Azithromycin: Uses, Dosage & Side Effects
A macrolide antibiotic with a uniquely long half-life, used to treat respiratory, skin, ear, and sexually transmitted bacterial infections
Azithromycin is a macrolide antibiotic widely used to treat a broad range of bacterial infections including respiratory tract infections, ear infections, skin infections, and sexually transmitted infections such as chlamydia. It belongs to the azalide subclass of macrolides and is distinguished by its uniquely long half-life of approximately 68 hours, which allows for convenient short-course treatment regimens of just 3 to 5 days. Listed on the WHO Model List of Essential Medicines, azithromycin is effective, generally well tolerated, and available as an affordable generic medication worldwide. It requires a prescription and should only be used for confirmed or strongly suspected bacterial infections.
Quick Facts: Azithromycin
Key Takeaways
- Azithromycin is a macrolide antibiotic effective against many common respiratory, skin, and sexually transmitted bacterial infections; it is on the WHO Model List of Essential Medicines and can be used as an alternative in patients with penicillin allergy.
- Do not take azithromycin if you are allergic to azithromycin, erythromycin, clarithromycin, or any other macrolide or ketolide antibiotic; seek immediate medical help if you develop signs of a severe allergic reaction or liver problems during treatment.
- Azithromycin has a uniquely long half-life of approximately 68 hours, allowing for short treatment courses of 3 to 5 days while maintaining therapeutic drug concentrations at the site of infection for up to 10 days after the last dose.
- Common side effects include diarrhea, nausea, abdominal pain, and headache; rare but serious effects include QT prolongation, liver injury, and severe allergic reactions including anaphylaxis and Stevens-Johnson syndrome.
- Tell your doctor about all medications you are taking, especially ergot derivatives (contraindicated), anticoagulants, digoxin, ciclosporin, and drugs that prolong the QT interval, as significant interactions can occur.
What Is Azithromycin and What Is It Used For?
Azithromycin is a semi-synthetic azalide antibiotic derived from erythromycin, first introduced into clinical practice in the early 1990s. Structurally, azithromycin differs from classic macrolides like erythromycin by the insertion of a nitrogen atom into the lactone ring, creating a 15-membered azalide ring structure. This modification confers several important pharmacological advantages, including improved acid stability (meaning it is not broken down by stomach acid), superior tissue penetration, a significantly longer elimination half-life, and better gastrointestinal tolerability compared to erythromycin.
The medication works by binding to the 50S ribosomal subunit of susceptible bacteria, blocking the transpeptidation and translocation steps of protein synthesis. This mechanism inhibits bacterial growth and reproduction. Azithromycin is primarily bacteriostatic (inhibiting bacterial growth) at standard concentrations, but can be bactericidal (killing bacteria) at higher concentrations achieved in tissues, particularly against certain organisms such as Streptococcus pyogenes and Haemophilus influenzae. Importantly, azithromycin concentrates extensively within phagocytes (white blood cells), which transport the drug to sites of infection and release it during active phagocytosis, resulting in tissue concentrations that greatly exceed plasma levels.
One of azithromycin's most distinctive pharmacokinetic properties is its remarkably long terminal elimination half-life of approximately 68 hours. This prolonged half-life means that therapeutic concentrations persist at infection sites for 5 to 7 days after the final dose. This unique property allows for significantly shorter treatment courses compared to most other antibiotics: a standard 3-day course of azithromycin provides antibiotic activity equivalent to approximately 10 days of treatment with many other antibiotics, greatly improving patient compliance.
Azithromycin has a broad spectrum of activity and is effective against numerous bacterial pathogens. Its clinical uses include:
- Upper respiratory tract infections: Acute bacterial sinusitis, acute bacterial otitis media (middle ear infection), and pharyngitis or tonsillitis caused by Streptococcus pyogenes (typically as a second-line alternative for patients who cannot take penicillin).
- Lower respiratory tract infections: Acute exacerbation of chronic bronchitis, mild to moderate community-acquired pneumonia (particularly useful for coverage of atypical pathogens such as Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella pneumophila).
