Antibiotics (Exam 2)

Question 1

Define Bacteriostatic

Answer 1

antibiotic INHIBITS bacterial growth

Question 2

Define Bactericidal

Answer 2

antibiotic has the ability to KILL bacteria

Question 3

What is a narrow spectrum antibiotic?

Answer 3

-Antibiotics that are only effective against a SMALL number of bacteria.

Example: Penicillin = effective against gram (+) & a few gram (-) bacteria

Question 4

What is a broad spectrum antibiotic?

Answer 4

Effective against MANY bacteria.

Example: Tetracycline = antibiotic w/ widest spectrum of kill = gram (+) & gram (-) bacteria, rickettsia & some viruses

Question 5

What is the normal micro-floras that populate a healthy individuals oral cavity?

Answer 5

-Predominant microbe of the oral cavity is gram (+) strep or staph (90-95%)

Question 6

Which organisms make up oral infections?

Answer 6

1) ALL oral/facial infections occur from resident microorganisms which are already in mouth
2) “outside” organisms causing oral infections must be introduced to oral cavity = e.g. trauma
3) Without even taking a culture, we know oral infection is most likely a gram (+) strep or staph

Question 7

What is the drug of choice for the treatment of orofacial infections?

Answer 7

• Penicillin is drug of choice

* PENICILLIN V is the best choice for orofacial infections

Question 8

How is Penicillins eliminated in the body? (main routes).

Answer 8

• Penicillin molecule excreted unchanged & very rapidly!
• 10% via glomerular filtration (passive transfer)
• 90% via tubular secretion (active transport)
• 70% of an oral dose of penicillin is excreted within the first 4 hours

Question 9

Explain the rationale for pretreating patients w/ PROBENECID prior to administration of penicillin.

Answer 9

1) Probenecid (benemid) = a medication used to treat gout
2) STOPS reabsorption of uric acid back into the bloodstream
3) Also excreted by ACTIVE TRANSPORT
4) Competes w/ penicillin molecule for the active transport mechanism
5) Has greater affinity for the carrier than penicillin does
6) If probenecid is given before penicillin is given, penicillin is NOT excreted as rapidly
7) ELEVATES blood level of penicillin 3-4 times; PROLONGS effect of penicillin

Question 10

What is Penicilinase?

Answer 10

A beta lactamase (enzyme) that breaks down the beta lactam ring of the penicillin molecule

Question 11

With respect to absorption from the GI tract, bacterial spectra, & susceptibility to beta-lactamase, which penicillin is the best match for the following ?

1) Bactericidal
2) Narrow spectrum
3) Acid-labile = broken down by gastric acid, 70-80% destroyed by gastric acid
4) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Answer 11

Penicillin G

Question 12

Describe the characteristics of Penicillin G, with respect to absorption from the GI tract, bacterial spectra, & susceptibility to beta-lactamase.

Answer 12

1) Penicillin G = bond penicillin molecule to PROCAINE molecule
2) Repository form, dissolved in oil, given IM
3) NARROW spectrum
4) Given IM, no GI absorption
5) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Question 13

Describe the characteristics of Benzathine Penicillin G, w/ respect to absorption from the GI tract, bacterial spectra, & susceptibility to beta-lactamase.

Answer 13

1) Penicillin G bonded w/ benzathine molecule, repository form, dissolved in oil
2) NARROW spectrum
3) Given IM after dose of aqueous penicillin, longest lasting, no GI absorption
4) Persists in plasma for 3 weeks
5) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Question 14

Describe the characteristics of Penicillin V, w/ respect to absorption from the GI tract, bacterial spectra, & susceptibility to beta-lactamase.

Answer 14

1) Sodium penicillin V= improved version of penicillin G b/c it’s ACID stabile
2) Taken ORALLY, not broken down by gastric acid
3) Better bioavailability when given in POTASSIUM salt form
4) NARROW spectrum
5) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Question 15

• What are examples of the Penicillinase resistant drugs?

