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Drugs Dictionary: Ampicillin

Ampicillin

Trade Name

Principen (historical brand name); generic ampicillin

Classification

Penicillin antibiotic; aminopenicillin, beta-lactam

Dosage/Route

  • * Dosage:
    •      – Capsules: 250 mg, 500 mg
    •      – Suspension: 125 mg/5 mL, 250 mg/5 mL
    •      – IV/IM: 250 mg, 500 mg, 1 g, 2 g vials
  • * Route: Oral (PO), intravenous (IV), intramuscular (IM)

Usual Dosage

  • * Adults:
    •      – PO: 250-500 mg every 6 hours (QID); max 4 g/day
    •      – IV/IM: 500 mg-2 g every 4-6 hours; max 12 g/day
  • * Children:
    •      – PO: 50-100 mg/kg/day divided q6h
    •      – IV/IM: 100-200 mg/kg/day divided q4-6h
  • * Duration: 7-14 days (e.g., 10 days for strep)

Mechanism of Action

Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins, disrupting peptidoglycan cross-linking. Bactericidal against susceptible gram-positive (e.g., Streptococcus) and some gram-negative bacteria (e.g., E. coli, H. influenzae); broader spectrum than penicillin G

Side Effects & Adverse Effects

  • * Side Effects: Nausea, diarrhea, rash
  • * Adverse Effects:
    •      – Hypersensitivity (rash, anaphylaxis; boxed warning for penicillin allergy)
    •      – Clostridioides difficile-associated diarrhea (CDAD)
    •      – Injection site reaction (IM/IV; phlebitis)
    •      – Rare: Seizures (high IV doses), hematologic effects

Nursing Management (Implications & Teachings)

  • * Implications:
    •      – Assess for penicillin allergy (anaphylaxis risk) before first dose
    •      – Monitor renal function (adjust dose if CrCl <50 mL/min), diarrhea (CDAD)
    •      – IV: Infuse over 30-60 min; reconstitute per label (e.g., 10 mL water for 500 mg)
    •      – PO: Give on empty stomach (1 hr before/2 hr after meals)
  • * Teachings:
    •      – Finish full course; don’t skip doses
    •      – Report hives, swelling, or bloody diarrhea
    •      – Take PO with water, shake suspension well
    •      – Store reconstituted IV in fridge if delayed (stable 24 hr)

Indication for This Patient

* Bacterial infections:

  •      – Respiratory (e.g., pneumonia, sinusitis)
  •      – UTI (e.g., E. coli)
  •      – Meningitis (e.g., Listeria, with other drugs)
  •      – Endocarditis prophylaxis (susceptible organisms)

Time

  • * Timing: PO: Every 6 hours; IV/IM: Every 4-6 hours
  • * Onset: Symptom relief in 1-3 days
  • * Duration: 7-14 days (infection-specific)

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