- Skin and soft tissue infections: Mild to moderate cellulitis, folliculitis, impetigo, erysipelas, and infected wounds caused by susceptible organisms.
- Sexually transmitted infections: Uncomplicated urethral, cervical, or rectal infections caused by Chlamydia trachomatis (a single 1,000 mg dose is highly effective). Azithromycin is one of the first-line treatments recommended by the WHO and CDC for uncomplicated chlamydia.
- Traveler's diarrhea: Used in some settings for the treatment of traveler's diarrhea caused by susceptible organisms.
- Mycobacterium avium complex (MAC) prophylaxis: Prevention and treatment of disseminated MAC infections in immunocompromised patients, particularly those with advanced HIV/AIDS.
Azithromycin also has notable anti-inflammatory and immunomodulatory properties beyond its direct antibacterial effects. These properties have led to its use in conditions such as diffuse panbronchiolitis, cystic fibrosis (where long-term low-dose azithromycin improves lung function), and other chronic inflammatory airway diseases, though these uses are generally considered off-label in most countries.
Azithromycin is included on the World Health Organization (WHO) Model List of Essential Medicines and is classified as a Watch antibiotic under the WHO AWaRe (Access, Watch, Reserve) classification system. This classification means that while azithromycin is an important antibiotic for specific indications, its use should be carefully monitored to help prevent the development of antimicrobial resistance. As a Watch antibiotic, it should be prescribed only when Access antibiotics (such as amoxicillin) are not appropriate.
Azithromycin only works against bacterial infections. It will not treat viral infections such as the common cold, influenza, or COVID-19. The widespread inappropriate use of azithromycin, including its use for viral infections, has contributed significantly to the development of macrolide resistance worldwide. Only take azithromycin when prescribed by a healthcare professional for a confirmed or strongly suspected bacterial infection.
What Should You Know Before Taking Azithromycin?
Contraindications
There are specific situations where azithromycin must not be used. Understanding these absolute contraindications is essential for safe medication use.
- Macrolide allergy: Do not take azithromycin if you have a known hypersensitivity (allergy) to azithromycin, erythromycin, clarithromycin, or any other macrolide or ketolide antibiotic. Allergic reactions may range from mild skin rash to severe, life-threatening anaphylaxis or serious skin reactions such as Stevens-Johnson syndrome or toxic epidermal necrolysis.
- Excipient allergy: Do not take this product if you are allergic to any of the inactive ingredients listed in the product information leaflet.
- Ergotamine use: Azithromycin must not be taken concurrently with ergotamine or dihydroergotamine (used for migraine treatment), as the combination may lead to ergotism, a condition characterized by severe vasospasm that can cause tissue ischemia and necrosis.
Warnings and Precautions
Azithromycin can cause prolongation of the QT interval on the electrocardiogram, which in rare cases may lead to a potentially fatal abnormal heart rhythm called torsades de pointes. Patients with known QT prolongation, uncorrected low potassium or magnesium levels, clinically significant slow heart rate, or those taking other medications that prolong the QT interval (such as certain antiarrhythmics, antipsychotics, or antidepressants) are at increased risk. Tell your doctor about any heart conditions before starting azithromycin.
You should inform your doctor before taking azithromycin if any of the following conditions apply to you:
- Liver disease: Azithromycin is metabolized by the liver, and cases of severe hepatotoxicity (liver damage) including fulminant hepatitis potentially leading to life-threatening liver failure have been reported. Your doctor may need to monitor liver function during treatment. If you develop signs of liver problems (dark urine, unusual fatigue, loss of appetite, yellowing of the skin or eyes), stop taking azithromycin and contact your doctor immediately.
- Severe kidney disease: While no dose adjustment is specifically recommended for mild to moderate kidney impairment, caution is advised in patients with severe renal impairment (GFR < 10 ml/min) as limited data are available. Your doctor will assess whether azithromycin is appropriate for you.
- Myasthenia gravis: Azithromycin has been reported to exacerbate symptoms of myasthenia gravis (a condition causing muscle weakness) and in some cases to trigger new-onset myasthenic syndrome. If you have myasthenia gravis, discuss the risks and benefits with your doctor before starting treatment.
