Vancomycin vs. Metronidazole

I don't think Vanco is even absorbed orally, so definitely IV...

vancomycin has zero oral bioavailability which means for systemic infections it must be given IV. However, c.diff is an intraluminal intestinal infection, so oral vanco is appropriate as it will treat directly at the area in question as it goes through the gut. Flagyl is first line DOC in general. Flagyl failures get oral vanco.

MRSA is a systemic infection, so oral vanco would not be absorbed and therefore would not work. So if need be (and there are other options for MRSA) vanco IV is the appropriate choice.

ShyRem said:

vancomycin has zero oral bioavailability which means for systemic infections it must be given IV. However, c.diff is an intraluminal intestinal infection, so oral vanco is appropriate as it will treat directly at the area in question as it goes through the gut. Flagyl is first line DOC in general. Flagyl failures get oral vanco.

MRSA is a systemic infection, so oral vanco would not be absorbed and therefore would not work. So if need be (and there are other options for MRSA) vanco IV is the appropriate choice.

Click to expand...

Thank you, too early in the morning, haha.

I'm going through UWorld for Step 3 right now and they've asked TWO questions on this so far in just the first third of the QBank I've done:

If WBC count <15,000 AND creatinine <1.5x baseline AND serum protein >2.5 g/dL = mild pseudomembranous colitis; Tx = oral metronidazole

If outside those parameters above = severe pseudomembranous colitis; Tx = oral vancomycin, NOT oral metronidazole

If ileus is present (which is severe), Tx = oral vancomycin + IV metronidazole, OR rectal vancomycin

If those treatments are refractory, then surgery (i.e., subtotal colectomy or diverting loop ileostomy with colonic lavage) may be indicated.

They also want you to know that if you give oral metro for mild illness and it doesn't work, the next best step is giving oral metro again. The first recurrence is Tx with oral metro again if mild or oral vanc if severe. This is because it's thought most first recurrences are due to germination of spores from the initial infection rather than a genuine second infection.

The second recurrence is treated with pulsed tapering of oral vancomycin for 6-7 weeks.

Subsequent recurrences are treated with fidaxomicin.


------------

On Step 1, the answer for this question as far as I had previously been aware was always oral metronidazole before oral vancomycin based on wanting to decrease resistance risk. I doubt at the Step 1 level they'd be nitpicky about the severity of it and want you to know most cases are treated first with oral metro. But UW Step 3 had a question with severe pseudomembranous, and most DOCTORS chose oral metro but it was oral vanc to start.

Phloston, do you think theres any benefit to skimming over disease management / treatment from a step 2 book (eg MTB) as far as step 1 is concerned?

DrPicard said:

Phloston, do you think theres any benefit to skimming over disease management / treatment from a step 2 book (eg MTB) as far as step 1 is concerned?

Click to expand...

No. Stick to Step 1 stuff.

I did a Uworld q on C.diff and it said 1st line : Metro or oral Vanc
Recurrent C.diff : Consider oral fidaxomicin and fecal transplant , but 1st line drugs are still viable