Antibacterial Drug Classes: Actions, Uses, and Adverse Effects

Posted on Jul 8, 2025 in Airports

Introduction to Antibacterial Drugs

Key Concepts in Antibacterial Therapy

  • Cross-Resistance: Occurs between antibacterial drugs with similar actions. Example: clindamycin and lincomycin.
  • Allergic Reactions: Hypersensitivity, rash, pruritus, hives, anaphylaxis.
  • Spectrum:
    • Narrow Spectrum: penicillin, erythromycin
    • Broad Spectrum: tetracycline, cephalosporins

Penicillins

General Information on Penicillins

  • Drug Names: End in “-icillin” (e.g., Amoxicillin).
  • Action: Inhibit bacterial cell wall synthesis. Can be bacteriostatic AND bactericidal (depends on drug and dose).
  • Side Effects/Adverse Reactions:
    • Hypersensitivity, Anaphylaxis
    • Superinfection
    • Tongue discoloration
    • GI distress, C. difficile-associated diarrhea (CDAD)
    • Important Note: Do not take with acidic juices or fruits.

Types of Penicillins

  • Basic Penicillins

    • Drugs: Penicillin G & V
    • Spectrum: Narrow (gram-positive with few gram-negative).
    • Use: Anthrax, tetanus, diphtheria, endocarditis, respiratory infections, syphilis.
    • Administration: IM (poorly absorbed orally).

  • Broad-Spectrum Penicillins

    • Drug: Amoxicillin
    • Spectrum: Broad (gram-positive & negative).
    • Use: Respiratory, skin, intra-abdominal, urinary tract, gynecologic infections, otitis media, sinusitis.

  • Penicillinase-Resistant Penicillins

    • Drug: Dicloxacillin Sodium
    • Spectrum: Narrow (gram-positive).
    • Use: Endocarditis, meningitis, bacteremia, skin, and respiratory infections.

  • Extended-Spectrum Penicillins

    • Use: Respiratory, intra-abdominal, and skin infections.

  • Beta-Lactamase Inhibitors

    • Action: Inhibit beta-lactamases, extending the antimicrobial spectrum.
    • Administration: Combined with penicillinase-sensitive penicillins (not given alone).

Cephalosporins

General Information on Cephalosporins

  • Drug Names: Start with “Cef-” (e.g., Ceftriaxone).
  • Structure: Beta-lactam structure.
  • Action: Inhibit bacterial cell wall synthesis. Bactericidal.
  • Use: Respiratory, urinary, skin, bone, joint, and genital infections (consider for penicillin allergies).
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Headache, Dysgeusia, GI distress, C. difficile-associated diarrhea (CDAD)
    • Nephrotoxicity, Stevens-Johnson Syndrome, Elevated Hepatic Enzymes
  • Drug Interactions:
    • Alcohol: May cause disulfiram-like reaction (flushing, dizziness, headache, nausea and vomiting, muscular cramps).
    • Uricosurics: Decrease cephalosporin excretion.
  • Nursing Interventions: Advise to take with food if GI upset occurs.

Generations of Cephalosporins

As generation increases, drug potency and resistance to beta-lactamase also increase.

  • First Generation Cephalosporins

    • Spectrum: Mostly gram-positive with some gram-negative.

  • Second Generation Cephalosporins

    • Spectrum: Gram-positive and gram-negative.

  • Third Generation Cephalosporins

    • Drug Prototype: Ceftriaxone
    • Spectrum: Gram-positive and gram-negative; increased resistance to beta-lactamases.

  • Fourth Generation Cephalosporins

    • Spectrum: Gram-positive and gram-negative; highly resistant to beta-lactamases (best penetration to CSF).

  • Fifth Generation Cephalosporins

    • Spectrum: Gram-positive and gram-negative; highly resistant to beta-lactamases (effective against MRSA).

