Antibiotics used in dentistry Terminologies History Classification of antibiotics Principles of antibiotics use Commonly used antibiotics Drug interaction Drug combination Antibiotic resistance Summary

1. Antibiotics used
in Dentistry
Resource Faculties
Dr. Jyotsna Rimal
Dr. Iccha Kumar Maharjan
Dr. Susma Pandey
Dr. Pragya Regmee
Presented by :
Sushant Pandey
653
Department of Oral Medicine and Radiology

2. Contents :
• Terminologies
• History
• Classification of antibiotics
• Principles of antibiotics use
• Commonly used antibiotics
• Drug interaction
• Drug combination
• Antibiotic resistance
• Summary

3. Antibiotics: Substances produced by microorganisms which
selectively suppress the growth of or kill other
microorganisms.
Antimicrobial agent: Includes synthetic as well as naturally
obtained drugs that attenuate microorganism.

4. History
Ehrlich’s Magic Bullets
Gerhard Domagk - Prontosil

5. v
Fleming
Selman Waksman

6. Classification
On the basis of chemical structure:
 B-lactams– Penicillins, cephalosporins, monobactams,
carbapenam
 Tetracycline-- Doxycycline, Oxytetracycline
 Aminoglycosides -- Gentamicin , Neomycin, streptomycin
 Macrolides -- Clarithromycin, Erythromycin,
Azithromycin
 Quinolones -- Ciprofloxacin , Norfloxacin
 Sulfonamides – Sulfadiazine
 Lincosamides – Clindamycin, Lincomycin
 Glycopoetides – Vancomycin
 Nitroimidazoles -- Metronidazole

7. On the basis of spectrum of activity:
- Narrow spectrum : Penicillin G, Streptomycin,
Erythromycin
- Broad spectrum : Tetracycline, Chloramphenicol
On the basis of type of action:
- Bacteriostatic: Macrolides, Tetracycline, Sulfonamides,
Chloramphenicol, Clindamycin
- Bactericidal: Penicillin, Cephalosporin, Fluoroquinolones,
Metronidazole, Aminoglycoside

8. Acting on cell
membrane
polypeptides
bacitracin
Daptomycin

9. Principles of antibiotics use
Identification of the infecting organism
Empiric therapy prior to identification of the organism
Determining antimicrobial susceptibility of infective organisms
Bacteriostatic versus bactericidal drugs
Minimum inhibitory concentration
Minimum bactericidal concentration
Patient factors
Age
Immune system
Renal dysfunction
Hepatic dysfunction
Pregnancy and lactation
Cost of therapy

10. Indicated clinical conditions for antimicrobial therapy
Pyrexia within last 24 hours – indicates a systemic
response to the infection
Systemic symptoms like malaise, fatigue, weakness,
dizziness, rapid respiration and local tender
lymphadenopathy – indicate an impending sepsis
Trismus – indicates spread to perimandibular spaces and
can extend to secondary spaces that can be potentially
dangerous.

11. As a prophylaxis in patients with systemic conditions like
rheumatic heart disease, endocarditis, heart / orthopaedic
prosthesis.
In patients with any kind of immunocompromise – AIDS,
cancer, autoimmune diseases, corticosteroid therapy,
patients with immune compromised diseases like cyclic
neutropenia, pancytopenia, uncontrolled diabetes to name
a few common ones.

14. Special Circumstances
What to do if prophylaxis could not be given
before procedure ?
Is prophylaxis necessary if the patients is already
receiving an antibiotic that is also recommended for
prophylaxis ?

