Principles of antibiotics ih

PRINCIPLES OF
ANTIBIOTIC
THERAPY
Presented by – Dr . Itrat Hussain
Moderate by – Dr . Vijay Mishra

CONTENTS
 HISTORY & INTRODUCTION
 CLASSIFICATION
 PRINCIPLES OF ANTIBIOTIC
THERAPY
 ANTIBIOTIC SIDE EFFEECTS
 ANTIBIOTIC RESISTANCE
 ANTIBIOTIC FAILURES
 MISUSE OF ANTIBIOTICS
 ANTIBIOTIC PROPHYLAXIS
 INDIVIDUAL DRUGS
- Chemistry
- Mechanisms of action
- Spectrum
- Sensitive organisms
- Resistance
- Adverse effects
- Uses
 SPECIAL CONDITIONS-
Pregnancy
- Chronic renal failure
- Hepatic failure
- Diabetes mellitus
- Head and neck infections in
immunocompromised state
 CONCLUSION
 REFERENCES

INTRODUCTION
ANTIBIOTIC TERMINOLOGY
DEFINITION: SUBSTANCES DERIVED FROM MICROORGANISMS
WHICH SUPPRESS THE GROWTH / KILL THE
MICROORGANISMS AT A VERY LOW CONCENTRATION
OR
A CHEMICAL SUBSTANCE PRODUCED BY MICROORGANISMS
HAVING THE PROPERTY OF INHIBITING THE GROWTH OF OR
DESTROYING OTHER MICROORGANISMS IN HIGH DILUTION
{K.D TRIPATHI}
CHEMOTHERAPY :TREATMENT OF SYSTEMIC INFECTIONS WITH
SPECIFIC DRUGS THAT SELECTIVELY SUPPRESS THE
INFECTING MICROORGANISM WITHOUT SIGNIFICANTLY
AFFECTING THE HOST.

HISTORY
 (A) The period of emperical use South American
Indians used the bark of the cinchona tree to extract
quinine to control malaria and mercury was known to
cure syphilis in the late 1400's,‘mouldy curd’ by Chinese
on boils, mercury by Paracelsus (16th century) for
syphilis, Cinchona bark (17th century) for fevers.
 (B) Ehrlich’s phase of dyes & organometallic
compounds (1890-1935): methylene blue, tryptan red,
etc.
He coined the term ‘Chemotherapy’
5

HISTORY
 (C) The Modern Era of chemotherapy was
ushered in by Domagk in 1935 by demonstrating
the therapeutic effect of prontosil , a sulfonamide
dye in pyogenic infection.
Other pioneers in the field of antibiotics were
Louis Pasteur, Alexander Fleming, Chain Florey ,
Waksman.
All received Nobel prizes for their discoveries.
6

 CLASSIFICATION OF ANTIBIOTICS

BASED ON TYPE OF ORGANISMS
AGAINST WHICH PRIMARILY ACTIVE
:
 Antibacterial
Penicillins, Aminoglycosides, erythromycin etc
 Antifungal
Griseofulvin, amphotericin B, ketoconazole etc
 Antiviral
Idoxuridine, Acyclovir, Amantadine, Zidovudine etc
 Antiprotozoal
Chloroquine, pyrimethamine, metronidazole etc
 Antihelminthic
Mebendazole, nicosamide, diethyl carbamazine etc

BASED ON MECHANISM OF ACTION:
1. Inhibit cell wall synthesis: penicillins
cephalosporins
cyclosporins
2. Leakage from cell membrane:
polypeptides-polymixin, bacitracin.
polyenes- amphotericin B,nystatin
3. Inhibits protein synthesis: tetracyclines, chloramphenicol,
erythromycin, clindamycin.
4. Causes misreading of m.RNA: aminoglycosides
5. Inhibits DNA gyrase: fluoroquinolones
6. Interfere with DNA function : rifampin,
metronidazole.
7. Interfere with DNA synthesis: acyclovir,
idoxuridine.

CHEMICAL STRUCTURE
Sulfonamides and related drugs :
○ Sulfadiazine, Sulfamethoxazole, Sulfadoxin
Diaminopyrimidines
○ Trimethoprim, pyrithamine
Quinolones
○ Nalidixic acid, Norfloxacin, Ciprofloxacin etc
 - lactam antibiotics
○ Penicillins, cephalosporins, monobactams, carbapenems
Tetracyclines
○ Oxytetracycline, Doxycycline etc
Nitrobenenzene Derivative
○ Chloramphenicol
Aminoglycosides
○ Streptomycin ,Gentamycin, Neomycin etc

 Macrolide antibiotics
 Erythromycin, Roxithromycin, Azithromycin etc
 Polypeptide antibiotics
 Polymyxin – B, colistin, Bacitracin, Tyrothricin etc
 Glycopeptides
 Vancomycin, Teicoplamin
 Oxazolidinase
 Linezolid
 Nitrofuran derivatives
 Nitrofurantoin, Furazolidine
 Nitroimidazoles
 Metronidazole, Tinidazole
 Polyene antibiotics
 Nystatin, Amphotericin – B, Hamycin
 Azole derivatives
 Miconazole, clotrimazole, ketoconazole, fluconazole

SPECTRUM OF ACTIVITY
 Narrow spectrum
Penicillin G, streptomycin and
erythromycin.
 Broad spectrum
Tetracyclines,
chloramphenicol.
 Extended spectrum
Semi synthetic Penicillins, new
cephalosporins, aminoglycoside.

CLASSIFICATION
(v) TYPE OF ACTION:
14
Primarily Bacteriostatic Primarily
Bactericidal
Sulfonamides
Tetracyclines
Chloramphenicol
Erythromycin
Ethambutol
Penicillins ,
Cephalosporins,
Aminoglycosides,
Vancomycin,
Ciprofloxacin, Isoniazid ,
Rifampin, Cotrimoxazole,

SOURCE
 Fungi
 Penicillin, Cephalosporin, Griseofulvin.
 Bacteria
 Polymyxin B, Colistin, Bacitracin, Tyrothricin
Aztreonam.
 Actinomycetes
 Aminoglycosides, Tetracyclines,
Chloramphenicol, Macrolides, Polyenes.

