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ID Learning Unit — Antibiotics with Excellent Oral Absorption

Posted May 16 2013 3:55pm

Guaranteed:  Every day at a hospital near you, a patient is receiving antibiotic therapy for an infection, and the orders include the following:

  • A slew of various oral medications, both continued from outpatient care and started anew on admission.
  • An intravenous antibiotic.
The odd thing about this combination is that there are many antibiotics with excellent oral absorption, so the IV antibiotic may be unnecessary. Provided that the patient is able to take pills and is eating, lots of antimicrobials can be safely and less-expensively given in their oral form.

Even worse, someone may be discharged from the hospital on intravenous antibiotics — risking all the problems of parenteral access (clots, infection, pain, and myriad catheter malfunctions which only happen in the middle of the night/weekends) — when there are multiple oral options that will do the job just as well.

As a result, all ID doctors have encoded deep in their genome a list of antibiotics that can be given orally in place of their IV counterparts, or even more importantly, substituted for something IV on discharge.

Here’s the list, with a miscellaneous comment or two:

  • Fluoroquinolones (levofloxacin, ciprofloxacin, moxifloxacin):  Yes, we both love them and hate them.
  • Trimethoprim-sulfamethoxazole:  1) A double-strength tablet is gigantic, but it also comes in liquid form for the pill-averse; 2) I always ask our ID fellows to tell me precisely (individual drugs and dose) what’s in a double-strength tablet of “Bactrim”, and about half of them know. Do you?
  • Metronidazole:  1) I am amazed that after decades of use of this drug, there is still no significant resistance among Bacteroides spp. 2) A ID colleague of mine, who is married to a gastroenterologist, named her bird “Flagyl.” How perfect is that?!!!
  • Clindamycin:  What a wonderful drug this would be — effective for a whole range of things – if it weren’t for that nasty C diff problem.
  • Doxycyline:  We’re heading into the “doxycycline deficiency” season here in New England. Start those tick checks!
  • Rifampin:  You can pretty much guarantee that if a patient needs intravenous rifampin, he/she also needs an ID consult.
  • Linezolid:  1) This is the only oxazolidinone antibiotic; 2) I don’t know what “oxazolidinone” means, nor how to pronounce it; 3) I do know that this is by far the most expensive oral antibiotic out there. Wow!
  • Fluconazole:  We take it for granted today, but the leap from ketoconazole to fluconazole when it first came out was truly gigantic. Sometimes newer really is better.

What’s missing? Most importantly, the entire class of beta-lactam and beta-lactam-like antibiotics — there isn’t a penicillin or cephalosporin that achieves high blood levels with oral administration (amoxicillin and cefadroxil the closest thing), and if there’s an oral carbapenem out there, someone has been hiding it from me.

Finally, as I went through this list on rounds, the residents and medical students were trying to come up with some sort of mnemonic, but were stymied since all the drugs start with consonants. Any suggestions? And did I miss anything?

(Part of a series inspired by attending .)

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