Walters-Macrolides

Question 1

What do macrolides contain?

Answer 1

a lactone ring + 1 or more deoxy-sugars

Question 2

What is the mechanism of macrolides?

Answer 2

inhibit translocation from A to P site on ribosome; release peptidyl tRNA from ribosomes; block formation of initiation complex

Question 3

what 2 drugs are effective against legionnaires disease?

Answer 3

erythromycin and Azithromycin

Question 4

how does erythromycin work?

Answer 4

metabolites complex with cytochrome heme Fe2+ and inhibit CYP3A4, the isozyme that also metabolizes erythromycin

Question 5

what does erythromycin do to cardiac repolarization?

Answer 5

prolongs it = Torsades de pointes (worse if taken with another Rx taht inhibits CYP3A4)

Question 6

what two drugs if taken with erythromycin increase the risk of sudden death?

Answer 6

diltiazem or verapamil (also metabolized by CYP3A4)

Question 7

how is erythromycin a prokinetic?

Answer 7

it stimulates GI motility via motilin receptors

Question 8

what drug is concentrated intracellularly?

Answer 8

azithromycin

Question 9

what is the only macrolide that doesn’t inhibit P450?

Answer 9

Azithromycin

Question 10

how might azithromycin affect the heart?

Answer 10

can cause abnormal changes in electrical activity of the heart that might lead to potentially fatal irregular rhythms. (risk greater in patients with known Q-T prolongation or low K+ or Mg2+ levels)

Question 11

what drugs can treat both community acquired pneumonia and mycobacterium avium complex (MAC)?

Answer 11

azithromycin and clarithromycin

Question 12

why do macrolides appear immumodulatory? and which drug is the best example of this?

Answer 12

they inhibit transcription of mRNA for proinflammatory cytokines.
clarithromycin is particularly active in this regard.

Question 13

how does clarithromycin affect sugar levels?

Answer 13

dangerously lowers blood sugar

Question 14

why do you need to be cautious when using clarithromycin with colchicine?

Answer 14

increases risk of fatal colchicine toxicity

Question 15

why might macrolides as a class increase digoxin toxicity?

Answer 15

because of their effects on K+ channels

Question 16

what type of drug is Telithromycin? and what is it effective against?

Answer 16

Ketolide - G+ activity

Question 17

how do ketolides differ from macrolides?

Answer 17

binds 2 separate domain on ribosome to decrease risk of resistance (this leads to broader activity)

Question 18

when would telithromycin be used? and what is it active against?

Answer 18

community acquired respiratory infections and concentrates in pulmonary tissues/ WBCs.
active against beta lactam and macrolide reistant organisms

Question 19

What is the black box warning for Telithromycin?

Answer 19

contraindicated if myasthenia gravis = fatal or life-threatening respiratory failure

Question 20

What are macrolides effective against?

Answer 20

G+ and G- (MSSA) - mostly static