Augmentin and Unasyn Conversions

Aminopenicillins

• some Gram positives (Strep, Enterococcus, Listeria) but NOT MSSA, and limited Gram negative coverage. 
• Notable gram negative holes include Klebsiella, Moraxella, and SPICE A organisms.
• Used for: Upper respiratory infections, sinusitis, otitis media, cellulitis, Listeria infections, UTI’s, early Lyme disease (alternative to Doxycycline), and more.
• Drug of choice for Enterococcal infections if susceptible (E.faecalis generally susceptible, E.faecium usually not).  Used with aminoglycosides for synergy for Enterococcal endocarditis.
• Amoxicillin is the best-absorbed beta lactam (75-90% bioavailability). 
• Little role for oral ampicillin due to inferior absorption vs Amoxicillin

Combined Penicillin / B Lactamase Inhibitors

• addition of beta lactamase inhibitor confers broader spectrum against common beta-lactamase producing organisms (such as MSSA, some gram negatives including H.influenza, Moraxella, and virtually all anaerobes).

Amoxicillin/Clavulanate (Augmentin) – PO

• Spectrum: Relatively broad spectrum with some gram positive (MSSA, Strep), some gram negatives, and anaerobes. 
• Notable holes include NO Pseudomonal activity and other SPICE A organisms.
• Used for:  Sinusitis, respiratory infections, otitis media, some skin/soft tissue infections (including bite wounds), and more. 

Ampicillin/Sulbactam (Unasyn) – IV

• Spectrum: Similar to Amoxicillin/Clavulanate, except has activity vs most Acinetobacter (sulbactam component has activity).
• Still no activity against other SPICE organisms.
• Used for: similar situations as for Amoxicillin/Clavulanate but where IV form is desirable; also, some intraabdominal and GYN infections, aspiration pneumonia and lung abscesses, and more. 
• Caution with Unasyn for polymicrobial intraabdominal infections due to high rate of resistance of E.coli (>50% at some institutions)

Bioavailability

• Oral bioavailability of both oral unasyn and augmentin are very high (about 80%)
• Oral Unasyn is a prodrug (sultamicilin). Peak ampicillin following sultamicillin are approximately twice that of an equal dose of oral ampicilin.

Conversions:

 References:

1. Focus on Converting From Iv to Oral Antibiotics. Omnicare 2016
2. How to Choose Among Myriads of Antibiotics?
3. http://errolozdalga.com/medicine/pages/OtherPages/AntibioticReview.ChanuRhee.html