Antibiotic Overview

By no means an exhaustive list, but this compilation may serve as a reference for basic antibiotic classifications, indications, and side effects.

Inhibitors of Cell Wall Synthesis (ICWS)

  • Beta-lactams
    • Penicillins: Major side effect profile = rash, anaphylaxis
      • 1st Generation: Target Gram-positive cocci
        • Pencillin G (oral/parenteral)
        • Penicillin V (oral)
      • 2nd Generation: Antistaphylococcal (Beta-lactamase resistant)
        • Nafcillin (“Naf for staph”)
        • Oxacillin
        • Cloxacillin
        • Dicloxacillin
      • 3rd Generation: Additional anti-pseudomonal coverage
        • Piperacillin (option of adding beta-lactamase inhibitor tazobactam)
        • Ticarcillin
        • Mezlocillin
      • 4th Generation: Extended spectrum (targets Gram-positive AND Gram-negative)
        • Ampicillin (option of adding beta-lactamase inhibitor sulbactam)
        • Amoxicillin (option of adding beta-lactamase inhibitor clavulanic acid)
    • Cephalosporins: Cross reaction with penicillins <3% (1)
      • 1st Generation: Mostly Gram-positive coverage
        • Cephalexin
        • Cefazolin
      • 2nd Generation: Increased Gram-negative coverage, less Gram-positive coverage
        • Cefuroxime
        • Cefotetan
        • Cefaclor
      • 3rd Generation: Increased Gram-negative coverage, less Gram-positive coverage
        • Ceftriaxone
        • Cefdinir
        • Cefotaxime
      • 4th Generation: Additional antipseudomonal coverage
        • Cefepime
    • Monobactams: Beta-lactamase resistant. NO cross-reaction with penicillin allergy. GNR and pseudomonas coverage. No Gram-positive coverage or anaerobic coverage
      • Aztreonam
    • Carbapenems
      • Imipenem: Gram-positive, Gram-negative, anaerobic coverage
      • Ertapenem: Gram-positive, Gram-negative, anaerobic coverage
      • Meropenem: Gram-positive, Gram-negative, anaerobic pseudomonal coverage
  • “Other” ICWS
    • Vancomycin: Inhibits transglycosylation of cell wall (step before transpeptidation)
      • Targets Gram-positive organisms
      • Use PO for C. diff colitis, IV for everything else (Not absorbed orally)
      • Major side effects: Nephrotoxicity, ototoxicity, “red man” syndrome
    • Fosfomycin: Treats Gram-negative UTIs
    • Bacitracin: Topical only (very nephrotoxic if absorbed systemically)
    • Polymyxins (B & E): Gram negative and anti-pseudomonal salvage therapy

Inhibitors of Protein Synthesis

  • Aminoglycosides: Inhibit 30S ribosome. Major side effects: nephrotoxicity, ototoxicity. Can be used to treat Yersinia pestis (plague)
    • Streptomycin
    • Gentamicin
    • Tobramycin
    • Amikacin
  • Tetracyclines: Inhibit 30S ribosome. Poor absorption with elemental metals. Major side effects: teeth discoloration, bone growth retardation, photosensitization. Target atypical bacteria as well tick-borne diseases.
    • Tetracycline
    • Doxycycline: May be used to cover MRSA but has poor streptococcal coverage
    • Tigecycline: Resistant to drug efflux pumps
  • Macrolides: Inhibit 50S ribosome. Major side effects: QT prolongation
    • Erythromycin
    • Clarithromycin
    • Azithromycin
  • Nitroimidazole
    • Metronidazole: Targets anaerobes and parasites
  • Other
    • Chloramphenicol: inhibits 50S ribosome. Treats typhoid fever, rocky mountain spotted fever in children. Major side effects: Aplastic anemia, gray baby syndrome.
    • Clindamycin: Can treat MRSA, anaerobes. Major side effect: C. diff colitis
    • Streptogramins: Inhibit 50S ribosome
      • Quinupristin and Dalfopristin: Treat VRE, MRSA
    • Oxazalidones: Prevents 70S ribosome formation
      • Linezolid: Treats VRE, MRSA. Good oral absorption. Bacteriostatic.

Folate Pathway Inhibitors

  • p-Aminobenzoic Acid (PABA) analogues: pteridine synthetase inhibitors
    • Silver sulfadiazine: Used topically for burns, not for use on face – concern for application to eye
    • Sodium sulfacetamide: Ophthalmic solution
    • Sulfasalazine: Used to treat ulcerative colitis
  • Dihydrofolate Reductase (DHFR) inhibitors: prevents USE of folate
    • Trimethoprim: Used in conjunction with sulfamethoxazole to treat MRSA, pneumocystis, UTIs, etc.
      • Studies have shown an increased resistance by S. pneumoniae (2), however, it does appear to still be efficacious in the treatment of S. pyogenes (3).
      • Trimethoprim/sulfamethoxazole (TMP-Sulfa) has potential side effects that include elevation in creatine as well as drug-induced liver injury (typically in a cholestatic or mixed pattern). It also reduces the ability of acetaminophen to undergo glucuronidation, leading to increased NAPQI formation and injury to hepatocytes.

DNA Gyrase Inhibitors

  • Quinolones
    • Nalidixic Acid
  • Fluoroquinolones: Good for intra-abdominal gram-negative coverage as well as UTIs. Can also treat Bacillus anthracis. Major side effects = QT prolongation, CNS toxicity, tendinopathy, C. diff colitis
    • Ciprofloxacin: Best pseudomonal coverage of fluoroquinolones
    • Levofloxacin: Additional anti-streptococcal pneumonia coverage. Also covers stenotrophomonas
    • Ofloxacin
    • Moxifloxacin: Additional anaerobe coverage. Does not cover pseudomonas except for ocular application

Urinary Tract Antiseptics

  • Nitrofurantoin: Causes oxidative stress to bacteria
    • May also cause anorexia, hemolytic anemia in individuals with G6PDH deficiency


  • Daptomycin: Bactericidal. Covers gram-positive including MRSA, VRE. Inactivated by surfactant, so not a recommended choice for lung infections


  1. Solensky, R., MD. (2012, December 1). Allergy to beta-lactam antibiotics. Retrieved November 6, 2020, from
  2. Jacobs MR;Good CE;Windau AR;Bajaksouzian S;Biek D;Critchley IA;Sader HS;Jones RN;. (n.d.). Activity of ceftaroline against recent emerging serotypes of Streptococcus pneumoniae in the United States. Retrieved December 30, 2020, from
  3. Imöhl, M., & Linden, M. (n.d.). Antimicrobial Susceptibility of Invasive Streptococcus pyogenes Isolates in Germany during 2003-2013. Retrieved December 30, 2020, from

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