Indications and spectrum
Azithromycin, widely known under the brand name Sumamed, belongs to the macrolide class of antibiotics. Its distinguishing feature is its ability to accumulate in tissues and maintain high concentrations long after the last dose, which makes short treatment courses possible. This pharmacological profile has made it one of the most commonly prescribed antibiotics worldwide, both in outpatient and hospital care.
The drug is active against a broad range of pathogens. Among Gram-positive bacteria, it covers many streptococcal and staphylococcal strains, although resistance is increasingly reported. It also acts against certain Gram-negative organisms such as Haemophilus influenzae and Moraxella catarrhalis. What makes azithromycin especially valuable is its activity against so-called “atypical” pathogens, organisms like Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Chlamydia trachomatis, which are not reliably treated with beta-lactam antibiotics.
In clinical practice, azithromycin is prescribed for a wide range of infections. Respiratory conditions are the most common: acute bacterial sinusitis, bronchitis, community-acquired pneumonia, and otitis media. Its efficacy against atypical bacteria explains why it is often chosen for pneumonia when Mycoplasma or Chlamydophila are suspected. Dermatologists and general practitioners also prescribe it for skin and soft tissue infections caused by susceptible organisms. Azithromycin has a role in treating sexually transmitted infections as well. A single oral dose is effective against uncomplicated genital chlamydia, making it a cornerstone of treatment in many guidelines. In some cases, it is also used in combination regimens for gonorrhea or pelvic inflammatory disease. Outside these areas, it may be given for traveler’s diarrhea caused by susceptible bacteria, though this is not its primary indication.
It is important to stress that azithromycin should not be used casually for colds or flu, which are viral and unaffected by antibiotics. Misuse not only fails to relieve symptoms but also fuels resistance in the community. The clinical scenarios where azithromycin is appropriate are outlined in
Indications by condition, helping distinguish between justified and unnecessary prescriptions.
Azithromycin demonstrates unique pharmacokinetics among macrolides, allowing for short, convenient courses with sustained tissue activity.
Forms and administration
Azithromycin is available in several pharmaceutical forms designed to suit both adults and children, as well as to simplify dosing. The most common are film-coated tablets and capsules, typically supplied in strengths of 250 mg and 500 mg. For patients who have difficulty swallowing tablets, dispersible or orally disintegrating versions are sometimes available.
For children, the standard option is oral suspension. It is usually provided as a dry powder that must be reconstituted with water before use. Once prepared, the suspension must be shaken thoroughly before each dose to ensure even distribution of the active ingredient. Storage rules are important: some suspensions remain stable at room temperature for only a limited period, while others require refrigeration. Correct storage conditions are essential to maintain potency and avoid underdosing. Dosing syringes or calibrated spoons are recommended to prevent errors, as ordinary kitchen utensils can give inaccurate volumes. Practical aspects of such formulations are described further in
Forms.
A distinctive feature of azithromycin compared to many other antibiotics is its prolonged half-life. Because the drug remains at therapeutic levels in tissues for several days, it can be prescribed as a once-daily regimen, and treatment courses are shorter — often only three to five days. This convenience improves adherence, since patients are more likely to complete the full course when fewer doses are required. For some infections, including uncomplicated chlamydial infection, a single 1 g oral dose is sufficient.
Intravenous formulations also exist and are used in hospitals for severe infections or when oral administration is not possible. However, for most outpatient settings, oral forms dominate because they are effective, easy to use, and well tolerated.
Dosages and regimens
Azithromycin’s dosing strategy is shaped by its long tissue half-life and high intracellular concentrations, allowing for shorter courses compared with many other antibiotics. Nevertheless, correct scheduling remains essential to achieve bacterial eradication and prevent the emergence of resistance.
For adults, respiratory tract infections such as bronchitis, sinusitis, or community-acquired pneumonia are typically treated with a five-day regimen: 500 mg on the first day, followed by 250 mg once daily from day two to day five. This “loading dose” strategy quickly achieves therapeutic levels and maintains them with smaller subsequent doses. An alternative regimen is 500 mg daily for three days, which is also widely used.
In the treatment of sexually transmitted infections, particularly uncomplicated genital Chlamydia trachomatis, a single 1 g oral dose is effective and recommended by many international guidelines. For gonorrhea, azithromycin may be combined with another antibiotic, such as ceftriaxone, to enhance efficacy and reduce resistance risks.
For skin and soft tissue infections, dosing typically mirrors the respiratory regimens, with either a three-day or five-day course depending on severity.
In children, weight-based dosing is essential. The most common schedule is 10 mg/kg on the first day, followed by 5 mg/kg once daily for the next four days. Alternatively, a three-day course of 10 mg/kg per day may be used. Details on safe pediatric dosing are discussed further in
Dosing — children.
Despite its short courses, completing therapy exactly as prescribed remains critical. Patients may be tempted to stop early if symptoms improve after one or two doses, but doing so risks relapse and the survival of resistant organisms. Guidance on what to do if a dose is missed, or how to combine azithromycin with food or other drugs, is provided in
How to take.