- Heart conditions: Beyond QT prolongation, tell your doctor if you have any heart condition, slow or irregular heartbeat, heart failure, or if you are taking medications that affect heart rhythm. This includes hydroxychloroquine and chloroquine.
- Electrolyte imbalances: Low levels of potassium (hypokalemia) or magnesium (hypomagnesemia) in the blood increase the risk of QT prolongation with azithromycin. These imbalances should be corrected before starting treatment.
- Neurological or psychiatric conditions: While uncommon, azithromycin has been associated with neurological and psychiatric adverse events including agitation, confusion, hallucinations, and delirium. Exercise caution if you have pre-existing neurological or psychiatric conditions.
- Superinfection: As with all antibiotics, treatment with azithromycin may result in overgrowth of non-susceptible organisms, including fungi (candida). If a new infection develops during treatment, consult your doctor.
Rarely, serious allergic reactions including angioedema (swelling of the face, lips, tongue, or throat), anaphylaxis, and severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis) have been reported with azithromycin. Some of these reactions have resulted in recurrent symptoms that required prolonged observation and treatment. If you develop any signs of a severe allergic reaction, stop taking azithromycin immediately and seek emergency medical attention.
Pregnancy and Breastfeeding
Azithromycin should only be used during pregnancy if the potential benefit to the mother justifies the potential risk to the fetus. Animal reproduction studies have not demonstrated direct harmful effects on fetal development, but there are no adequate and well-controlled studies in pregnant women. Azithromycin is sometimes used during pregnancy when other antibiotics are not suitable, particularly for the treatment of chlamydia infection, where it is considered a first-line treatment by many international guidelines including those from the CDC.
Azithromycin is excreted in human breast milk. While the amount transferred to the nursing infant is generally considered small, the potential effects on the breastfed infant (including sensitization, diarrhea, or thrush) should be considered. If you are breastfeeding, discuss the benefits and risks with your doctor before taking azithromycin. The decision to continue or discontinue breastfeeding or treatment should take into account the clinical need for the drug and the potential risks to the infant.
Driving and Operating Machinery
Azithromycin may cause dizziness in some patients. If you experience dizziness or any other side effects that could affect your ability to concentrate, you should not drive or operate machinery until the symptoms have resolved. While significant impairment of driving ability is uncommon with azithromycin, individual responses may vary, and you should assess your own fitness to drive or operate equipment.
How Does Azithromycin Interact with Other Drugs?
Although azithromycin has fewer drug interactions than older macrolides such as erythromycin and clarithromycin (because it does not significantly inhibit cytochrome P450 enzymes), several clinically relevant interactions still exist. Always inform your doctor, pharmacist, or nurse about all prescription and over-the-counter medications, vitamins, herbal remedies, and dietary supplements you are taking.
Major Interactions
| Interacting Drug | Effect | Clinical Advice |
|---|---|---|
| Ergotamine / Dihydroergotamine | Co-administration may cause ergotism (acute ergot toxicity) with symptoms including severe peripheral vasospasm, ischemia, and potential gangrene | Contraindicated. Do not take azithromycin together with any ergot derivative. Choose an alternative antibiotic or migraine treatment. |
| Ciclosporin (Cyclosporine) | Azithromycin may increase blood levels of ciclosporin, potentially leading to increased toxicity including nephrotoxicity | Monitor ciclosporin blood levels closely during and after azithromycin treatment. Dose adjustment of ciclosporin may be necessary. This is particularly important for transplant recipients. |
| Warfarin and oral anticoagulants | Azithromycin may potentiate the anticoagulant effect of warfarin, increasing the risk of bleeding events | Monitor INR (international normalized ratio) more frequently during and shortly after azithromycin treatment. Report any unusual bleeding or bruising to your doctor immediately. |