PRINCIPLES OF ANTIBIOTIC THERAPY
PRINCIPLE 1: TO DETERMINE THE SEVERITY
OF INFECTION
PRINCIPLE 2: TO EVALUATE STATE OF
PATIENT’S HOST DEFENSE MECHANISMS
PRINCIPLE 3:TO DETERMINE WHETHER
PATIENT SHOULD BE TREATED BY
GENERAL DENTIST OR SPECIALIST
PRINCIPLE 4:TO TREAT INFECTION
SURGICALLY

PRINCIPLE 5 :TO SUPPORT THE PATIENT
MEDICALLY
PRINCIPLE 6 : CHOOSE AND PRESCRIBE
APPROPRIATE ANTIBIOTIC
PRINCIPLE 7 : PROPER ANTIBIOTIC
ADMINISTRATION
PRINCIPLE 8 :MONITORING THE PATIENT

DETERMINATION OF THE SEVERITY OF INFECTIO
 Complete history-Time of onset
-Duration of infection
-Rapidity of progress
 Eliciting patient’s symptom
 Physical examination

DIFFERENCES BETWEEN CELLULITIS
AND ABSCESS
CHARACTERISTIC CELLULITIS ABSCESS
Duration Acute Chronic
Pain Severe and generalized Localized
Size Large Small
Localization Diffuse borders Well circumscribed
Palpation Doughy to indurated Fluctuant
Presence of pus No Yes
Bacteria Aerobic Anaerobic

2)TO EVALUATE STATE OF
PATIENT’S HOST DEFENSE
MECHANISMS
 Uncontrolled metabolic diseases
e.g. – uremia, alcoholism, malnutrition,
severe diabetes (decreased function of leucocytes,
decreased chemotaxis, decreased phagocytosis,
decreased bacterial killing)
 2- Immuno Suppressing diseases
Interfere with host defense mechanism
e.g.- leukemias, lymphomas, malignant tumours
 3- Immuno Suppressing drugs
e.g.- cancer chemotherapeutic drugs
Immunosuppressive agents

3)TO DETERMINE WHETHER PATIENT SHOULD
BE TREATED BY GENERAL DENTIST OR
SPECIALIST
 Criteria for referral to a specialist :
1.Rapid progressive infection
2.Difficulty in breathing
3.Difficulty in swallowing
4.Fascial space involvement
5.Elevated temperature(>101* F)
6.Severe jaw trismus(<10mm)
7.Toxic appearance

4)TO TREAT INFECTION SURGICALLY
GOALS :
1.To remove the cause of infection
2.To provide drainage of accumulated
pus and necrotic debris
MODES :
1.Endodontic treatment
2.Extraction
3.Incision and drainage
+extraction endodontic treatment
Drainage of pus
Reduction in tissue tension
Improved local blood supply and increased
delivery of host defenses

5)TO SUPPORT THE PATIENT MEDICALLY
Odontogenic infection
Pain and swelling
No adequate fluid and nutritional
intake
Depressed host defenses
Adequate analgesics and fluid intake

6)CHOOSE AND PRESCRIBE
PRINCIPLES FOR CHOOSING
Identification of causative organism
 Scientifically determined either in the
laboratory, where the organism can be
isolated from pus, blood or tissue
or
 Empirically based upon the knowledge of
the pathogens and clinical presentation of
specific infection.

PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(I) IDENTIFICATION OF THE
CAUSATIVE ORGANISM:-
 Scientifically - laboratory
 Emperically – knowledge of
the pathogenesis & clinical
presentation.
 Initial emperical therapy
instituted with a fair degree of reliability.
25

ANTIBIOTIC
 Typical odontogenic infection is caused by a
mixture of aerobic & anaerobic bacteria (70%)
 Aerobic bacteria – 5% (gm positive cocci)
 Pure anaerobic bacteria – 25% (gm positive cocci
– 30% & gm negative rods – 50%)
 All are sensitive to penicillin & penicillin like drugs,
but Fusobacterium frequently resistant to
erythromycin (apprx. 50%)
26

TYPE OF INFECTION MICROORGANISMS
ODONTOGENIC
CELLULITES/ABSC
ESS
STREPTOCOCCUS MILLERI GROUP
PEPTOSTREPTOCOCCI
PREVOTELLA AND PORPHYROMONAS
FUSOBACTERIA
RHINOSINUSITIS ACUTE STREPTOCOCCUS PNEUMONIAE
HAEMOPHILUS INFLUENZAE
HEAD AND NECK ANAEROBES
(PEPTOSTREPTOCOCCI, PREVOTELLA
PORPHYROMONAS, FUSOBACTERIA)
GROUP A BETA-HEMOLYTIC STREPTOCOCCI
STAPHYLOCOCCUS AUREUS
MORAHELLA CATARRHALIS
VIRUSES
CHRONIC HEAD AND NECK ANAEROBES
FUNGAL ASPERGILLUS
RHIZOPUS SP. (MUCOR)
NOSOCOMIAL
(ESPECIALLY IF
INTUBATED)
ENTEROBACTERIACEAE (ESPECIALLY
PSEUDOMONAS, ACINETOBACTER,
ESCHERICHIA COLI)
S. AUREUS
YEASTS (CANDIDA SPECIES)
Major pathogens of head and neck infectionsOral and
Maxillofacial Surgery Clinics of NA :2003

ANTIBIOTIC
Pathobiology of mixed odontogenic infection:-
28
Entry of organisms
(aerobic)
Effects
underlying
tissues
Cellulitis develops Condtion resolves on
treatment
Hypoxic acidotic condition
Tissue destruction and
abscess formation
(anaerobic)
Production of
enzymes and
toxins

ANTIBIOTIC
CULTURES SHOULD BE PERFORMED:-
1. Pt. with an infection has compromised host
defenses
2. Received appropriate treatment for 3 days without
improvement
3. Postoperative wound infection
4. Recurrent infection
5. Actinomycosis is suspected, or
6. Osteomyelitis is present
29

ANTIBIOTIC
(II) DETERMINATION OF ANTIBIOTIC
SENSITIVITY:-
 Not responded to initial antibiotic therapy or a
postoperative wound infection – causative agent
identified & the antibiotic sensitivity determined.
30

DISK DIFFUSION METHOD
RATIONALE :
 Antibiotics diffuse into the agar and inhibit the
growth of sensitive bacteria in a semicircular zone
around the disc.
 When the resistance to a given agent is present,
the zone radius will be reduced or these will be no
zone at all.

Advantages :
 Simple to perform
 Inexpensive
 Provides data within 18 to 24 hours
Disadvantages :
 It is only semi quantitative and is not useful
for many flow growing or fastidious
organisms.
 It has not been adequately standardized for
anaerobic bacteria.

ANTIBIOTIC
 The result of these studies provide the information needed
to prescribe the most appropriate antibiotic.
 Penicillin is excellent for treatment of streptococcus infection
& is good to excellent for the major anaerobes of
odontogenic infections.
 Erythromycin - Streptococcus, Peptostreptococcus & Prevotella
but is ineffective against Fusobacterium.
33

ANTIBIOTIC
 Clindamycin – streptococcus & major anaerobic
groups.
 Cephalexin – moderately active against streptococcus
& is good to excellent against anaerobes.
 Metronidazole – no activity against streptococcus but
has excellent activity against anaerobes.
34

ANTIBIOTIC
(III) USE OF A SPECIFIC, NARROW
SPECTRUM ANTIBIOTIC:-
Advantages -
 less chances of developing resistant organisms.
E.g. streptococcus sensitive to penicillin , cephalosporin
and tetracycline.
 Minimizes the risk of super infections.
E.g. moniliasis and gram negative pneumonias
35

ANTIBIOTIC
(IV) USE OF THE LEAST TOXIC
ANTIBIOTIC:-
 Equally effective but less toxic drugs have to be
used.
E.g. bacteria causing odontogenic infection
susceptible to both penicillin and chloramphenicol.
 More toxicity present with the latter drug.
36

