Antibiotic Lecture Part 3 Flashcards by Kyle Tuttle

Clarithromycin is bacteriocidal or bacteriostatic

Bacteriostatic in low doses

Bactericidal at doses used for SBE prophylaxis

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Primary indication for Clarithromycin

Used to treat Helicobacter pylori (bacteria that causes gastric and duodenal ulcers)

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Primary indication for Azithromycin

Drug of choice for upper respiratory tract infections

- also used for STDs

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Clindamycin is semi-synthetic derivative of what? What is the drug family?

lincomycin

- lincosamide family

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T or F, Clindamycin is a macrolide

False, Even though it ends in “mycin” it belongs to the lincosamide family

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What drug has a half-life of 70 hours and because of this half life can be taken for only 5 days instead of usual 7-10 days

Azithromycin (Zithromax)

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Mechanism of action for Clindamycin

antibacterial = interferes with bacterial protein synthesis
Inhibits peptide bond formation

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Clindamycin indication:

Alternative drug of choice if penicillin-allergic

- Drug of choice for mild to early odontogenic infections

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T or F, Clindamycin is highly effective against most aerobic gram-positive cocci but not against anaerobic gram-negative organisms such as Bacteroides

False, It is effective against bactericides and anaerobic gram-negative and gram-positive organisms

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What indications does Clindamycin have orally?

Orofacial infections and periodontal infections caused by anaerobic bacteria
Anaerobic osteomyelitis (good for oral bone infections because this drug penetrates the bone)
Drug of choice for orofacial infections in penicillin allergic patients
Endodontic infections, bactericides are prevalent

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What is the brand name of clindamycin

Cleosin

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What is the preparation of clindamycin

clindamycin HCl (Cleosin)

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Clindamycin spectrum of kill

Broad spectrum
Primarily effective against gram positive organisms
Bacteriostatic at therapeutic doses
Potential to be bactericidal

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How is Clindamycin excreted?

Majority as inactive metabolites in feces (90%) via bile

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Adverse events of Clindamycin

Gastrointestinal
- Diarrhea
- Nausea/vomiting
- Abdominal cramps
- **Pseudomembranous colitis
Super Infection

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What is a super infection

An infection that results when an antibiotic kills the normal flora of the body and thus opens the door for a new bacteria to take over.

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Greatest number of antibiotic-associated cases of C diff diarrhea are from:

Cephalosporins

2. Clindamycin

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What is the process behind a antibiotic-associated C diff diarrhea?

Antibiotic causes diarrhea because resident bacteria of GI tract have been killed. Clostridium difficile takes over the reign of the GI tract and produces an exotoxin that is very irritating to the colon. The resulting irritation is pseudomembranous colitis. Life-threatening form of diarrhea

Is it ok to give an anti-diarrheal to one with pseudomembranous colitis?

No! May cause an ulceration/perforation, allowing the bacteria into peritoneum, causing peritonitis = potentially fatal

If a patient is taking antibiotic and gets diarrhea, the protocol is:

Stop the antibiotic
Do Not give an anti-diarrheal
If diarrhea doesn’t stop within 72 hours, patient should be medically evaluated for C diff infection (stool culture)

What is given to treat C diff?

Metronidazole (Flagyl), a broad spectrum antibacterial

Describe Tetracycline chemistry

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

Mechanism of action of Tetracycline

Binds to 30S ribosome = inhibits bacterial protein synthesis
- Prevent access of ammoniacal tRNA to the acceptor site on the mRNA-ribosome complex, preventing the addition of amino acids to the growing peptide chain.

2 processes are required for the antibiotic to come into contact with ribosomes during the mechanism of action of tetracycline

Passive diffusion through hydrophilic pores in outer cell membrane
Energy-dependent active transport system that pumps drug through the inner cytoplasmic membrane = a protein carrier is required

Tetracyclines spectrum of kill: Bactericidal or Bacteriostatic Broad or Narrow spectrum

Bacteriostatic Broad spectrum - Dentistry used for spirochetes specifically PD

How is absorption of tetracylines impaired?

By milk products, aluminum, sodium bicarbonate, divalent cations, iron - Mechanism is chelation and increased gastric pH

Where is tetracycline stored?

Stored in gingival crevicular fluid, dentin and enamel of unerupted teeth (teratogenic effect) - Widely distributed

How are tetracyclines excreted?

Primarily in urine | Contraindicated in renal disease

Adverse events of Tetracyclines:

1. Gastrointestinal 2. Superinfection = Candidiasis: Oral, vaginal 3. Photosensitivity: Exaggerated response to sun exposure 4. Hepatotoxicity: especially in pregnant women 5. Renal toxicity: especially in pregnant women

What tissues do tetracyclines effect?

Calcified tissues because of chelating effects, drug is incorporated into teeth and bone - Drug becomes permanent part of enamel as it calcifies = irreversible, since enamel doesn't remodel like bone - Teeth become yellow/gray color and fluoresce under black light

T or F, Tetracycline effects on calcified tissues is a dose-related phenomenon and NOT related to the length of time that you are taking the drug

True

T or F, Tetracycline staining is cosmetic and can be removed easily by bleach

False, it is intrinsic (Structural) and cannot be removed/bleached

Tetracycline indications:

1. Medical - broad range of infections (Acne) | 2. Dental - Aggressive forms of periodontitis

Tetracycline preparations associated with dentistry

1. Doxycycline 2. Minocycline 3. Tetracycline

What is the most used tetracycline in dentistry

Doxycycline (Vibramycin; many brand names)

Mechanism of action for Doxycycline

Inhibits collagenase, the enzyme that breaks down connective tissue and bone

Doxycycline might be indicated in what uses within dentistry

Periodontal infection

What is doxycycline hyalite (Periostat)?

Is a subantimicrobial dose that only inhibits collegians but doesn't kill bacteria. This is not an antibiotic. This is offered as a supplement or support to scaling and root planing

What is the name of Doxycycline that can be applied subgingivally

Atridox

What is the most potent tetracycline?

Minocycline (Minocin)

T or F, Minocycline causes staining of teeth in adults

True - Travels up dentinal tubules and is deposited at the DEJ - Exposure to light causes the actual staining because it oxidizes the molecule

Minocycline can be applied locally or subgingivally and is called what?

Arestin

Tetracyclines are contraindicated with what?

Penicillin/amoxicillin | -cidal + static

If a patient is on a tetracycline and requires AHA antibiotic premedication, you have to use another drug indicated as?

Clindamycin (static)