| Digoxin | Azithromycin may increase absorption of digoxin by reducing the gut bacterial metabolism of digoxin, leading to elevated digoxin blood levels and potential toxicity (nausea, arrhythmias) | Monitor digoxin blood levels during and after treatment. Watch for signs of digoxin toxicity (nausea, visual disturbances, irregular heartbeat). |
| Colchicine | Co-administration may increase the risk of colchicine toxicity (including fatal cases), as azithromycin may inhibit the P-glycoprotein efflux transporter involved in colchicine elimination | Avoid concurrent use if possible. If the combination is necessary, reduce the colchicine dose and monitor closely for colchicine toxicity (nausea, vomiting, diarrhea, muscle pain). |
| QT-prolonging drugs | Co-administration with other drugs that prolong the QT interval (e.g., cisapride, hydroxychloroquine, chloroquine, certain antiarrhythmics, antipsychotics) increases the risk of potentially fatal cardiac arrhythmias | Avoid combination where possible. If co-administration is necessary, ECG monitoring may be required. Correct any electrolyte abnormalities before starting treatment. |
Minor Interactions
| Interacting Drug | Effect | Clinical Advice |
|---|---|---|
| Antacids (aluminium/magnesium) | Antacids can reduce the peak blood concentration of azithromycin by approximately 24%, though the overall absorption (AUC) is not significantly affected | Take azithromycin at least 1 hour before or 2 hours after antacids. This timing separation minimizes any reduction in absorption. |
| Atorvastatin | Co-administration may slightly increase atorvastatin plasma concentrations, though clinically significant interactions appear rare | No routine dose adjustment needed for short courses. Report any unexplained muscle pain, tenderness, or weakness (possible signs of rhabdomyolysis). |
| Theophylline | Unlike erythromycin and clarithromycin, azithromycin does not significantly alter theophylline metabolism. However, caution is still advised as individual variations may occur | Monitor theophylline levels if clinically indicated. The interaction risk is substantially lower than with other macrolides. |
| Zidovudine (AZT) | Azithromycin may slightly increase the bioavailability of zidovudine and its active metabolite, though the clinical significance is unclear | No dose adjustment is usually required. Monitor for increased zidovudine side effects if used concurrently. |
| Fluconazole | Fluconazole may slightly decrease the clearance of azithromycin, though this is generally not clinically significant | No dose adjustment typically required. Both drugs are commonly used together safely in clinical practice. |
| Rifabutin | Co-administration may increase the risk of neutropenia (low white blood cell count). Rifabutin may also reduce azithromycin concentrations | Monitor complete blood counts during concurrent use. This combination is sometimes used in MAC prophylaxis and treatment. |
There is no direct pharmacological interaction between azithromycin and alcohol. Moderate alcohol consumption does not reduce the antibacterial effectiveness of azithromycin. However, both azithromycin and alcohol can independently cause gastrointestinal side effects (nausea, stomach upset, diarrhea), which may be compounded when combined. Alcohol also impairs immune function and can delay recovery from infection. It is generally advisable to limit or avoid alcohol while taking any antibiotic and while recovering from an infection.
What Is the Correct Dosage of Azithromycin?
Azithromycin dosing is simplified by its long half-life, which allows for once-daily dosing and short treatment courses. The following recommendations are based on international guidelines including the EMA SmPC, FDA-approved labeling, and BNF. Always follow your doctor's specific instructions, as doses may be adjusted based on your individual clinical situation.
Adults and Adolescents (Over 45 kg Body Weight)
| Infection | Dose | Total Dose |
|---|---|---|
| Acute bacterial sinusitis | 500 mg once daily for 3 days | 1,500 mg |
| Acute otitis media | 500 mg once daily for 3 days | 1,500 mg |
| Pharyngitis / Tonsillitis | 500 mg Day 1, then 250 mg Days 2–5 | 1,500 mg |
| Acute exacerbation of chronic bronchitis | 500 mg Day 1, then 250 mg Days 2–5 | 1,500 mg |
| Community-acquired pneumonia (mild to moderate) | 500 mg Day 1, then 250 mg Days 2–5 | 1,500 mg |
| Skin and soft tissue infections | 500 mg Day 1, then 250 mg Days 2–5 | 1,500 mg |
| Chlamydia (urethral/cervical) | 1,000 mg as a single dose | 1,000 mg |
How to Take Azithromycin Tablets
Swallow the tablets whole with water. Do not chew or crush the tablets. Azithromycin film-coated tablets can be taken with or without food, as food does not significantly affect absorption of the tablet formulation.
