IDStewardship

Amoxicillin (Amoxil)

Amoxicillin

KEY POINTS

  • Amoxicillin (Amoxil) is an amino-penicillin and beta-lactam antibiotic that works by inhibiting the bacterial cell wall in susceptible organisms
    • Amoxicillin’s injectable counterpart is ampicillin (which also comes oral)
  • Available as an oral pill or oral suspension
    • The oral suspension shown above is good for pediatrics and tastes like bubble gum
  • Has activity versus Gram positives, Gram negatives and anaerobes
    • Does not work against penicillin-resistant Staphylococcus aureus
      • Most MSSA is penicillin-resistant
    • A good drug for beta-hemolytic Streptococci (e.g., Strep. pyogenes & Strep. agalactiae)
    • Beware resistance with alpha-hemolytic Streptococci (e.g., Strep. pneumoniae & Viridans Streptococci)
    • Aminopenicillins are widely considered the drugs of choice for susceptible Enterococci
    • Many Gram negative anaerobes are resistant to amoxicillin alone, add beta-lactamase inhibitor clavulanic acid aka clavulanate to expand this coverage and hit susceptible Bacteroides fragilis
      • Note amoxicillin-clavulanic acid is brand name Augmentin
      • Amox-clav has activity versus MSSA, but amoxicillin alone only has activity against penicillin-sensitive Staphylococcus aureus
  • Requires dosage adjustment for renal insufficiency
  • In pediatric patients, “regular-dose amoxicillin” is 40-45 mg/kg/day and “high-dose amoxicillin” is 80-90 mg/kg/day
  • Beware hypersensitivity reaction and anaphylaxis
    • Note that exposure to aminopenicillins during an Epstein Barr Virus (EBV) infection can result in a non-allergic rash that can physically appear similar to an IgE-mediate allergic reaction
      • This has led to inappropriate penicillin allergy labels, especially in children
      • Penicillin skin testing can assist in ruling out most unclear penicillin allergy labels

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