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Individual drugs


Class 1 (A, B, C)

  1. Quindine
    1. Cinchona alkaloid (dextroisomer of quinine)
      1. Short acting
      2. Anticholinergic, alpha blocking
    2. Well absorbed
    3. Basic drug, bound to alpha-1 glycoproteins
    4. Undergoes glucoronidation; eliminated by kidneys
    5. Use
      1. Atrial & ventricular arrhythmias


GI upset (MC)                   

  1. Thrombocytopenia (can potentiate warfarin)
  2. Tachycardia (paradoxical)          
  3. Hypotension (alpha block)   
  4. Cinchonism at high doses
  • Drug interactions
  1. Quinidine reduces renal digoxin clearance; hence increases plasma levels
  2. Enzyme inhibitor; inhibits metabolism of warfarin---bleeding
  3. Drugs of 1a class have negative inotropic activity; hence avoided in CHF
  4. Drugs accelerate AV nodal conduction-hence they reduce extent of AV block (1:1 block may become 4:1 block) 
  1. Procainamide
    1. Short acting; prodrug
    2. Forms N-acetylprocainamide; mediates pharmacological actions
    3. Alpha blocking (ganglion blocker)
    4. DOC
      1. ​​Lidocaine refractory ventricular arrhythmias (given IV)
    5. Undergoes acetylation
    6. Produces drug induced SLE
    7. Drug induced SLE; kidneys & brain are not involved
  1. Disopyramide
    1. Anticholinergic activity; avoided in elderly
    2. Used in HOCM because of high negative inotropic activity: useful in reducing muscle mass. 
  2. Lidocaine
    Least cardiotoxic
    1. Potent Na+ channel blocker (blocks Na+ channels more in presence of ischemia)
    2. ECG neutral drug
    3. Half life=1 hour (Given IV, first pass metabolism)


  1. VT                      
  2. VF                      
  3. Digoxin induced arrhythmias
  4. Anesthesia induced                
  5. Arrhythmias in ICU      
  6. AMI induced arrhythmias


  1. Produces a toxic metabolite-named monoethylxylidide (MEX)-neurotoxicity-treated by dizepam
  2. Earliest manifestation-perioral numbness, followed by facial twitching & frank seziures
  1. Phenytoin   (Dilantin)
    1. Used now a days, as it causes hypotention & cardio-depression
    2. Is past DOC for digoxin induced arrhythmias
  2. Mexilitine
    1. l substitute of lidocaine
    2. Lidocaine is not given orally, due to high first pass metabolism
    3. Mexilitine has antineuropathic properties
    4. Used in phantom limb
  3. Tocainide
    1. o an oral lidocaine substitute
    2. Causes agranulocytosis, pulmonary fibrosis
    3. Not used often
  4. Encainide/flecainide
    1. Block ischemic sodium channels (inactivated)
    2. Short acting drugs
    3. Block conduction-used in ectopic beats-however, DOC are beta-blockers
    4. Useful in WPW syndrome, 1a drugs are alternative
    5. Proarrhythmics-not used prophylactically
  5. Propafenone
    1. A blocker with 1c property    
    2. ​Used in patients with refractory arrhythmia
  6. Moricizine
    1. Phenothiazine derivative            
    2. Also alpha-blocker      
    3. ​Useful in ventricular arrhythmias

Class II


  1. Produce automaticity
  2. Membrane stabilizing properties
  3. Reduce influence of catecholamines on heart
  • DOC
  1. Exercise induced arrhythmias
  2. Arrhythmias caused by pheochromocytoma
  3. Thyrotoxicosis induced arrhythmias

Class III

K+ channel blockers

  1. Amiodarone
    1. Most efficacious            
    2. Broadest spectrum      
    3. Most toxic             
    4. Longest acting              
    5. Half life=100 days        
    6. Cumulative drug


  1. Atrial arrhythmias (maintenance phase)
  2. In acute atrial arrhythmias (IV ibutilide is preferred)


  1. Pulmonary fibrosis-MC-can be detected by DLco uptake (decreases)
  2. This is followed by dry cough, breathlessness
  3. Cumulative dose=200mg
  4. Hypothyroidism (block of thyroid peroxidase)-frequency-13.5%, more than normal frequency of hypothyroidism even in hilly areas
  5. Hyperthyrodism (iodine overload)
  6. Hyperpigmentation (brown)
  7. Hepatitis (granulomatous)
    1. Fatty liver occurs in beginning
    2. This is followed by microgranuloma
    3. This leads to cirrhosis
  8. Neuropathy-visceral-constipation
  9. Corneal microdeposits (? Does it interfere with vision: NO)
  10. Photosensitity
  1. Bretylium
    1. Pharmacological defibrilator
    2. Decreases release of NE initially, later produces complex ganglion block
    3. Use
      1. Hypothermia induced arrhythmias
      2. Bupivacaine induced arrhythmias
      3. Drug refractory arrhythmias
      4. Not given in CAD induced arrhythmias
  1. Ibutilitide
    1. It is a pure k+ blocker, not given in renal failure
    2. Very good drug to treat atrial fibrillation
  2. Dofetilide
    1. Dofetilide can be given orally; food increases its absorption
    2. Both ibutilide, doefetilide prolong QT interval

Recent Advances:

Dronaderone- it is a new drug and actions similar to amiodarone but not having iodine in its structure, there fore not associated with amiodarone like side effects. It is the first drug, which has shown reduced mortality in atrial fibrillation patients.

Vernakalant-new drug which is also multiple channel blocker like amiodarone.


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