Antibiotics (1)

Antibiotics

Antibiotics or anti-bacterials are a chemical used in the treatment and prevention of bacterial infection

What are antibiotics?

Antibiotics are classified several ways. On the basis of mechanism of action On the basis of spectrum of activity On the basis of mode of action

Classification of antibiotics

Cell Wall Synthesis inhibitors: Penicillins

CephalosporinsVancomycinBeta-lactamase InhibitorsPolymycinBacitracin

Protein Synthesis Inhibitors Inhibit 30s Subunit

Aminoglycosides (gentamycin)TetracyclinesInhibit 50s SubunitMacrolidesChloramphenicolClindamycin

Streptogramins

DNA Synthesis Inhibitors Fluoroquinolones (ciprofloxacillin)

Metronidazole

RNA synthesis Inhibitors Rifampin

Mycolic Acid synthesis inhibitors Isoniazid

Folic Acid synthesis inhibitors Sulfonamides

Trimethoprim

On the basis of mechanism of action:

Broad spectrum antibiotics :

Amoxicillin Tetracycline cephalosporin Chlorampenicol Erythromycin

Short spectrum antibiotics: Penicillin –G Cloxacillin vancomycin Bacitracin Fluxacillin

On the basis of spectrum activity :

Bacteriostatic antibiotics

Tetracycline Chlorampenicol Erythromycin Lincomycin

Bacteriocidal antibiotics Cephalosporin Penicillin Erythromycin Aminoglycosides Cotrimoxazole

On the basis of mode of action:

Most common side-effects of antibiotics:

Diarrhea  Fungal infections of the mouth, digestive tract and vagina.

Rare side-effects of antibiotics: Formation of kidney stones (when taking sulphonamides). Abnormal blood clotting (when taking some

cephalosporins). Sensitivity to sun (when taking tetracyclines). Blood disorders (when taking trimethoprim). Deafness (when taking erythromycin and the

aminoglycosides).

What are the side-effects of antibiotics?

Some patients may develop an allergic reaction to

antibiotics - especially penicillins. Side effects might include a rash, swelling of the tongue and face, and difficulty breathing.

Allergic reactions to antibiotics may be immediate or delayed hypersensitivity reactions.

Reactions to antibiotics can be very serious, and sometimes fatal - they are called anaphylactic reactions.

Use antibiotics with extreme caution if: The patient has reduced liver or kidney function. The patient is pregnant The patient is breastfeeding

Allergic reactions to antibiotics

The ability of a microorganism to produce a protein that disables

an antibiotic or prevents transport of the antibiotic into the cell.    

Antibiotics resistance

Cross-resistance to a particular antibiotic that

often results in resistance to other antibiotics, usually from a similar chemical class, to which the bacteria may not have been exposed.

Cross-resistance can occur, for example, to both colistin and polymyxin B or to both clindamycin and lincomycin.

Cross-resistance

Antibiotics are usually taken orally , injection, or topically. Most antibiotics start having an effect on an infection within a

few hours. It is important to remember to complete the whole course of the medication to prevent recurrent infection.

Some antibiotics should not be consumed with certain foods and drinks. Others should not be taken with food in your stomach - these would normally be taken about an hour before meals, or two hours after. It is crucial that you follow the instructions correctly if you want the medication to be effective. If you are taking metronidazole do not consume alcohol.

Dairy products should not be consumed if you are taking tetracyclines, as they might affect the absorption of the medication.

How to use antibiotics

Thank you

Common PathogensNecrotic pulp and apical abscesses

Obligate anaerobic bacteriaGram negative rods

Prevotella & porphyomonas spp.Fusobacterium spp.

Campylobacter rectusGram positive rods

Eubacterium spp.Actinomycetes spp.

Gram positive cocciPeptostreptococcus spp.

Facultative anaerobic bacteriaGram positive cocci

Strep and Entercoccus spp.

Common Pathogens

Periodontal Diseases Gingivitis

Fuso, strep, & actinomycetesAdult peritonitis

Bacteroides, porphyomonas, peptostreptococcus & prevotellaAcute necrotizing ulcerative gingivitisSpirochetes, prevotella, fuso

Localized juvenile periodontitisActinobacillus

Common Pathogens Fungal Infections

Candida spp.Mucorales spp.

