Macrolide Lecture

Question 1

Protein synthesis inhibitors, specifically 50s ribosome inhibitors include…

Answer 1

erythromycin, chloramphenicol, clindamycin

other: oxazolidinone, quinupristin, dalfopristin

Question 2

T/F… 50s inhibitors are bactericidal

Answer 2

F… most inhibitors of protein synthesis (ie 50s ribosome inhibitors) are bacteriostatic with the exception of aminoglycoside

Question 3

Where are 70s ribosomes found? 80s? what are their subunits

Answer 3

70s in prokaryotic (30s and 50s subunits), 80s in eukaryotic (60s,40s)

Question 4

List the general classes of protein synthesis inhibitors..

Answer 4

macrolides, ketolides, steptogramins, oxazolidinones, aminoglycosides, broad spectrum antibiotics

Question 5

Name all the Macrolide antibiotics

Answer 5

*erythromycin - oral,IV
clarithromycin (Biaxin) - oral
Azithromycin (Zithromax) - oral, IV

Question 6

name all the ketolide antibiotics

Answer 6

• Telithromycin (ketek)

* Clindamycin (cleocin)

Question 7

Name all the streptogramins

Answer 7

*dalfopristin; Quinupristin (synercid)

Question 8

name all the oxazolidinones

Answer 8

*Linezolid (zyvox)

Question 9

Name all the aminoglycosides

Answer 9

*Streptomycin
gentamicin (garamycin)
Tobramycin (nebcin)
Amikacin (amikin)
Neomycin (NeoTab)

Question 10

What is the MOA for macrolides (erythromycin -oral/IV, clarithromycin (biaxin) -oral, Azithromycin (Zithromax)- oral/IV)

Answer 10

inhibit translocation step by targeting the 50s ribosome and binding reversibly thus inhibition protein synthesis
*note: the reversible binding contributes to why macrolides are bacteriostatic not bactericidal

Question 11

Activity/excretion/elim of Macrolides and general rules to go by..

Answer 11

G+ most susceptible
oral absorption, BILIARY excretion, FECAL elimination

General rule:
*erythromycin, clarithromycin is like erythromycin, azithromycin has better PHK

Question 12

Antibacterial spectrum of Macrolides

Answer 12

• similar to PCN G
• most G- are resistant to erythromycin
• some s. aureus in hospitals are becoming resistant
• clarithromycin + omeprazole + ampicillin: alt therapy for H. pylori

Question 13

Ways bacteria develops resistance to macrolides (erythro, clarithro, azithro)

Answer 13

efflux pumps, meythlation of ribsome (drug binding site)

Question 14

toxicity of macrolides (erythro, clarithro, azithromycin)

Answer 14

HA, GI, N/V, diarrhea.. (erythro most GI side effects, clarithro least)

mild allergic rxn, hives

IV erythro - ototoxicity

Hepatic changes (jaundice, abn liver func test)

Question 15

Potential drug interactions of macrolides

Answer 15

Erythro is POTENT CYP3A4 inhibitor (thus can inhibit other drug metab and increase the drug concentration = toxicity) *clarithro has same effect, azithro has least drug interactions

Question 16

Potential drug interactions of macrolides specific to the heart

Answer 16

QT prolongation, cardiac arrythmias when
erythromycin coadmin with:
*Cisapride or pimozide
*sparfloxacin or grepafloxacin

*note: clarithro has similar results, azithro better

Question 17

Best for GI of macrolides? Best for Drug int?

Answer 17

GI best: clarithromycin
Drug int best: Azithromycin

*erytho is always most severe