ANTIBIOTICS USED IN DENTISTRYDr. Mohamed ShokryOral & Maxillofacial Surgery Department Faculty of Dentistry- Alexandria University- Egypt

DEFINTIONAntibiotics are chemical substances elaborated by various species of micro-organisms such as fungi, actinomyces and bacteria. They suppress the growth of other micro-organism and may destroy them.Antibacterial agents Naturally or Synthetic occurring agent which can kill or inhibit the growth of bacterial cells. Antibacterial agents may be: Natural chemicals that are produced by microorganisms: e.g. penicillins, cephalosporins, tetracyclines & chloramphenicol.Synthetic agents: sulfonamides and quinolones. History 3500 BC the Sumerian doctors would give patients beer soup mixed with snake skins and turtle shells. Babylonian doctors would heal the eyes by using an ointment made of frog bile and sour milk.The Greeks used many herbs as medications . All of these "natural " treatments contained some sort of antibiotic.

Modern history: In 1935, Domagk discovers synthetic antimicrobial chemicals (sulfonamides(. During World War II, penicillin was isolated and injected. It was found to be extremely useful in curing infections. 1940-1950: streptomycin, chloramphenicol, & tetracycline were discovered

Classification of antibiotics:1. Agents that inhibits synthesis of bacterial cell wall e.g Penicillin & cephalosporin 2. Agent that act on the cell membrane of the microorganism affecting its permeablity e.g: polymyxin & polyene antifungal agent nystatin3. Agent that affect the function of 30 s or 50 s ribosomal subunit to cause reversible inhibition of protein synthesis e.g chloramphenical ,Tetracycline, Erythromycin, Clindamycin

Classification According to spectra: Antibiotic effective against gram positive bacteria e.g. erythromycin, lincomycin. Antibiotic effective against gram negative bacteria e.g. strepomycin & other aminoglycosides Antibiotic mainly effective against gram ve & +ve bacteria e.g. ampicillin, amoxycillin, cephalosporin Effective against acid fast bacilli. e.g. streptomycin, rifampicin & viomycin Effective against protozoa e.g. Tetracyclin Effective against fungi e.g.nystatine

PRINCIPLES OF ANTIBIOTIC THERAPY IN DENTAL INFECTION:1- Bacterial flora causing most odontogenic infections 2- The basic mechanism of host defenses 3- The principles to choose antibiotics Bacterial flora causing most odontogenic infectionsThe main microbial flora of the mouth is bacteria, which are almost always the cause of odontogenic infections. The usual flora is both aerobes & anaerobesThe basic mechanism of host defensesfactors affecting the host defenses mechanism: Physiologic depression of host defence Obesity Disturbances of circulation Fluid imbalance Diseases that may inhibit host defense Patient with cancer and leukemia Total body radiation therapy Poorly controlled diabetics Therapeutic drugs that impares host defense mechanism Cytotoxic drugs Immunosuppressive drugs

Principles to choose Antibiotics:1- Identification of causative organism:Causative organism can be isolated from:BloodTissue fluidspus2- Determination of antibiotic sensitivityWhen treating an infection that has not responded to initial antibiotic therapy or when treating a postoperative wound ,the causative agent must be previously identified and the antibiotic sensitivity must also be determined.3- Choice of antibiotics: Upon the culture and sensitivity report, there may be a choice of four or five antibiotics. Selection should be based on: Patients previous history of allergy Antibiotics with narrow spectrum Drug that cause fewest adverse reactions Drug which is least toxic Bactericidal rather than bacteriostatic drug The less expensive but still effective antibotic1-Patient`s history of allergy Allergic reaction to drugs should be considered first. When it exists, alternative drugs must be used. Example: erythromycin or clindamycin is usually use if the patient is allergic to penicillin

2- Antibiotics with narrow spectrum The only majour indication for use of broad spectrum antibiotics coverage is in severe life threatening infection where identification of causative agent is obscure. Each time bacteria are exposed to antibiotics, the opportunity for development of resistant strains is present. If narrow spectrum antibiotics is used ,fewer organisms have the opportunity to become resistant. 3- Drug that cause fewest adverse reactions The goal of antibiotic therapy is to provide an effective Drug that causes least problem to the patient.4- Drug which is least toxic Toxicity reactions are those that occur as a result of excessive dose or duration of therapy, but can occur in individual patients with normal doses. 5- Bactericidal rather than bacteriostatic drugBactericidal drug:Actually kills the organism.Bacteriostatic drug :Prevents the organism from reproducing or growing.6- The less expensive still effective antiboticMost effective but less expensive drug should be considered first.

