ZOSYN 3.375g. ZOSYN 4.5g. Pharmacological Class: Broad-spectrum penicillin + β-lactamase inhibitor. Adverse Reactions: Diarrhea, constipation, nausea, headache, insomnia; rash (may be severe), pruritus, local reactions, C. difficile-associated diarrhea; rare: bleeding. How Supplied: Single-dose vials—10