Page 1


INDIAN DENTAL ACADEMY Leader in continuing dental education

ANTIBIOTICS • Substances produced by microorganisms which suppress the growth or kill the microganisms at very low concentrations.

HISTORY • The phenomenon of antibiosis was demonstrated by Pasteur (1877):growth of anthrax bacilli in urine was inhibited by air born bacteria. • Flemming (1929) found that diffusible substance was elaborated by penicillium mould which could destroy staphylococcus.





BASED ON TYPE OF ORGANISM THEY ACT UPON: Antibacterial – penicillin amino glycosides erythromycin Antifungal griseofulvin amphotericin ketoconazole Antiviralacyclovir amantidine zidovudine Antiprotozoal- metronidazole chloroquine




4. 5. 6. 7.

Inhibit cell wall synthesis: penicillins cephalosporins cyclosporins Cause leakage from cell membrane: polypeptides-polymixin, bacitracin polyenes- amphotericin B ,nystatin Inhibits protein synthesis: tetracyclines, chloramphenicol, erythromycin, clindamycin. Causes misreading of m.RNA: aminoglycosides Inhibits DNA gyrase: fluoroquinolones Interfere with DNA function : rifampin, metronidazole. Interfere with DNA synthesis: acyclovir, idoxuridine.

INTRODUCTION • The selection of an appropriate antibiotic for head and neck infections requires the integration of many factors related both to the host and the pharmacology of the antibiotic it self. • Empiric antibiotic selection is based on a knowledge of the flora of orofacial infections in the non compromised host and dependence on laboratory studies.

• • • • • • • •

Pharmacokinetic & pharmacodynamic issues in the use of antibiotics include: Spectrum of activity, Absorption, Bioavailability, Serum half life & duration of action, Tissue penetration, Distribution, Metabolism and clearance, Concentration dependent and concentration independent killing of organisms.

THE DECISION TO USE OF ANTIBIOTIC THERAPY • An appropriate decision about whether the antibiotic therapy is necessary or not will depend on some of the factors like: A) PRESENCE OF INFECTION: Locally the classic signs and symptoms of pain, swelling, surface erythema, pus formation and limitation of motion. systemically ,fever, lymphadenopathy, malaise, elevated WBC count.

• Noninfectious conditions similar to the infectious conditions to be carefully diagnosed are: • Painful tooth • Removal of 3rd molar(2nd day) • Major maxillofacial procedures performed under G.A. etc • These must be excluded as possible causes of patients discomfort.

B) STATE OF HOST DEFENSES: • antibiotics help in situations in which the host has been overwhelmed by bacteria or especially virulent bacteria are involved, and when patient’s defenses are impaired.

Cause of depressed defense: • 1) physiological :shock, disturbances in circulation caused in old ages or obesity and fluid imbalances. • 2) Disease related: malnutrition syndrome (alcoholism), cancers, leukemia, poorly controlled diabetics. • 3) Defective immune system related: congenital defects such as agammaglobulinemia, multiplemyeloma, total body irradiation therapy, children who have had splenectomy. • 4) Drug suppression related: cytotoxic drugs in malignancies, glucocorticoids, cyclosporine.

PRINCIPLES FOR CHOOSING THE APPROPRIATE ANTIBIOTIC • Once the decision has been made to use antibiotics as an adjunct to treating an infection ,the antibiotic should be properly selected. • Some of the guide lines which can be helpful in antibiotic selection are:

IDENTIFICATION OF CAUSATIVE ORGANISM: • The typical odontogenic infection is caused by a mixture of aerobic and anaerobic bacteria. • Approximately 70%-mixed flora 5%-pure aerobic 25%-pure anaerobic

• AEROBIC: with in the viridans group of facultative streptococi, streptococus milleri group is most frequently associated with orofacial cellulitis and abscess. • All most all the these aerobic groups are sensitive to penicillins.

ANAEROBIC: anaerobic preptostreptococci, members of prevotella, porphyromonas, • provitella-sensitive to penicillins • 25% of prevotella and porphyromonas- are penicillin resistant.