Bacterial resistance to antibiotic: When the drug does not reach its target The drug is not active Target is altered

Antibiotics are used in three general ways: Empirical therapy (Initiative therapy) Definitive therapy Prophylactic or preventive therapy

Factors affecting the selection of antibiotics: Pharamacokinetic factor Host factors Local factors Genetic factors pregnancy Drug allergyPharamacokinetic factor that affect the selection of antibioticLocation of the infection. Access of antibiotic to sites of infection.e.g. if the infection in the CSF the drug must pass the blood brain barrier. Host factors1. Host defense mechanismsa. The immunocompetant host: can be cure by slowing the multiplication of microorganism (bacteriostatic effect.(b. The immunocompromised host: bacteriostatic activity may be inadequate and a berteriocidal agent may be required for cure. e.g. - pt with bacterial endocarditis pt with AIDSLocal factorsAntimicrobial activity may be significantly reduces in pus.Penetration of antibiotic into infected areas such abscess is imparied because vascular supply is reduce .Presence of foreign bodies reduces the effectiveness of antibiotic.Genetic factorsA no. of drug (e.g. sulfanamides, chloramphenicol ) may produces acute hemolysis in pt with glucose 6- phosphate dehydrogenase deficiency.pregnancyHearing loss in child with administration of streptomycin to the mother during pregnancy.Tetracycline can affect bones & teeth of fetus , may develop fatal acute fatty necrosis of liver pancreatitis & associated renal damage.Drug allergyA antibiotics especially- B-lactum can provoke allergic reaction.Sulfonamides & erythromycin also has been associated with hypersentitivity reaction especially rash.Other antimicrobial agent can caused drug fever.

Combined antimicrobial therapy: Empirical therapy of severe infections in which a cause is unknown Treatment of polymicrobial infection Enhancement of antibacterial activity in the treatment of specific infection

Some commonly used antibioticsPenicillinDerived from Penicilliumfungi.Belong to group called beta lactam antibiotics.Types of penicillin: Penicillin G (intravenous use) not orally because it is destroyed by gastric acid (not acid stable). Penicillin V (oral use) treatment of choice for odontogenic infection procaine penicillin, andbenzathine penicillin(intramuscularuse) Mechanism of actionAct by inhibiting cell wall synthesis in bacteria.Antibacterial spectrum of penicillin gram ve cocci gram +ve some gram +ve bacilliAdverse effect of penicillin1. Thrombophlebitis2. Superinfection e.g. candida3. Allergy with manifestation like:i. skin rash.ii. Renal disturabane.iii. Anaphylaxis

AMINOGLYCOSIDESThey are the first bactericidal parentral antibiotics that was effective against gram ve rods and less effective against gram +ve rods . Administrated only through I.V. injection.Play a role in the treatment of sever progressive cellulites or in the patient with depressed host resistance who has a sever cellulites . Examples - Garamycin amp.{ Gentamycin} . - Streptomycin vials - Amikin 100 mg, 250 mg, 500 mg {Vials} Gentamycin and streptomycin cause ototoxicity and nephrotoxicity

Tetracycline Bacteriostatic gram +ve some gram ve Some antiviral effect broad spectrum Indications: 1- Management of sever periodontal disease as LJP2- Concentrate in the periodontal tissues& destroying anaerobic bacteria 3- Have anti-collagenase enzyme so inhibit tissue destruction & aid in bone regeneration

