antibiotics

2. 
Antibiotics or anti-bacterials are a chemical used in
the treatment and prevention of bacterial infection
What are antibiotics?

3. 
Antibiotics are classified several ways.
 On the basis of mechanism of action
 On the basis of spectrum of activity
 On the basis of mode of action
Classification of antibiotics

4. 
 Cell Wall Synthesis inhibitors:
Penicillins
Cephalosporins
Vancomycin
Beta-lactamase Inhibitors
Polymycin
Bacitracin
 Protein Synthesis Inhibitors
 Inhibit 30s Subunit
Aminoglycosides (gentamycin)
Tetracyclines
Inhibit 50s Subunit
Macrolides
Chloramphenicol
Clindamycin
Streptogramins
DNA Synthesis Inhibitors
Fluoroquinolones (ciprofloxacillin)
Metronidazole
 RNA synthesis Inhibitors
Rifampin
 Mycolic Acid synthesis inhibitors
Isoniazid
 Folic Acid synthesis inhibitors
Sulfonamides
Trimethoprim
On the basis of mechanism of action:

5.  Broad spectrum antibiotics :
 Amoxicillin
 Tetracycline
 cephalosporin
 Chlorampenicol
 Erythromycin
 Short spectrum antibiotics:
 Penicillin –G
 Cloxacillin
 vancomycin
 Bacitracin
 Fluxacillin
On the basis of spectrum activity :

6. 
 Bacteriostatic antibiotics
 Tetracycline
 Chlorampenicol
 Erythromycin
 Lincomycin
 Bacteriocidal antibiotics
 Cephalosporin
 Penicillin
 Erythromycin
 Aminoglycosides
 Cotrimoxazole
On the basis of mode of action:

7. 
 Most common side-effects of antibiotics:
 Diarrhea
 Fungal infections of the mouth, digestive tract and vagina.
 Rare side-effects of antibiotics:
 Formation of kidney stones (when taking sulphonamides).
 Abnormal blood clotting (when taking some
cephalosporins).
 Sensitivity to sun (when taking tetracyclines).
 Blood disorders (when taking trimethoprim).
 Deafness (when taking erythromycin and the
aminoglycosides).
What are the side-effects of antibiotics?

8. 
 Some patients may develop an allergic reaction to
antibiotics - especially penicillins. Side effects might
include a rash, swelling of the tongue and face, and
difficulty breathing.
 Allergic reactions to antibiotics may be immediate or
delayed hypersensitivity reactions.
 Reactions to antibiotics can be very serious, and
sometimes fatal - they are called anaphylactic reactions.
 Use antibiotics with extreme caution if:
 The patient has reduced liver or kidney function.
 The patient is pregnant
 The patient is breastfeeding
Allergic reactions to antibiotics

9. 
 The ability of a microorganism to produce a protein that disables
an antibiotic or prevents transport of the antibiotic into the
cell.
Antibiotics resistance

10. 
 Cross-resistance to a particular antibiotic that often
results in resistance to other antibiotics, usually from
a similar chemical class, to which the bacteria may
not have been exposed.
 Cross-resistance can occur, for example, to both
colistin and polymyxin B or to both clindamycin and
lincomycin.
Cross-resistance

11. 
 Antibiotics are usually taken orally , injection, or topically.
 Most antibiotics start having an effect on an infection within a
few hours. It is important to remember to complete the whole
course of the medication to prevent recurrent infection.
 Some antibiotics should not be consumed with certain foods
and drinks. Others should not be taken with food in your
stomach - these would normally be taken about an hour before
meals, or two hours after. It is crucial that you follow the
instructions correctly if you want the medication to be effective.
If you are taking metronidazole do not consume alcohol.
 Dairy products should not be consumed if you are taking
tetracyclines, as they might affect the absorption of the
medication.
How to use antibiotics

13. Necrotic pulp and apical abscesses
Obligate anaerobic bacteria
Gram negative rods
Prevotella & porphyomonas spp.
Fusobacterium spp.
Campylobacter rectus
Gram positive rods
Eubacterium spp.
Actinomycetes spp.
Gram positive cocci
Peptostreptococcus spp.
Facultative anaerobic bacteria
Gram positive cocci
Strep and Entercoccus spp.

14. 
Common Pathogens
 Periodontal Diseases
Gingivitis
Fuso, strep, & actinomycetes
Adult peritonitis
Bacteroides, porphyomonas, peptostreptococcus &
prevotella
Acute necrotizing ulcerative gingivitis
Spirochetes, prevotella, fuso
Localized juvenile periodontitis
Actinobacillus

15. 
Common Pathogens
 Fungal Infections
Candida spp.
Mucorales spp.

16. 
β-Lactam Characteristics
 Mechanism: Inhibit cell wall synthesis.
 Bactericidal (except against Enterococcus sp.)
 Short elimination half-life
 Primarily renally eliminated (except nafcillin ,
oxacillin , ceftriaxone , cefoperazone)
 Cross-allergenicity-except aztreonam

17. 
β-Lactams
Adverse Effects
 Hypersensitivity……3 to 10 %
 Higher incidence with parenteral administration
 Mild to severe allergic reactions – rash to
anaphylaxis and death
 Anti-bodies produced against metabolicby-products
or penicillin it self
 Cross-reactivity exists among all penicillins and even
other β-lactams

