppress abnormal pacemakers by ⬇️slope of phase 4

AV node sensitive drugs : ⬆️PR interval

Question 7

Class II clinical use

Answer 7

SVT

ventricular rate control for atrial fibrillation and atrial flutter

Question 8

Class II Adverse effect

Answer 8

Impotence 
COPD. Exacerbation
Asthma exacerbation
Cardiovascular effect : bradycardia, AV block, HF 
CNS effect : sedation,sleep alteration
Mask the signs of hypoglycemia 
Metoprolol : dyslipidemia
Propranolol exacerbates vasospasm in spastic angina

If Beta blockers are used alone for Pheo or cocaine toxicity (except non-selective alpha and beta antagonists carvedilol and labetalol) cause unopposed Alpha 1 agonism

Tx beta blocker overdose : saline /atropine/glucagon

Question 9

Class III general

K channel blocker

Answer 9

Amiodarone
Ibutilide
Defotilide
Sotalol

AIDS

Question 10

Class III mechanism

Answer 10

AP⬆️
⬆️ERP
⬆️QT Interval

Clinical use:
A. Fibrillation
A. Flutter
V. Tach (amiodarone, sotalol)

Question 11

Class III adverse effect

Answer 11

Sotalol : torsade de point, excessive beta blockade
Ibutilide : torsade de point
Amiodarone: pulmonary fibrosis, hepatotoxic, hypothyroidism,hyperthyroidism, act as hapten (corneal deposits, blue gray skin deposit result in photodermitis), neurologic effect, constipation, cardiovascular effect (bradycardia, HF, heart block)

Question 12

Amiodarone

Answer 12

Has class 1,2,3, & 4 effect
Check PFT, LFT, TFT when using amiodarone

Question 13

Class IV
Calcium channel blockers

Verapamil
Diltiazem

Answer 13

⬇️conduction velocity
⬆️ERP
⬆️PR interval

Question 14

Class IV clinical use

Answer 14

Prevention of nodal arrhythmia (SVT)

Rate control in AF

Question 15

Class IV adverse effect

Answer 15

Constipation
Flushing
Edema
Cardiovascular effect (HF, AV block, sinus node depression)

Question 16

Adenosine

Other antiarrhythmic

Answer 16

⬆️K out of cell : hyperpilarization
⬇️AV node conduction
Drug of choice in diagnosing and terminating SVT
very short acting
Effect blunted by theophylline and caffeine (both are adenosine receptor antagonists)

Adverse : flushing, hypotension, chest pain, sense of impending doom, bronchospasm,

Question 17

Mg

Answer 17

Effective in torsade de points and digoxin toxicity