16. Beta-Lactam Antibiotics
Includes Penicillin, Cephalosporin, Monobactam, Carbapenem
MOA :
Inhibits cell wall formation by inhibiting transpeptidase

18. Penicillin
Types:
• Natural penicillin : Penicillin G and Penicillin V ---
grampositive and gram-negative cocci, gram-positive bacilli
• Anti-staphylococcal penicillins : Methicillin, nafcillin, oxacillin,
dicloxacillin
(penicillinase resistant penicillin)
• Extended-spectrum penicillins : Ampicillin, Amoxycillin ---
additional action against gram negative bacilli
• Antipseudomonal penicillins: Piperacillin, Ticarcillin

19. Natural Penicillins
They are obtained from the fungus Penicillium chrysogenum.
Penicillin G (Benzyl Penicillin)
Active against a number of gram positive and gram negative
cocci and gram positive bacilli.
Poor oral absorption as it is readily destroyed by gastric
acids.
Penicillin V (Phenoxymethyl penicillin)
Similar to Penicillin G in action but it is resistant to gastric
acids and can be taken orally.
They are ineffective against Penicillinase producing
bacteria.

20. Penicillinase resistant penicillin (Anti-staphylococcal penicillins )
Methicillin, nafcillin, oxacillin, dicloxacillin
Extended-spectrum penicillins : Ampicillin, Amoxycillin
Antibacterial spectrum is similar to penicillin G but they have
an additional action against gram negative bacilli.

21. Beta-lactamase inhibitors:
• Clavulanic acid + amoxicillin [Clavum, Mega-CV]
• Clavulanic acid + ticarcillin
• Sulbactam + ampicillin
• Tazobactam + piperacillin
Adverse reactions :
Elimination = by kidney
Jarisch Herxheimer reaction ?

22. Dose :
Amoxicillin [Amoxil, Ranoxyl]
Adult : 250-500 mg every 8 hour
Child 125-250 mg every 8 hour
Ampicillin [Ampilin, Zycilin]
Adult : 250-500 mg every 6 hour
Child : 50-100 mg/kg daily
Cloxacillin [Klox]
Adult : 250-500 mg every 4 hour
Child : 50-100 mg/kg daily
Amoxicillin is the most commonly used to treat odontogenic
infections followed by amoxicillin + clavulanic acid
Amoxycillin is available as : capsules, tablets, chewable
tablets, oral suspension

23. MRSA (Methicillin-resistant Staphylococcus aureus)
Staphylococcus aureus that have become resistant to
antibiotics that once destroyed it like methicillin, amoxicillin,
penicillin, oxacillin, and many other common antibiotics. They
have acquired penicillin binding protein which has low affinity
for β-lactam antibiotics.
About 2% Staphylococcal infections are caused by MRSA
Treated by : Vancomycin, Linezolid

24. Cephalosporins
First generation – action similar to penicillin G
Second generation – greater action against gram negative organism
Third generation -- enhanced activity against gram-negative bacilli
Fourth generation – wide antibacterial spectrum
GENERATION: PARENTERAL ORAL
FIRST GENERATION •CEFAZOLIN •CEPHALEXIN
•CEPHADROXIL
SECOND GENERATION •CEFUROXIME
•CEFOXITIN
•CEFACLOR
•CEFUROXIME AXETIL
•CEFPROZIL
THIRD GENERATION •CEFOTAXIME
•CEFTIZOXIME
•CEFTRIAXONE
•CEFTAZIDIME
•CEFOPERAZONE
•CEFEXIME
•CEFPODOXIME PROXETIL
•CEFDINIR
•CEFTIBUTEN
•CEFTAMET PIVOXIL
FOURTH GENERATION CEFEPIME
CEFPIROME

25. Adverse reactions :
Similar to Penicillin
Patients who have had an anaphylactic response,
Stevens-Johnson syndrome to penicillins should not
receive cephalosporins
The cross-reactivity between penicillin and
cephalosporins is around 3% to 5%
Elimination – by kidney but ceftriaxone is excreted through
the bile into the feces and, should be employed in patients
with renal insufficiency.

26. Tetracyclines
Doxycycline, Minocycline, Demeclocycline
Mechanism of action:
Inhibits protein synthesis by binding to 30s ribosomes
Uses
• Localized aggressive periodontitis (inhibits the growth of
Actinobacillus actinomycetemcomitans)
• Refractory periodontitis
• Actinomycosis
• Juvenile periodontitis
• Chronic periodontal disease

27. Adverse reactions
Why is tetracycline prescribed for periodontal diseases?
• They are effective in treating periodontal diseases because
their concentration in the gingival crevice is 2-10 times that
in serum
• They inhibit synthesis and release of collagenase from
human polymorphonuclear leukocytes and inhibit tissue
destruction and may aid bone regeneration.

