179: Macrolides

Question 1

What biochemical structure do macrolides have in common?

Answer 1

Macrocyclic lactone ring

Question 2

Explain the special classification of azithromycin

Answer 2

azithromycin is not technically a macrlide but rather an azalide
azithromycin shares most of the properties of macrolides and is therefore often grouped togheter with them

Question 3

Are macrolides bacteriostatic or bactericidal?

Answer 3

Bacteriostatic at clinical concentrations

Question 4

Explain the mechanism of action of macrolides

Answer 4

work by reversibly binding the 50s ribosome and therefore suppress the ribonucleic acid-depenedent protein synthesis

Question 5

What is the spectrum of Macrolids?

Answer 5

• gram positive bacteria
• Mycoplasma spp.
• some anarobes

Question 6

What potentiates high drug concentration of macrolides at the site of infection?

Answer 6

Macrolides actively concentrate in macrophages

Question 7

What tissues/organs/cells do macrolides concentrate in?

Answer 7

concentrates in tissues including lungs, heart, and macrophages

Macrolides have a low serum concentration and large volume of distribution

Question 8

How are macrolides mainly excreted?

Answer 8

The main route of excretion is through bile and the intestinal tract

Question 9

How does resistance to macrolides occur?

Answer 9

one-step mutation leading to development/enhancement of an efflux pump, excreting drug out of the bacterial cell

will lead to widespread mutation and resistance when methylation of the drugs target site on the cells happens and the gene coding for this is transmitted via plasmids between bacteria

Question 10

Other than bacterial infections, what are 2 indications for erythromycin use?

Answer 10

• prokinetic effects on GI smooth muscles
• limitation of growth of ammonia-producing organisms within the GI tract

Question 11

How does the spectrum of Azithromycin differ from other macrolides?

Answer 11

better activity against gram-negative organisms

Question 12

How and why does the oral bioavailability between erythromycin and azithromycin differ?

Answer 12

Azithromycin has a greater oral bioavailability due to higher stability in acid
Erythromycin i rapidly regraded in the stomach due to gastric acid

Question 13

What can be an disadvantage of high macrophage concentration of azithromycin?

Answer 13

can suppress phagocytic activity

concentration 200-500 times higher in macrophages than serum

Question 14

How do the side effects of erythromycin and azithromycin compare?

Answer 14

azithromycin does not exhibit any effect on GI smooth muscles and therefore GI adverse effects are uncommon