Who Owns Zithromax?

Azithromycin, the active ingredient in Zithromax, was discovered in 1980 by researchers at Pliva, a pharmaceutical company based in Zagreb, Croatia (then part of Yugoslavia). The compound was derived from erythromycin, an older macrolide antibiotic, through a modification of the chemical structure that improved its pharmacokinetic properties. Azithromycin has a longer half-life than erythromycin, allowing for shorter treatment courses and less frequent dosing.

Pliva patented azithromycin and licensed the rights to Pfizer for the United States and other markets. Pfizer conducted clinical trials and submitted a New Drug Application to the FDA. The FDA approved Zithromax in December 1991 for the treatment of respiratory tract infections, skin infections, and certain sexually transmitted diseases. The initial approval covered the 250 mg tablet formulation for adults.

The brand's most recognizable product is the Z-Pak, a blister pack containing six 250 mg tablets designed for a five-day treatment course. Patients take two tablets on the first day and one tablet daily for the remaining four days. The Z-Pak format improved patient adherence by simplifying the dosing regimen and providing a convenient, pre-packaged course of treatment. The Z-Pak became one of the most prescribed outpatient antibiotic packages in the United States during the 1990s and 2000s.

In 1996, the FDA approved a pediatric formulation of Zithromax as an oral suspension, expanding the brand's use to children. Subsequent approvals expanded the labeled indications to include acute bacterial sinusitis, community-acquired pneumonia, and prevention of mycobacterial infections in patients with HIV.

In 2005, the composition-of-matter patent for azithromycin expired in the United States, opening the market to generic competition. Multiple generic manufacturers introduced azithromycin tablets, and the generic market grew rapidly. Pfizer continued to market branded Zithromax alongside generic versions, though the brand's market share declined as generic alternatives captured volume at lower price points.

In 2013, the FDA issued a Drug Safety Communication warning that azithromycin can cause changes in the electrical activity of the heart, specifically QT interval prolongation, which may lead to abnormal and potentially fatal heart rhythms. The FDA updated the Zithromax label to include information about this risk. The warning recommended that healthcare providers consider the risk of QT prolongation when prescribing azithromycin, particularly for patients with existing heart conditions or those taking other medications that affect heart rhythm.

In 2026, the FDA approved Zithromax for the treatment of pediatric community-acquired pneumonia in patients aged 6 months and older. The approved dosing regimen is 10 mg/kg on Day 1, followed by 5 mg/kg daily for Days 2 through 5. This approval formalized a therapeutic use that had previously been prescribed off-label, establishing specific pediatric dosing and safety parameters supported by controlled clinical trial data.

In April 2026, Pfizer notified the FDA that it is permanently discontinuing the manufacture of branded Zithromax 250 mg and 500 mg tablets. The FDA Drug Shortages Database lists both products as "To Be Discontinued" with the reason "Discontinuation of the manufacture of the drug." Pfizer did not publicly disclose a specific reason for the decision. Generic azithromycin tablets in both strengths remain available from multiple manufacturers, ensuring continued patient access to the medication.

In July 2025, Pfizer had already discontinued Zithromax oral powder for suspension in 1-gram packets, leaving no manufacturers for that specific formulation. The 1-gram packet formulation, commonly used in single-dose treatment for sexually transmitted infections, remains in shortage as of July 2026.