I rank Metoprolol 25 out of the 33 drugs I carry.

Our indication for Metoprolol is for rapid atrial fibrillation and PSVTs in patients already on oral beta blockers. We do not use Metoprolol for Acute Coronary Syndrome care. A few years back Metoprolol was considered life-saving in ACS care, but then more research came out and while it is life-saving for some patients, it is detrimental to others and the experts felt it would be too difficult for us (and I agree0 to distinguish the best candidates lacking our ability to know the patient’s ejection fractions and other considerations.

Despite not being used for ACS, I was very excited to get Metoprolol and anxious for the first time I could use it.

The patient, an elderly gentleman on Atenolol (another beta blocker), was in a rapid afib in the 160-170 range. I drew up the 5 mg of Metoprolol, pushed it slowly and waited. Nothing happened. I waited and waited. Nothing. Our next step is to call medical control, but since we were already arriving at the hospital, I just brought him on in. I gave my report, got him in the room, went and wrote my run form, came back, looked up at the monitor and saw he had slowed considerably and was in a controlled afib in the 70′s.

“So, the Metoprolol finally worked,” I said to the nurse.

“No,” she said, “We gave him Cardizem.”

After that episode I would be tempted to put Metoprolol at the bottom of my list. Here was a drug that prevented me from giving a drug that would have done the trick. But, subsequently I have talked to medics who have given the 5 mg and had it work. I have also learned that the 5 mg is often followed with another 5 mg after five minutes or so and then another 5 mg to a total of 15 mg. That usually does the trick, and if it doesn’t, well then you can go to Cardizem if the blood pressure is still decent.

And I have to ask myself, if I am on beta blockers, and I go into a rapid afib, would I rather have more beta blocker or Cardizem, which can really drop my pressure? A little more beta blocker seems the most reasonable. I just need to be prepared to call medical control and ask for additional doses if needed and indicated.


Metoprolol (Lopressor)

Class: Beta Blocker

Action: Partial blockade of Beta Receptors

Indication: Atrial fibrillation, Atrial flutter, narrow complex tachycardia

Contraindication: Hypotension (SBP < 110mmHg)
Bradycardia (HR < 70bpm)
Hypersensivity to drug
1st, 2nd or 3rd Degree Heart Block
Acute Pulmonary Edema
Recent Cocaine Use

Side effect: Pulmonary Edema

Dose: 5mg SIVP

Route: IV push (bolus) given over 5 minutes

Pedi dose: None

Important points: Utilize Metoprolol for patients experiencing narrow complex tachycardias that
are taking oral Beta Blockers.


  • Spankymedic says:

    OK, I have to ask… WHY did you even consider a beta blocker when it’s not first-line therapy for A Fib w/RVR? 5mg…another 5mg…why wait so long when AF responds nicely to a Ca++ channel blocker to begin with? Obviously if the patient was already on beta blockade therapy, my first thought would be to attempt something a bit different, as his Rx’d meds are apparently refractory. Secondly, I’ve read nothing that supports the statement that diltiazem “drops B/P”. If anything, beta blockade therapy runs a much higher incidence of secondary hypotension than do Ca++ channel blockers. “A little more beta blocker” is going to do more to drop your pressure than will Ca++ channel blockers. Hopefully this was a lesson learned.

    • medicscribe says:

      thanks for the comments-

      Here’s what our regional guidelines say as first line for “stable” rapid afib:

      Diltiazem 15-20mg SIVP (0.25mg/kg, may repeat in 15-20min 20-25mg SIVP OR Metoprolol 5mg SIVP

      These are two of the PEARLS:

      Monitor for hypotension after administration of Diltiazem.
      Utilize Metoprolol when patient takes PO Beta Blockers.

      Having only used metoprolol once, I don’t have too much experience with it. I have used cardizem quite a bit over the years and have seen pressures drop. I usually always have two lines running when I give it.

      The drug insert for Cardizem IV lists hypotension under Contraindications, Warnings and Adverse events. Curiously, the insert also says not to administer IV beta blockers and IV cardizem within several hours of each other. I will have to ask our medical Control about that.

      Our guidelines are much more aggressive that the AHA’s which says ‘consider expert consultation’ a step prior to considering cardizem of betablockers.

      I enjoy fixing the problem, but I will say I have found few of these cases that truly had to be fixed in the field. I will talk more about this when I get to Cardizem on my list.

      thanks again for the interesting points and discussion,


  • totwtytr says:

    The rule used to be that if a patient was already on a Beta Blocker, even if it wasn’t working, then Calcium Channel Blockers were out. That’s relaxed a bit, but more medical control doctors prefer that we stick with the same class of drug. We’ve run into a spate of dysrhythmias of late, including a patient in A-Fib with an accelerated Ventricular Response. Since he was already on Metoprolol, that’s what we gave him. It worked, but not all that quickly. Still, it worked. We too have removed it from the treatment protocol for ACS.

  • VaMedic says:

    Our system has both in the box and a contraindication for Cardizem is being on the beta blockers. Age is also a precaution with a stipulation to cut the dosage in half over 70yo. I have successfully used Cardizem 3 times in the last year, twice over 70, and haven’t had any success with metoprolol.

    On a side note, my father has A-fib and his cardiologist started him on beta blockers. His A-fib took off, he went to the ER, was treated with Cardizem that converted on the second dose, but dropped his rate to 28… he was released 2 days later with a follow up to his cardiologist that reccomended a pacemaker so they could more aggressively treat him with metoprolol…

    I just wish we could get the medical community to agree on stable patform to deal with common issues.

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Peter Canning

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