Rocky transition from metoprolol succ to amiodarone

Hi! Newbie here. Name is Al (female). Glad to be here and thank you for creating this forum.
New patient w afib w RVR w structural heart dz - AVR/MVR and Marfans. On metoprolol succinate after hospital admit and having hard time transitioning to amiodarone w an ER med that stays in system for 3 days. Can only get met down to 50 mg as starting amio and then HR plummets to 43-48. Was taking 200 mg amio once a day first 3 days on first attempt and yanked off once HR went too low. Second time tried 200 amio first day then 100 next two days with 50 mg met by second day. Again, HR plummeted and was cycling from 50 -70 and back when not super low.
So my question is ... Is there any easier way to transition from metoprolol succinate to amiodarone w less overlap? (metoprolol tartrate? bed rest? amio twice a day 50 mg?) Does this happen to everyone or is it just my system is sensitive? I’m 53 yrs old and have been anticoagulated w warfarin at 3.0 - 3.5 for 20 years, and so you can kinda see why they went amio after an unsuccessful attempt w flecainide (QT and QRS issues and really not great candidate w structural anyway).
Would be very grateful for any thoughts or experiences you veterans of this testy affliction would be willing to share. Thanks again

Hi, and welcome. I had an ablation in late July, but was in the local ER six days later with a lot of PACs and tachycardia. The attending internist at the ER managed to get ahold of the electrophysiologist who had 'done me' and the two agreed on a prescription for amiodarone.

First thing to know is that I was still prescribed 25 mg metoprolol tartrate (the fast acting, short-lived kind) BID (twice a day). This was a simple prophylaxis to help my heart heal from the lesions. However, I felt terrible, and when my GP did his week-later pulse check, he knew I was in AF and sent me to the hospital. What alarmed everyone was the severe bradycardia. My heart was slowing to 30 BPM, and there were looonng pauses. So, much like you are experiencing. I know there's almost any other place you'd rather be.

The decision was to stop metoprolol cold...I'd already had the 'last' dose. They loaded me for a week with 800mg of amiodarone (two tablets twice a day). The amiodarone had me controlled over night and I was release around noon. A week later, the maintenance dose became 400mg (a single 200mg tablet BID), and after three weeks I went to a terminal dose of one tablet a day..200mg. There's more to the story, but it's not really relevant for this topic.

The point is, all the literature I have seen says that metoprolol should be discontinued with a weaning period, maybe two weeks? That wasn't what they did for me. All the literature says metoprolol and amiodarone are not to be used concurrently. They followed that protocol. And, the amiodarone worked, and they wanted me off it ASAP to clear my system for the end-blanking period Holter monitor.

Metoprolol only needs to be weaned slowly if you've been on it a very long time. Whether it's succinate or tartrate doesn't really matter.

I don't understand why they didn't stop the metoprolol outright when they started the amio since amio will take over the function the metoprolol was providing. Combining them is almost surely the reason for the bradycardia. But a rate of 43-48 isn't really alarming unless you're fainting due to it.

Thank you so much for your response and sharing your experience Gloaming. This helps immensely as I was unaware that met + amio are a no-can-do duo.
I hope the ablation stabilized you eventually and you are back to as close to a normal existence as possible these days. Take care and be as well as possible

Good to hear Carey that 40s wasn’t as awful as I thought. Gives me a lot more hope for being able to make this go a bit smoother on the third try. Thank you so much for your reply and perspective. Two folks responding here with similar takes on how it is done successfully is so much more reassuring. So glad I decided to ask... You take care and be well also.