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ampicillin

J01CA01

Forms & Strengths

Capsule: 250 mg, 500 mg
Oral suspension: 125 mg/5 mL, 250 mg/5 mL
Injection, powder for reconstitution: 1 g, 2 g, 10 g

Adult Dosing

Systemic infections (IM/IV): 1-2 g every 4-6 hours
Meningitis (IV): 150-200 mg/kg/day divided every 3-4 hours (max 12 g/day)
Uncomplicated UTI (Oral): 500 mg every 6 hours

Pediatric Dosing

Neonates <= 7 days: 50-100 mg/kg/day divided every 8-12 hours
Neonates > 7 days: 75-150 mg/kg/day divided every 6-8 hours
Children > 1 month (systemic): 100-200 mg/kg/day divided every 4-6 hours
Children > 1 month (meningitis): 200-300 mg/kg/day divided every 4-6 hours

Indications

Infections caused by susceptible gram-positive and gram-negative organisms
Listeriosis
Enterococcal infections
Uncomplicated gonococcal urethritis

Mechanism of Action

Binds to penicillin-binding proteins (PBPs) located inside the bacterial cell wall
Inhibits third and final stage of bacterial cell wall synthesis
Results in cell lysis mediated by bacterial cell wall autolysins

Contraindications

History of serious hypersensitivity reaction (e.g., anaphylaxis) to ampicillin or other beta-lactams
History of ampicillin-associated cholestatic jaundice or hepatic dysfunction

Adverse Reactions

Diarrhea / Pseudomembranous colitis
Hypersensitivity reactions (rash, urticaria, anaphylaxis)
Nausea and vomiting
Clostridioides difficile-associated diarrhea
Elevated transaminases

Drug Interactions

Allopurinol: Increased risk of maculopapular rash
Probenecid: Decreases renal tubular secretion of ampicillin, increasing serum levels
Oral contraceptives: May decrease efficacy and increase breakthrough bleeding
Bacteriostatic antibiotics (e.g., tetracyclines, erythromycin): May antagonize the bactericidal effect of ampicillin

Curated Content: Needs Vetting Before Put to Clinical Use