ANTIBIOTIC
(V) PATIENT DRUG HISTORY:-
 Previous allergic reactions
 Previous toxic reactions
 Allergy rate to penicillin - 5 %
 Cross sensitivity Penicillins and cephalosporins.
 Toxic reactions - identify the drug and precise
reaction
 Likely to happen again.
37

ANTIBIOTIC
(Pharmacologic factors in antibiotic selection)
(VI) USE OF A BACTERICIDAL RATHER THAN A
BACTERIOSTATIC DRUG:-
Advantages:
1. Less reliance on the host resistance
2. killing of the bacteria by the antibiotic itself
3. Faster results
4. Greater flexibility with dosage intervals.
Used especially when the host defenses are low.
38

ANTIBIOTIC
(VII) USE OF THE ANTIBIOTIC WITH A
PROVEN H/O SUCCESS:-
Critical observation of the clinical effectiveness over
a prolonged period -----assessment of
 Frequency of treatment success and failures
Frequency of adverse reactions
Frequency of side effects
Standards for use
39

ANTIBIOTIC
(VIII) COST OF THE ANTIBIOTIC:-
 Difficult to place a price tag on health.
 In some situations, more expensive antibiotic is
the drug of choice.
 In other situations, there may be a substantial
difference in price for drugs of equal efficacy.
 Surgeon should consider the cost of the antibiotic
prescribed.
40

ANTIBIOTIC
(IX) ENCOURAGE PATIENT COMPLIANCE:-
 Dosage interval that encourages compliance
OD 80%
BID 69%
TID 59%
QID 35%
 Non-compliant start feeling better
3-5 days 50%
>7 days 20%
 Antibiotic that would have the highest compliance
would be the drug given OD for 4 or 5 days.
41

Indications for use of antibiotics
 Rapidly progressive swelling
 Diffuse swelling
 Compromised host defenses
 Involvement of facial spaces
 Severe pericoronitis
 Osteomyelitis

Use of antibiotics is not
necessary
 Chronic well localized abscess
 Minor vestibular abscess
 Dry socket
 Mild pericoronitis

INDICATIONS OF EMPIRICAL ANTIBIOTIC
THERAPY :
 The site and feature of the infection have
been well defined.
 The circumstances leading to the infection
are well known.
 Organisms that most commonly cause such
infections.

EMPIRIC ANTIBIOTIC TREATMENT
Early infection (first 3 days of symptoms and mildly
immunocompromised)
 Penicillin
 Clindamycin
 Cephalexin
Late infection (After 3 days of symptoms or moderately to
severely immunocompomised)
 Clindamycin
 Revicillin and metranidazole.
 Ampicillin and sulbactam.
 Cephalosporin (first or second generation).
-Mild, moderate and severe compromised based on CD4 /
viral loads, glycemic control, and the degree of alcoholic
related disease.

7)PROPER ANTIBIOTIC ADMINISTRATION
 Principles of antibiotic administration
 Proper dose.
 Proper time interval.
 Proper route of administration.
 Combination antibiotic therapy.

PRINCIPLES OF ANTIBIOTIC DOSING
 GOAL :
1.To aid the body’s defenses to clear
the tissues of microbial pathogen by
achieving antibiotic levels in the infected
area to or greater than the MIC

MINIMAL INHIBITORY CONCENTRATION
 Is the lowest antibiotic concentration that prevents
growth of microorganism after an incubation period
of 18 – 24 hours incubation period with a standard
inoculum of 104 to 105 cfu/ml
MINIMAL BACTERICIDAL CONCENTRATION
 Is the lowest concentration of drug that causes the
complete destruction of the organisms or permits
survival of less than 0.1% of the inoculum

ANTIBIOTIC DOSING VARIABLES
 PHARMACOKINETIC FACTORS
Diffusion to the site of action
1.Tissue pH.
2.Lipid and water solubility
3.Plasma protein binding
 INOCULUM EFFECT- It is defined as a laboratory
phenomenon that results in significantly increased MIC
required of an antibiotic, when the number of
inoculated organisms increases. It generally occurs in
case of b-lactum antibiotics and b-lactamase producing
bacteria
(review of infectious diseases vol.2 number.3 may- june 1989)
 SURFACE AREA TO VOLUME RATIO

Lipophilic antibiotics
Tetracyclines,macrolides,fluoroquinolones
Pass better through tissue barriers
Effective against intracellular pathogens
Drug depot within macrophages

Hydrophilic antibiotics
Beta-lactams,vancomycin,aminoglycosides
Confined to ECF
Poor diffusion through capillaries

PLASMA PROTEIN BINDING
Limited plasma protein binding
Diffuse easily through capillary walls
and
other barriers

PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(I) PROPER DOSE:-
 Dose – 3 to 4 times the MIC
for e.g. penicillinase producing staphylococcus -
MIC 6 µg/ ml , plasma level - 18µg /ml
 Administration of doses above this level –
increases the likelihood of toxicity & is wasteful.
 Sub therapeutic levels - mask the infection
,recurrence.
53

DRUG DOSE CALCULATION
 BASED ON BODY SURFACE AREA
Individual dose = BSA[m2] x adult dose
1.7
 BASED ON BODY WEIGHT
Individual dose = BW[kg] x average
70 adult dose

IN PEDIATRICS
YOUNG’S FORMULA :
CHILD DOSE = Age x adult dose
Age + 12
DILLING’S FORMULA :
CHILD DOSE = Age x adult dose
20

 LOADING DOSE; This is a single or few
quickly repeated doses given in the
beginning to attain target concentration
capacity.
 MAINTAINANCE DOSE: This is the dose
repeated at specific interval after attainment
of target cycles per second

ANTIBIOTIC LOADING DOSES
 INDICATIONS :
1.The half-life of the antibiotic is
longer than 3-hours.
2. A delay of longer than 12-hours to
achieve therapeutic blood levels is
unacceptable.
Because most acute orofacial infections
begin and peak rapidly

DURATION OF ANTIBIOTIC DOSING
 The ideal antibiotic duration is the
shortest time that will prevent both
clinical and microbiological relapse.
Clinical improvement of the patient
Remission of infection.

MISCONCEPTIONS IN LONGER DURATION OF ANTIBIOTIC
 Prolonged antibiotic therapy destroys
resistant bacteria.
 Prolonged antibiotic therapy is necessary to
prevent rebound infections.
 The dosage and duration of therapy can be
extrapolated from one infection to another.
 The prescriber knows how longer the
infection will last.

