Antibiotics for Oral Surgery

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Anaesthesia & Exodontia
Third Year

Antibiotics for Oral Surgery

  1. 1. Pharmacological Drugs Used After Tooth Extraction Dr. Wael M. Talaat
  2. 2. Antibiotic/Antimicrobial • Antimicrobial agent: Chemical that kills or inhibits the growth of microorganisms
  3. 3. Antibiotic Spectrum of Activity • No antibiotic is effective against all microbes
  4. 4. Common routes of administration Parentral intravenous (i.v) & intramuscular (i.m) Rectal Enema, Ointments & Suppositories Oral Capsule, Tablet & Solution Topical Cream, Ointment & Transdermal patch
  5. 5. Parentral Rectal rapid rapid precise precise •toxicity •invasive •skill avoid avoid first-pass Oral Oral not recommended Oral Convenient Convenient economical economical non-invasive non-invasive safer safer route Topical  minimize side effects •Incomplete ab. (pH)
  6. 6. TREATMENT of INFECTION • Remove the cause of infection is the most important of all, by either spontaneously or surgically drain the pus. • Antibiotics are merely an adjunctive therapy. Drainage Host defense Antibiotics
  7. 7. INDICATIONS for ANTIBIOTICS 1. Severity of the infection • Acute onset • Diffuse swelling involves fascial spaces 2. Adequacy of removing the source of infection • When drainage can’t be established immediately 3. The state of patients’ host defense • When the patient is febrile • Compromised host defenses • For prophylaxis
  8. 8. MICROBIOLOGY • Most oral infections are mixed in origin consisting of aerobic and anaerobic gram positive and gram negative organisms • Anaerobes predominant (75%)
  9. 9. SELECTION of A/B • Use the narrowest spectrum antibiotics • Use the antibiotics with the lowest toxicity and side effects • Use bactericidal antibiotics if possible • Be aware of the cost of antibiotics
  10. 10. Mechanisms of Antimicrobial Action • Bacteria have their own enzymes for – Cell wall formation – Protein synthesis – DNA replication – RNA synthesis – Synthesis of essential metabolites
  11. 11. Mechanisms of Antimicrobial Action • Viruses use host enzymes inside host cells • Fungi and protozoa have own eukaryotic enzymes • The more similar the pathogen and host enzymes, the more side effects the antimicrobials will have
  12. 12. Modes of Antimicrobial Action
  13. 13. Antibacterial Antibiotics Inhibitors of Cell Wall Synthesis • Penicillin (over 50 compounds) – Share 4-sided ring (β lactam ring) • Natural penicillins • Narrow range of action • Susceptible to penicillinase (β lactamase)
  14. 14. Prokaryotic Cell Walls
  15. 15. Penicillins Fig 20.6 Figure 20.6
  16. 16. Penicillinase (β Lactamase) Figure 20.8
  17. 17. Semisynthetic Penicillins • Penicilinase-resistant penicillins • Carbapenems: very broad spectrum • Monobactam: Gram negative • Extended-spectrum penicillins • Penicillins + β-lactamase inhibitors
  18. 18. Other Inhibitors of Cell Wall Synthesis • Cephalosporins – 2nd, 3rd, and 4th generations more effective against gramnegatives Figure 20.9
  19. 19. Other Inhibitors of Cell Wall Synthesis • Polypeptide antibiotics – Bacitracin • Topical application • Against gram-positives – Vancomycin • Glycopeptide • Important "last line" against antibiotic resistant S. aureus
  20. 20. Other Inhibitors of Cell Wall Synthesis • Antibiotics effective against Mycobacteria: interfere with mycolic acid synthesis or incorporation – Isoniazid (INH) – Ethambutol
  21. 21. Inhibitors of Protein Synthesis • Broad spectrum, toxicity problems • Examples – Chloramphenicol (bone marrow) – Aminoglycosides: Streptomycin, neomycin, gentamycin (hearing, kidneys) – Tetracyclines (Rickettsias & Chlamydia; GI tract) – Macrolides: Erythromycin (gram +, used in children)