2 groups:1-Ordinary TetracyclineDose is reduced with pt. of impaired renal function because excreted in kidney Ex: Tetracycline Hcl :Cap. 250 mg {QID}Tetracid:Cap.250 mg {OID}Hostacyclin:Tab.500 mg {TID}2-New GenerationNo adjustment of the doseBecause there are 2 routes of Excretion {renal . Fecal }Ex:Vibramycin:10 caps., 100 mg {BID} Doxymycin: 10 caps, 100 mg {BID}

Disadvantages: Diahrroea Nausea & Vomiting Candida superinfection Fetal hepatic dysfuction Chelating effect in teeth & bone Renal impairment

CephalosporinsHave broader spectrum than penicillin. E.g. Cephradine, cefadroxil, CephalexinAbout 10 % of patient have hypersensitivity to penicillin may be allergic to cephalosporin.Cephalosporin have 4 generations. Thecephalosporins are a class of-lactam antibioticsoriginally derived from thefungusAcremonium, which was previously known as "Cephalosporium"Generations First-generation cephalosporins are active predominantly againstGram-positivebacteria, and successive generations have increased activity againstGram-negative bacteria. (often with reduced activity against Gram-positive organisms)Adverse effect: Diarrhea Nausea Rash Pain & inflammation at injection site Nephrotoxicity

Macrolides They are antibiotics having a macrocyclic lactone ring with attached sugars.They are bacteriostatic drug.Macrolides 1. Azithromycin2. Clarithromycin3. Erythromycin4. TelithromycinThe antimicrobial spectrum of macrolides is slightly wider than that ofpenicillin, and, therefore, macrolides are a common substitute for patients with a penicillin allergy.Indications: Infections caused byGram-positivebacteria (e.g., Streptococcus pneumoniae. Haemophilus influenzae infections such as respiratory tract and soft-tissue infections. Urinary tract infection Otitis media Adverse effects: Vomiting Nausea Diahrroea Hypertention Cardiac arrythmias Revesible hearing lossQuinolones syntheticbroad-spectrumantibacterialdrugs for: Oral infection GIT infection skin and soft tissue infections urinary tract infection active against: Gram +ve Gram ve Anerobic bacteria Pseudomonas

Imidazoles: First developed to treat protozoal infections Bactericidal to anaerobic organisms e.g. Metronidazole Indications ANUG Gingivitis Adult periodontitis Contraindications First trimester of pregnancy Blood dyscrasias Neurogenic diseases

Adverse effects: Anorexia Metallic taste Nausea Glossitis Dryness of mouth

Indications for antibiotic: Congnital or acquired heart ( Rheumatic heart disease , Valvular diseases( Severe kidney diseaes as pt undergoing dialysis Active leukemia, agranulocytosis, aplasia , anemia Metabolic disturbances diabetes Pt on chemotherapeutic drugs Hard and soft tissue trauma Odontogenig infection / pericoronitis / osteomyelitis

Contraindications: Minor chronic localized abscess Localized ostitis Pt with mild pericoronitis, minor gingival oedema & mild pain

Prophylactic antibiotic therapy: Antimicrobial agent is chosen on basis of most likely microorganisum to cause infection Antibiotic loading dose should be employed Antibiotics should be continued only as long as microbial contamination from operative site persist Patient benefits from prophylaxis vs antibiotic adverse effects included allergy , toxicity , superinfectionStandard recommendationCephalosporin ( cefadroxil) preoperatively 500 mg orally 1hr before surgery.postoperatively 250 mg orally 6 hr after initial dose.Alternative recommendationClindamycin in penicillin allergic pt.preoperatively 300 mg orally 1 hr before surgery.postoperatively 150 mg orally 6 hr after initial dose

Dental procedure that require endocarditis prophylaxis: Tooth extraction Subgingival dental scaling Incision & Drainage of infection Endodontic surgery Periodontal suergery

Dental procedures that do not require endocardiatis prophylaxis: Supragingival prophylaxis Restorative tooth preparation Placement of orthodontic appliances Conserative endodontic therapy

Reasons for antibiotic failure: Inappropriate choice of antibiotics Too low blood concentration Poor penetration to infected site Limited or decreased vascularity Impaired host defence Unfavourable local factors Antibiotic resistant organisms Patient failed to take antibiotics Failure to eradicate source of infection