Lecture Notes: Antibiotics - Tetracyclines and Glycylcyclines

Overview

• Tetracyclines are broad-spectrum antibiotics derived from Streptomyces bacteria.
• Treat various infections: CNS (meningitis), respiratory (community-acquired pneumonia), GI (cholera), skin (acne), genito-urinary (chlamydia, syphilis), and rare infections (rocky mountain spotted fever, anthrax, lyme disease, tularemia).
• Effective against both gram-positive and gram-negative bacteria, as well as atypical bacteria.
• Glycylcyclines are a newer generation addressing resistance to tetracyclines, effective in complicated skin and intra-abdominal infections.

Mechanism of Action

• Enter bacteria, inhibit protein synthesis, and stop bacterial growth (bacteriostatic).

Classification

• Tetracyclines:
  • Short-acting: Tetracycline (half-life ~8 hours)
  • Long-acting: Doxycycline, Minocycline (half-life 16-22 hours)
• Glycylcyclines: Tigecycline (half-life ~42 hours)

Routes of Administration

• Tetracyclines: Oral (PO) or Intravenous (IV)
• Glycylcyclines: Intravenous (IV)

Indications

• Tetracyclines: CNS infections (meningitis), respiratory (pneumonia), GI (cholera), skin (acne), genito-urinary (chlamydia, syphilis).
• Glycylcyclines: Complicated skin and intra-abdominal infections.

Side Effects

• Common: Headache, dizziness, abdominal pain, nausea, vomiting, esophageal irritation, diarrhea.
• Phototoxicity: Increased risk of sunburn.
• Hypersensitivity: Skin rash, exfoliative dermatitis, Stevens-Johnson syndrome, anaphylaxis.
• Superinfection: Fungal (Candida) or bacterial (Clostridioides difficile) overgrowth.
• Dental: Discoloration of teeth, potential effects on bone growth.

Contraindications

• Boxed warning for tigecycline: Increased mortality; use alternatives if possible.
• Avoid in pregnancy, breastfeeding, and children under 8 years due to dental and bone effects.
• Caution with certain drugs (theophylline, warfarin, antacids, mineral supplements).
• Avoid in pre-existing hepatic and renal disease.

Nursing Considerations

• Assessment & Monitoring:

  • Assess symptoms, lab tests (renal/liver function, pregnancy test).
  • Monitor for side effects and therapeutic effects.

• Client Education:

  • Purpose: Treat infection and resolve symptoms.
  • Administration: Twice daily on empty stomach with water; remain upright for 30 mins.
  • Avoid dairy/calcium/magnesium/iron/zinc around administration.
  • Complete full course of medication.
  • Use reliable birth control if of childbearing age.
  • Increase fluids, small meals for GI discomfort; protect against sun exposure.
  • Frequent oral care for dental effects.
  • Report any signs of superinfection or esophageal injury.

Author: Anuj Paul, Reviewed by Antonella Melani, MD, et al.