Antiarrythmics Flashcards
What is the mechanism of action of adenosine?
Agonist of A1 receptor in AV node, which drives potassium out of cells and therefore increases the time for depolarisation
What are important interactions of adenosine?
Dipyridamole - enhanced effect
Theophyllines - block adenosine
What are the common side effects of adenosine?
Bronchospasm - avoid in asthmatics
Chest pain
What is the mechanism of action of atropine?
Muscarinic acetylcholine receptor antagonist
What is the mechanism of action of amiodarone?
Blocks potassium channels inhibiting depolarisation of the cells and prolongs action potension
p450 inhibitor
What are important interactions of amiodarone?
Warfarin - increases INR
Digoxin - increases dig level
Statins
What are the common adverse effects of amiodarone?
Bradycardia, long QT
Thyroid dysfunction
Pulmonary fibrosis/pneumonitis
Liver fibrosis/hepatitis
Peripheral neuropathy
Photosensitivity
Blue/grey skin discolouration
Corneal deposits
What monitoring is required on amiodarone?
TFTs, LFTs and CXR at commencing and every 6 months
What is the mechanism of action of digoxin?
Cardiac glycoside
Decreased conduction through AV node and inhibits Na/K ATPase pump, leading to decreased force of contraction
What are therapeutic levels of digoxin?
0.8-2
To be taken at least 6 hours post dose
What ECG changes are seen with digoxin?
Downsloping ST depression (reverse tick)
Flattened or inverted T waves
Short QT
Bradycardia
What are the features of digoxin toxicity?
Generally unwell, lethargic
N&V
Confusion
Yellow-green vision
Arrythmias
What are the common precipitating factors for digoxin toxicity?
Classic = hypokalaemia (digoxin normally binds to potassium receptors - less potassium means more dig can bind)
Renal impairment
What common drugs can increase digoxin level?
Amiodarone
Verapamil
Diltiazem
Spironolactone
What is the mechanism of action of flecinide?
Class I antiarrythmic
Blocks Nav1.5 sedum channel slowing conduction of action potential
