Amiodarone Flashcards
What are common indications?
Atrial fibrillation
Atrial flutter
SVT
refractory ventricular VF
Generally good if other treatment are ineffective or contraindicated
What is its mechanism of action?
Has many effects on myocardial cells;
Blockade of sodium and potassium channels
Antagonises alpha and beta adrenergic blockers
These effects reduce spontaneous depolarisation, slows speed of conduction and increase resistance to depolarisation
What are important adverse effects?
Hypotension during IV infusion
(less likely to cause myocardial depression compared to other antiarrythmatic drugs)
Extremely Long half life
When used chronically what side effects can occur ti each major organ ?
Lung- Pneumonitis
Heart-Bradycardia/AV block
liver-hepatitis
skin-photosensitivity/ grey discolouration
eyes- corneal micro-deposits
optic neuropathy/neuritis
Why could it cause thyroid abnormalities?
-Due to iodine content (AmIODarone) and structural similarities to thyrOID hormone.
When should it be avoided?
Severe hypotension
heart block
Active thyroid disease
Should only be used when risks outweighs the benefits.
Why is amiodarone only used when necessary?
Interacts with many foods and drugs.
Ick, bradycardia
Chronic use can cause severe side effects
What should be done to drugs have an increased plasma concentration when taken with amiodarone and why?
Diltiazem
verapamil
digoxin
The doses of these drugs should be halved.
interaction may increase the risk of bradycardia, AV block and heart failure-
BB, Rate limiting CCBs
Increased risk of myopathy-
statins
QT prolongation-
quinlones, macrocodes, TCAs,SSRI, Lithium, Quinine, Antimalarials, Antipsychotics. Hydroxychloroquine
Enzyme inhibitor:
warfarin, phenytoin
What is another important interaction?
Grapefruit juice,
Enzyme inhibitor
by down regulating cytochrome p450 3a4, which can increase exposure to amiodarone
Why should caution still be taken with drug interaction even after it has been stopped?
Due to its long half life (25-100 days) interactions can still occur after stopping the drug.
Who can intiate amiodarone?
Experienced and specialist prescribers
requires senior involvement
Under what circumstances does it not need to be initiated by a specliast?What doses?
Cardiac arrest
- for VF or pulseless VT
-has to be given immediately after third shock in the advanced life support algorithm.
-Dose:
300mg IV followed by 20ml of 0.9% NaCl or a glucose flush
Why should you only give amiodarone via a central line IV(not for cardiac arrest)?
Peripheral IV can cause significant phlebitis
(if continuous or repeated IV infusions are anticipated)
What are monitoring requirements?
IV infusions should be monitored by continuous cardiac monitoring
Long term-
baseline tests :
renal, liver, thyroid profiles, chest x-ray.
annual eye test
LFT- every 6 months
BP and ECG
Serum potassium
What must be considered when stopping amiodarone?
Should be guided by specialist, taking account of cardiac rhythm control, alt treatment options and cumulative risks of long term treatment.
