Unasyn is a combination drug used for the treatment of infections as well as a prophylactic intervention prior to surgical or endoscopic interventions. Unasyn is a broad spectrum antibiotic of the penicillin family that inhibits beta-lactamases, ensuring activity of the ampicillin against resistant organisms. Peak serum levels of Unasyn are reached in 15 min to 1 hr after an IV infusion of 15 min.