Lec. 8: Macrolides Flashcards
Name three macrolides.
- Erythromycin
- Clarithromycin
- Azithromycin
What binds to the 50S ribosomal subunit and inhibits proteins synthesis, is bacteriostatic, and will develop resistance quickly?
Erythromycin
What are the three mechanisms of resistance seen in erythromycin?
- Decreased transport
- Modification of ribosomal target by methylases
- Hydrolysis of drug by esterases
Erythromycin is a ? spectrum drug that has high uptake in gram-?. It is well distributed to soft tissues and does/does not cross the BBB.
- Narrow
- Gram-Positive
- Does not
Erythromycin is concentrated in the liver and is excreted where?
In the bile
T or F. Erythromycin inhibits cytochrome P450 enzyme.
True
What is an effect of inhibition of cytochrome P450 enzyme?
Increased concentration of concurrent drug that are substrates for CYP3A
Erythromycin is second after ? for gram-postive infections.
Pencillin G
What can be given to treat Listeria monocytogenes, corynebacterium deptheria, lyme disease, legionnaire’s disease, and mycoplasma pneumonia infections?
Erythromycin
What is more acid-stable than erythromycin, is similar to effectiveness to penicillins V, and the absorption of oral dose increase with food?
Clarithromycin
How does clarithromycin compare to erythromycin?
Clarithromycin has a longer half-life, has slightly better activity against gram-positive, and has more anaerobic coverage.
Clarithromycin inhibits what enzyme?
Cytochrome P450 3A4 enzyme
Which is a stronger inhibitor of cytochrome P450 3A4 enzyme, erythromycin or clarithromycin?
Erythromycin
What drug has a very long half life (35-40 hours), absorption of oral dose is REDUCED by food, and is more acid-stable than erythromycin?
Azithromycin
What is a major advantage of Azithromycin over other macrolides?
No inhibition of CYP enzymes
Z-pack is associated with what macrolide?
Azithromycin
What drug inhibits protein synthesis, binds to the 50S subunit of ribosome, has cross-resistance to the macrolide antibiotic, and penetrates bone?
Clindamycin
What drug is useful for orodental pathogens and has prophylactic coverage when allergic to penicillin?
Clindamycin
What inhibits protein synthesis by binding to the 30S ribosome, is bacteriostatic, is a BROAD spectrum drug that acts on both gram positive and gram negative drugs?
Tetracyclines
T or F. Resistance to one tetracycline provides resistance to all tetracyclines.
True
Tetracycline is inhibited by ?. Some examples are Ca++, Mg++, Fe++, and Al+++. It should not be given with dairy products or iron-containing supplements.
Di- and trivalent cations
Does tetracycline cross the placenta and move into breast milk?
Yes
Superinfections are common with tetracyclines. Which one is more completely absorbed and least likely to cause problems?
Doxycycline
Chelation of Ca++ when giving ? results in what?
- Tetracyclines
2. Discoloration of teeth when given during gestation or to children, and induced staining of the dentition in adults
Depression of bone growth, hepatic toxicity from large paraenteral dose, vestibular toxicity, and photosensitivity is common with what drug?
Tetracyclines
Vestibular toxicity is characteristic of what tetracycline?
Minocycline
What is the difference in doxycycline and minocyclines?
Doxycyclines require fewer doses and have less GI disturbances. Minocylcline are useful for prophylactic treatment for meningococcal infection, but frequently cause vomiting and vertigo.
What drug penetrates the CSF, and causes effects on bacterial DNA replication?
Metronidazole
How does metronidazole become active?
Through enzymatic reduction of the drug by the organism
What drug inhibits P450 isozyme, CYP 2C9, can be combined with beta-lactam for serious acute orofacial infections, and is active against gram-negative anaerobes?
Metronidazole
Induced staining of the dentition in adults is cause by what tetracycline?
Minocycline