28. Elimination = by kidney
In renally compromised patients, doxycycline is preferred, as it is
primarily eliminated via the bile into the feces.
The tetracyclines should not be used in pregnant or
breast-feeding women or in children less than 8 years of
age. May cause discoloration and hypoplasia of teeth.
Do not take tetracyclines with antacids, iron, dairy
products.
Dose : [Doxy, Emdox]
Fanconi syndrome – a disorder with clinical features of
polyuria, polydipsia and dehydration
100-200 mg once daily

29.  20 mg of Doxycycline Hyclate is used in host
modulation therapy.
 Used as an adjunct to SRP in treatment of chronic
periodontitis.
 Taken twice daily for 3-9 months.
 Suppress the activity of Collagenase.
 No antibacterial activity.
Doxycycline as Host modulating agent

30. Doxycycline gel (10%):
Applied in periodontal pocket in cases of chronic
periodontits

31. Macrolides
Azithromycin Clarithromycin Erythromycin
Telithromycin
MOA : The macrolides bind irreversibly to a site on the 50S
subunit of the bacterial ribosome, thus inhibiting translocation
steps of protein synthesis.
Alternative to penicillin in individuals with an allergy to β-lactam
antibiotics in treatment of acute oro-facial infection.
Erythromycin Dose : 250-500 mg orally every 6 hours

32. Adverse reactions
Should be used cautiously in patients with hepatic
dysfunction.
Interference with the metabolism of drugs, such as
theophylline, statins, antiepileptics, digoxin

33. LINCOSAMIDE
CLINDAMYCIN
MOA : similar to macrolides
Better bone penetration due to relatively small molecular size. So
used in treatment of Osteomyelitis.
Most common adverse effect is diarrhea, due to
pseudomembranous colitis caused by overgrowth of C. difficile.
significant activity against many gram-positive and gram negative
anaerobic and aerobic microorganisms, including Bacteroides,
Prevotella, Porphyromonas, Veillonella,
Dose : 600mg IV/PO

34. Fluoroquinolones
Inhibits bacterial DNA gyrase which results in relaxation of
supercoiled DNA, promoting DNA strand breakage.
1st Generation : Nalidixic acid
2nd Generation: Norfloxacin, Ciprofloxacin
3rd Generation: Levofloxacin
4th Generation: Moxifloxacin
effective against gram-negative organisms

35. ADR : Phototoxicity, Diarrhea, Nausea, Headache,
Tendon rupture
They are not indicated for any acute orofacial infections unless
dictated by culture and sensitivity tests. Drugs with better
antimicrobial spectra are readily available.
So they should be avoided in athletes and in old patients.
Prescribed in dentistry if a patient is allergic to penicillin and/or
has substantial gastrointestinal upset with erythromycin and
clindamycin.

36. Metronidazole
MOA: Nitro group reacts with bacterial DNA, causing inhibition of
DNA replication, fragmentation of existing DNA
Effective against Gram-negative anaerobes such as Prevotella
intermedia, Porphyomonas gingivalis , Bacteroides ,
Fusobacterium
Used in :
-Necrotizing ulcerative gingivitis
-Aggressive periodontitis
-Abscesses
-Orofacial infection along with Penicillins
Developed as antiprotozoal drug

37. Ingestion of alcohol when taking metronidazole could
cause Disulfiram like reaction i.e hallucinations and
confusion, abdominal cramps, nausea, facial flushing
and headache can occur.
Also avoid alcohol containing mouth rinses.
Decreases the metabolism of Warfarin resulting in
bleeding
ADR :
Dose: [Metron, Flagyl]
200-400 mg 8 hourly

