Azithromycin Flashcards
Why do some people like using macrolides for respiratory infections?
Emerging pneumococcal resistance to penicillin and the recognition that resistance can lead to more serious complications
Atypical bacteria
Better side effect profile
Azithro - once daily dosing and fewer days of treatment
What are the important pharmacokinetic characteristics of azithromycin?
Stable in acidic PH
Bioavailability > 30%
Long half life up to 96hours
Superior pattern of distribution - significant infusion to the intracellular compartment (100X higher than plasma levels) and neutrophils
Why is it important that azithromycin infuses inside phagocytic cells?
It can facilitate killing intracellular pathogens
What is the typical length of therapy for azithromycin and why is this possible
Five days
Because it reaches such high concentrations inside of cells (100x its plasma concentration), so it stays in there longer and keeps killing
In which group of kids is azithromycin not safe, and why?
In kids who have a high risk of bacteria. There have been observed breakthrough pneumococcal bacteremia in kids being treated wth azithromycin.
WHY: because azithromycin is transported in cells, not in the blood, so it may not be able to fight infection in the blood. There is also growing resistance of a number of pneumococcal strains to macrolide.
What is the mechanism of action of azithromycin?
It inhibits bacterial protein synthesis by binding to 50S unit of ribosomes and blocking protein translocation
What is the spectrum of activity of azithromycin?
Low activity against gram positive bacteria, including strep pneuma
Good activity against gram negative bacteria, H influenza and Moraxella catarrhalis
If a pneumococcal strain is resistant to penicillin, is azithromycin a good alternative?
No. If the strain is resistant to penicillin, it is very likely that it will be resistant to azithromycin
Why is the use of azithromycin concerning for pneumococcus?
Misusing azithromucin has important consequences on nasopharyngeal carriage of pneumococci. The antibiotic exerts a selection pressure enhanced by its own pharmacokinetic characteristics: the long half-life of azithromycin results in sub inhibitory concentrations at carriage sites over a period of several days and promotes the emergence of resistant strains.
What are the problems with using azithromycin for AOM and pharyngitis?
Recurrent resistant pneumococcal strains
Suboptimal clinical efficacy against H Influenza
NB azithromycin should only be used if there is a penicillin anaphylzaix
What are the problems with using azithromycin for CAP? When can you use it?
Recurrent resistant pneumococcal strains
Suboptimal clinical efficacy against H Influenza
Low plasma concentrations and risk of bacteremia
Can use: atypical infections and with a cephalosporin in severe infections
What are features that would support the diagnosis of an atypical pneumonia?
Subacute Prominent cough Minimal leukocytosis Nonlocal infiltrate School age child
