Section 15 · Monograph
Ampicillin
Reviewed Nov 2026FDA label
PrincipenAminopenicillin
- Forms
- IV: 250mg, 500mg, 1g, 2g vials
- Dose
- Listeria coverage: 2g IV q4h
- MOA
- Inhibits bacterial cell wall synthesis
Indications
- Bacterial meningitis (Listeria coverage in adults over 50, immunocompromised patients and neonates)FDA-labeled
- Respiratory, urinary, GI infections, sepsis, endocarditisFDA-labeled
Mechanism of Action
- Aminopenicillin that inhibits bacterial cell wall synthesis by binding penicillin-binding proteins
Full Dosing
Adult / usual
- Listeria meningitis coverage: 2g IV every 4 hours
- Infuse over 15-30 minutes
Renal
- Adjust for renal impairment
Contraindications
- Hypersensitivity to penicillins
Drug Interactions
- Allopurinol increases rash risk
- Increases methotrexate toxicity
- Probenecid increases ampicillin levels
Adverse Effects
- Rash (especially with mononucleosis)
- Diarrhea, C. difficile infection
- Anaphylaxis
- Seizures with very high doses or renal impairment
- Interstitial nephritis
Monitoring Parameters
- Renal function
- CBC and liver tests with prolonged therapy
Pregnancy & Lactation
- Generally considered safe in pregnancy
- Compatible with breastfeeding (monitor infant for diarrhea or thrush)