Children and Adolescents (Under 45 kg Body Weight)
Pediatric Dosing
Azithromycin film-coated tablets are not recommended for infants or young children under 2 years of age, or for children and adolescents weighing less than 45 kg. For these patients, other formulations of azithromycin are available, such as oral suspension (liquid form), which allows for accurate weight-based dosing.
Standard pediatric dose (using oral suspension): 10 mg/kg once daily for 3 days (total dose: 30 mg/kg), or 10 mg/kg on Day 1 followed by 5 mg/kg on Days 2–5 (total dose: 30 mg/kg).
Pharyngitis/tonsillitis: 20 mg/kg/day (maximum 500 mg/day) for 3 days for streptococcal pharyngitis when penicillin cannot be used.
Children and adolescents who weigh 45 kg or more can use the same adult dosing regimens described above. Always use the measuring device provided with the oral suspension for accurate dosing in children. Your pediatrician will determine the correct dose based on your child's body weight and the type of infection being treated.
Elderly Patients
No specific dose adjustment is required for elderly patients with normal organ function. Elderly patients may use the same dose as younger adults. However, elderly patients are more likely to have conditions or take medications that increase the risk of QT prolongation, and they may also have reduced hepatic or renal function. Your doctor will take these factors into account when prescribing azithromycin.
Renal and Hepatic Impairment
Dose Adjustments
Mild to moderate kidney impairment: No dose adjustment is required.
Severe kidney impairment (GFR <10 ml/min): Caution is advised as there are limited data. Your doctor will assess whether azithromycin is appropriate.
Liver impairment: Azithromycin should be used with caution in patients with significant liver disease. Your doctor may need to monitor liver function. Azithromycin should not be used in patients with severe hepatic impairment due to the risk of hepatotoxicity.
Missed Dose
If you miss a dose of azithromycin, take it as soon as you remember. However, if it is nearly time for your next scheduled dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. Because azithromycin has such a long half-life, a single missed dose is less likely to significantly compromise treatment effectiveness compared to shorter-acting antibiotics, but it is still important to complete the full prescribed course.
Overdose
If you suspect an azithromycin overdose, contact your local emergency services, poison control center, or emergency department immediately. Take the medication packaging with you if possible.
Symptoms of azithromycin overdose may include severe nausea, vomiting, diarrhea, and temporary hearing loss or deafness. Treatment is supportive, focusing on managing symptoms and maintaining hydration. There is no specific antidote for azithromycin overdose. In cases of significant overdose, gastric lavage (stomach pumping) may be considered if performed within a short time after ingestion. Activated charcoal may also be administered to reduce further absorption. Audiological monitoring may be necessary if hearing symptoms develop.
What Are the Side Effects of Azithromycin?
Like all antibiotics, azithromycin can cause side effects, although not everyone experiences them. Most side effects are mild and self-limiting, resolving after the treatment course is completed. The following section classifies potential side effects by frequency, based on data from regulatory authorities, clinical trials, and post-marketing surveillance from sources including the EMA, FDA, and BNF.
