Antidysrhythmia drugs Flashcards
Class 1 V-W
Sodium Channels, Lidocaine
Class 2 V-W
Beta Blockers, Atenolol
Class 3 V-W
Potassium channels, Amiodarone
Class 4 V-W
Calcium channels, Verapamil
Class 1 clinical
Supraventricular origin, adenosine, Verapamil
Class 2 clinical
Supraventricular or ventricular origin, Amiodarone, propranolol
Class 3 clinical
Ventricular origin, lidocaine
Class 4 clinical
Atrial fibrillation, atenolol (with sympathetic involvement), Amiodraone
Classification of Amiodarone
Clinical, class 2, and class 4 V-W, Class 3, but also classes 1 & 4
Effect of Amiodarone
Increases length of refactoryperiod by blocking K+ channels
Physiochemical properties of Amiodarone
Analogue of thyroid hormone, Very lipophilic, Large apparent volume of distribution, deposition of microcrystals in tissue, Months to reach stable plasma conc, 100 days for t1/2
Side effects of Amiodarone
Microcrystals in cornea -increased dazzle by light
Crystal in skin are photoxic
Hyperthyroidism
toxic to the liver
causes Bradycardia and conduction disruption
Classification of Adenosine
Class 1 clinical, unclassified
V-W
Action of Adenosine
Activates A1 Purinoceptors on cardiac myocytes, through a GPCR this opens K+ ach channels. this leads to inhibition of voltage sensitive calcium channels reducing action potential duration and reducing slope of pacemaker potential. This lowers the discharge rate of SA node reducing conduction and increasing refactory period of AV node
Uses of adenosine
suppresses Paroxysmal (occurs in attacks) supra ventricular tachycardia
Physiochemical properties of adenosine
naturally occurring purine nucleoside
effect lasts 30s
Plasma t1/2 is 10s
rapid uptake by erythrocytes and metabolism
side effects of adenosine
Severe bradycardia
Facial flushing
chest pain
Dyspnoea and Bronchospasm (should be avoided in asthma patients)
