Pharmacology of major antimicrobial (bacterial, fungal, and viral) medication classes used

Organisation by mechanism

Major antibacterial classes are organised by mechanism of action - cell wall synthesis inhibitors (beta-lactams, glycopeptides), protein synthesis inhibitors (macrolides, aminoglycosides, tetracyclines), nucleic acid synthesis inhibitors (fluoroquinolones, metronidazole), and folate synthesis inhibitors (trimethoprim-sulfamethoxazole) - mechanism determines both spectrum of activity and characteristic adverse effect/resistance patterns
Foundational pharmacological knowledge underlying rational antibiotic selection across all of infectious diseases and general medical practice

Beta-lactams (penicillins, cephalosporins, carbapenems) inhibit bacterial cell wall peptidoglycan cross-linking via penicillin-binding proteins - bactericidal, generally well tolerated, with beta-lactamase enzyme production being the principal bacterial resistance mechanism
Aminoglycosides inhibit bacterial protein synthesis (30S ribosomal subunit) - highly effective against Gram-negative organisms but carry dose-dependent nephrotoxicity and ototoxicity, requiring therapeutic drug monitoring
Fluoroquinolones inhibit bacterial DNA gyrase/topoisomerase - broad spectrum but carry specific adverse effect concerns (tendon rupture, QT prolongation, and in some jurisdictions restricted use given resistance and adverse effect profile)

Mechanism-based understanding predicts likely cross-resistance patterns (e.g. resistance to one beta-lactam via beta-lactamase production may confer resistance to related agents unless beta-lactamase-stable) and guides rational empirical combination selection when broad cover is needed

Agent selection should match spectrum to the clinical syndrome and likely/confirmed organism, narrowest effective option preferred (antimicrobial stewardship), with therapeutic drug monitoring for agents with a narrow therapeutic index (aminoglycosides, vancomycin)
Renal function-adjusted dosing is required for renally cleared agents (most beta-lactams, aminoglycosides, vancomycin) to avoid toxicity while maintaining efficacy

Aminoglycoside nephrotoxicity/ototoxicity monitoring, fluoroquinolone tendon rupture/QT prolongation risk, beta-lactam allergy and cross-reactivity (see ), vancomycin therapeutic drug monitoring
Aminoglycosides require therapeutic drug monitoring (peak/trough or area-under-curve dosing) given their narrow therapeutic index and dose-dependent nephrotoxicity/ototoxicity - dosing by weight alone without level monitoring risks either subtherapeutic treatment or preventable toxicity, particularly with renal impairment or prolonged courses

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