- What are they used for?

Answer 15

1) Cloxacillin (canadian drug)
2) Dicloxacillin (canadian drug)
3) Piperacillin and tazobactam sodium
4) Ticarcillin and clavulanate potassium
- Only used for infections w/ penicillinase producing bacteria

Question 16

With respect to absorption from the GI tract, bacterial spectra, & susceptibility to beta-lactamase, which penicillin is the best match?

1) BacteriCIDAL, BROAD spectrum
2) ACID stable
3) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Answer 16

-Ampicillin

Question 17

Principen with Probenecid

is a ___________spectrum

Answer 17

Broad

Question 18

Which antibiotic is:

1) Broad spectrum
2) Penicillinase-labile = broken down by penicillinase-producing microorganisms

Answer 18

Amoxicillin (Amoxil)

Question 19

Which antibiotic is:
1) Clavulanic acid added to amoxicillin

2) Broad spectrum
3) Synthetic = inhibits the penicillinase enzyme (beta lactamase)

Answer 19

Augmentin

Question 20

What are the MOST common adverse effects of penicillin?

Answer 20

1) Oral candidiasis, black hairy tongue
2) Maculopapular rash due to toxicity to amoxicillin
3) Diarrhea due to augmentin
4) Allergy to penicillin

Question 21

Name two types of repository penicillin.

Answer 21

1) Procaine Penicillin G = repository form

2) Benzathine Penicillin G = repository form

Question 22

What is the mechanism of action of penicillin?

Answer 22

1) Bactericidal
2) Blocks bacterial cell wall synthesis by interfering with structural glycopeptides
3) Bacterial cell death results from lysis

Question 23

Detail penicillins w/ regard to bacterial spectra, toxicity, mechanism of action, & absorption from GI tract.

Answer 23

1) Bacterial spectra: narrow or broad depending on type
2) Toxicity: Oral candidiasis, black hairy tongue, maculopapular rash due to toxicity to amoxicillin, diarrhea due to augmentin, allergy to penicillin
3) Mechanism of action: Bactericidal. Blocks bacterial cell wall synthesis by interfering w/ structural glycopeptides. Bacterial cell death results from lysis.
4) Absorption: Acid liable. Oral: natural penicillins (penicillin G) is incomplete & variable due to destruction by gastric juices (given parenterally). Semi-synthetic (penicillin V) is more acid stable, therefore more uniform absorption.

Question 24

Detail cephalosporins w/ regard to bacterial spectra, toxicity, mechanism of action, & absorption from GI tract.

Answer 24

1) Generations designate extent of antimicrobial action 1st generation = narrower than second. The HIGHER the generation, the MORE broad spectrum of kill.
2) Toxicity reactions: anaphylaxis, fever, rash (erythema multiforme), eosinophilia, GI upset, glossitis, stomatitis, candididis, nephrotoxicity
3) Patients intolerant to penicillins may be intolerant to cephalosporins
4) Mechanism of action: INHIBIT bacterial cell wall synthesis similar to penicillin. Results in defective cell walls & cells become osmotically unstable causing lysis. RAPIDLY dividing bacteria are MOST susceptible. Bactericidal.
5) Absorption: Acid stable. MOST absorbed well through GI tract, may be delayed by food in stomach.

Question 25

What is the first generations of cephalosporins used in dentistry?

Answer 25

1) Cephalexin (KEFLEX)* know this one 2) Cefadroxil (duricef) *know this one 3) Cephradine (velosef) *know this one

Question 26

What is the second generations of cephalosporins used in dentistry?

Answer 26

1) Cefaclor (raniclor)

Question 27

Name the most frequently observed adverse effect of the macrolide antibiotics: (erythromycin, azithromycin, clarithromycin).

Answer 27

Gastrointestinal Side Effects: 1) Stomach pain 2) Nausea/vomiting 3) Cramping 4) Diarrhea Other: 5) Cholestatic jaundice (hepatitis) 6) Allergic Reactions 7) Fever 8) Eosinophilia 9) Skin eruptions

Question 28

What is mechanism of action of erythromycin?

