Unasyn (ampicillin-sulbactam) is an intravenous antibiotic that I most often use for ENT-related infections/prophylaxis but sometimes gynecologic and intraabdominal infections as well (Zosyn being another common alternative).

Ampicillin, a beta-lactam, is often times degraded by beta-lactamase, an enzyme produced by bacteria to confer “resistance” to this class of antibiotics. We fight back by combining ampicillin with sulbactam, a beta-lactamase inhibitor, so ampicillin is protected from degradation as it exerts its bacteriocidal effects by disrupting bacterial cell wall synthesis. Remember, this kind of antibiotic combination provides great anaerobic coverage and probably doesn’t need additional clindamycin/metronidazole therapy.

Protip: When I reconstitute powder-based antibiotics like Unasyn or Zosyn, I always shake the powder before adding the solvent to help disperse particles which may have conglomerated in the vial. This helps expose more of the drug to solvent to (hopefully) make it easier to reconstitute.

Drop me a comment below with questions! 🙂

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  1. I find using warm diluent also eases dissolving – I usually draw from a warm LR or Saline bag in our OR warmers ( that bag goes up next on the IV)

    Thanks for you informative and useful information


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