179: Macrolides Flashcards
What biochemical structure do macrolides have in common?
Macrocyclic lactone ring
Explain the special classification of azithromycin
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
Are macrolides bacteriostatic or bactericidal?
Bacteriostatic at clinical concentrations
Explain the mechanism of action of macrolides
work by reversibly binding the 50s ribosome and therefore suppress the ribonucleic acid-depenedent protein synthesis
What is the spectrum of Macrolids?
- gram positive bacteria
- Mycoplasma spp.
- some anarobes
What potentiates high drug concentration of macrolides at the site of infection?
Macrolides actively concentrate in macrophages
What tissues/organs/cells do macrolides concentrate in?
concentrates in tissues including lungs, heart, and macrophages
Macrolides have a low serum concentration and large volume of distribution
How are macrolides mainly excreted?
The main route of excretion is through bile and the intestinal tract
How does resistance to macrolides occur?
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
Other than bacterial infections, what are 2 indications for erythromycin use?
- prokinetic effects on GI smooth muscles
- limitation of growth of ammonia-producing organisms within the GI tract
How does the spectrum of Azithromycin differ from other macrolides?
better activity against gram-negative organisms
How and why does the oral bioavailability between erythromycin and azithromycin differ?
Azithromycin has a greater oral bioavailability due to higher stability in acid
Erythromycin i rapidly regraded in the stomach due to gastric acid
What can be an disadvantage of high macrophage concentration of azithromycin?
can suppress phagocytic activity
concentration 200-500 times higher in macrophages than serum
How do the side effects of erythromycin and azithromycin compare?
azithromycin does not exhibit any effect on GI smooth muscles and therefore GI adverse effects are uncommon