• Penicillin-sensitive streptococci predominate during the first 3 days of clinical symptoms and the more resistant gram positive obligate anaerobes appear in significant numbers there after. • In long standing cases aerobic bacteria can not survive in hypoxic and acidic environment and so anaerobes predominate. • This fact suggests the selection of the penicillins over other antibiotics in early cases.

DETERMINATION OF ANTIBIOTIC SENSITIVITY • In the treatment of an infection that has not responded to initial antibiotic therapy or a post opp wound infection, the causative agent must be precisely identified, and the antibiotic sensitivity must also be determined. • The results of this provides information needed to prescribe most appropriate antibiotic.

USE OF SPECIFIC AND NARROW SPECTRUM ANTIBIOTICS • Antibiotic with the narrowest spectrum of activity should be used, which will prevent the development of resistant organisms. • When broad spectrum antibiotics are used, many different bacteria also present in the body are exposed to antibiotic. • But in the case of narrow spectrum antibiotics only fewer organisms have opportunity to become resistant.

• Use of narrow spectrum antibiotics also minimizes the risk of supra infections. • When large numbers of normal host flora are eliminated, overgrowth of resistant organisms occurs, and this may result in clinical infection in some patients

NARROW SPECTRUM --- BROAD SPECTRUM 1. Penicillin G 2. Streptomycin 1. Erythromycin

1. Tetracyclines 2. chloramphenicol

USE OF LEAST TOXIC ANTIBIOTICS • Drugs which are having lower toxicity should be used. • Some antibiotics which are used to kill living bacteria may also kill or injure human cells. Thus can be highly toxic. Exmp: in case of odontogenic infections chloramphenicol is 2-3% more effective than penicillins. But at the same time it causes severe bone marrow depression. But penicillins are least toxic.

ALLERGY OR INTOLERANCE • Penicillins are the antibiotic most frequently prescribed for infections in the oral cavity. • Between 1%-10% of patients who initially take penicillins develop an allergic reactions. • And 1% of chance of developing an allergic reaction with reexposure , who did not have allergic reaction for the first time. • Approximately 10%-15% of penicillin allergic patients are also sensitive to cephalosporins, hence should be avoided in these patients.

• History of adverse reactions or intolerance of antibiotic would preclude its subsequent use unless strictly indicated. like: Tetracycline –photo toxicity Clindamycin – antibiotic associated colitis (omfs clinics of N.A vol 15 feb 2003)

USE OF BACERICIDAL RATHER THAN BACTERIOSTATIC • Bactericidal drugs exert their influence after they are incorporated into the bacterial cells and the cell eventually dies. • On other hand bacteriostatic exerts their influence only when present in the patient’s tissues. therefore bacteria acquire their normal growth after the drug is eliminated . So they should be used according to rigorous time schedule. • Patients who are pathologically and therapeutically immunosupressed should be given bactericidal.

BACTERICIDAL 1. 2. 3. 4. 5. 6.

Penicillins Cephalosporins Monobactums Aminoglycosides Metronidazoles fluoroquinolones


Macrolides Clindamycin Tetracyclines sulfonamides

PREVIOUS ANTIBIOTIC THERAPY • The previous use of different antibiotics during the course of an acute infection clouds the bacteriological picture. • In this situation the clinician has the choice of changing the current antibiotic or increasing its dose , perhaps by using the parenteral route. • Increasing in efficacy afforded by the parenteral route of administration may be more advantageous than changing to another antibiotic that is less effective. (omfs clinics of N.A vol 15 feb 2003)

TISSUE DISTRIBUTION OF THE ANTI BIOTICS • Although abscess cavities are not vascular, some penetration of antibiotic dose occur. • Clindamycin best penetrates in to an abscess and attains abscess concentration of 33% of serum levels. So it may be best in odontogenic infections. • Bone penetration of the antibiotics is an important ,especially in osteomyelitis. tetracyclins, fluroquinolones, clindamycin best penetrates in to the bone. (omfs clinics of N.A vol 15 feb 2003)

• Cerebrospinal fluid penetration, or ability of an antibiotic to cross bloodbrain barrier, is paramount in the treatment of infections that threaten the CNS, as in actual or impending cavernous sinus thrombosis.