Macrolides

General Information on Macrolides

  • Drug Names: End in “-thromycin” (e.g., erythromycin, clarithromycin, azithromycin).
  • Spectrum: Broad (gram-positive and some gram-negative).
  • Action: Inhibits protein synthesis. Bacteriostatic with low to moderate doses, bactericidal with high doses.
  • Use: Mild to moderate respiratory, sinus, skin, soft tissue, GI tract infections, diphtheria, impetigo, STIs.
  • Administration: Erythromycin is very painful by IM injection; request change of administration route.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Tinnitus, Headache, Seizure, Dysgeusia, GI distress, C. difficile-associated diarrhea (CDAD), Stevens-Johnson Syndrome (SJS)
    • Ototoxicity, Tooth discoloration, Hepatotoxicity
  • Drug Interactions:
    • Increased levels of: Warfarin, theophylline, carbamazepine.
    • Erythromycin levels increase with fluconazole, ketoconazole, itraconazole (all “-conazole” antifungals), verapamil, diltiazem.
    • Clarithromycin: Risk of sudden cardiac death.
    • Azithromycin levels may be reduced by antacids.
    • Increased risk of hepatotoxicity with acetaminophen.
  • Nursing Interventions:
    • Monitor vital signs, urine output, lab values.
    • Monitor for signs and symptoms of liver damage.
    • Administer 2 hours before or after antacids.
    • Tell patient to report onset of loose stools or diarrhea.

Oxazolidinones

General Information on Oxazolidinones

  • Drug Names: End in “-zolid” (e.g., linezolid).
  • Spectrum: Gram-positive.
  • Action: Inhibit protein synthesis. Bacteriostatic and bactericidal (depends on dose).
  • Use: Bacteremia, sepsis, MRSA, VREF, respiratory and skin infections.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Seizure
    • Tongue and tooth discoloration
    • GI distress, Peripheral neuropathy
    • Anemia, Thrombocytopenia, Neutropenia
    • C. difficile-associated diarrhea (CDAD)
    • Serotonin Syndrome

Lincosamides

General Information on Lincosamides

  • Drug: Clindamycin.
  • Spectrum: Mostly gram-positive.
  • Action: Inhibit protein synthesis. Bacteriostatic and bactericidal (depends on dose).
  • Use: Gynecological infections, acne, bacteremia, septicemia, MRSA, respiratory, intra-abdominal, skin, gynecologic, and bone/joint infections.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Xerosis, Dysgeusia, Glossitis, Stomatitis, GI distress
    • Pancytopenia
  • Drug Interactions: Clindamycin and lincomycin are incompatible with:
    • Aminophylline
    • Phenytoin
    • Barbiturates
    • Ampicillin

Glycopeptides

General Information on Glycopeptides

  • Drug: Vancomycin.
  • Spectrum: Gram-positive (including MRSA).
  • Action: Inhibit cell wall synthesis. Bactericidal.
  • Use: Respiratory, skin, bone/joint infections, bacteremia, septicemia, endocarditis, MRSA, C. difficile-associated diarrhea (CDAD).
  • Administration: Draw peak and trough levels when given IV.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Red Neck/Red Man Syndrome (occurs when IV infusion is too rapid, leading to severe hypotension, red blotching of face, neck, chest, and extremities).
    • Disulfiram-like reaction to alcohol.
    • Ototoxicity and Nephrotoxicity
    • C. difficile-associated diarrhea (CDAD).

Ketolides

General Information on Ketolides

  • Drug: Telithromycin.
  • Action: Blocks bacterial protein synthesis.
  • Use: Community-acquired pneumonia (including MRSA), Streptococcus pneumoniae, Haemophilus influenzae.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis
    • Visual Disturbances
    • GI distress, Dysgeusia, C. difficile-associated diarrhea (CDAD)
    • Hepatotoxicity
    • Exacerbation of Myasthenia Gravis
  • Drug Interactions:
    • Levels increase with lipid-lowering agents (e.g., statins).
    • Life-threatening dysrhythmias with antiarrhythmics.

Lipopeptides

General Information on Lipopeptides

  • Drug: Daptomycin.
  • Action: Inhibit protein, RNA, and DNA synthesis. Bactericidal.
  • Use: Complicated skin infections, septicemia, endocarditis.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfections
    • Insomnia, Anemia, Bleeding, Chest pain
    • GI distress, Peripheral neuropathy
    • Hypo/hypertension, Hypo/hyperkalemia, Hypo/hyperglycemia
    • Rhabdomyolysis
  • Drug Interactions:
    • HMG-CoA reductase inhibitors (statins) increase CPK levels.
    • Increases effects of warfarin.