  22. 22. Injury to the Plasma Membrane • Polymyxin B (Gram negatives) – Topical – Combined with bacitracin and neomycin (broad spectrum) in overthe-counter preparation
  23. 23. Inhibitors of Nucleic Acid Synthesis • Rifamycin – Inhibits RNA synthesis – Antituberculosis • Quinolones and fluoroquinolones – Ciprofloxacin – Inhibits DNA gyrase – Urinary tract infections
  24. 24. Competitive Inhibitors – Sulfonamides (Sulfa drugs) • Inhibit folic acid synthesis • Broad spectrum Figure 5.7
  25. 25. Antifungal Drugs • Fungi are eukaryotes • Have unique sterols in their cell walls • Pathogenic fungi are often outside the body
  26. 26. Antiviral Drugs • Viruses are composed of nucleic acid, protein capsid, and host membrane containing virus proteins • Viruses live inside host cells and use many host enzymes • Some viruses have unique enzymes for DNA/RNA synthesis or protein cutting in virus assembly Figure 20.16a
  27. 27. Antiviral Drugs Nucleoside and Nucleotide Analogs Figure 20.16a
  28. 28. Analogs Block DNA Synthesis Figure 20.16b, c
  29. 29. Antiviral Drugs Enzyme Inhibitors • Inhibit assembly – Indinavir (HIV) • Inhibit attachment – Zanamivir (Influenza) • Inhibit uncoating – Amantadine (Influenza)
  30. 30. Antiviral Drugs Enzyme Inhibitors • Interferons prevent spread of viruses to new cells (Viral hepatitis) • Natural products of the immune system in viral infections
  31. 31. Antiprotozoan Drugs • Protozoa are eukaryotic cells • Many drugs are experimental and their mode of action is unknown
  32. 32. Measuring Antimicrobial Sensitivity • E Test • MIC: Minimal inhibitory concentration
  33. 33. Measuring Antimicrobial Sensitivity: Disk Diffusion
  34. 34. Antibiotic Resistance Figure 20.20
  35. 35. Antimicrobial Resistance • Relative or complete lack of effect of antimicrobial against a previously susceptible microbe
  36. 36. Mechanisms of Antibiotic Resistance • Enzymatic destruction of drug • Prevention of penetration of drug • Alteration of drug's target site • Rapid ejection of the drug
  37. 37. Antibiotic Selection for Resistant Bacteria
  38. 38. What Factors Promote Antimicrobial Resistance? • Exposure to sub-optimal levels of antimicrobial • Exposure to microbes carrying resistance genes
  39. 39. Inappropriate Antimicrobial Use • Prescription not taken correctly • Antibiotics for viral infections • Antibiotics sold without medical supervision • Spread of resistant microbes in hospitals due to lack of hygiene
  40. 40. Inappropriate Antimicrobial Use • Lack of quality control in manufacture or outdated antimicrobial • Inadequate surveillance or defective susceptibility assays • Poverty or war • Use of antibiotics in foods
  41. 41. Consequences of Antimicrobial Resistance • Infections resistant to available antibiotics • Increased cost of treatment
  42. 42. Proposals to Combat Antimicrobial Resistance • Speed development of new antibiotics • Track resistance data nationwide • Restrict antimicrobial use • Direct observed dosing (TB)
  43. 43. Proposals to Combat Antimicrobial Resistance • Use more narrow spectrum antibiotics • Use antimicrobial cocktails
  44. 44. The Future of Chemotherapeutic Agents • Antimicrobial peptides – Broad spectrum antibiotics from plants and animals • Squalamine (sharks) • Protegrin (pigs) • Magainin (frogs)
  45. 45. The Future of Chemotherapeutic Agents • Antisense agents – Complementary DNA or peptide nucleic acids that binds to a pathogen's virulence gene(s) and prevents transcription

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