Pharmacology: Pharmacodynamics: Azithromycin is macrolide antibiotic that exerts its antibacterial action by binding to the 50S ribosomal subunit of susceptible organisms, resulting in inhibition of protein synthesis. Nucleic acid synthesis is not affected.
Pharmacokinetics: Absorption: Rapid oral absorption with oral bioavailability is 38%, Cmax is 0.5 mcg/mL (single 500 mg dose) and Tmax 2-3 hours.
Distribution: Azithromycin is widely distributed throughout the body with tissue concentrations exceeding serum concentrations by 10- to 100-fold. Volume of distribution is 31.1 L/kg (oral). It distributes well into skin, lungs, sputum, tonsils and cervix: penetration into CSF is poor.
Metabolism: Some hepatic metabolism to inactive metabolites.
Elimination: Primarily excreted unchanged in bile; about 6% of dose is excreted unchanged in urine.