Very Common
- Diarrhea: The most frequently reported side effect; usually mild and self-limiting, caused by disruption of normal gut flora
Common
- Headache: Usually mild and resolves without treatment
- Nausea and vomiting: Gastrointestinal upset, generally mild
- Abdominal pain: Stomach discomfort or cramping
- Changes in white blood cell counts: Altered levels of certain blood cells
- Low blood bicarbonate: Changes in blood chemistry values
Uncommon
- Oral or vaginal candidiasis (thrush): Fungal overgrowth due to disruption of normal bacterial flora
- Dizziness and drowsiness: May affect ability to drive
- Taste disturbance (dysgeusia): Altered or metallic taste
- Tingling or numbness (paresthesia): Abnormal sensations in hands or feet
- Visual disturbances: Blurred vision or other changes
- Hearing impairment or tinnitus: Reduced hearing or ringing in the ears
- Palpitations and hot flushes: Awareness of heartbeat, warmth
- Constipation, flatulence, dyspepsia: Various digestive complaints
- Skin rash, itching, urticaria (hives): Allergic skin reactions
- Joint pain and muscle pain: Musculoskeletal complaints
- Fatigue and malaise: General tiredness and feeling unwell
- Insomnia and nervousness: Sleep difficulties and anxiety
Rare
- Abnormal liver function: Elevated liver enzymes, jaundice (yellowing of skin/eyes)
- Photosensitivity: Increased skin sensitivity to sunlight
- Acute generalized exanthematous pustulosis (AGEP): Widespread pustular skin eruption with fever
- Drug reaction with eosinophilia (DRESS): Serious multi-organ reaction with rash, fever, and swollen lymph nodes
Reported (Frequency Not Known)
- Anaphylaxis: Severe, life-threatening allergic reaction requiring immediate epinephrine and emergency care
- Stevens-Johnson syndrome / Toxic epidermal necrolysis: Severe blistering and peeling skin reactions requiring hospital care
- QT prolongation and torsades de pointes: Potentially life-threatening abnormal heart rhythm
- Fulminant hepatitis and liver failure: Severe liver damage that can be life-threatening
- Pancreatitis: Inflammation of the pancreas causing severe abdominal pain
- Hemolytic anemia: Destruction of red blood cells
- Thrombocytopenia: Low platelet count causing unusual bleeding or bruising
- Syncope (fainting): Sudden loss of consciousness
- Seizures: Very rare neurological events
- Agitation, aggression, hallucinations, delirium: Psychiatric and behavioral changes
- Loss of smell or taste (anosmia, ageusia): Sensory disturbances
- Myasthenia gravis exacerbation: Worsening of pre-existing muscle weakness
- Interstitial nephritis and renal failure: Kidney inflammation and impairment
- Tongue discoloration: Harmless but noticeable color change
Stop taking azithromycin and seek emergency medical care if you experience: swelling of the face, lips, tongue, or throat; difficulty breathing or swallowing; severe skin rash with blistering or peeling; rapid or irregular heartbeat, dizziness, or fainting; severe or bloody diarrhea; dark urine, loss of appetite, or yellowing of the skin or eyes (jaundice); unexplained bleeding or bruising; severe abdominal pain.
Diarrhea is the most common side effect of azithromycin, occurring in approximately 5–10% of patients. It is usually mild and resolves after completing the course. However, if you develop severe, persistent, or bloody diarrhea during or after treatment, this could indicate Clostridioides difficile-associated colitis (pseudomembranous colitis), a serious condition that requires medical attention. Do not take anti-diarrheal medications without consulting your doctor, as they can worsen certain types of infective diarrhea.
If you experience any adverse effects while taking azithromycin, even if they are not listed here, you can report them directly to your national pharmacovigilance authority (e.g., the MHRA Yellow Card scheme in the UK, the FDA MedWatch program in the US, or the EMA EudraVigilance system in Europe). Reporting helps monitor the ongoing safety of medicines.
How Should You Store Azithromycin?
Proper storage of azithromycin is important to ensure the medication remains effective and safe throughout its use. Follow these guidelines:
- Film-coated tablets: No special storage conditions are required for azithromycin film-coated tablets. Store at room temperature in the original packaging. Keep the tablets in their blister pack until you are ready to take them to protect from moisture.
- Expiry date: Do not use azithromycin after the expiry date printed on the packaging (after "EXP"). The expiry date refers to the last day of the stated month.
- Child safety: Keep all medicines securely out of the sight and reach of children.
- Disposal: Do not dispose of medications via household waste or down drains. Return unused or expired azithromycin to your local pharmacy for safe disposal. This helps protect the environment.
If the tablets appear discolored, damaged, or the packaging is compromised, do not take them. Consult your pharmacist for a replacement.
What Does Azithromycin Contain?
All azithromycin tablet formulations contain azithromycin as the active pharmaceutical ingredient, in the form of azithromycin dihydrate. The inactive ingredients (excipients) serve various pharmaceutical functions and may vary slightly depending on the manufacturer and tablet strength.
