Pharmacy Author: Omudhome Ogbru, PharmD
Medical and Pharmacy Editor: Jay W. Marks, MD

GENERIC NAME: azithromycin

BRAND NAME: Zithromax, Zmax

DRUG CLASS AND MECHANISM: Azithromycin is a semi-synthetic macrolide antibiotic chemically related to erythromycin and clarithromycin (Biaxin). It is effective against a wide variety of bacteria such as Hemophilus influenzae, Streptococcus pneumoniae, Mycoplasma pneumoniae, Staphylococcus aureus, mycobacterium avium, and many others. Azithromycin, like all macrolide antibiotics, prevents bacteria from growing by interfering with their ability to make proteins. Due to the differences in the way proteins are made in bacteria and humans, the macrolide antibiotics do not interfere with production of proteins in humans. It is an unusual antibiotic in that it stays in the body for quite a while (has a long half-life), allowing for once a day dosing and for shorter treatment courses for most infections. The FDA approved azithromycin in November 1991.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 250, 500, and 600 mg. Suspension: 100 mg/ teaspoon, 200 mg/teaspoon, 167 mg/teaspoon or 1 g/packet. Powder for Injection: 500 mg.

STORAGE: Tablets should be stored at room temperature between 15-30°C (59-86°F). Suspension and solution for injection should be kept between 5-30°C (41-86°F).

PRESCRIBED FOR: Azithromycin is effective against susceptible bacteria causing otitis media (infection of the middle ear), tonsillitis, laryngitis, bronchitis, pneumonia, and sinusitis. It also is effective against several sexually transmitted infectious diseases such as nongonococcal urethritis and cervicitis.

DOSING: Azithromycin (except Zmax) can be taken with or without food, but food reduces stomach upset. Zmax should be taken on an empty stomach 1 hour before or 2 hours after a meal since food reduces its absorption. The adult azithromycin dose is 500-2000 mg in multiple or single doses. For most infections, azithromycin is taken once daily for a relatively short course of treatment (usually five days). The first dose is often a "double dose," twice as much as the remainder of the doses given. For acute bacterial sinusitis, azithromycin way be taken once daily for three days. Zmax usually is given as a single 2 gm dose.

DRUG INTERACTIONS: Azithromycin (except Zmax) should not be taken at the same time as aluminum- or magnesium- based antacids, such as Mylanta or Maalox because antacids will bind the azithromycin and prevent it from being absorbed from the intestine.

PREGNANCY: There are no adequate studies of azithromycin in pregnant women. Azithromycin should only be used during pregnancy if it is clearly necessary.

NURSING MOTHERS: It is not known if azithromycin is secreted in breast milk.

SIDE EFFECTS: Azithromycin is generally well tolerated. The most common side effects are diarrhea or loose stools, nausea, abdominal pain, and vomiting which may occur in fewer than one in twenty persons who receive azithromycin. Rare side effects include abnormal liver tests, allergic reactions, and nervousness.

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