1. 2. 3. 4. 5. 6. 7. 8.

1. 2. 3. 4. 5. 6.

Penicillins Ampicillins Ciprofloxacin Fluroquinalones Metronidazole Trimethoprin Fluconazole acyclovir

Cephalosporins Clindamycin Macrolides Aminoglycosides Amphotericin Ethambutol

(omfs clinics of N.A vol 15 feb 2003)


• Clinician should consider the cost of the antibiotics prescribed.

PRINCIPLES OF ADMINISTRATION OF ANTIBIOTIC • Once it has been established that the patient has an infection that requires antibiotic therapy, and the kind of antibiotic has chosen it must be administrated properly. • Some of principles must be fallowed in administration of antibiotics.

PROPER DOSE • The goal of any drug therapy should be to prescribe or administer sufficient amount to achieve the desired therapeutic effect but not enough to cause injury to the host. • The dosage prescribed must be capable of establishing a concentration of antibiotic that is 3 to 4 times the MIC . • Therapeutic levels greater than 3 to 4 times the MIC generally do not improve the therapeutic results. But increases the toxicity and is wasteful • Increased dose may be indicated in cases like abscess formation or non vital tissues. • Under dosing – gives rise to resistant bacteria.

PROPER TIME INTERVAL • The frequency of doing is also of importance in administration of antibiotics. • Plasma half life (t 1/2): is the time with in which one half of the absorbed dose of drug is excreted. The time interval has been established for various antibiotics. • The usual dosage interval for the therapeutic use of antibiotics is four times the t ½. • Because most antibiotics are eliminated by the kidneys, the patients with preexisting renal disease and subsequent decreased clearance may require longer intervals between the doses to avoid overdosing.

PROPER ROUTE OF ADMINISTRATION • Oral route is the most common route and comfortable to both clinician and the patient. • But some of the bacteria are not susceptible to the drug plasma concentrations produced by oral administrations. but they are achieved by parenteral routes. • Most of the oral antibiotics should be taken in fasting state (30min before or 2hrs after the meal) for maximum absorption.

CONSISTENCY OF ROUTE OF ADMINISTRATION • If the infection is mild enough oral administrations are sufficient. • When treating a serious, established infections, parenteral antibiotic therapy is frequently the method of choice. • After an initial response has been achieved immediate, discontinuation of parenteral therapy, and oral administration should not be done, which can lead to fall in blood levels of the antibiotic causing recurrence of the infection. • Bacteria usually are not eradicated until the antibiotic is given for 5 to 6 days. • So after 5th day of parenteral administration , the blood levels achievable with oral administrations are sufficient.

COMBINATION ANTIBIOTIC THERAPY • In routine infections the combination therapy should be avoided to prevent the opportunity for resistant bacteria to emerge. • Antibiotic combinations are clearly indicated in situations like:

• A) when it is necessary to increase the antibacterial spectrum in the patients with life threatening sepsis of unknown cause. • B) increased bactericidal effect against a specific organism is desired. eg: treatment of enterococus infection (penicillins & aminoglycocides) • C) prevention of the rapid emergence of resistant bacteria . (like in tuberculosis) • D) emphiric treatment of odontogenic infections like cellulitis/abscess which can progress to more serious like retropharyngeal space infections. (penicillin and metronidazole)

RESPONSE TO THE TREATMENT • Most commonly, the response begins by the 2nd day and initially is a subjective sense of feeling better. • There after objective signs of improvement occur, including a decrease in temperature, swelling, pain and lessening of trismus. • DURATION OF A.THERAPY: usually eradication of infection generally is reached by the 3rd day and the patient becomes relatively asymptomatic. and additional 2 days course will complete 5 days which will be more safer. (omfs clinics of N.A vol 15 feb 2003)

CAUSES OF FAILURE OF TREATMENT. 1. Inadequate surgical treatment, 2. Depressed host defense, 3. Presence of foreign body, 4. Antibiotic problems: Drug not reaching infection, Dose not adequate, Wrong bacterial diagnosis, Wrong antibiotic.