(II) Proper time interval:-
 Established plasma t 1/2 – one half of the
absorbed dose is excreted.
 Usual dosage interval for therapeutic use of
antibiotics - Four times the half life.
E.g. cefazolin t 1/2 - 2 hours.
60

(III) Proper route of administration:-
In some antibiotics , only the parenteral route
produces necessary serum levels
For e.g. Penicillin V oral - 2 gm
Plasma level - 4 µG/ mL
Oral route - variable absorption.
Serious well established infection - parenteral route
61

(IV) Consistency in Route of Administration:-
After initial response , immediate discontinuation of
parenteral route - Recurrence
Maintenance of peak blood levels of antibiotic for an
adequate period is important – max. tissue
penetration & effective bactericidal action.
After the 5th day of parenteral administration, the
blood levels achievable with oral administration are
usually sufficient.
62

(V) Combination Antibiotic therapy:-
 Life threatening sepsis of unknown cause
 Increased bactericidal effect against a specific
micro organism is desired.
E.g. treatment of infections caused by enterococcus
 Prevention of rapid emergence of resistant
bacteria
E.g. tuberculosis
 Empiric treatment of certain odontogenic infections
E.g. Penicillin G & Metronidazole
63

ADVANTAGES vs DISADVANTAGES
 Broad antibacterial
spectrum
 Reduced dose for
each agent.
 Antibiotic synergism
 Decreased adverse
drug reactions
 Greater likelihood of
adverse reactions
 Antibiotic antagonism
 Increased financial
costs
 Greater microbial
resistance
 Resistance genes
 Increased risk of
superinfection

SYNERGISTIC ANTIBIOTIC COMBINATION
 Cell wall inhibitors and aminoglycosides
 Beta-lactams with beta-lactamase inhibitor
 Sulfonamides and trimethoprim

 Should be avoided when not specifically indicated.
 Usual result – broad spectrum exposure that leads
to depression of the normal host flora & inc
opportunity for resistant bacteria to emerge.
 For routine infections, the disadvantages of
combination therapy outweigh the advantages.
66

FACTORS INFLUENCING
 Minimal Inhibitory Concentration
 Post-antibiotic effects
 Microbial persistence and regrowth.
 Dosing and resistance
 Antibiotic loading dose
 Duration of antibiotic dosing
 Incision and Drainage
 Special conditions

RULE OF THUMB
 The concentration of the antibiotic in
the blood should exceed the MIC by
a factor of 2-8 times to offset the
tissue barriers that restrict access to
the infected site.

CONCENTRATION DEPENDENT
Vs
TIME DEPENDENT ANTIBIOTICS
CONCENTRATION
DEPENDENT
TIME DEPENDENT
ANTIBIOTICS
1. Aminoglycosides,
metronidazole,
fluroquinolones
2. Bactericidal activity
depends on the drug
concentration
1. Beta-lactams and
vancomycin
2. Long time of exposure of
the organisms
3. Better the bactericidal
concentration
4. Require organisms in the
process of cell division

POSTANTIBIOTIC EFFECTS
 Is the persistent supression of microbial
growth after short time exposure to an
antimicrobial agent.
 MECHANISM :
Is the time necessary to recover from
sublethal structural and metabolic alterations
that prevents resumption of bacterial
regrowth.

MICROBIAL PERSISTENCE AND REGROWTH.
 The subpopulation of organisms that is not
inhibited or killed during a given dose interval
which can then reestablish themselves and
continue growth.
 FACTORS DETERMINING :
1.Initial inoculum size
2.Bactericidal activity
3.Organism MIC
4.Post-antibiotic effects
5.Antibiotic pharmacokinetics
6.Doubling time of the organism.

8)MONITORING THE PATIENT
1)Response to treatment.
Reasons for treatment failure:
-Inadequate surgical treatment.
-Depressed host defences.
-Presence of foreign body.
-Antibiotic problems – Drugs not reaching infection.
Dose not adequate
Wrong bacterial
diagnosis.
Wrong antibiotic.
2)Development of adverse reactions:
3)Superinfection and recurrent infection:

ANTIBIOTIC SIDE EFFECTS
Side effects are unwanted but often unavoidable
pharmacodynamic effects that occur at therapeutic doses.
1) HAEMATOLOGIC EFFECTS
a) Leucopenia and thrombocytopenia: Beta lactams
sulfonamides(Cotrimazole)
b) Anaemia: Beta lactam- Autoimmune anaemia
Cotrimazole- Folate deficiency- Megaloblastic anaemia
Chloramphenicol- Aplastic anaemia.
c) Platelet dysfunction: Anti pseudomonal penicillins- Impaired
platelet aggregation.
d) Clinical bleeding: Trovafloxacin- Increases prothrombin time.

2) HYPERSENSITIVITY EFFECTS
Drug fever: 10-15% of unexplained fever in hospitalized patients.
Beta lactams, Sufonamides.
Drug rashes: Itching, urticaria, maculo popular rashes.
Beta lactams, sulfonamides.
Anaphylactic reactions: Beta lactams, rare in Sulfonamides.
Serum sickness: Develops 2 weeks after exposure- Beta lactams.
Photosensitivity reactions: Tetracycline, Sparfloxacin
Rare with Doxycyclin, minocycline
Drug induced Systemic Lupus Erythematosus(SLE):
Minocyclin, Isoniazide, Nitrofurantoin, Griseiofulvin.

3) NEUROLOGIC EFFECTS
a) Encephalopathy:
Trovafloxacin- Mental confusion
Clarithromycin
b) Seizures: Ciprofloxocin, Imipenem, Trovafloxacin.
c) Neuromuscular blockade: Aminoglycosides
d) Peripheral neuropathy: Isoniazide, Griseiofulvin
e) Muscular tremors and myalgias: Trovafloxacin
f) Ototoxicity: Aminoglycisides, Parenteral Erythromycin
g) Blindness: Ethambutol, Chloroquine.

4) PULMONARY EFFECTS
a) Acute pulmonary reactions: Rifampicin- Flu like illness.
Nitrofurantoin: Varying degrees of respiratory
Insufficiency, Pleural effusion.
b) Chronic pulmonary reaction: Nitrofurantoin-
Pulmonary fibrosis.
5) CARDIAC EFFECTS
a) Ventricular arrhythmias: Erythromycin
b) Hypotension: Trovafloxacin, Amphotericin-B

6) GASTROINTESTINAL EFFECTS
a)Nausea and vomiting
Clarithromycin,Ampicillin/Clavulanate,Azithromycin,
Doxicycline,Minocycline.
b) Non-clostridium difficile diarrhea:
Macrolides,Ampicillin, Trovafloxacin
c)Cl. Difficile diarrhoea
Beta lactums, Quinolones

7)HEPATIC SIDE EFFECTS
a) drug induced hepatitis
-Isoniazide- elevates serum transaminase, Trovafloxacin,Oxacillin
b) Cholestasis
-Erythromycin,Nitrofurantoin
c) Hepatic necrosis
-Ketoconazole or Trovafloxacin
8)NEPHROTOXIC SIDE EFFECTS
a) Nephrotoxicity
Aminoglycosides-Tubular toxicity.
Tetracyclines, Polymyxin –B
b) Interstitial nephritis
Beta lactamase therapy.

ANTIBIOTIC RESISTANCE
 The organisms continue to multiply even in the
presence of antibiotic.
 Resistance to an antimicrobial can arise
(1) Mutation in the gene that determines
sensitivity/resistance to the agent or
(2) Acquisition of extrachromosomal DNA
(plasmid) carrying a resistance gene.
(3) Bacteriophages.
(4) Mosaic genes
Mutation: random, undirected, heritable variation caused by an alteration
in the nucleotide sequence at some point of the DNA of the cell.

