Azithromycin dihydrate
[CAS# 117772-70-0]

Identification

• Classification: API >> Antibiotics >> Other antibiotics
• Name: Azithromycin dihydrate
• Molecular Formula: C₃₈H₇₂N₂O₁₂.2(H₂O)
• Molecular Weight: 785.01
• CAS Registry Number: 117772-70-0
• EC Number: 641-134-5
• SMILES: CC[C@@H]1[C@@]([C@@H]([C@H](N(C[C@@H](C[C@@]([C@@H]([C@H]([C@@H]([C@H](C(=O)O1)C)O[C@H]2C[C@@]([C@H]([C@@H](O2)C)O)(C)OC)C)O[C@H]3[C@@H]([C@H](C[C@H](O3)C)N(C)C)O)(C)O)C)C)C)O)(C)O.O.O

Properties

• Solubility: <10 mg/mL (DMSO)

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Risk Statements: H317-H334
• Safety Statements: P233-P260-P261-P271-P272-P280-P284-P302+P352-P304+P340-P321-P333+P317-P342+P316-P362+P364-P403-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin sensitization	Skin Sens.	1	H317
Respiratory sensitization	Resp. Sens.	1	H334
Specific target organ toxicity - repeated exposure	STOT RE	2	H373

Discovery and Applications

Azithromycin dihydrate, a macrolide antibiotic, was first discovered in 1980 by a team of researchers at Pliva, a Croatian pharmaceutical company. The team, led by Dr. Slobodan Ðokic, aimed to develop a new antibiotic with an extended spectrum of activity and improved pharmacokinetic properties compared to existing macrolides like erythromycin. Azithromycin is derived from erythromycin but features a methyl-substituted nitrogen in the lactone ring, which enhances its stability in acidic environments and broadens its antimicrobial spectrum.

It was first introduced to the market under the brand name Zithromax in the early 1990s and has since become one of the most widely prescribed antibiotics globally.

Azithromycin is highly effective in treating respiratory tract infections, including community-acquired pneumonia, bronchitis, and sinusitis. Its ability to concentrate in lung tissues and macrophages enhances its efficacy against respiratory pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and Mycoplasma pneumoniae. The extended half-life of azithromycin allows for once-daily dosing and shorter treatment courses.

Azithromycin is also used to treat skin and soft tissue infections caused by susceptible bacteria, including Staphylococcus aureus and Streptococcus pyogenes. Its anti-inflammatory properties and tissue penetration make it effective for conditions such as cellulitis, impetigo, and infected wounds.

Azithromycin is a first-line treatment for several sexually transmitted infections (STIs), including chlamydia and gonorrhea. It is effective against Chlamydia trachomatis and Neisseria gonorrhoeae, making it a key component of STI management protocols.

Azithromycin is used in the treatment of gastrointestinal infections, such as traveler's diarrhea caused by enteric pathogens like Escherichia coli and Campylobacter jejuni. Its broad-spectrum activity and excellent tissue penetration make it an effective option for eradicating these bacteria.

In certain populations, azithromycin is used prophylactically to prevent bacterial infections. For instance, it is administered to individuals with cystic fibrosis to reduce the frequency of pulmonary exacerbations. It is also used to prevent Mycobacterium avium complex (MAC) infections in HIV/AIDS patients, where its long half-life and tissue penetration provide sustained antimicrobial activity.

References

2024. Azithromycin in severe malaria bacterial co-infection in African children (TABS-PKPD): a phase II randomised controlled trial. BMC Medicine.
DOI: 10.1186/s12916-024-03712-5

2024. Seroepidemiology of trachoma in a low prevalence region receiving annual mass azithromycin distribution in Maradi, Niger. PLOS Neglected Tropical Diseases.
DOI: 10.1371/journal.pntd.0012727

2025. Azithromycin inhibits the intracellular persistence of Acinetobacter baumannii by inducing host cell autophagy in human bronchial epithelial cells. Microbial Pathogenesis.
DOI: 10.1016/j.micpath.2024.107152