ADVERSE REACTIONS • Adverse reactions occur all too commonly. • Hypersensitivity reactions occur with all antibiotics.(penicillins, cephalosporins) • These reactions may include accelerated anaphylactic reactions (type 1) or less severe reactions associated with edema, utricaria, and itching. • The less sever reactions that develops as a rash or utricaria may begin immediately or many hours after exposure (type 2 & 3)

• Delayed hypersensitivity reactions (type 4) are mediated by T-lymphocytes, most common sign is persistent low grade temperature even after pain, swelling and other problems subsides. DC-eosinophil count is increased the temperature elevation resolves in 24 to 48 hrs after the drug is withdrawn. • Antibiotics frequently causes gastrointestinal distress.


it is one of the toxic reaction which is associated with antibiotics. clindamycin ampicillin/amoxicillin cephalosporins

• The pseudomembranous colitis is caused by toxins from clostridium difficile. • Patients receiving antibiotics that alter colonic flora may have an overgrowth of c.difficile, which leads to ACC.

• Usually occur in medically compromised patients inpatients Elderly people females • C/F- profuse watery diarrhea that may be bloody cramping abdominal pain fever and leukocytosis • Treatment :discontinuation of anti biotic restoration of fluid and electrolyte balance administration of ant-clostridia antibiotics (oral vancomycin, metronidizole)

Common adverse reactions associated with commonly used antibiotics 1.



4. 5.

Penicillins :hypersensitivity direct toxicity (convulsions,muscular twitchings) Cephalosporins :nephrotoxicity(cephaaloridine) hypersensitivity neutropenia & thrombocytopenia Aminoglycosides: ototoxicity nephrotoxicity neuromuscular blockede Macrolides: GI pain , hypersensitivity. Quinolones: neurological




Metronidazole:anorexia metaalic taaste, abdominal cramps, perepharal neuropathy (prolonged use) Tetracyclins: phototoxicity, liver & kidney toxicity staining of teeth (chellation effect) bone deformities diabetes insipidus vestibular toxicity . Chlormphenicol :graybaby syndrome bone marrow depressions

SUPERINFECTIOSNS AND RECURRENT INFECTIONS • Refers to the appearance of a new infection as a result of antibiotic therapy. • In normal state, the normal flora present in the body live in peaceful coexistence with the host and by their physical presence prevent bacteria capable of producing disease from growing in large numbers. • Thus normal flora acts as a defense mechanism against infections, but when the indigenous flora is eliminated or altered by an antibiotic, the pathogenic bacteria resistant to antibiotics may cause secondary infection, or super infection..

• CADIDIASIS: (thrush) overgrowth of Candida occur when high doses of long term penicillin therapy is given , which eliminates gram-positive cocci. patients treated for osteomyelitis or actinomycosis with high doses of antibiotics are more susceptible to thrush . thrush should be treated with anti fungal agents like cotrimazole. • HOPITALIZED PATIENTS: high incidence of secondary infections. such infections may be related to: use of broad spectrum antibiotics high percentage of patients taking broad spectrum antibiotics

• Jarisch-herxheimer reaction: - produced by penicillin when injected in syphilitic patients( secondary syphilis) - shivering, fever, myalgia, exacerbation of lesion, vascular collapse - dose not need interruption of therapy -Aspirin & sedation gives relief.

RECURRENT INFECTIONS: recurrent infections occasional in odontogenic infections .careful monitoring of the patients is needed even after the clinical signs of infection are subsided. treatment of osteomyelitis, actinomycosis are usually associated with recurrent infections, because non vital bone provides barrier to antibiotic effectiveness and potential site of focus of infection. in these cases reculture and readministration of antibiotic therapy and surgical intervention are needed.

DRUG INTERACTIONS 1. Clindamycin / penicillins + erythromycin lowered antibiotic effect 2. Penicillins + oral contraceptives contraceptive failure 3. Metronidazole + disulfiram acute toxic psychosis 4. Tetracyclines + antacids/ vitamins decreased absorption- antibiotic .


