Azithromycin is a macrolide antibiotic mainly used to treat bacterial infections. Its mechanism of action is to exert antibacterial effects by inhibiting bacterial protein synthesis.

The efficacy of azithromycin

Azithromycin exerts antibacterial effects by binding to the bacterial 50S ribosomal subunit, inhibiting protein synthesis. It has good activity against various Gram positive bacteria, Gram negative bacteria, and atypical pathogens such as Mycoplasma pneumoniae and Chlamydia.

(1) Antibacterial spectrum

Azithromycin is effective against common respiratory pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. In addition, it also has inhibitory effects on Gram positive bacteria such as Staphylococcus aureus (MSSA) and Streptococcus pyogenes, as well as Gram negative bacteria such as Neisseria gonorrhoeae.

(2) Pharmacokinetic characteristics

Azithromycin has unique pharmacokinetic properties, high tissue concentration, and long half-life (approximately 68 hours), which makes it suitable for short course treatment regimens (such as 3-day or 5-day courses) to improve patient compliance.

Drug interactions of Azithromycin 2

Azithromycin is mainly metabolized through CYP3A4, and its drug interactions mainly involve QT interval prolongation effects and metabolic interference with other drugs.

(1) Interaction with antiarrhythmic drugs

Azithromycin may prolong the QT interval, and when used in combination with antiarrhythmic drugs such as amiodarone, quinidine, and sotalol, it may increase the risk of apical torsion to ventricular tachycardia. Combination use or close monitoring of electrocardiogram should be avoided.

(2) Interaction with warfarin

Azithromycin may enhance the anticoagulant effect of warfarin and increase the risk of bleeding. When used in combination, INR values should be closely monitored, and warfarin doses should be adjusted if necessary.

(3) Interaction with digoxin

Azithromycin may alter gut microbiota, increase the bioavailability of digoxin, and increase the risk of digoxin poisoning. When used in combination, the blood concentration of digoxin should be monitored.

(4) Interaction with ergot derivatives

The combination of azithromycin with ergotamine, dihydroergotamine and other ergotamine derivatives may increase the risk of ergotamine poisoning (such as vasospasm and ischemia), and should be avoided.

(5) Interactions with other drugs

Azithromycin may increase the blood drug concentration of drugs such as cyclosporine and tacrolimus. When taking antacids together, it is recommended to take them every 2 hours to avoid affecting absorption.