The half-life of the drug in humans appears to vary between 5 and 11 hours, depending on the dose. Peak concentrations are attained between 1.5 and 3.3 hours after oral administration. The drug is protein bound in serum and appears to be eliminated slowly, possibly because of low serum clearance and extensive distribution in the tissues. Thus, detectable levels of the drug can be found in the urine 7 to 14 days after the administration of a single dose. Biliary excretion, predominantly as unchanged drug, is a major route of elimination.
Studies suggest that the drug attains active concentrations in the inflamed central nervous system.
Other Major Uses Used to treat bacterial upper and lower respiratory tract infections, skin and skin structure infections, and sexually transmitted diseases. Concurrent use of macrolides and theophylline has been associated with increased serum concentrations of theophyline. Monitoring of prothrombin time is indicated in patients receiving azithromycin and warfarin. Dose adjustments are not indicated when azithromycin and zidovudine, didanosine or rifabutin are coadministered. Careful monitoring is needed when azithromycin is used with digoxin, ergotamine, triazolam, or drugs that are metabolized by the cytochrome P450 system, such as carbamazepine, cyclosporine, hexobarbital and phenytoin.