18. 
β-Lactams
Adverse Effects
 Neurologic–especiallywithpenicillinsand
 Carbapenems(imipenemandmeropenem)
 Especiallyin patientsreceiving highdosesin
 Thepresenceofrenalinsufficiency
 Irritability, confusion,seizures
 • Hematologic:
 Leucopenia,neutropenia, thrombocytopenia
prolongedtherapy(>2weeks)

19. 
β-Lactams
Adverse Effects
 Gastrointestinal:
 Nausea ,vomiting ,diarrhea ,pseudo-membranous
 colitis(C. difficile diarrhea)
 • Interstitial Nephritis:
 Cellular infiltration in renal tubules (Type IV
 hypersensitivity reaction – characterized by
 Abrupt increase in serum creatinine; can lead to
renal failure
 Especially with methicillin or nafcillin

20. 
ß-Lactams
 Natural penicillins
 Pen VK and Pen G
 Mechanism of action: Inhibit cell wall synthesis
 Dose: 250-500 mg qid x 7-10 days
 Contraindications:
 Allergies
 Poor renal fxn
 Adverse events: GI upset
 Drug interactions: oral contraceptives
 Pregnancy category B

21. 
ß-Lactams
 Natural penicillins
 Pen VK and Pen G
 Bactericidal
 Allergic reaction: rare (4 per 100,000)
 Spectrum:
 Strep, staph, enterococcus, neiseria, treponema, listeria
 Resistance:
 Mostly staph (>80%)

22. 
ß-Lactams
 Amino-penicillins
 Amoxicillin, ampicillin
 Mechanism of action: Inhibit cell wall synthesis
 Dose: 250-500 mg q 8 h x 7-10 days
 Contraindications:
 Allergies
 Poor renal fxn
 Adverse events: GI upset
 Drug interactions: oral contraceptives
 Amoxicillin and clavulanic acid (Augmentin)

23. 
ß-Lactams
 Amino-penicillins
 Amoxicillin, ampicillin
 Bactericidal
 “ampicillin” rash (4-10%)
 Spectrum:
 Strep, staph, enterococcus, neiseria, treponema, listeria, E.
coli, proteus, H. Flu, shigella, salmonella
 Resistance:
 Entero, citro, serratia, proteus vulagris, provedincia,
morganella, pseudomonas aeriginosa, acinetobacter

24. 
Cephalosporins
 Cephalexin (Keflex)
 Mechanism of action: Inhibit cell wall synthesis
 Dose: 250-1000mg q 6 h x 7-10 days
 Contraindications:
 Allergies
 Poor renal fxn
 Adverse events: mild GI
 Drug interactions: probenecid
 Pregnancy category B

25. 
Cephalosporins
 Cephalexin (Keflex)
 Bactericidal
 Spectrum:
 Gram +
 Resistance:
 Methicillin resistant gram +
 Low cross sensitivity with PCN

26. 
Tetracyclines
Doxycycline (Vibramycin)
 Mechanism of action: inhibit protein synthesis by
preventing aminoacyl transfer RNA from
entering the acceptor sites on the ribosome
 Dose: 100mg qd-bid x 7-14 days
 Contraindications:
 Food
 pregnancy
 Adverse events: GI
 Drug interactions: anti-epileptics
 Pregnancy category D

27. 
Tetracyclines
 Doxycycline
 Bacteriostatic
 Spectrum:
 Broad, Gram +, -, anaerobes, aerobes, and spirochetes
 Resistance:
 Widespread, cross resistance
 PHOTO SENSITIVITY!!!

28. July 1997

29. 
 Antibiotic prophylaxis is NOT recommended for
dental patients with plates, pins, or screws, nor is it
routinely recommended for MOST dental patients
with TOTAL JOINT REPLACEMENTS.
AAOS Statement

30. 
AAOS
recommendations
 Prophylaxis recommended
 Total joint replacement within the last two years AND:
 Compromised immune system OR
 Type 1 DM OR
 Previous prosthetic joint infections OR
 Malnourishment OR
 Hemophilia

31. 
AAOS recommendations
 Prophylaxis antibiotic recommendations
 Same as AHA OR
 No specific regimen recommended
 Keflex is often the first drug of choice

32. 
Legal Considerations
 The dentist may not be aware of the patient’s medical
condition.
 Physician may not be aware of the advisory
statements or of the dental procedure to be performed.
 Vicarious Liability: “The devil made me do it”
 “I forgot to take my antibiotic.”
 Documentation.

33. 
Legal Considerations
 I forgot my antibiotics!
 Animal studies have shown antibiotics are effective
up to 2 hours after the procedure.
 Differentiate between prophylaxis vs. treatment of
an early infection.
 Take into consideration patient’s risk factors.
 Legal twists.

34. 
In Summary….

35. 
Principles of Antibiotic
Therapy
 Therapeutic effectiveness
 Clinical indications
 Pharmcodynamics, pharmacokinetics
 Age and extent of infection

36. 
Patient factors
 Age, allergies, compliance, pregnancy risk
 Patient function
 Renal, hepatic, immunosuppresion, route applicability
 Cost
 Brand name, length of course, alternatives?

37. Dental Infection
Acute—Rapid growth
< 3 days
Chronic > 3 days
Pen VK 500mg q6h or
Amox 500mg q8h or
Cephalosporin
Allergic to PCN
Clindamycin 300mg q8h or
Cephalosporin (check allergic Rxn) or
Azith or Clarithromycin
Think Anaerobes
Add Metronidazole 250-500mg
To PCN, Amox, or Ceph
Clindamycin 300mg q8h