The concentration of azithromycin in the tissues can be over 50 times higher than in plasma due to ion trapping and its high lipid solubility. Azithromycins half-life allows a large single dose to be administered and yet maintain bacteriostatic levels in the infected tissue for several days.Following a single dose of 500 mg, the apparent terminal elimination half-life of azithromycin is 68 hours. Biliary excretion of azithromycin, predominantly unchanged, is a major route of elimination. Over the course of a week, about 6% of the administered dose appears as an unchanged drug in urine. History
A team of researchers at the pharmaceutical company Pliva in Zagreb, Croatia,—Gabrijela Kobrehel, Gorjana Radobolja-Lazarevski, and Zrinka Tamburašev, led by Slobodan Đokić—discovered azithromycin in 1980. The company Pliva patented it in 1981. In 1986, Pliva and Pfizer signed a licensing agreement, which gave Pfizer exclusive rights for the sale of azithromycin in Western Europe and the United States. Pliva put its azithromycin on the market in Central and Eastern Europe under the brand name Sumamed in 1988. Pfizer launched azithromycin under Plivas license in other markets under the brand name Zithromax in 1991. Patent protection ended in 2005. Society and culture
Available forms
Azithromycin is available as a generic medication. Azithromycin is commonly administered in film-coated tablet, capsule, oral suspension, intravenous injection, granules for suspension in sachet, and ophthalmic solution. Usage
In 2010, azithromycin was the most prescribed antibiotic for outpatients in the US, whereas in Sweden, where outpatient antibiotic use is a third as prevalent, macrolides are only on 3% of prescriptions.
Extensive use of azithromycin has resulted in growing Streptococcus pneumoniae resistance.Aerobic and facultative Gram-positive microorganisms

Staphylococcus aureus (Methicillin-sensitive only)
Streptococcus agalactiae
Streptococcus pneumoniae
Streptococcus pyogenesAerobic and facultative anaerobic Gram-negative microorganisms

Haemophilus ducreyi
Haemophilus influenzae
Moraxella catarrhalis
Neisseria gonorrhoeae
Bordetella pertussis
Legionella pneumophilaAnaerobic microorganisms

Peptostreptococcus species
Prevotella biviaOther microorganisms

Chlamydophila pneumoniae
Chlamydia trachomatis
Mycoplasma genitalium
Mycoplasma pneumoniae
Ureaplasma urealyticum

Pregnancy and breastfeeding
No harm has been found with use during pregnancy. However, there are no adequate well-controlled studies in pregnant women.The safety of the medication during breastfeeding is unclear. It was reported that because only low levels are found in breast milk and the medication has also been used in young children, it is unlikely that breastfed infants would have adverse effects. Nevertheless, it is recommended that the drug be used with caution during breastfeeding. Airway diseases
Azithromycin appears to be effective in the treatment of chronic obstructive pulmonary disease through its suppression of inflammatory processes. And potentially useful in asthma and sinusitis via this mechanism. Azithromycin is believed to produce its effects through suppressing certain immune responses that may contribute to inflammation of the airways. Adverse effects
Most common adverse effects are diarrhea (5%), nausea (3%), abdominal pain (3%), and vomiting. Fewer than 1% of people stop taking the drug due to side effects. Nervousness, skin reactions, and anaphylaxis have been reported. Clostridium difficile infection has been reported with use of azithromycin. Azithromycin does not affect the efficacy of birth control unlike some other antibiotics such as rifampin. Hearing loss has been reported.Occasionally, people have developed cholestatic hepatitis or delirium.