Macrolides Flashcards
MOA
Reversibly bind to the 50S ribosomal subunit to induce dissociation of peptidyl transfer RNA so protein synthesis is suppressed and bacterial growth is inhibited
Bacteriostatic–> Time-dependent
MOR
Active efflux–> low-level resistance to macrolides
Alteration in the erm binding site–> high-level resistance to all macrolides and other antibiotics that bind to 50S
Cross-resistance is usually observed among the macrolides
Erythromycin
Absorption–> F= 15 to 45%
- Degraded by gastric acid
Distribution–> widely distributed into tissues (except for the CSF)
Elimination–> excreted in bile and metabolized by CYP450
- NO DOSE ADJUSTMENTS
Clarithromycin
Absorption–> well absorbed from the GI tract (regardless of the presence of food)
Distribution–> widely distributed into tissues (except for the CSF)
Elimination–> metabolized in the liver by CYP450 and eliminated by the kidney
Dose adjustment if CrCl < 30 mL/min
Azithromycin
Absorption–> acid stable; F= 37%
Distribution–> widely distributed into tissues (except for the CSF)
Elimination–> Biliary excretion
T1/2= 68 hours
Spectrum of Activity
Gram (+) aerobes (C>E>A)–> PSSP
Gram (-) aerobes (A>C>E)–> NOT Enterobacteriaceae
Anaerobes–> ADA
Atypical bacteria–> ALL MACROLIDES
- DOC for Legionella
- Chlamydia spp.
- Mycoplasma
- Ureaplasma
Other: Mycobacterium avium complex (MAC)
Clinical uses
Respiratory tract infections
Community-acquired pneumonia–> especially for atypical coverage; monotherapy for outpatients or combines with ceftriaxone for inpatients
STDs–> A single 1 gram dose of Azithromycin for Chlamydia trachomatis
Can be used as an alternative for Penicillin allergic patients
Adverse effects
GI–> N/V/D most common with oral administration of Erythromycin
Thrombophlebitis and infusion site irritation
QTc prolongation
Drug interactions
Erythromycin and clarithromycin are inhibitors of CYP450
Theophylline
Carbamazepine
Valproate
Cyclosporine
Digoxin
Phenytoin
Warfarin
