Metoprolol PO to IV

[Questions88]

Patient with afib is currently rate controlled with HR in the 90's on PO metoprolol tartrate 75 mg BID. Eventually patient becomes NPO. What should you do?

A) transition patient to metoprolol IV push 15 mg q6h. (metop PO to IV is 2.5:1 ratio, therefore 150 mg PO daily is equivalent to 60 mg IV daily, and then divided by 4 is 15 mg IV q6h)

B) transition patient to metoprolol 5 mg IV push q6h

C) discontinue standing metoprolol and just put in orders for PRN metop IV pushes 5 mg q6h.

Which option do you choose and why?

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[Egghead34]

As our cardiologists teach it, none of the above...

1) IV metoprolol has immediate action, PO has slow and graded release over hours. 15mg q6hr, even if equivalent, is hitting them with a whopping dose upfront
2) Despite a reported duration of 5-8 hours, the peak/effective duration for IV is 30-60 minutes at best
3) You have other, longer lasting or easier-to-infuse IV options for rate control than metoprolol. Digoxin, diltiazem, amiodarone, etc...
4) HR currently in the 90's, well within goal parameters set by the RACE II trial
5) Metoprolol IV should be given in conjunction with PO for control of afib tachyarrythmias. Give PO (takes 30 minutes to kick in) plus IV (lasts 30 minutes). Not generally used for baseline rate control