Azithromycin is an azalide, a subclass of macrolide antibiotics. Azithromycin (brand names Zithromax® in Italy and the United States; Vinzam® / Zitromax® in Spain; Zmax®; Sumamed®; Aztrin®, Zitrocin®, Azibiot®) is one of the world's best-selling antibiotics, and is derived from erythromycin; however, it differs chemically from erythromycin in that a methyl-substituted nitrogen atom is incorporated into the lactone ring, thus making the lactone ring 15-membered. Azithromycin is used to treat certain bacterial infections, most often bacteria causing middle ear infections, tonsillitis, throat infections, laryngitis, bronchitis, pneumonia and sinusitis. It is also effective against certain sexually transmitted infectious diseases, such as non-gonococcal urethritis and cervicitis. Recent studies have also indicated it to be effective against late-onset asthma, but these findings are controversial and not widely accepted as of yet.
Available forms
Azithromycin is commonly administered in tablet or oral suspension (a one-dose version was made available in 2005). It is also available for intravenous injection. Tablets come in 250 mg and 500 mg doses. Oral suspension comes in 100 mg/teaspoon and 200 mg/teaspoon strengths. The 250 mg tablets are often dispensed in packages of six and commonly referred to as a "Z-Pak," whereas the 500 mg tablets are commonly available commercially in a pack of three tablets, or "Tri-Pak," intended as a three-day treatment. A common dose of oral azithromycin therapy consists of a "double dose" of medication on the first day of treatment and subsequent treatment for four or five additional days. With the "Z-Pak," this means two 250 mg tablets (a total of 500 mg) on the first day and one 250 mg tablet once daily for the next four days.
Azithromycin tablets are mottled pink, unscored, film-coated, modified-oval-shaped tablets containing azithromycin monohydrate equivalent to 250 mg or 500 mg azithromycin and the following inactive ingredients: butylated hydroxytoluene, calcium phosphate, carmine, colloidal silicon dioxide, FD&C red # 40 lake, FD&C yellow # 6 lake, hypromellose (2910, 15cP), lactose monohydrate, magnesium stearate, pregelatinized starch, sodium lauryl sulfate, talc, titanium dioxide and triacetin. The 250 mg tablets have the following appearance: they are mottled pink, of a modified-oval-shape, and have "Pfizer" engraved into one side with "306" engraved into the other. The 500 mg tablet is similar in appearance with the exception of its relative size and "ZTM500" engraved onto one side with "Pfizer" on the reverse. As with all medications, generic azithromycin tablets produced by companies other than Pfizer without the Zithromax brand name may have different appearances, but they tend to share the same general shape and coloration.
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