Tetracyclines

General Information on Tetracyclines

  • Drug: Doxycycline.
  • Spectrum: Broad.
  • Action: Inhibit protein synthesis.
  • Use: H. pylori, MRSA, acne, anthrax, plague, gingivitis, cholera, STIs, skin, urinary, and respiratory infections.
  • Drug Interactions:
    • Milk products: Decreased drug effects.
    • Oral Contraceptives: Decreased effectiveness.
    • Penicillins: Decreased effects of penicillins, increased bacterial resistance.
    • Aminoglycosides: Increased risk of nephrotoxicity.
    • Increased effect of warfarin and digoxin.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection, Photosensitivity, Diplopia
    • Discoloration of permanent teeth: Do not give to children younger than 8 years.
    • Stomatitis, Glossitis, GI distress, C. difficile-associated diarrhea (CDAD)
    • Ototoxicity, Hepatotoxicity, Nephrotoxicity
    • Pancytopenia
  • Nursing Interventions:
    • Monitor lab values for renal/hepatic function.
    • Advise use of another form of birth control.

Glycylcyclines

General Information on Glycylcyclines

  • Drug: Tigecycline.
  • Action: Blocks protein synthesis. Bacteriostatic.
  • Use: Complicated skin and intra-abdominal infections, community-acquired pneumonia.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection, Photosensitivity
    • Dizziness, Insomnia, GI distress
    • Hyperglycemia, Hypokalemia
    • C. difficile-associated diarrhea (CDAD)

Aminoglycosides

General Information on Aminoglycosides

  • Drug: Gentamicin.
  • Action: Inhibit protein synthesis. Bactericidal.
  • Use: Serious respiratory, skin, urinary, bone/joint, intra-abdominal infections, plague, tularemia, bacteremia, septicemia, endocarditis, meningitis, hepatic encephalopathy, bowel preparation.
  • Administration: IM, IV (Narrow Therapeutic Range: requires peak and trough monitoring).
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection, Seizures, Photosensitivity, Anemia, GI distress
    • Ototoxicity, Nephrotoxicity, Neurotoxicity
    • C. difficile-associated diarrhea (CDAD)
  • Drug Interactions:
    • Penicillins decrease effect of aminoglycosides.
    • Increased action of oral anticoagulants.
    • Ethacrynic acid with aminoglycosides may increase ototoxicity.
  • Nursing Interventions:
    • Check for hearing loss and renal function.
    • Encourage patient to increase fluid intake.

Fluoroquinolones

General Information on Fluoroquinolones

  • Drug Names: End in “-floxacin” (e.g., ciprofloxacin, levofloxacin).
  • Spectrum: Broad (gram-positive and gram-negative).
  • Action: Interfere with DNA gyrase enzyme to inhibit bacterial DNA synthesis. Bactericidal.
  • Use: Anthrax, skin, soft-tissue, bone/joint, gynecologic, intra-abdominal, urinary, and respiratory tract infections.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Photosensitivity, Eye damage, Visual disturbances
    • Tendinitis, Tendon rupture
    • C. difficile-associated diarrhea (CDAD), Stevens-Johnson Syndrome (SJS), Thrush
  • Nursing Interventions:
    • Check lab values and renal function.
    • Advise patients with diabetes to monitor blood glucose levels as it can increase the effects of oral hypoglycemics.

Sulfonamides

General Information on Sulfonamides

  • Drug: Trimethoprim-Sulfamethoxazole (TMP-SMZ).
  • Action: Inhibit bacterial synthesis of folic acid. Bacteriostatic.
  • Use: Otitis media, meningitis, malaria, respiratory, and urinary tract infections.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis
    • Photosensitivity
    • GI distress, Stomatitis, Insomnia, Tinnitus
    • Crystalluria, Renal failure
    • Blood dyscrasias
  • Nursing Interventions:
    • Administer with a full glass of water.
    • Observe for hematologic reactions.

Nitroimidazoles

General Information on Nitroimidazoles

  • Drug Names: End in “-azoles” (e.g., metronidazole).
  • Action: Disrupt DNA and protein synthesis in bacteria and protozoa.
  • Use: C. difficile-associated diarrhea (CDAD), amebiasis, giardiasis, trichomoniasis, bacterial vaginosis, acne, meningitis, gynecologic, skin, intra-abdominal, and respiratory infections.
  • Side Effects/Adverse Reactions:
    • Anaphylaxis, Superinfection
    • Headache, Dizziness, Insomnia, Weakness
    • Dry mouth, Tongue/tooth discoloration (reversible)
    • Peripheral neuropathy, Seizures
    • Leukopenia
    • Disulfiram-like reactions (avoid alcohol).