Macrolides Flashcards Preview

Respiratory Exam 2 > Macrolides > Flashcards

Flashcards in Macrolides Deck (14):
1

MOA of macrolides

Binds the 50S ribosomal subunit of bacteria and inhibits transpeptidation.
-High affinity for Domain V of 23S part of 50S subunit
-bacteriostatic at low dose, bactericidal at high dose

2

MOA of the ketolides

Telithromycin
Binds the 50S subunit
-specifically binds both Domain V and Domain II of the 23S part of the 50S subunit

3

Advantage of Ketolides over Macrolides

If a mutation in domain V occurs that confers resistance to macrolides, ketolides can still work by binding Domain II

4

Describe the 3 forms of resistance to macrolides.

1. Increased Efflux pump activity: mediated by macrolide efflux (mef) genes

2. Modification of ribosomal binding site: erythromycin ribosome methylase (erm) genes methylate Domain V decreasing macrolide affinity

3. Production of esterases that degrade macrolides: mediated by erythromycin esterase (ere) genes

5

What are the 3 macrolides we need to know?

Erythromycin
Clarithromycin
Azithromycin

6

Which macrolide is destroyed by stomach acid and needs enteric coating?

Erythromycin

7

What is unique about the distribution of Clarithromycin and Azithromycin?

Very high tissue penetration especially in the lungs with minimal CSF penetration.

8

DOC for STIs and why?

Azithromycin
-very long half-life and very high tissue concentration

9

Which drug is not heavily metabolized by CYP3A4 enzymes?

Azithromycin

10

Which macrolide is highly excreted by the kidneys?

Carithromycin

11

What are the cardio and GI side effects of macrolides?

Cardio: QT prolongation
GI: vomiting, diarrhea (increased motility) and serious hepatotoxicity (mainly with Telithromycin)

12

Use of which 5 drugs is contraindicated when a patient is taking a macrolide and why? (or which 5 drugs prevent macrolide use)

1. Theophylline: less active 3A4
2. Warfarin: less active 3A4
3. Calcium Channel Blockers: less active 3A4
4. Cyclosporine: less active 3A4
5. Digoxin: macrolides inhibit P-glycoprotein mediated renal excretion and macrolides destroy the normal flora that metabolizes digoxin

13

MOA of Linezolid

Oxazolidinone drug
-binds 50S bacterial ribosome at a unique site and interferes with formation of the complex that associates mRNA, fmet-tRNA and the 50S ribosome

14

Major adverse effect of Linezolid

Thrombocytopenia