Antarrhythmic drugs Flashcards
General class I Na channel blocker
⬇️slope of phase 0 of depolarization
⬇️conduction in depolarized cell
Selectively depress tissues that are frequently depolarized
Class IA
Quinidine
Procainamide
Disopyramide
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)
Class I B
Lidocaine
Mexiltine
Phenytoin
⬇️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
Class I C
Flecainide
Propafenone
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
Class II
Beta blocker
Propranolol Esmolol Atenolol Timolol Carvedilol Metoprolol
Class II mechanism
⬇️cAMP»_space; ⬇️ SA and AVnodal activity
Suppress abnormal pacemakers by ⬇️slope of phase 4
AV node sensitive drugs : ⬆️PR interval
Class II clinical use
SVT
ventricular rate control for atrial fibrillation and atrial flutter
Class II Adverse effect
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
Class III general
K channel blocker
Amiodarone
Ibutilide
Defotilide
Sotalol
AIDS
Class III mechanism
AP⬆️
⬆️ERP
⬆️QT Interval
Clinical use:
A. Fibrillation
A. Flutter
V. Tach (amiodarone, sotalol)
Class III adverse effect
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)
Amiodarone
Has class 1,2,3, & 4 effect Check PFT, LFT, TFT when using amiodarone
Class IV
Calcium channel blockers
Verapamil
Diltiazem
⬇️conduction velocity
⬆️ERP
⬆️PR interval
Class IV clinical use
Prevention of nodal arrhythmia (SVT)
Rate control in AF
Class IV adverse effect
Constipation
Flushing
Edema
Cardiovascular effect (HF, AV block, sinus node depression)
Adenosine
Other antiarrhythmic
⬆️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,
Mg
Effective in torsade de points and digoxin toxicity
