Beta-Lactams
Penicillins (bactericidal — cell wall synthesis inhibitors). Cephalosporins: 1st gen (gram+), 2nd gen (gram+/−), 3rd gen (gram−, CNS penetration), 4th gen (broad). Carbapenems (meropenem, imipenem): broadest spectrum, reserved for resistant organisms. Allergy: cross-reactivity 1–10% between penicillins and cephalosporins.
Macrolides & Fluoroquinolones
Macrolides (azithromycin): inhibit protein synthesis. Good for atypical pneumonia, community-acquired RTIs. Side effects: QT prolongation, GI upset. Fluoroquinolones (ciprofloxacin, levofloxacin): DNA gyrase inhibitors. Side effects: tendon rupture, QT prolongation, aortic dissection, C. diff risk.
Aminoglycosides & Vancomycin
Aminoglycosides (gentamicin, tobramycin): nephrotoxic and ototoxic — therapeutic drug monitoring (peak/trough). Vancomycin: gram-positive coverage (MRSA). Monitoring: trough levels. Red Man Syndrome: infusion reaction — slow infusion to 60+ min. Nephrotoxicity risk.
Antifungals & Antivirals
Antifungals: azoles (fluconazole — oral, IV), amphotericin B (broad, nephrotoxic). Antivirals: acyclovir (HSV/VZV), oseltamivir (influenza — within 48h of symptom onset), antiretrovirals (HIV).
Antimicrobial Stewardship
Principles: right drug, right dose, right duration. Obtain cultures BEFORE first dose. De-escalate from broad to narrow when sensitivities available. Reassess daily: can stop? switch to oral? shorten duration? Document indication and planned duration.
Important Notes
- Vancomycin: Red Man Syndrome is infusion-rate related (not true allergy) — slow infusion, antihistamine.
- Fluoroquinolones: FDA warning for tendon rupture, aortic dissection, and mental health side effects.
Clinical Tips
- Always obtain blood cultures BEFORE administering first antibiotic dose in suspected sepsis.
Summary
Antibiotic therapy requires understanding of drug classes, mechanisms, side effects, and stewardship principles. Nurses play a key role in antimicrobial stewardship through timely administration and culture collection.
