When should you hold anti-arrhythmic drugs like amiodarone?


#1

I understand amiodarone is an antiarrhythmic drug typically prescribed for patients either in or with a history of atrial fibrillation. If the orders do not specify holding parameters, when would you consider not administering amiodarone in regards to both blood pressure and heart rate?


#2

Most drugs that lower BP and HR have similar parameters for holding the medication. In my practice, we typically start holding these types of drugs around a systolic BP of 100mmHg, but I’ve also seen lower at 90 mmHg. As far as heart rate, the cutoff is usually 60-70bpm. Of course you’d want physician specified parameters, but I understand sometimes you don’t have them and can’t seem to get them.

Personally, I start getting cautious when the SBP is right around 100mmHg or if the pulse is around the low 60s. This goes for antiarrhythmics, beta blockers, calcium channel blockers, etc.

A note about amiodarone since you mentioned that in your question:

Amiodarone has an insanely long half-life and duration of action. We’re talking weeks and months, and sometimes the range goes up to half a year. Also realize, that it’s going to be longer on average in the elderly, and I assume that most hospitalized patients receiving amio are going to be geriatric. My point is that by giving or holding a dose, you’re probably not going to change much. Then again, I understand that you probably wouldn’t want to explain why you helped contribute to making a bad situation worse in the event that things went south. Just thought I’d point out the pharmacology of this drug for brain food.


#4

Great answer… couldn’t have said it better myself :wink:


#5

Just to be clear, you are speaking about PO amiodarone. IV numbers are shorter, specifically the onset of action. If the patient were on IV amio, you would definitely want to discontinue the use if the patient became severely bradycardic, hypotensive, symptomatic, etc. I’ve seen many people crash after the initial amio bolus.

Maybe it’s just bad luck on my floor… I think UpToDate mentions about 6% occurrences for horrible brady/hypotensive reactions, but we’ve coded a few people and they all died.

Pharmacodynamics/Kinetics
Onset of action: Oral: 2 days to 3 weeks; IV: (electrophysiologic effects) within hours; Antiarrhythmic effects: 2 to 3 days to 1 to 3 weeks; mean onset of effect may be shorter in children vs adults and in patients receiving IV loading doses

Peak effect: 1 week to 5 months

Duration after discontinuing therapy: Variable, 2 weeks to months: Children: less than a few weeks; Adults: Several months

Note: Duration after discontinuation may be shorter in children than adults

Absorption: Oral: Slow and variable

Half-life elimination: Note: Half-life is shortened in children vs adults

Amiodarone:

Single dose: 58 days (range: 15 to 142 days)

Oral chronic therapy: Mean range: 40 to 55 days (range: 26 to 107 days)

IV single dose: Mean range: 9 to 36 days

N-desethylamiodarone (active metabolite):

Single dose: 36 days (range: 14 to 75 days)

Oral chronic therapy: 61 days

IV single dose: Mean range: 9 to 30 days

Time to peak, serum: Oral: 3 to 7 hours

https://www.uptodate.com/contents/amiodarone-drug-information