DEVELOPMENT OF DRUG RESISTANCE
 Refers to unresponsiveness of a microorganism to
an AMA
 Natural Resistance
 Acquired Resistance
80

DEVELOPMENT OF DRUG RESISTANCE
 Single step mutation
E.g. Enterococci to Streptomycin, E.coli &
Staphylococci to rifampin
 Multistep mutation
E.g. resistance to erythromycin,
tetracyclines & chloramphenicol by
many organisms.
81

ANTIBIOTIC RESISTANCE MECHANISMS
1.ENZYMATIC ANTIBIOTIC INACTIVATION
a.Beta-lactams - beta lactamases
b.Aminoglycosides - aminoglycosides
modifying enzymes
c.Chloramphenicol - acetyl transferases
2.MODIFICATION PROTECTION OF TARGET
SITE
a.Beta-lactams-altered PBPs
b.Fluoroquinolones:altered DNA gyrases
c.Rifampin:altered RNA polymerase
d.Sulfonamides: altered dihydrofolate
synthase

3.LIMITING ACCESS OF ANTIBIOTIC
Beta-lactams and fluoroquinolones
Altered outer membrane porins
4.ACTIVE ANTIBIOTIC EFFLUX
5.FAILURE TO ACTIVATE ANTIBIOTIC
Metronidazole - flavodoxin production

6.USE OF ALTERNATE GROWTH
REQUIREMENTS
7.OVERPRODUCTION OF TARGET SITES
a.Sulfonamides:overproduction of
PABA
b.Entericbacilli:overproduction of beta-
lactamases

ANTIBIOTIC FAILURES
Common reasons for antibiotic failure:
1.Failure to surgically eradicate - source of
infection
2.Too low - blood antibiotic concentration
3.Inability to penetrate the site of infection
4.Impaired host defenses
5.Patient failure to take the antibiotic

6.Inappropriate choice of antibiotic
7.Limited vascularity or blood flow
8.Decreased tissue ph or oxygen tension
9.Antibiotic resistance
10.Delay or incorrect diagnosis
11.Antibiotic antagonism

MISUSE OF ANTIBIOTICS
 1) Treatment of untreatable infections
 2) Therapy of fever of unknown origin
 3) Improper dosage
 4) Inappropriate reliance on
chemotherapy alone
 5) Lack of adequate bacteriological
information

PRINCIPLES OF PROPHYLACTIC
ANTIBIOTICS
It is the use of antibiotics before, during, or
after a diagnostic, therapeutic, or surgical
procedure to prevent infectious complications.
ADVANTAGES:
1.Prevention of infection.
2.Decrease patient morbidity and mortality.
3.Decrease hospital stay.
4.Decreased medical cost.
5.Decreased total antibiotic usage.
6.Decrease numbers of resistant bacteria – because
of short term course.

DISADVANTAGES
 No reduction of infection.
 Development of increased number of
resistant bacteria.
 Delay in onset of infection.
 Adverse effect on surgical technique

THE PRINCIPLES FOR PROPHYLACTIC
ANTIBIOTICS
 Increased risk of significant bacterial contamination and a
high incidence of infection.
 Organism must be known.
 Antibiotic susceptibility must be known.
 To be effective and to minimize adverse effects the
antibiotic must be in the tissue at the time of contamination
(operation) and it must be continued for not more than 4
hours after cessation of contamination.
 Four times the MIC of the causative organisms.
 Timing the antibiotic correctly.
 Shortest effective antibiotic exposure.

PRINCIPLE 1: PROCEDURE SHOULD HAVE A
SIGNIFICANT RISK OF INFECTION
1.Bacterial inoculum of sufficient size
2.Extensive and prolonged surgery
3.Insertion or presence of foreign body
4.Depressed host resistance

Type I. Clean wounds (no opening of mucosa in the oral cavity):
Confirmed infection rate of 1 to 4%. Antibiotic prophylaxis not
required.
Type II. Clean-contaminated wounds (opening of mucosa in the oral
cavity, insertion of dental implants or intervention on inflammatory
pathology):
Confirmed infection rate of 5 to 15%. These require antibiotic
prophylaxis with drugs covering Gram positive and anaerobic micro-
organisms.
Type III. Contaminated wounds (oncological pathology in which there is
simultaneous action on the oral cavity and the neck): Confirmed
infection rate of 16 to 25%. Antibiotic prophylaxis must be carried out
to cover Gram negative organisms whose coverage in clean and
cleancontaminated surgeries is disputed.
Type IV. Dirty and infected wounds. Confirmed infection rate of above
26%. These always need adequate antibiotic treatment.
CLASSIFICATION OF SURGICAL WOUNDS

PRINCIPLE 2: TO CHOOSE CORRECT
ANTIBIOTIC
1.Effective against the most likely organism
2.Narrow spectrum antibiotic
3.Least toxic antibiotic
4.Bactericidal antibiotic

PRINCIPLE 3: ANTIBIOTIC PLASMA
LEVEL MUST BE HIGH
 To ensure diffusion of antibiotic into all fluid
and tissue components
 USUAL RECOMENDED DOSE: Two times
the usual therapeutic dose

PRINCIPLE 4: TO TIME ANTIBIOTIC
ADMINISTRATION CORRECTLY
 Antibiotic must be administered before the
surgery begins
Prolonged surgery
Additional antibiotic is required
Intraoperative dose intervals should be one
half the usual therapeutic dose interval

PRINCIPLE 5: USE OF SHORTEST EFFECTIVE
ANTIBIOTIC EXPOSURE
 Continued antibiotic administration - no benefit once
the surgical procedure is complete
 Procedure lasts for Short procedure
more than three hours
2nd dose of antibiotic is Single preop dose is
required adequate

ANTIBIOTIC PROPHYLAXIS AGAINST
INFECTIVE ENDOCARDITIS
 GOALS :
1.To reduce the intensity of bacteremia.
2.Assist the host defenses in killing the
bacteria.
3.Decrease the bacterial adherence to the
damaged heart valves and vegetations.

* Except for the conditions listed above, antibiotic prophylaxis is no longer recommended for any other form of
CHD.
† Prophylaxis is reasonable because endothelialization of prosthetic material occurs within six months after the
procedure.
CARDIAC CONDITIONS ASSOCIATED WITH THE HIGHEST RISK OF ADVERSE
OUTCOME FROM ENDOCARDITIS FOR WHICH PROPHYLAXIS WITH DENTAL
PROCEDURES IS REASONABLE
 Prosthetic cardiac valve or prosthetic material used for cardiac valve repair
 Previous infective endocarditis
 Congenital heart disease (CHD)*
 Unrepaired cyanotic CHD, including palliative shunts and conduits
 Completely repaired congenital heart defect with prosthetic material or device,
whether placed by surgery or by catheter intervention,
during the first six months after the procedure †
 Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or
prosthetic device (which inhibit endothelialization)
 Cardiac transplantation recipients who develop cardiac valvulopathy

Circulation. 2007;116:1746. Reprinted with permission ©2007, American Heart Association.
DENTAL PROCEDURES FOR WHICH ENDOCARDITIS PROPHYLAXIS IS
REASONABLE FOR PATIENTS
 “All dental procedures that involve manipulation of gingival tissue or the
periapical region of teeth or perforation of the oral mucosa”
 The following procedures and events do not need prophylaxis:
• routine anesthetic injections through non-infected tissue
• taking dental radiographs
• placement of removable prosthodontic or orthodontic appliances
• adjustment of orthodontic appliances
• placement of orthodontic brackets
• shedding of deciduous teeth
• bleeding from trauma to the lips or oral mucosa.

