Pediatric Residents

Drug Name: Amoxicillin/Ampicillin

Click on the titles below for drug details

  • Binds penicillin-binding proteins
    • Impairs formation of the peptidoglycan layer of cell wall, which leads to cell death
  • Bactericidal.
  • Amoxicillin is enteral only, ampicillin is administered parenterally (IV or IM) only.
    • Amoxicillin Dosage Forms:
      • 250mg and 500mg capsules
      • 500mg and 875mg tablet
      • 125mg and 250mg chewable tablets
      • 125mg/5mL, 200mg/5mL, 250mg/5mL, 400mg/5mL suspensions
  • Amoxicillin (Enteral only in USA: with or without food)
    • Standard-dosing: 40-45 mg/kg/DAYin divided doses TID(maximum 500 mg/dose)
    • High-dose regimen: 80-90 mg/kg/day divided doses BID; maximum dose 4g/day
      • Used for infections with concern for Strep. Pneumoniae, including Acute Otitis Media, Community-acquired Pneumonia, and bacterial rhinosinusitis
    • Group A Strep: 50 mg/day once daily or divided q12 hours (max 1000mg/day)
    • UTI Treatment (with identified pathogen):
      • Infants: 25-50 mg/kg/dose q12hr
      • Children/Adolescents: 25 mg/kg/dose q8hrs
    • UTI Prophylaxis (in infants ≤2 months): 10-15 mg/kg once daily
    • Patients with abnormal renal function (<30 mL/minute/1.73 m2) require renal dosing adjustment, generally extending the dosing interval. Talk to your friendly pharmacist.
  • Ampicillin (Parenteral only)
    • Meningitis: 100 mg/kg/dose q6 hours (single dose max 3g; daily max dose 12g/day)
    • Other infection indications: 50 mg/kg/dose q6 hours (single dose max 3g)
    • Patients with abnormal renal function (<50 mL/minute/1.73 m2) require renal dosing adjustment, generally extending the dosing interval. Talk to your friendly pharmacist.
  • Spectrum of Activity:
    • Good coverage of streptococci (gram positive cocci) such as strep. pneumoniae, pyogenes, Viridans-Group streptococci and Enterococcus. Also covers some non-beta-lactamase producing gram-negative bacilli, such as E. coli, Klebsiella pneumoniae, H. influenzae, Gram-negative coccobacilli Neisseria meningitidis
    • "High-dose" amoxicillin (45 mg/kg/dose BID) can be used to overcome Streptococcus pneumoniae with amoxicillin resistance (with less affinity to the PBP). Higher-dose amoxicillin overcomes the reduced affinity and still causes cell death.
      • For use in Community-acquired pneumonia, sinus infections, and acute otitis media
        • Rhinosinusitis typically requires Amoxicillin-clavulanate, but amoxicillin may be used in younger children with mild infections.
  • Indications:
    • Amoxicillin
      • Acute Otitis Media
      • Community-Acquired Pneumonia
      • Sinusitis (mild cases in younger children only. Otherwise, typically would use Augmentin)
      • Helicobacter pylori Infection, in combination with other antibiotics
      • Lyme disease
      • Streptococcal Pharyngitis
      • Prophylaxis of bacterial endocarditis
      • Prophylaxis of pneumococcal infection in patients with sickle cell disease or asplenia
      • Prophylaxis of peritonitis in patients undergoing dental treatment
      • Treatment of exit-site or tunnel infections in patients with peritoneal dialysis catheters
      • Urinary tract infection prophylaxis in infants < 2 months
      • Previously used TID for Lyme Disease in children <8 years old. AAP has stated short-term doxycycline use in young children is safe, making amoxicillin rarely used for Lyme Disease except for late-stage presentations in young children (e.g., Lyme arthritis, which requires 28 days of treatment, in a 5-year-old).
    • Ampicillin
      • Meningitis - for Listeria coverage (used in tandem with other antibiotics for empiric coverage in select populations, such as neonates)
  • Allergy to amoxicillin
  • Hypersensitivity to other Penicillin-type Beta Lactams.
  • Diarrhea, upset stomach, or throwing up
  • Headache
  • Allergic reaction
  • Low risk of Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN)
  • Morbilliform-like rash with use with concurrent Epstein Bar Virus (EBV) infection
  • Amoxicillin is readily distributed throughout the body, but has poor penetration into cerebrospinal fluid with uninflamed meninges (higher concentrations into CSF with inflamed meninges).
  • Amoxicillin may cause diarrhea which typically improves after completing the antibiotic.
  • Amoxicillin rash occurs in 5% to 10% of children and is a generalized dull red, maculopapular rash, generally appearing 3 to 14 days after the start of therapy (especially with concurrent EBV infection). Rash does not necessarily mean the patient has an allergy but should be carefully monitored for signs of difficulty breathing, significant itching, persistent vomiting.