Metronidazole + alcohol flushing, headache, nausea, palpitations 7. Tertacyclins /cephalosporins + warfarin increased anticoagulation 8. Cephalosporins + aminoglycosides increased nephrotoxicity 9. Fluoroquinolones /sulfonamides + oral hypoglycemic agents hypoglycemia 10. Sulfanomides + methotrexate increased methotrexate concentration (omfs clinics of N.A vol 15 feb 2003)


1. 2. 3. 4.

Generally bacteria acquires antibiotic resistance in any one of the fallowing ways Alteration of drug’s target site Inability of a drug to reach its target. Inactivation of an antimicrobial agent Active elimination of an antibiotic from the cell.


1. 2. 3. 4.

Acquisition of antibiotic resistant gene by bacteria occurs in these 4 specific mechanisms: Spontaneous mutations Gene transfer Bacteriophages Mosaic genes (omfs clinics of N.A vol 15 feb 2003)

ANTIBIOTIC RESISTANCE MECHANISM 1. Drug inactivation or modification: destruction or inactivation by induction of specific drug inactivating enzymes. eg; staphylococus aureus enterococcus pseudomonas bacteroids & prevotella penicillins , aminoglycosides are affected. ability to produce neutralizing enzymes like penicillinase and like in methylation of erythromycin , clindamycin.

2. Alteration of microbial membrane permiability: causes decreased uptake or increased efflux of antibiotic. -E.coli ,salmonella 3.Alteration of target site: enzymes responsible for cell wall synthesis (transpeptidase) are altered to produce less affinity for penicillins. -s.aureus, s.pneumoniae 4.Alteration in concentration of drug target receptors: .coli, proteus, enterobacter, these have the ability to alter the number of drug receptors that bind the antibiotic. (omfs clinics of N.A vol 15 feb 2003)

PRE OPERATIVE USE OF PROPHYLACTIC ANTIBIOTICS Principles of prophylactic antibiotics: 1. Intended procedure must carry a significant risk of post op infection. 2. Correct antibiotic must be selected. 3. Proper administration. (omfs clinics of N.A vol 15 feb 2003)

• JOMFS vol 10 1990 by LARRY J.PETERSON OHIO UNIVERSITY ,CLOMBUS. ANTIBIOTIC PROFILAXIS AGAINST WOUND INFECTION IN OMFS. principles of antibiotic prophylaxis: 1)surgical procedure should have significant risk of infection. 2)select correct antibiotic for surgical procedure. 3)the A.B level must be high 4)time A.B administration correctly. 5)use the shortest effective A.B exposure. •

short term (1 day ) prophylactic usage has little or no influence on the growth of resistant bacteria.

THERAPEUTIC USES OF A.B IN OROFACIAL INFECTIONS 1. ODONTOGENIC INFECTIONS: penicillin, clindamycin, metronidazole, cephlosporins, amoxicillin+clavunate. tetracyclins & quinalones are not effective towards severe anaerobic infections. erythromycin –poorly absorbed and less efffective in odontogenic infections.

2.OSTIOMYELITIS OF THE JAWS: regimen 1:for hospitalized, medically compromised or when i.v therapy is indicated. penicillin 2 millon U I.V Q4th + metronidazole 500mg,Q 6h. when improved for 48 to 72 hrs switch to: penicillin v, 500mg po Q4th + metronidazole 500mg po Q 6h, for an additional 4 to 6 weeks. or ampicillin/salbactum 1.5 to 3 g iv Q6h when improved for 48 to 72 hrs switch to : amoxycillin/clavulanate 875/125 mg po bid for 4 to 6 weeks.

Regimen 2:for out patients penicillin v 2g + metronidazole 0.5g Q8h po, for 2 to 4 weeks after last sequestrum removed and patient with out symptoms. or clindamycin 600 to 900 mg Q6h iv then: clindamycin 300 to 450 mg Q6h po. or cefoxitin 1 g Q8h iv or 2g Q 4h im or iv untill no symptoms, then switch to, cephalexin 500 mg Q 6h po, for 2 to 4 weeks. for penicillin allergic patients :clindamycin.