Answer 28

1) Bacteriostatic. Bactericidal at HIGH doses or when used against highly susceptible organisms 2) ONLY effective against ACTIVELY DIVIDING organisms 3) INHIBITS protein synthesis by binding to 50S ribosomal subunits of sensitive microorganisms. 4) BINDS to ribosome at a site near peptidyltransferase to inhibit peptide bond formation. 5) SUPPRESSES bacterial growth due to the lack of protein production.

Question 29

What are the absorption patterns of erythromycin?

Answer 29

Absorption: 1) Absorbed from upper part of intestine. 2) Food reduces absorption. 3) Effectiveness is dependent upon particular derivative, dosage form, acid stability of the derivative & gastric emptying time 4) Unknown as to whether drug is absorbed to any substantial extent when applied topically to mucous membranes

Question 30

What are the distribution patterns of erythromycin?

Answer 30

1) Diffuses readily into tissues 2) Crosses placenta 3) Distributed to most body tissues

Question 31

What are the excretion patterns of erythromycin?

Answer 31

1) Absorbed from the stomach to the liver 2) Metabolized by the liver & excreted into the bile 3) As it goes thru bile duct, causes smooth muscle to constrict, causing bile to back up into liver resulting in cholestatic hepatitis a potentially fatal condition 4) Urine 5) Feces (primarily) = Large size of the molecule causes it to be excreted here

Question 32

What are two alternative macrolide antibiotics used for antibiotic premedication in dentistry?

Answer 32

1) Clarithromycin (Biaxin) | 2) Azithromycin (Zithromax)

Question 33

Describe the mechanism of action of clindamycin.

Answer 33

1) Similar to erythromycin. Antibacterial | 2) Interferes w/ bacterial protein synthesis & inhibits peptide bond formation

Question 34

What are indications for the use of clindamycin?

Answer 34

1) Infections caused by anaerobic organisms 2) Orofacial infections & periodontal infections caused by anaerobic bacteria 3) Anaerobic osteomyelitis (good for oral bone infections b/c drug penetrate bone) 4) Drug of choice for orofacial infections in penicillin allergic patients 5) Used for endo infections, as in mature endodontic infections, Bacteroides are prevalent & particularly susceptible to clindamycin.

Question 35

What are 2 classes of antibiotics that are MOST often associated w/ Clostridum difficule infections resulting in pseudomembraneous colitis?

Answer 35

1) Clindamycin 2) Cephalosporins *may not appear until weeks/months after antibiotic exposure (80% = nosocomial) * Pseudomembranous colitis* - Super infection - Clindamycin causes diarrhea be/c resident bacteria of GI tract have been killed

Question 36

What is the influence of divalent cations on TETRACYCLINE absorption from the GI tract?

Answer 36

1) 4 (tetra) ring structure w/ a lot of OH & O groups = reason why these drugs chelate cations 2) Chelate divalent cations (Ca, Mg, Fe, Al) = reason why can’t have dairy, iron or antacids w/ this drug

Question 37

What is the route of administration for tetracyclines that might indicate a contraindication in some patients?

Answer 37

- Contraindicated in children w/ developing teeth/bone, pregnant patients - Incorporated in to teeth/bone thru chelation causing pitting & yellowing

Question 38

What is the hard tissue related adverse effects of tetracyclines during pregnancy & small children?

Answer 38

1) Crosses placenta, category D 2) Because of chelating effects, drug is incorporated into teeth and bone 3) Drug becomes permanent part of enamel as it calcifies, irreversible b/c enamel doesn’t remodel like bone 4) Teeth become yellow/gray color & fluoresce under black light 5) Binding to bone may result in depression of skeletal growth in growing children, may be partially reversible w/ bone remodeling

Question 39

What are three tetracycline preparations?