IM indicates intramuscular; IV, intravenous.
* Or other first-or second-generation oral cephalosporin in equivalent adult or pediatric dosage.
† Cephalosporins should not be used in an individual with a history of anaphylaxis, angioedema, or urticaria with
penicillins or ampicillin.
Circulation. 2007;116:1747. Reprinted with permission © 2007, American Heart Association, Inc.2

ANTIBIOTICS USEFUL FOR OROFACIAL
INFECTIONS:
 Penicillins.
 Cephalosporins.
 Erythromycins.
 Clindamycin and Lincomycin.
 Metronidazole.
 Aminoglycosides.
 Fluoro quinolones – ciprofloxacin.
 Sulfonamides and trimethoprim

PENICILLINS
 Discovered in 1929, it was first antibiotic
drug to be used.
 The drug of choice for the initial empirical
management of odontogenic infections
remains penicillin
 Bactericidal
 Narrow but appropriate spectrum
 Little or no toxicity

CLASSIFICATION OF PENICILLIN
I) Natural penicillins :
Penicillin G (Benzyl penicillin)
II) Acid resistant penicillins :
Phenoxymethyl penicillin (penicillin V)
III) Penicillinase – resistant penicillins :
Methicillin, nafcillin, cloxacillin, dicloxacillin
IV) Penicillins effective against gram +ve and some
gram –ve organisms :
Ampicillin, Amoxicillin
V) Extended spectrum penicillins :
Carboxypenicillins : Carbenicillin,piperacillin

PENICILLIN-G ( Benzyl Penicillin )
-Narrow spectrum activity
Spectrum of activity- Streptococci except enterococci,
Staph. aureus, N. gonorrhoea, N. meningitides,
Anthracis, C.diphtheriae, Clostridia, Listeria.
PHARMACOKINETICS: PnG is acid liable destroyed by
gastric acid.
-Absorption of sodium PnG from i.m. site is rapid and
complete.
-Distributed extracellularly, penetration into serous cavity
and CSF is poor.
-Plasma T1/2 is 30 min.
-Extreted through kidneys by glomerular filtration.

 PREPARATION AND DOSE: 1) Sod. PnG or Crystallin
penicillin injection: 0.5-5 MU i.m. 6-12 hrly
 Repository PnG injections: These are insoluble salts
must be given deep i.m. never given i.v. Drug is
released slowly from the injection site.
 Procaine PnG: 0.5-1MU i.m.12hrly
 Fortified Procaine PnG : Contains 3lakhU
 Procaine PnG and 1lakhU Sod. PnG
 Benzathine PnG : 0.6-2.4MU i.m. every 2-4 weeks.
It releases drug very slowly and effective for
prophylactic purposes.

AMPICILLIN
Semi synthetic penicillin belongs to aminopenicillins.
Spectrum: Active against all organisms sensitive to
PnG,
H.Influenza, E.Coli, Proteus, Salmonella, Shigella,
Strepto.
Viridans, Enterococci, Pseudomonas, Klebsiella.
Kinetics : Not degraded by gastric acid.
Oral absorption is incomplete but adequate.
Food interferes with absorption.
Plasma T1/2 is 1 hr, excreted through kidneys.
Dose: 0.5-2g oral /i.m. /i.v. every 6th hrly.
Children 25-50mg /kg /day.

Uses: Urinary tract infections, Respiratory tract infections,
Meningitis,
Gonorrhoea, Typhoid fever, Bacillary dysentery,
Cholecystitis, SABE.
Adverse effects: Diarrhea is frequent after oral administration,
rashes
Avoided in patients with a H/O hypersensitivity to PnG.
AMOXICILLIN
It is a close congener of Ampicillin, similar to it
except
- Oral absorption is better food does not interferes
- Incidence of diarrhea is less.
- Less active against Shigella, H.Influenza.
Dose: 0.25-1g orally /i.m /i.v TDS.

BROAD SPECTRUM EFFECT WITH
CLAVULANIC ACID
 Clavulanic acid- streptomyces clavuligerous-
inhibiting β lactamase enzymes
 Broaden antibacterial spectrum of
amoxicillins

SULBACTAM
 Semisnythetic betalactamase inhibitor
 Related chemically in activity to clavulanic acid
 Progressive inhibitor ,highly active against
betalactamase
 Oral absorption- inconsistent,preferably im/iv
 Sulbactam+ ampicillin=Dicapen
 SULBACIN, AMPITUM
1g+ 0.5g per vial im/iv 6-8hourly
1g+500mg tab

 ADVERSE EFFECTS :
a) Local irritancy and direct toxicity
b)Jarisch-Herxheimer reaction
c) Hypersensitivity or drug allergy(1-10%)

DESENSITIZATION IN PENCILLIN
ALLERGIC PATIENTS
 Administration of a penicillin to a allergic
patient, who requires penicillin for clearly
defined medical reasons.
Ex; Endocarditis, meningitis.
-Done in Intensive care setting…
-Penicillin doses of 1,5,10,100 and
1000U administered intradermally ,60
min interval b/n doses.
-well tolerated- 10000U-50,000U given
s.c.

Therapeutic Uses :
 Streptococcal infections
 Pneumococcal infections
 Meningococcal infections
 Staphylococcal infections
 Gonorrhoea
 Syphilis
 Diphtheria
 Tetanus and gas gangrene
 Antibiotic prophylaxis

CEPHALOSPORINS
 These are a group of semisynthetic
antibiotics derived from "cephalosporin –
C" obtained from a fungus
cephalosporium.
 They are chemically related to
penicillins, the nucleus consists of a -
lactam ring fused to a dihydrothiazine
ring.

CEPHALOSPORINS
1ST GENERATION CEPHALOSPORINS
Good against methicillin sensitive S. aureus,
streptococci and many Enterobacteriaceae.
Members include: Cephalexin (Keflex),
Cefazolin (Ancef), Cephapirin (Cefadyl) and Cefadroxil.
2ND GENERATION CEPHALOSPORINS
More stable to Gram negative b-lactamase
and less active against S. aureus.
Members include: Cefuroxime (Ceftin [oral]
and Zinocef), Cefaclor (Cefotan), and Cefoxitin
(Mefoxin).