Tablet Composition
250 mg film-coated tablets: Each tablet contains 250 mg azithromycin (as azithromycin dihydrate). The tablet core contains microcrystalline cellulose (E460), pregelatinized potato starch, sodium lauryl sulfate, hypromellose (E464), croscarmellose sodium (E468), colloidal anhydrous silica (E551), and magnesium stearate (E470b). The film coating contains hypromellose 5 cP (E464), titanium dioxide (E171), and macrogol 400. The tablets are white to off-white, capsule-shaped, and marked with "S19" on one side.
500 mg film-coated tablets: Each tablet contains 500 mg azithromycin (as azithromycin dihydrate). The tablet core has the same composition as the 250 mg tablets. The film coating contains macrogol poly(vinyl alcohol)-graft copolymer, titanium dioxide (E171), talc, glycerol monocaprylocaprate, and poly(vinyl alcohol). The tablets are white to off-white, capsule-shaped, marked with "S5" on one side, and have a score line on the other side. The tablet can be divided into two equal doses.
This medicine contains less than 1 mmol (23 mg) sodium per dose, and is therefore essentially sodium-free. This information is relevant for patients on a sodium-restricted diet.
Pack sizes: 250 mg tablets are available in cartons of 4 and 6 tablets in blisters. 500 mg tablets are available in cartons of 2, 3, and 30 tablets in blisters. Not all pack sizes may be marketed in all countries.
If you have known allergies to any excipients (such as sodium lauryl sulfate or titanium dioxide), always check the specific product's patient information leaflet or consult your pharmacist before taking any azithromycin product. Different manufacturers may use slightly different inactive ingredients.
Frequently Asked Questions About Azithromycin
Azithromycin is a macrolide antibiotic used to treat various bacterial infections. The most common indications include acute bacterial sinusitis, acute bacterial otitis media (ear infections), pharyngitis and tonsillitis (throat infections), acute exacerbation of chronic bronchitis, mild to moderate community-acquired pneumonia, skin and soft tissue infections (such as cellulitis, folliculitis, and erysipelas), and sexually transmitted infections caused by Chlamydia trachomatis. Azithromycin is also used in the prevention and treatment of Mycobacterium avium complex (MAC) infections in immunocompromised patients. Azithromycin does not work against viral infections such as the common cold, flu, or COVID-19.
Azithromycin has a remarkably long elimination half-life of approximately 68 hours, which is much longer than most other antibiotics. This means that even after your last dose, the drug continues to work at the site of infection for approximately 5 to 7 additional days. After a typical 3-day treatment course, effective antibiotic concentrations remain in infected tissues for up to 10 days. This unique pharmacokinetic property is why short 3- to 5-day courses of azithromycin are as effective as 10-day courses of many other antibiotics. The drug is eventually eliminated from the body primarily via the liver and feces, with a small proportion excreted through the kidneys.
Yes, azithromycin film-coated tablets can be taken with or without food, as food does not significantly affect the absorption of the tablet formulation. This makes the tablets convenient to take at any time during the day. However, it is important to note that azithromycin oral suspension (liquid form, commonly used for children) may have different food interaction requirements – some liquid formulations are better absorbed on an empty stomach. If you are taking antacids containing aluminium or magnesium hydroxide, take them at least 1 hour before or 2 hours after your azithromycin dose, as they can reduce peak drug absorption.
There is no direct pharmacological interaction between azithromycin and alcohol, meaning alcohol does not make azithromycin less effective or create a dangerous chemical reaction. However, both azithromycin and alcohol can independently cause gastrointestinal side effects such as nausea, vomiting, and diarrhea, which may be worsened when combined. Alcohol also impairs your immune system's ability to fight infections and can delay recovery. Additionally, azithromycin can in rare cases affect the liver, and alcohol is also metabolized by the liver, so combining them may place additional stress on liver function. It is generally advisable to avoid or minimize alcohol consumption while you are taking antibiotics and recovering from an infection.
