Saturday, October 12, 2024

Penicillins

1. Natural Penicillins   (quick reference table)

  • Examples: Penicillin G (IV,IM), Penicillin V po
  • Spectrum:
    • Gram-positive: Effective against Streptococcus species, Enterococcus (limited)
    • Gram-negative: Limited (mainly Neisseria species)
    • Anaerobes: Limited anaerobic coverage
  • Key Notes:
    • First-line treatment for syphilis.
    • No MSSA coverage.
    • Good for streptococcal infections.

2. Aminopenicillins

  • Examples: Ampicillin IV, Amoxicillin po
  • Spectrum:
    • Gram-positive: Streptococcus, Enterococcus faecalis, Listeria
    • Gram-negative: Limited, covers some H. influenzae and E. coli
    • Anaerobes: Limited anaerobic activity
  • Key Notes:
    • Listeria coverage makes it a drug of choice for Listeria infections.
    • Commonly used in respiratory and urinary tract infections.

3. Anti-Staphylococcal Penicillins

  • Examples: Nafcillin, Oxacillin
  • Spectrum:
    • Gram-positive: Effective against MSSA, Streptococcus
    • Gram-negative: No coverage
    • Anaerobes: No coverage
  • Key Notes:
    • First-line treatment for MSSA infections.
    • No activity against MRSA, Gram-negative, or anaerobes.

4. Penicillins with β-lactamase Inhibitors

  • Examples: Amoxicillin/Clavulanate (po Augmentin), Ampicillin/Sulbactam ( IV Unasyn)
  • Spectrum:
    • Gram-positive: MSSA, Streptococcus, Enterococcus
    • Gram-negative: Extended coverage for H. influenzae, E. coli, Klebsiella, Acinetobacter (Sulbactam)
    • Anaerobes: Good anaerobic coverage
  • Key Notes:
    • The β-lactamase inhibitors expand coverage to resistant Gram-negative and anaerobic organisms.
    • Used for mixed infections (e.g., respiratory, intra-abdominal).

5. Anti-Pseudomonal Penicillins with β-lactamase Inhibitors

  • Examples: Piperacillin/Tazobactam (Zosyn IV)
  • Spectrum:
    • Gram-positive: MSSA, Streptococcus, Enterococcus
    • Gram-negative: Broad, including Pseudomonas, Enterobacteriaceae
    • Anaerobes: Good anaerobic coverage
  • Key Notes:
    • Used in severe infections, especially where Pseudomonas and mixed infections are suspected.

Summary

  • Natural Penicillins: Great for Streptococcus, syphilis, but no MSSA coverage.
  • Aminopenicillins: Broader Gram-positive coverage with Listeria activity, used in respiratory and urinary tract infections.
  • Anti-Staphylococcal Penicillins: Best for severe MSSA infections but limited in other coverage.
  • Penicillins with β-lactamase Inhibitors: Expands to MSSA, Gram-negative and anaerobic coverage, used in mixed infections.
  • Anti-Pseudomonal Penicillins: Broad-spectrum, including Pseudomonas and anaerobic coverage, used in severe infections.

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