Serious and occasionally severe or fatal hypersensitivity (anaphylactoid) reactions reported, especially with history of β-lactam hypersensitivity, history of sensitivity to multiple allergens, or previous IgE-mediated reactions (use with caution in asthmatic patients). Avoid intra-arterial administration or injection into or near major peripheral nerves or blood vessels since such injections may cause severe and/or permanent neurovascular damage. Prolonged use may result in fungal or bacterial superinfection, including C. difficile-associated diarrhea and pseudomembranous colitis. Use with caution in renal impairment, and in history of seizure disorder (high levels, particularly in the presence of renal impairment, may increase risk of seizures). Neonates may have decreased renal clearance of penicillin (dosage adjustments). Product contains sodium and potassium (high doses of I.V. therapy may alter serum levels). Prolonged use or use associated with high serum concentrations (e.g. in renal insufficiency) may be associated with increased risk for some adverse reactions (neutropenia, hemolytic anemia, serum sickness).