Azithromycin and amoxicillin belong to different antibiotic classes and work by different mechanisms. Azithromycin is a macrolide that inhibits bacterial protein synthesis, while amoxicillin is a penicillin that disrupts bacterial cell wall synthesis. Key differences include: Dosing frequency: Azithromycin is taken once daily for 3–5 days thanks to its long 68-hour half-life, while amoxicillin typically requires 2–3 doses per day for 5–14 days. Allergy cross-reactivity: Azithromycin is safe for patients with penicillin allergy, making it an important alternative. Spectrum of activity: Azithromycin has better coverage of atypical respiratory pathogens (Mycoplasma, Chlamydophila, Legionella), while amoxicillin has stronger activity against Streptococcus pneumoniae. Resistance: Macrolide resistance is increasing globally, which sometimes limits azithromycin's effectiveness. Your doctor will choose the most appropriate antibiotic based on the type of infection, local resistance patterns, and your medical history.
Azithromycin should be used during pregnancy only when the potential benefit justifies the potential risk to the fetus. While animal studies have not shown harmful effects, controlled studies in pregnant women are limited. Azithromycin is sometimes used during pregnancy when other antibiotics are unsuitable, particularly for chlamydia treatment, where it is considered a first-line option by major guidelines including the CDC. Regarding breastfeeding, azithromycin is excreted in breast milk in small amounts. The effects on the nursing infant are not well studied, but potential concerns include diarrhea, candidiasis, or sensitization. Your doctor will weigh the benefits of treatment against any potential risks when advising on use during pregnancy or breastfeeding.
References
This article is based on current international medical guidelines, regulatory documents, and peer-reviewed research. All sources meet evidence level 1A standards.
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List. Geneva: WHO; 2023. Azithromycin is listed as an essential antibiotic for the treatment of common bacterial infections and sexually transmitted infections.
- European Medicines Agency (EMA). Azithromycin – Summary of Product Characteristics. EMA/CHMP; 2024. Comprehensive regulatory document covering indications, dosing, contraindications, interactions, and safety data.
- U.S. Food and Drug Administration (FDA). Zithromax (Azithromycin) Prescribing Information. FDA; 2023. Approved labeling including pharmacology, clinical studies, and adverse reactions.
- Joint Formulary Committee. British National Formulary (BNF) – Azithromycin Monograph. London: BMJ Group and Pharmaceutical Press; 2024. Evidence-based prescribing reference for UK healthcare professionals.
- Parnham MJ, Erakovic Haber V, Giamarellos-Bourboulis EJ, Perletti G, Verleden GM, Vos R. Azithromycin: mechanisms of action and their relevance for clinical applications. Pharmacol Ther. 2014;143(2):225-245. doi:10.1016/j.pharmthera.2014.03.003
- World Health Organization (WHO). AWaRe Classification of Antibiotics for Evaluation and Monitoring of Use. Geneva: WHO; 2023. Framework for responsible antibiotic use classifying azithromycin as a Watch antibiotic.
- Ray WA, Murray KT, Hall K, Arbogast PG, Stein CM. Azithromycin and the risk of cardiovascular death. N Engl J Med. 2012;366(20):1881-1890. doi:10.1056/NEJMoa1003833
- Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep. 2021;70(No. RR-4):1-187. Azithromycin recommended as first-line treatment for chlamydia.
- National Institute for Health and Care Excellence (NICE). Antimicrobial Prescribing Guidelines. NICE; 2024. Evidence-based guidelines for the management of common infections in primary and secondary care.
- Saiman L, Marshall BC, Mayer-Hamblett N, et al. Azithromycin in patients with cystic fibrosis chronically infected with Pseudomonas aeruginosa: a randomized controlled trial. JAMA. 2003;290(13):1749-1756. doi:10.1001/jama.290.13.1749
Editorial Team
This article has been written and reviewed by the iMedic medical editorial team according to our strict editorial standards. Our team consists of licensed physicians, pharmacists, and medical researchers with expertise in clinical pharmacology and infectious disease.
Content developed by iMedic's medical writing team based on current international guidelines (WHO, EMA, FDA, BNF, NICE) and peer-reviewed pharmacological research.
Independently reviewed and fact-checked by the iMedic Medical Review Board, comprising board-certified specialists in clinical pharmacology and infectious disease medicine.
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