38. Drug interactions
ß-lactams :
Tetracyclines and other bacteriostatic antibiotics = effectiveness is
decreased
Allopurinol = increase incidence of ampicillin allergy
Tetracyclines:
Antacids and dairy products = decreases absorption
Metronidazole:
Ethanol = severe disulfiram like reaction
Lithium = decreases its excretion
Carbamazepine = increases blood level
Cephalosporins and macrolides:
Warfarin = increased anticoagulant effect

39. Combination of antimicrobial drugs
To achieve synergism
To broaden the spectrum of antimicrobial action
To reduce severity or incidence of adverse effects
To prevent emergence of resistance

40. Commonly used combinations
Ampicillin (250mg) + Cloxacillin (250mg) [Megapen, Ampikem]
Amoxicillin (500mg) + Clavulanic Acid (125mg) [Clavam, mega-
cv]

41. Quadrajel dental gel: Lidocaine hydrochloride 2 % w/w +
Metronidazole benzoate 1 % w/w + Chlorhexidine gluconate 1
% w/w
Delta gel: Metronidazole + Lidocaine + Chlorhexidine

42. Disadvantages of combination :
1.Increased incidence and variety of adverse effects
• Vancomycin + gentamicin  exaggerated kidney
failure
2.Increases the chance of superinfections
3.Inadequate dose of non-synergistic drugs  emergence
of resistance
4.Higher cost of therapy

43. Topical antibiotics : Chlorhexidine digluconate
MOA : has antibacterial and antiplaque action.
At low concentration increases the permeability of cell membrane
causing leakage of intracellular components including potassium. At
high concentration, chlorhexidine causes precipitation of bacterial
cytoplasm and cell death.
Effective against : Bacteria, Some fungi (candida), some viruses (HIV,
HBV)
Shows Substantivity i.e gets adsorbed to tooth surfaces and shows a
persistent antibacterial action lasting in excess of 12 hours
Available as : Mouthrinse (0.2%, 0.12% )
Gels [Hexi gel chlorhexidine gluconate 1 %]
Spray 0.1 %

44. Adverse effects :
Enhanced supragingival calculus formation

45. Uses :
1. As an adjunct to oral hygiene and professional
prophylaxis
2. Post oral surgery including periodontal surgery or root
planning
3. Medically compromised individuals predisposed to oral
infections
4. Recurrent oral ulceration
5. Denture stomatitis
6. Oral malodor

46. Enzymatic inactivation
Modification/protection of the target site
Limited access of antibiotic (altered cell membrane
permeability)
Active drug efflux
Use of alternative growth requirements
Antibiotic resistance

48. Summary

50. Reference : A review of use of antibiotics in dentistry and recommendations for rational antibiotic usage by
dentists, Dr. Akilesh Ramasamy, THE INTERNATIONAL ARABIC JOURNAL OF ANTIMICROBIAL AGENTS

51. MCQs:
Which antibiotic acts by interfering with DNA
function in the bacteria ?
A. Doxycycline
B. Ciprofloxacin
C. Erythromycin
D. Amoxycillin

52. Cloxacillin is indicated in infections caused by
the following organism(s):
A. Staphylococci
B. Streptococci
C. Gonococci
D. All of the above

53. An 8-year-old child presented with brownish
discoloured and deformed anterior teeth. History of
having received an antibiotic about 4 years earlier
was obtained. Which antibiotic could be responsible
for the condition:
A. Chloramphenicol
B. Tetracycline
C. Erythromycin
D. Gentamicin

54. Antimicrobial drug combinations are aimed at
achieving the following except:
A. Faster and more complete elimination of
the infecting organism
B. Treat infection when nature and sensitivity
of the infecting organism is not definite
C. Prevent emergence of resistant strains
D. Prevent superinfection

55. Prophylactic dose of Amoxycillin for adults is :
A.1 gm 1 hour before procedure
B.1 gm 2 hours before procedure
C. 2 gm 1 hour before procedure
D. 2 gm 2 hours before procedure

56. References :
1.Lippincott Illustrated Reviews, Pharmacology
2.Essentials of medical pharmacology, KD Tripathi
3.Pharmacology and therapeutics for dentists, John
A. Yeigla
4.Carranza’s clinical periodontology

57. Thanks!
Any questions?