Answer 39

1) doxycycline *know this one 2) minocycline *know this one 3) tetracycline *know this one

Question 40

How does doxycycline hyalite differs from doxycycline?

Answer 40

-Doxycycline hyclate (Periostat) is a subantimicrobial dose that only inhibits collagenase but doesn’t kill bacteria

Question 41

What is an example of antibiotic antagonism using tetracyclines?

Answer 41

1) Tetracyclines are contraindicated w/ penicillin/amoxicillin 2) Tetracycline (static); penicillin (cidal) 3) If a patient is on a tetracycline an requires AHA antibiotic premedication, you have to use another static drug like Clindamycin

Question 42

What are the contraindications for the use of tetracyclines?

Answer 42

1) Pregnancy 2) Children 3) Patients taking penicillin/amoxicillin

Question 43

What are the major Medical and Dental indications for quinolines?

Answer 43

Medical: 1) Respiratory infections 2) Bronchitis, community-acquired pneumonia 3) Urinary tract infections Dental: 1) Rarely used in dentistry 2) Used to treat periodontal disease when other agents are not effective

Question 44

What is the mechanism of action of quinolines?

Answer 44

1) Targets DNA topoisomerases 2) Blocks action of 2 bacterial topoisomerases — enzymes that relieve coils that form in DNA when helix is opened in preparation for replication, transcription, or repair.

Question 45

33. Compare and contrast the quinolones with respect to bacterial spectra

Answer 45

1) Bactericidal | 2) Broad spectrum

Question 46

Compare and contrast the quinolines with respect to their mechanism of action

Answer 46

1) Targets DNA topoisomerases 2) Blocks action of 2 bacterial topoisomerases — enzymes that relieve coils that form in DNA when helix is opened in preparation for replication, transcription, or repair.

Question 47

Compare and contrast the quinolines with respect to their toxicity and adverse effects (GI, CNS, & allergy).

Answer 47

Gastrointestinal: 1. Nausea/vomiting 2. Diarrhea 3. Xerostomia Central Nervous System: 1. Headache 2. Dizziness 3. Vertigo/syncope Allergy: 1. Pruritus 2. Urticaria

Question 48

What is the mechanism of action of metronidazole and its use in dentistry? -What is it taken up by? What is it non-enzymatically reduced by? - As many as how many enzymes are affected? -

Answer 48

1) Taken up by diffusion, is selectively absorbed by anaerobic bacteria & sensitive protozoa. - Non-enzymatically reduced by reacting w/ reduced ferredoxin, (generated by pyruvate oxido-reductase) - Many reduced intros intermediates form sulfonamides & thioether linkages w/ cysteine-bearing enzymes, deactivating enzymes. - As many as 150 separate enzymes are affected. 2) Metronidazole metabolites are taken up into bacterial DNA, & form unstable molecules. This function only occurs when metronidazole is partially reduced, & b/c this happens only in anaerobic cells, it has relatively little effect upon human cells or aerobic bacteria. 3) Used to supplement other antibiotics when periodontal condition is not responding

Question 49

What are the common adverse oral side effects associated with antibiotics?

Answer 49

1) Candidiasis (black hairy tongue) 2) Stomatitis 3) Glossitis

Question 50

What are the drug interaction of oral contraceptives w/ antibiotics & recommend related strategies for patient education & compliance?

Answer 50

1) Hormones activated by gut flora: if DECREASED flora, DECREASED active hormone, possible ovulation 2) Site of drug interaction: small intestine 3) Use alternative birth control until next cycle

Question 51

What are the effects of antibiotics on warfarin (Coumadin)?

Answer 51

1) Patients on warfarin have hypoprothombinemia 2) Drug competes with vitamin K for synthesis of prothombin 3) Vitamin K synthesized by gut bacteria 4) Antimicrobials kill these bacteria, causing decreased levels of vitamin K 5) Warfarin then has no competitor, and causes excessive anticoagulation (very thin blood) 6) Quinolones