Azithromycin Dihydrate is a macrolide antibiotic that belongs to the antibiotics category. It is available as a pill in strengths of 250 mg, 500 mg, and 1000 mg. In Hong Kong, azithromycin is a prescription-only medication overseen by the Department of Health. This article covers Azithromycin Dihydrate, available as a generic medication and marketed under brand names such as Zithromax and Azermet.
Azithromycin inhibits bacterial protein synthesis by binding to the 23S rRNA of the 50 S ribosomal subunit. This blocks the translocation step of peptide chain elongation, preventing bacteria from growing and replicating. Because it concentrates inside cells and tissues, the drug achieves high intracellular levels, which is useful for infections involving intracellular organisms. Onset of action generally occurs within a few hours, while the drug’s long half-life (approximately 68 hours) provides a prolonged therapeutic effect, allowing short-course regimens.
Azithromycin is approved by the Hong Kong regulatory authorities for the treatment of:
These indications reflect the drug’s activity against common Gram-positive and some Gram-negative organisms, as well as atypical pathogens like Mycoplasma and Chlamydia.
Azithromycin has been studied for several off-label purposes. When used outside approved indications, it must be prescribed under medical supervision.
Disclaimer: Off-label use requires individualized risk assessment and monitoring by a qualified healthcare provider.
Absolute contraindications
Relative contraindications
Special populations such as the elderly may experience a higher incidence of gastrointestinal side effects and should be monitored for drug-related cardiac events.
This article provides educational information about azithromycin and is not a substitute for professional medical advice. Treatment decisions, including use for unapproved indications, must be made under the guidance of a qualified healthcare provider. The content is intended for informational purposes and does not constitute medical recommendations. Always consult a physician before starting, stopping, or changing any medication regimen.
Azithromycin has no activity against viruses; prescribing it for viral illnesses such as the common cold or flu is not supported by evidence and may contribute to antibiotic resistance.
Azithromycin is classified as Category B in Hong Kong, indicating no proven fetal risk in animal studies. It may be used during pregnancy when clearly needed, but the prescriber should weigh benefits against potential risks.
Due to its long half-life, detectable levels may remain for up to 5 days after the final dose, which is why short-course regimens are effective.
Yes. Antacids containing aluminium or magnesium can reduce azithromycin absorption. Take the antibiotic at least 2 hours apart from such antacids.
If you remember within 2 hours of the scheduled time, take the missed tablet. If it’s closer to the next dose, skip the missed one and continue as prescribed. Do not double the dose.
Rarely, azithromycin can elevate liver enzymes or cause hepatitis. Patients with existing liver disease should be monitored regularly for signs of hepatotoxicity.
The medication may be taken with or without food. Taking it with a meal can lessen stomach upset, but no specific foods must be avoided.
Azithromycin is not typically screened for in standard workplace or sports drug tests, as it is not a controlled substance.
Keep the pills in their original container, protected from heat, moisture, and direct sunlight. Avoid storing them in the luggage compartment of an aircraft where temperatures can become extreme.
Most OTC cold remedies do not have clinically significant interactions with azithromycin. However, avoid combining it with other QT-prolonging agents found in some decongestants.
