Adults: 250–500 mg every 6 hours orally or 1–2 g IV/IM every 6 hours
Children: 50–100 mg/kg/day in divided doses every 6–8 hours
Note: Adjust dose in renal impairment and according to infection severity.
Route of Administration
Oral (capsule, suspension)
Intravenous (IV)
Intramuscular (IM)
Mechanism of Action
Ampicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, leading to bacterial lysis and death. Effective against many Gram-positive and some Gram-negative bacteria.
Common Adverse Effects
Nausea, vomiting
Diarrhea
Skin rash
Abdominal discomfort
Serious Adverse Effects
Anaphylaxis
Severe hypersensitivity reactions
Clostridioides difficile–associated diarrhea
Hepatic dysfunction (rare)
Contraindications
Hypersensitivity to penicillins
History of severe beta-lactam allergy
Precautions
History of allergy or asthma
Renal impairment (dose adjustment may be needed)
Monitor for diarrhea and liver function if prolonged use
Drug Interactions
Allopurinol – increased risk of rash
Oral contraceptives – possible reduced effectiveness
Warfarin – may increase anticoagulant effect
Pregnancy & Lactation
Generally considered safe in pregnancy and breastfeeding if used as prescribed.
Patient Counseling
Complete full course of therapy
Take on empty stomach for better absorption (or as prescribed)
Report rash, diarrhea, or allergic reactions promptly