3. Head & neck surgery: • parenteral therapy instituted before the skin incision and maintained for no longer than 48hrs. Ampicillin + Sulbactum 1.5g Q 6h Clindamycin 900mg Q 6h Cefazolin 2g Q 8h Metronidazole 500mg Q8h • if the wound is contaminated : irrigation with Clindamycin 900mg in 1lt normal saline solution.

• JOMFS VOL 49 1991: • SURVEY OF ANTIBIOTIC PROPYLAXIS FOR INTRA ORAL ORTHOGNATHIC SURGERY: • survey done with 114 omfs residency programs. • conclusion: rapid I.V administration of penicillin G 600,00 U achieves a peak of, which is greater than 3 to 4 times more than the MIC for susceptible organisms. • penicillin should be given parenterally in dose of 1 or 2 million U preoperatively and an additional dose every 11/2 to 2 hrs. least A.B dose should be given in recovery room. • it can prevent prolonged use of A.B coverage.


Cephalexin Pencillins Augmentin Macrolides-alternative drugs

ACTINOMYCOSIS • Pencillin-G : 3-12 million units IV • Pencillin-V : 2- 4 gms per oral 3-12 months ALTERNATIVE CHOICE • Erythromycin : 2 gms per oral • Clindamycin : 1.2 gms per oral • Tetracyclins : 2 gms per oral • Minocyclin : 2 gms per oral;

CANDIDIASIS • Topical : nystatin amphotericin B clotrimazole miconazole • Systemic : amphotericin B ketoconazole fluconazole itraconazole.


PREGNANCY To be avoided, 1. Tetracyclines 2. Aminoglycosides 3. Metronidazole 4. Fluconazole 5. Sulphonamides 6. Rifampicin

Preferable 1. Penicillins 2. Erythromycin 3. Cephalosporins

LACTATION To be avoided 1. Tetracyclines 2. Metronidazole 3. Aminoglycosides 4. Sulphonamides 5. fluconazole

1. 2. 3. 4.

Preferable Penicillins Erythtromycin Rifampicin cephalosporins


Tetracyclines – permmenant intrinsic dental staining Fluoroquinoloneschondrotoxicity in growing cortilage Carbapenems, imipenemrisk of seizures (omfs clinics of N.A vol 15 feb 2003)


LIVER DISEASES To be avoided 1. Tetracyclines 2. Erythromycin 3. talampicilin

preferable 1. amoxicillin

CHRONIC RENAL FAILURE Safe Cloxacillin erythromycin Ketoconazole rifampicin

fairly safe Ampicillin Amoxicillin Clindamycin metronidazole

less safe Aminoglycoside Cphalosporins Fluconazole vancomycin

avoid Sulphonamides Cephaloridine Cephalothin tetracycline

• Safe - no dosage change usually needed • Fairly safe - dosage change only in sever renal failure. • Less safe - dosage reduction is needed • Avoid - in all the patents


A.B 1. Ampicillin

ADULTS 1-2g div.dos4-6hr

2. Amoxicillin

250 -500mg tid

3. Cephelexin

1-4g daily in 4 doses 250-500mg 8hr 1-2g im/iv 12hrs 250-500mg bid 400mg bid

4. 5. 6. 7.

Cefaclor Cefotaxime Ciprofloxacn Norfloxacin

CHILDREN 50-100mg/kg b.wt 3-4 div.dos 20-40mg/kg in 3 div.dos 25-50mg/kg in 4 div.doses 20mg/kg/day 8hr 50mg/kg 12hr 100-200mg bid Not used

A.B 8. Gentamicin 9. Erythromicin 10. Clindamycin

11. Tetracycline 12. Metronidazole

ADULTS 3-5mg/kg im 8hr 250-500mg tid 600-1800mg in 4 div.dos. 300-2400mg/day 2-4 div.dos 1g/day in 4 div.dos 100ml iv 8 hr. 250-500mg tid orally

CHILDREN 30-50 mg/kg 6hr 15-20mg/kg/day

25-50mg/kg in 3 div.dos. 30-40mg/kg/day oral

Thank you For more details please visit

Antibiotic selection/ dental implant courses by Indian dental academy  

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide r...

Read more
Read more
Similar to
Popular now
Just for you