Beta-Lactam Antibiotics Revision Sheet---

1. 📌 Essentials

• Beta-lactam antibiotics include penicillins, cephalosporins, carbapenems, monobactams, and combinations with inhibitors.
• Core structure: Beta-lactam ring essential for activity.
• Main mechanism: Bind to Penicillin-Binding Proteins (PBPs), inhibiting peptidoglycan synthesis → bactericidal.
• Spectrum:
  • Penicillins: Gram-positive cocci, Treponema.
  • Cephalosporins: Broader with higher generations.
  • Carbapenems: Broad, resistant to beta-lactamases.
  • Monobactams: Gram-negative only.
• Resistance: Mainly via beta-lactamase enzymes; also permeability and PBP modifications.
• Pharmacokinetics: Low oral bioavailability, renal elimination, short half-life (~0.5-3h).
• Adverse effects: Allergies (most common), GI disturbances, skin rashes, hematological issues.
• Cross-reactivity: High among beta-lactams, especially penicillins and cephalosporins.
• Combination therapy: Clavulanic acid + amoxicillin restores activity against beta-lactamase producers.
• Clinical relevance: Used for bacterial infections, resistance management, and synergy with other antibiotics.

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