For adults with special conditions, such as liver disease or cardiac arrhythmia, dosing may require adjustment or closer monitoring due to safety concerns, though the drug is generally well tolerated. As with all antibiotics, self-adjusting the regimen is unsafe; decisions should rest with the prescribing physician.
Short-course regimens are a defining feature of azithromycin therapy, improving adherence while maintaining efficacy.
Macrolide antibiotics like azithromycin achieve sustained activity through intracellular accumulation, allowing flexible and convenient dosing.
Side effects and safety considerations
Azithromycin is usually well tolerated, but like all antibiotics it can produce unwanted effects. Understanding what is common, what is rare, and when medical attention is required helps patients use it more safely.
The most frequent adverse events are gastrointestinal. Diarrhea, abdominal discomfort, nausea, and occasional vomiting are reported by many patients, though symptoms are usually mild and resolve after treatment ends. These effects are linked both to the drug’s action on gut flora and its direct effect on motility. Compared with amoxicillin or broader-spectrum antibiotics, azithromycin may cause fewer disturbances to the microbiome, but clinically relevant diarrhea still occurs. Another important area is cardiac safety. Azithromycin has the potential to prolong the QT interval, a measure of electrical conduction in the heart. In most people this is harmless, but in those with pre-existing arrhythmias, electrolyte imbalances, or concurrent use of other QT-prolonging drugs, the risk of serious rhythm disturbances such as torsades de pointes increases. For this reason, physicians weigh cardiac history before prescribing and may avoid azithromycin in high-risk individuals.
Allergic reactions are rare but possible, ranging from mild rash to severe anaphylaxis. Any sign of swelling of the face or difficulty breathing requires urgent medical care. Less commonly, liver enzyme elevations or hepatitis-like symptoms occur; patients with jaundice, dark urine, or persistent fatigue should stop the drug and consult a doctor.
Overall, azithromycin’s safety record is strong, which explains its widespread use even in pediatric populations. But patients should remember that seemingly minor side effects, like persistent diarrhea or palpitations, can signal something more serious if ignored. A clear discussion with the prescriber about risks and monitoring is therefore essential. Broader context on antibiotic-related adverse effects is available in Side effects overview.
Contraindications and interactions
Azithromycin should not be used in individuals with a known allergy to macrolide antibiotics, such as erythromycin or clarithromycin. A history of severe hypersensitivity reactions rules out its use entirely, and alternative drug classes must be considered.
Caution is also warranted in patients with liver disease. Because the drug is metabolized hepatically, impaired function may raise systemic levels, increasing the risk of toxicity. Patients with a history of hepatitis or abnormal liver enzymes should be monitored closely if azithromycin is prescribed.
The most significant interactions involve its effect on cardiac rhythm. Azithromycin can prolong the QT interval, so combining it with other QT-prolonging agents including certain antiarrhythmics, antipsychotics, and fluoroquinolones heightens the risk of dangerous arrhythmias. Electrolyte disturbances such as low potassium or magnesium further increase this risk.
Antacids containing aluminum or magnesium can reduce azithromycin absorption if taken simultaneously. While the interaction is not severe, it can lower drug levels enough to compromise efficacy. Patients are usually advised to separate doses by at least two hours.
Azithromycin may also interact with warfarin, increasing anticoagulant effects and raising bleeding risk. Careful monitoring of INR values is recommended in patients on long-term anticoagulation.
Other interactions are less common but still clinically relevant. The drug can raise concentrations of certain immunosuppressants or anti-epileptic medications, though such cases are rare and usually detected during specialist care. A more detailed discussion of antibiotic-related drug combinations can be found in Drug interactions, which outlines the broader principles of safe prescribing.
Buying azithromycin safely online
Azithromycin’s popularity and short-course convenience have made it a frequent target for unauthorized online sales. Numerous websites advertise it without requiring a prescription, often under names like “Sumamed” or generic “Zithro,” but such offers pose significant risks. Tablets may contain substandard ingredients, incorrect dosages, or even counterfeit compounds that provide no therapeutic effect.
Legally, azithromycin is a prescription-only medication. Obtaining it without a physician’s evaluation bypasses safeguards designed to ensure the right diagnosis, the correct dose, and the monitoring of side effects. Self-treatment purchased from unverified sources not only exposes patients to potentially dangerous products but also fuels the spread of resistance by encouraging inappropriate use.
The safest route to purchase is through telemedicine platforms. After completing a questionnaire and, if needed, a remote consultation, a doctor can issue an electronic prescription that is filled by a licensed pharmacy. This ensures authenticity, proper labeling, and professional oversight. The process is described in
Is it legal and Telemedicine flow.
Patients should evaluate any online pharmacy carefully. Trusted services provide licensing details, customer support, and secure payment systems. Red flags include sites that advertise antibiotics “over the counter,” bulk packages at suspiciously low prices, or a lack of verifiable contact information. Practical steps for safe verification are summarized in Checklist – safe pharmacy.
For conditions like urinary tract infections, azithromycin is not the first-line choice; alternatives such as Nitrofurantoin may be more appropriate. This reinforces why professional guidance is indispensable before obtaining antibiotics online.
Buying azithromycin online can be safe only if done legally, with a prescription, and through accredited services. Any other pathway risks patient health and contributes to the growing problem of resistance.