Amiodarone Flashcards
What two formulations can amiodarone be absorbed with?
IV and PO
What percent is IV absorbed?
100%
Is amiodarone PO absorbed fast or slow?
Very slow - incomplete absorption
Is it best to take PO amiodarone with food or without food?
With food - it increases the rate of absorption
Where is amiodarone mainly distributed?
To lipophilic tissues
(T/F) - Amiodarone has enterohepatic circulation
TRUE - long half life
How is amiodarone metabolized?
By CYP3A4 in the liver
Does amiodarone inhibit any enzymes and/or transporters?
CYP3A4, 2D6, 2C9 and P-gp
Which drugs need to be automatically decreased when amiodarone is concomitantly given with them?
Digoxin
Warfarin
By how much percent should digoxin be adjusted when given with amiodarone?
Decrease by 50%
By how much percent should warfarin be adjusted when given with amiodarone?
Decrease by 25%
Phenytoin is a drug that interacts with amiodarone. What will happen to the levels of amiodarone when given with phenytoin, increase or decrease? By how much percent?
Increase by 50%
In which route is amiodarone mainly eliminated/excreted?
Biliary
What is the chronic half-life of amiodarone?
53 days
What are some factors that can affect the elimination of amiodarone?
- Elderly
- Cirrhosis
The onset of action for amiodarone is when?
Variable - 1 to 3 weeks
What are the therapeutic levels for amiodarone? Why is it a questionable clinical value?
0.5 to 2 mg/mL
It’s questionable because amiodarone does not hang out in the blood as much - it likes fatty tissue
What is the loading dose (LD) of amiodarone in an oral formulation? How many grams should it get up to for it to be effective?
1.2 to 1.8 g/day - divided doses
10 grams
What is the LD of amiodarone in an IV formulation? How many grams should it get up to for it to be effective?
5 to 7 mg/kg over 30-60 mins followed by 1.2 to 1.8 g/day
10 grams
What is the maintenance dose (MD) of amiodarone?
200 to 400 mg/day
How is amiodarone IV converted to PO if it has been less than or equal to 1 week of usage?
800 to 1600 mg/day for 1-2 weeks then MD 200 to 400 mg/day
How is amiodarone IV converted to PO if it has been 1 week to less than 3 weeks of usage?
600 to 800 mg/day for 1-2 weeks then MD 200 to 400 mg/day
How is amiodarone IV converted to PO if it has been more than 3 weeks of usage?
Begin MD 200 to 400 mg/day
How is amiodarone PO converted to IV?
PO MD will be 30 to 70%
What are some cardiac toxicities involved with amiodarone?
- Bradycardia
- AV block or torsades de pointes
What factors affect cardiac toxicities of amiodarone in an IV form?
Rate and concentration of drug
(T/F) - If amiodarone has a concentration > 2 mg/mL, it should be administered in a peripheral line to avoid phlebitis
FALSE - in a central line
To reduce the risk of cardiac toxicities of amiodarone in an IV form, how should IV be administered?
With an IV filter and mixed in glass
What are some pulmonary toxicities involved with amiodarone?
- Pulmonary fibrosis
- Hypersensitivity pneumonitis
- Pulmonary inflammation
- Interstitial and alveolar pneumonitis
What are some hepatic toxicities involved with amiodarone?
- Transient elevation in LFT (15-30%)
- Clinical hepatitis and cirrhosis (< 3%)
What are some thyroid toxicities involved with amiodarone?
Hypothyroidism (20%)
Hyperthyroidism (3%)
What are some ocular toxicities involved with amiodarone?
- Corneal microdeposits (70-100%)
- Optic neuropathy (< 1%)
What are some dermatologic toxicities involved with amiodarone?
- Photosensitivity (25-75%)
What tests should be done in patients w/ amiodarone at baseline?
- EKG
- Pulmonary function tests
- Chest X-ray
- LFT
- Thyroid function
- Eye exam
What tests should be done in patient w/ amiodarone every 6 months?
- LFT
- Thyroid function
- Eye exam
What tests should be done yearly in patients w/ amiodarone?
- Chest X-ray
- EKG
- Pulmonary function tests (if symptoms occur)
Is dronedarone a better option than amiodarone?
No - causes more potential harm than benefits