3RD GENERATION CEPHALOSPORINS
Broader activity against Gram negatives.
Members include: Cefdinir (Omnicef),
Cefoperazone (Cefobid), Ceftazidime (Fortaz), and
Ceftriaxone (Rocephin), and Cefotaxime (Claforan).
4TH GENERATION CEPHALOSPORINS
More resistant to destruction by chromosomal
b-lactamases, but not completely resistant to the b-
lactamases of Serratia, Enterobacter and
Pseudomonas.
Cefepime (Maxipime).
Cefepirome

Adverse effects :
 Pain
 Diarrhoea
 Hypersensitivity
 Nephrotoxicity
 Neutropenia
 Thrombocytopenia

USES :
 As alternatives to PnG in patients developing rashes or other
allergic reactions with PnG.
 Respiratory, urinary and soft tissue infections caused by gram
negative organisms.
 Penicillinase producing staphylococcal infection.
 Septicaermias caused by gram negative organisms : an
aminoglycotide may be combined with a cephalosporin.
 Surgical prophylaxis; surgical prosthesis such as artificial heart
valves, artificial joints etc. The first generation drugs are used. .

 Meningitis caused by H.influenzae,
enterobacteriaceae.
 Gonorrhoea caused by penicillinase producing
organisms.
 Typhoid : as alternative to fluoroquinolones
(specially in children)
 Mixed aerobic – anaerobic infections seen in cancer
patients those undergoing colorectal surgery,
obstetric complications.
 Prophylaxis and treatment of infections in
neutropenic patients

MACROLIDES (ERYTHROMYCIN), LONG ACTING MACROLIDES
(AZITHROMYCIN), LINCOSAMIDES (CLINDAMYCIN)
 Bind to the 50s ribosomal subunit.
 Block chain elongation.
 Bacteriocidal or bacteriostatic depending
upon the organism.

ERYTHROMYCIN
USES
Gram positive organisms.
Used to treat Legionella, Mycoplasma,
syphilis, diphtheria carriers and pertussis.
Safe in pregnancy.
SIDE EFFECTS
Erythromycin estolate - cholestatic
hepatitis (1/1000).
Ototoxic in high doses.

CLARITHROMYCIN
A.Uses
Spectrum is similar erythromycin and
respiratory Gram-negative pathogens
Clarithromycin can be used - H. pylori and
atypical mycobacteria infections.
B.Side Effects
Teratogenic.
Ototoxic in high doses.

CLINDAMYCIN
 A.USES
Used against Gram positive cocci
and anaerobes, both Gram-positive and
Gram-negative rods.
 B.SIDE EFFECTS
Significant risk of pseudo-
membranous colitis due to the
overgrowth of C. difficile.

AMINOGLYCOSIDES
 MECHANISM :
Works by binding to a specific protein,
S12, on the 30s ribosomal subunit.
Blocks normal activation of the initiation
complex.
At low concentrations - the mRNA is
misread and the wrong amino acid is inserted.
At higher concentrations - inhibit translation.

METABOLISM
 Excreted by glomerular filtration.
 Aminoglycosides have a low toxic to
therapeutic ratio. Blood levels need to be
monitored to insure safety and efficacy.
 If the GFR falls below 70mL/min, the daily
dose must be reduced to prevent toxicity.

SIDE EFFECTS
 Ototoxicity
 Nephrotoxicity
 Very high concentrations - neuromuscular
blockade.

GENTAMICIN
 It is effective against gram positive and negative bacteria including
penicillinase resistant staphylococci.
 Gentamicin and ampicillin should be administered separately
because gentamicin gets destroyed.
 It is indicated in severe anaerobic infections.
 Dose – Adult – 3-7mg/kg/day in 2-3 divided dose.
Child – 1-3mg/kg/day in 2-3 divided dose.
 Toxicity – It causes ototoxicity (vestibular and cochlear). If serum
concentrations exceeds 10mg/ml transient tinnitus may occur.
 When used over a weak, nephrotoxicity occurs.
 Allergic reactions – not recommended in lactating mothers.

QUINOLONES
CLASSIFICATION
1. NALIDIXIC ACID
2. FLUOROQUINOLONES
First generation:
Ciprofloxacin, Ofloxacin,
Norfloxacin, Levofloxacin
Second generation:
Gatifloxacin, Sparfloxacin,
Levofloxacin, Moxifloxcin.

QUINOLONES
 Mechanism
Interfere with the activity of DNA
gyrase.
Prevent winding of the DNA helix
into the supercoiled form.
Actions are bacteriocidal.

THERAPEUTIC USES
 Used against Enterobacteriaceae.
 Ciprofloxacin most active against
Pseudomonas.
 Fluoroquinolones used for
UTIs
Pneumonia
Atypical pneumonia and
Bacterial gastroenteritis.

SIDE EFFECTS
 High drug levels are neurotoxic.
 Prolonged use leads to tendon damage
(rupture of Achilles tendon).
 Not approved for children causes cartilage
damage.
 Safety in pregnancy is not established

METRONIDAZOLE
Belongs to Nitroimidazole group.
Mechanism
-In a reducing environment, metronidazole
is reduced to a substance - inhibits
bacterial DNA synthesis.
-Its action is broadspectrum bacteriocidal
-Its use is limited to anaerobic organisms.
* Plasma t1/2 is 8hrs.

SIDE EFFECTS
 Anorexia nausea and abdominal cramps.
 Produces metallic taste in the mouth.
 Peripheral neuropathy, seizures and ataxia
have been seen with prolonged use.
 Thromboflebitis of injected vein occurs if the
solution is not well diluted.

CONTRAINDICATIONS
-Neurological disease.
-Blood dyscrasias.
-First trimister of pregnancy.
-Chronic alcoholism.
Preparations: Tab Metrogyl 200mg 400mg
200mg/5ml susp
500mg/100ml i.v. infustion

USES
 Amoebiasis
 Giardiasis
 Trichomonas vaginitis
 Anaerobic bacterial infections
 Pseudomembranous enterocolitis
 Ulcerative gingivitis, trench mouth
 Helicobacter pylori gastritis/peptic ulcer

SULFONAMIDES AND TRIMETHOPRIM:
 These are bacteriostatic agents.
 inactivated by presence of pus.
 They act by inhibition of bacterial synthesis
of folic acid from para amino benzoic acid
(PABA).
 The concentration of sulfonamides in the
urine is greater than in blood this leads to
formation of crystals of sulfonamides
termed as crystalluria and leads to renal
damage.

Toxic effects:
 Allergic reactions
 Prolonged therapy can lead to
macrocytic anemia
 Also cause kernicterus by displacing
bilirubin from plasma albumin in babies
during intrauterine life. They may also
cause foetal malformation.
 Sulfadizine: It penetrates blood brains
barrier. It is commonly used in traumatic
meningitis.

