| Class | Mechanism | Key Coverage | Clinical Pearls |
|---|
| Penicillins | Inhibit cell wall synthesis (PBPs) | GPC, some GNC, anaerobes | β-lactamase vulnerable; combine with β-lactamase inhibitor (clavulanate, sulbactam, tazobactam) |
| Cephalosporins (1st–5th gen) | Cell wall synthesis | Progressive GNC coverage; 3rd/4th/5th cross BBB | Cephalosporin allergy cross-reactivity ~1–2% with penicillins (side-chain specific) |
| Carbapenems | Cell wall; resistant to most β-lactamases | Broadest (GPC, GNC, anaerobes, ESBL) | Reserve for MDR; seizure risk (imipenem); meropenem preferred |
| Monobactam (Aztreonam) | Cell wall (PBP3) | Aerobic GNC only (Pseudomonas) | No cross-reactivity with penicillin allergy (safe alternative) |
| Glycopeptides (Vancomycin, Teicoplanin) | Inhibit peptidoglycan polymerization | GPC (MRSA, VRE – teicoplanin) | Trough monitoring (AUC-guided); red man syndrome (infusion rate) |
| Macrolides (Azithro, Clarithro, Erythro) | 50S ribosomal → protein synthesis inhibition | Atypicals, GPC, some GNC | QT prolongation; CYP3A4 inhibition (clarithro); GI motility (erythro) |
| Tetracyclines (Doxy, Minocycline, Tigecycline) | 30S ribosomal | Broad (atypicals, rickettsia, acne, some MRSA) | Photosensitivity; avoid in pregnancy/children <8 yrs (teeth/bone) |
| Aminoglycosides (Gentamicin, Amikacin, Tobramycin) | 30S ribosomal → misreading | Aerobic GNC (Pseudomonas), some GPC | Nephro/ototoxicity; once-daily dosing; TDM essential |
| Fluoroquinolones (Cipro, Levo, Moxi) | DNA gyrase/topoisomerase IV inhibition | Broad GNC, atypicals, some GPC | Black box: tendinitis, neuropathy, aortic dissection; restrict use |
| Oxazolidinones (Linezolid, Tedizolid) | 50S ribosomal (initiation) | GPC (VRE, MRSA) | Myelosuppression (linezolid >2 wks); serotonin syndrome risk |
| Lipopeptides (Daptomycin) | Membrane depolarization (Ca²⁺-dependent) | GPC (MRSA, VRE) | Inactivated by pulmonary surfactant (not for pneumonia); CK monitoring |
