Antibiotic Lecture Part 3 Flashcards
Clarithromycin is bacteriocidal or bacteriostatic
Bacteriostatic in low doses
Bactericidal at doses used for SBE prophylaxis
Primary indication for Clarithromycin
Used to treat Helicobacter pylori (bacteria that causes gastric and duodenal ulcers)
Primary indication for Azithromycin
Drug of choice for upper respiratory tract infections
- also used for STDs
Clindamycin is semi-synthetic derivative of what? What is the drug family?
lincomycin
- lincosamide family
T or F, Clindamycin is a macrolide
False, Even though it ends in “mycin” it belongs to the lincosamide family
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)
Mechanism of action for Clindamycin
- antibacterial = interferes with bacterial protein synthesis
- Inhibits peptide bond formation
Clindamycin indication:
Alternative drug of choice if penicillin-allergic
- Drug of choice for mild to early odontogenic infections
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
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
What is the brand name of clindamycin
Cleosin
What is the preparation of clindamycin
clindamycin HCl (Cleosin)
Clindamycin spectrum of kill
- Broad spectrum
- Primarily effective against gram positive organisms
- Bacteriostatic at therapeutic doses
- Potential to be bactericidal
How is Clindamycin excreted?
Majority as inactive metabolites in feces (90%) via bile
Adverse events of Clindamycin
Gastrointestinal - Diarrhea - Nausea/vomiting - Abdominal cramps - **Pseudomembranous colitis Super Infection
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.
Greatest number of antibiotic-associated cases of C diff diarrhea are from:
- Cephalosporins
2. Clindamycin
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:
- Gastrointestinal
- Superinfection = Candidiasis: Oral, vaginal
- Photosensitivity: Exaggerated response to sun exposure
- Hepatotoxicity: especially in pregnant women
- 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:
- Medical - broad range of infections (Acne)
2. Dental - Aggressive forms of periodontitis
Tetracycline preparations associated with dentistry
- Doxycycline
- Minocycline
- 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)
