Antibiotics and Tetracyclines in Dentistry

Macrolides

• Azithromycin is the preferred penicillin-alternative drug of choice in penicillin allergic patients and those who cannot tolerate clindamycin due to its favourable pharmacokinetics.
• Azithromycin is concentrated in neutrophils and macrophages, giving it a long half-life and allowing for once-daily dosing.
• Dental uses of Azithromycin include:
  • Prophylactic use: endocarditis prophylaxis (oral: 500 mg 1 hour before procedure, parenteral: 500 mg IV 1 hour before procedure)
  • Therapeutic uses: second-line treatment for syphilis, treatment of acute orofacial infections (e.g., acute periapical abscess, sinusitis)
• Azithromycin can interact with:
  • Penicillin: antagonizes the bactericidal effect of penicillin
  • Oral anticoagulants: increases the effect of anticoagulants, increasing the risk of bleeding
  • Anticonvulsant drugs: can alter levels in the presence of macrolides
  • Theophylline: can increase the level of Theophylline, leading to toxicity
• Adverse effects of Azithromycin include:
  • GIT issues: nausea, vomiting, and diarrhea
  • Cardiotoxicity: associated with high serum levels
  • Hepatotoxicity: in pregnant women with Erythromycin
  • Hearing loss: rare

Lincosamides

• Clindamycin is a semisynthetic lincosamide that inhibits protein synthesis by binding to bacterial ribosomes.
• Dental uses of Clindamycin include:
  • Prophylactic use: in penicillin allergic patients (oral: 600 mg 1 hour before procedure, parenteral: 600 mg IV/IM 1 hour before procedure)
  • Therapeutic uses: in penicillin allergic patients (300 mg PO QID for 5 days)
• Adverse effects of Clindamycin include:
  • Diarrhea
  • Nausea
  • Abdominal cramps
  • Inflammation of the colon or colitis

Tetracyclines

• Tetracyclines are broad-spectrum bacteriostatic antibiotics that inhibit bacterial protein synthesis.
• Pharmacokinetics:
  • Partially absorbed from the stomach and upper GIT
  • Poor absorption if taken with calcium (e.g., milk)
  • Distributed to all body fluids, but cannot penetrate CSF even in the presence of infection
  • Metabolized in the liver
  • Excreted in the urine
• Dental uses of Tetracyclines include:
  • Anticollagenase effect (inhibit the break down of tissue)
  • High bioavailability in the gingival sulcus
  • Treatment of periodontal and peri-implant disease

Inhibitors of Bacterial Protein Synthesis

• Macrolides (Erythromycin, Clarithromycin, Azithromycin) inhibit bacterial protein synthesis by binding to bacterial ribosomes.
• General properties of Macrolides:
  • Stable in stomach acid and readily absorbed
  • Extensively metabolized by the liver
  • Excreted in the bile (safe in renal dysfunction patients) except Clarithromycin, which is excreted in the urine
• Erythromycin is not preferred as a penicillin-alternative drug when a severe infection exists or when the patient is immunocompromised and requires bacteriocidal activity.