COTRIMOXAZOLE (SULFAMETHOXAZOLE AND
TRIMETHOPRIM)
 This agent inhibits the conversion of folic acid to
folinic acid which is important for bacterial synthesis of
DNA and RNA.
 It is active against strep pyogens and most
staphylococci and haemophili.
 It is indicated in acute exacerbations in post
irradiation osteomyelitis secondary to
osteoradionecrosis.
 It is also used in mixed actinomycotic infections along
with penicillin.
 Dose 80 mg of Trimethoprim + 400 mg of
sulfamethoxazole
2 tablets 12 hourly
Child : 20 mg + 100 mg

USES :
Cotrimoxazole is widely used
 Urinary tract infections
 Respiratory tract infections
 Typhoid
 Bacterial diarrhoeas and dysentery
 Chancroid
 Granuloma inguinale
 It is an effeictive alternative to penicillin for
protecting agranulocytosis patients and treating
respiratory and other infections in them.
 Pneumocystitis carinii.

TOPICAL ANTIBIOTICS
These are the antibiotics used for external application of drugs to the
surface for local action.
POLYPEPTIDE ANTIBIOTICS
 Low molecular weight cationic drugs.
 Powerful bactericidal
 Toxic when used systemically.
 They are: Polymyxin-B, Colstin, Bacitracin, neomycin.
POLYMYXIN-B & COLISTIN
 Active against g-ve bacteria.
 They have a detergent like action on cell membrane causing
leak in cell constituents. No cross resistance with other drugs.
 Adverse effects: No systemic absorption after oral or topical
administration.
 Given orally causes G.I.T. disturbances.
 Systemic effects are flushing, paraesthesia, renal and CNS
disturbance.

Uses: 1. Topically used in combination with other anti microbials
for skin infections, burns, otitis externa, conjunctivitis, corneal
ulcers.
2. Orally for g-ve bacillary dysentery, diarrhea in children
and infants.
Preparation and dose: 1. Neosporin powder: 5000u
polymyxin with neomycin sulphate 3400u and
bacitracin 400u per g.
 Neosporin eye drops.
 Neosporin-H ear drops.
BACITRACIN
 Discovered from Bacillus Subtilis.
 Active against g+ve organisms like Neisseria, H.Influenza,
Staph, Strepto, Clostridium, Corynebacterium.
 Not absorbed orally and does not penetrate the intact skin.
 Commonly combined with Neomycin and Polymyxin-B.

NEOMYCIN
It is an aminoglycoside, obtained from Steptomyces Fradiaea.
Binds to ribosomal 30S subunit to inactivate DNA polymerase cause
misreading of genetic code.
Spectrum: Active against g+ve and g-ve bacteria less active against
Pseudomonas, Strepto. Pyogens.
It is not used systemically because of nephro and ototoxicity.
No systemic absorption from topical and oral administration.
Uses: a) Topical: Combined with Polymyxin-B & Bacitracin for infected
wound, ulcers, burns, external ear infection,
conjunctivitis.
 Oral: -For preparation of bowel before surgery to decrease post
operative infection.
I

SPECIAL CONDITIONS-PREGNANCY
FOUR CATEGORIES BASED ON HOW SAFE OR RISKY IT
IS TO USE ANTIBIOTICS DURING PREGNANCY.
Category A – No evidence of foetal harm.
Eg : Nystatin
Category B – No known association with birth defects
Eg : Amoxicillin, Augmentin, Metronidazole
Category C – Information only from animal
studies
Eg : Bactrim, isoniazid, rifampin
Category D – Clear - cut problems
Eg : Tetracyclines, minocycline, sulfa drugs.

DRUG ADMINISTRATION DURING PREGNANCY AND
BREAST FEEDING :
Drug Use during
pregnancy
Risk Use during
Breast feeding
Antibiotics
Pencillins YES - YES
Erythromycin YES - Avoid
estolate form
- YES
Cephalosporins YES - YES
Tetracylines AVOID Tooth
discoloration
inhibits bone
formation
Avoid
Metronidazole YES - YES
Clindamycin YES - YES

RENAL FAILURE
 Concentration-dependent antibiotics
Dose is decreased
 Time-dependent antibiotics
Dosage interval should be increased

ANTIMICROBIALS NEED DOSE
REDUCTION IN RENAL FAILURE
- Aminoglycosides
- Cotrimoxazole
- Cephalexin
- Carbenicillin
- Ethambutol
- Cefotaxime
- Vancomycin
- Norfloxacin
- Amphotenicin –B
- Metronidazole

DRUGS TO BE AVOIDED IN CHRONIC
RENAL FAILURE :
 Cephalothin
 Nalidixic acid
 Nitrofurantoin
 Tetracycline (except doxycline).

LIVER DISEASES
 Antimicrobials to be avoided or used at lower dose in
liver disease are :
 Drugs to be avoided Dose reduction
needed
 Erythromycin Chloramphenicol
Pyrazinamide Metronidazole
Tetracycline Isoniazid
Nalidixic acid Rifampin
Clindamycin
 The biliary concentration of ampicillin may be significantly
reduced in patients with hepatic disease, rendering the
antibiotic less effective.

DIABETIC PATIENT
 Antibiotic prophylaxis.
 Amoxicillin is better choice.
 Uncontrolled diabetes.
 PRECAUTION;Gatifloxacilin- causes both
hypoglycemia and hyperglycemia.
 Compared with macrolides- Gatifloxacilin
4.3 times higher risk hypoglycemia
16.7times higher risk hyperglycemia

MANAGEMENT OF HEAD AND NECK INFECTIONS IN
THE IMMUNOCOMPROMISED PATIENT :
 The immunocompromised host has a
potential risk for severe head and neck
infections that usually require aggressive
antimicrobial therapy and prolonged
hospitalization.

Management steps
 Airway monitoring and possible surgical airway
establishment.
 Comprehensive history and physical examination.
 Obtaining appropriate laboratory and imaging
studies.
 Empiric antimicrobial therapy.
 Surgical debridement and irrigation, as needed.
 Culture and antibiotic sensitivity testing of
infectious organisms to appropriately adjust
antibiotic therapy.
 Close follow-up to monitor for resolution and
recurrence.

CONCLUSION
 Antibiotics are used to treat infections
and are also responsible for making
them more difficult to treat because of
their misuses and development of
bacterial resistance. The only way to
keep antibiotics useful is to use them
appropriately and judiciously.

 NEVER ACCEPT CONCEPT OF ANTIBIOTICS ON DEMAND
 NEVER USE A BROAD SPECTRUM ANTIBIOTICS WHEN NARROW
SPECTRUM IS INDICATED
 NO LONG COURSE OF ANTIBIOTICS
 NO NEED OF ANTIBIOTIC PROPHYLAXIS FOR SIMPLE SURGICAL
PROCEDURES or WHEN THERE IS LESS CHANCE OF POST
SURGICAL INFECTION
 WHEN NO SIGNS OF INFECTIONS SUCH AS
SWELLING,LYMPHADENOPATHY, ELEVATED TEMPERATURE
 ALWAYS MAKE SURE THE SOURCE OF INFECTION IS ELIMINATED-
EXTRACTION OF TOOTH and / or INCISION AND DRAINAGE

REFERENCES
 Oral and maxillofacial infections
Topazian
 Medical pharmacology.
- K.D. Tripathi.
 Contemporary oral and maxillofacial surgery.
- Lary J. Peterson 4th Edition.

Thank you
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