Azalides such as

azithromycin Azithromycin, sold under the brand names Zithromax (in oral form) and Azasite (as an eye drop), is an antibiotic medication used for the treatment of a number of bacterial infections. This includes middle ear infections, strep throat, pneumo ...

are a class of

macrolide The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. Ma ...

antibiotics that were originally manufactured in response to the poor acid stability exhibited by original macrolides ( erythromycin). Following the clinical overuse of macrolides and azalides,

ketolide Ketolides are antibiotics belonging to the macrolide group. Ketolides are derived from erythromycin by substituting the cladinose sugar with a keto-group and attaching a cyclic carbamate group in the lactone ring. These modifications give keto ...

s have been developed to combat surfacing macrolide-azalide resistance among streptococci species. Azalides have several advantages over erythromycin such as more potent gram negative antimicrobial activity, acid stability, and side effect tolerability. Although there are few drug interactions with azithromycin, it weakly inhibits the CYP4A4 enzyme.

Structure

Azalides feature a nitrogen atom in their 15-membered macrolide ring resulting in improved pharmacokinetic properties and greater stability when compared to earlier generation macrolides.^, Replacement of the ketone group in traditional macrolides with a tertiary amine group confers greater acid stability.^, See

Beckmann rearrangement The Beckmann rearrangement, named after the German chemist Ernst Otto Beckmann (1853–1923), is a rearrangement of an oxime functional group to substituted amides. The rearrangement has also been successfully performed on haloimines and nitrone ...

Mechanism of action

Azalides bind to the bacterial 50S ribosomal subunit and inhibit polypeptide elongation by hindering peptidyl transfer RNA translocation.

Pharmacokinetics

Applicable pharmacokinetic indexes are free azalide AUC₂₄/MIC because of the

post antibiotic effect Antimicrobial pharmacodynamics is the relationship between the concentration of an antibiotic and its ability to inhibit vital processes of endo- or ectoparasites and microbial organisms.C.H. Nightingale, T. Murakawa, P.G. Ambrose (2002) Antimicrob ...

they exhibit, and free azalide concentration/MIC.^,{{Cite journal, last=Jacobs, first=Michael R., date=March 2003, title=How can we predict bacterial eradication?, journal=International Journal of Infectious Diseases, language=en, volume=7, pages=S13–S20, doi=10.1016/s1201-9712(03)90066-x, pmid=12839703, issn=1201-9712, doi-access=free Due to their large volume of distribution and lipophilic structure, azalides concentrate effectively in tissue.

References

Macrolide antibiotics