β-Lactam

Characteristics Mechanism: Inhibit cell wall synthesis. Bactericidal (except against Enterococcus sp.) Short elimination half-life Primarily renally eliminated (except nafcillin ,

oxacillin , ceftriaxone , cefoperazone) Cross-allergenicity-except aztreonam

β-Lactams

Adverse Effects

Hypersensitivity……3 to 10 % Higher incidence with parenteral

administration Mild to severe allergic reactions – rash to

anaphylaxis and death Anti-bodies produced against metabolicby-

products or penicillin it self Cross-reactivity exists among all penicillins

and even other β-lactams

β-Lactams

Adverse Effects

Neurologic–especiallywithpenicillinsand Carbapenems(imipenemandmeropenem) Especiallyin patientsreceiving highdosesin Thepresenceofrenalinsufficiency Irritability, confusion,seizures • Hematologic: Leucopenia,neutropenia, thrombocytopenia

prolongedtherapy(>2weeks)

β-Lactams

Adverse Effects

Gastrointestinal: Nausea ,vomiting ,diarrhea ,pseudo-membranous colitis(C. difficile diarrhea)

• Interstitial Nephritis: Cellular infiltration in renal tubules (Type IV hypersensitivity reaction – characterized by Abrupt increase in serum creatinine; can lead

to renal failure Especially with methicillin or nafcillin

ß-Lactams

Natural penicillins Pen VK and Pen G

Mechanism of action: Inhibit cell wall synthesis Dose: 250-500 mg qid x 7-10 days Contraindications:

Allergies Poor renal fxn

Adverse events: GI upset Drug interactions: oral contraceptives Pregnancy category B

ß-Lactams

Natural penicillins Pen VK and Pen G

Bactericidal Allergic reaction: rare (4 per 100,000) Spectrum:

Strep, staph, enterococcus, neiseria, treponema, listeria

Resistance: Mostly staph (>80%)

ß-Lactams

Amino-penicillins Amoxicillin, ampicillin

Mechanism of action: Inhibit cell wall synthesis Dose: 250-500 mg q 8 h x 7-10 days Contraindications:

Allergies Poor renal fxn

Adverse events: GI upset Drug interactions: oral contraceptives Amoxicillin and clavulanic acid (Augmentin)

ß-Lactams

Amino-penicillins Amoxicillin, ampicillin

Bactericidal “ampicillin” rash (4-10%) Spectrum:

Strep, staph, enterococcus, neiseria, treponema, listeria, E. coli, proteus, H. Flu, shigella, salmonella

Resistance: Entero, citro, serratia, proteus vulagris, provedincia,

morganella, pseudomonas aeriginosa, acinetobacter

Cephalosporins

Cephalexin (Keflex) Mechanism of action: Inhibit cell wall synthesis Dose: 250-1000mg q 6 h x 7-10 days Contraindications:

Allergies Poor renal fxn

Adverse events: mild GI Drug interactions: probenecid Pregnancy category B

Cephalosporins

Cephalexin (Keflex) Bactericidal Spectrum:

Gram + Resistance:

Methicillin resistant gram + Low cross sensitivity with PCN

Tetracyclines

Doxycycline (Vibramycin) Mechanism of action: inhibit protein synthesis

by preventing aminoacyl transfer RNA from entering the acceptor sites on the ribosome

Dose: 100mg qd-bid x 7-14 days Contraindications:

Food pregnancy

Adverse events: GI Drug interactions: anti-epileptics Pregnancy category D

Tetracyclines

Doxycycline Bacteriostatic Spectrum:

Broad, Gram +, -, anaerobes, aerobes, and spirochetes

Resistance: Widespread, cross resistance

PHOTO SENSITIVITY!!!

ADA/AAOS Advisory

StatementJuly 1997

Antibiotic prophylaxis is NOT recommended

for dental patients with plates, pins, or screws, nor is it routinely recommended for MOST dental patients with TOTAL JOINT REPLACEMENTS.

AAOS Statement

AAOS

recommendations Prophylaxis recommended

Total joint replacement within the last two years AND: Compromised immune system OR Type 1 DM OR Previous prosthetic joint infections OR Malnourishment OR Hemophilia

AAOS

recommendations Prophylaxis antibiotic recommendations

Same as AHA OR No specific regimen recommended Keflex is often the first drug of choice

Legal Considerations

The dentist may not be aware of the patient’s medical condition.

Physician may not be aware of the advisory statements or of the dental procedure to be performed.

Vicarious Liability: “The devil made me do it” “I forgot to take my antibiotic.” Documentation.

Legal Considerations

I forgot my antibiotics! Animal studies have shown antibiotics are

effective up to 2 hours after the procedure. Differentiate between prophylaxis vs.

treatment of an early infection. Take into consideration patient’s risk factors. Legal twists.

In Summary….

Principles of Antibiotic

Therapy Therapeutic effectiveness

Clinical indications Pharmcodynamics, pharmacokinetics

Age and extent of infection

Patient factors

Age, allergies, compliance, pregnancy risk Patient function

Renal, hepatic, immunosuppresion, route applicability

Cost Brand name, length of course, alternatives?

Dental Infection

Acute—Rapid growth< 3 days Chronic > 3 days

Pen VK 500mg q6h orAmox 500mg q8h or

Cephalosporin

Allergic to PCN

Clindamycin 300mg q8h orCephalosporin (check allergic Rxn) or

Azith or Clarithromycin

Think AnaerobesAdd Metronidazole 250-500mg

To PCN, Amox, or Ceph

Clindamycin 300mg q8h