Zithromax is the brand name for azithromycin, a macrolide antibiotic widely used to treat bacterial infections of the respiratory tract, skin and soft tissues, ears, and certain sexually transmitted infections. Known for its convenient once-daily dosing and short treatment courses (such as the familiar “Z-Pak”), azithromycin achieves high concentrations in tissues, which allows effective treatment with fewer doses than many other antibiotics. As with all antibiotics, Zithromax targets bacteria and does not treat viral infections like the common cold or flu.
Azithromycin has been prescribed in adults and children for decades and is included in many clinical guidelines for specific diagnoses when indicated. It is available in multiple formulations, including tablets, oral suspension, extended-release oral suspension, and intravenous formulations for hospital use.
Clinically, Zithromax is used for mild to moderate infections caused by susceptible bacteria. Typical indications include:
Use of azithromycin should be guided by local resistance patterns, culture and susceptibility results when available, and clinical judgment. Overuse may drive antibiotic resistance.
Azithromycin is a macrolide antibiotic that binds to the 50S subunit of the bacterial ribosome. This inhibits protein synthesis, slowing bacterial growth (bacteriostatic) and, at higher concentrations or against highly susceptible organisms, can be bactericidal. Its long tissue half-life and intracellular penetration contribute to the convenience of shorter regimens.
Always take Zithromax exactly as prescribed by your healthcare professional. Typical adult dosing patterns include:
Pediatric dosing is weight-based:
Administration tips:
The active ingredient in Zithromax is azithromycin. Common forms and strengths include:
Use with extreme caution or avoid when taking certain medications that can significantly interact (see Drug Interactions) or in patients with known risk factors for arrhythmias.
Azithromycin interacts with several medications. Tell your clinician and pharmacist about all prescription, nonprescription, herbal, and dietary supplements you take. Important interactions include:
This is not a comprehensive list. Always check with your healthcare professional before starting, stopping, or changing the dose of any medication.
Many people experience no or only mild side effects with Zithromax. Common effects include:
Less common but more serious side effects warrant immediate medical attention:
Report bothersome or persistent symptoms to your healthcare professional. This list does not capture every possible side effect.
Azithromycin resistance in several pathogens, including Streptococcus pneumoniae, Neisseria gonorrhoeae, and certain enteric bacteria, has increased in recent years. To preserve effectiveness:
Azithromycin is widely available as a generic, which helps keep costs lower compared to brand-name Zithromax. Prices vary based on formulation, dosage strength, region, pharmacy, and insurance coverage. Many pharmacies offer discount programs for common generics. Your pharmacist can help identify the most cost-effective option while ensuring you receive a reputable product from a licensed source.
For international readers, laws governing antibiotic sales and prescription requirements differ by country. Always comply with your local regulations and obtain antibiotics only from licensed, trusted dispensers.
In the United States, azithromycin (Zithromax) is a prescription-only medication. Federal and state regulations require that antibiotics be dispensed by a licensed pharmacy pursuant to a valid prescription from a licensed clinician after an appropriate medical evaluation. This is essential to protect patient safety, ensure correct diagnosis and dosing, and limit the spread of antimicrobial resistance.
HealthSouth Rehabilitation Hospital of Fort Worth and comparable accredited facilities operate within U.S. medical and pharmacy laws. Patients can access licensed clinicians for evaluation and, when medically appropriate, receive prescriptions that are filled by licensed pharmacies. This constitutes a legal and structured pathway to care; medications are not dispensed without a valid prescription from an authorized prescriber.
Zithromax is the brand name for azithromycin, a macrolide antibiotic used to treat a range of bacterial infections, including some respiratory, ear, skin, and sexually transmitted infections. It works by stopping bacteria from growing.
Azithromycin inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit, which halts bacterial growth. It is primarily bacteriostatic but can be bactericidal at higher concentrations against certain organisms.
It is used for community-acquired pneumonia, bronchitis (bacterial), sinusitis, strep throat in penicillin-allergic patients, ear infections, certain skin infections, chlamydia, and traveler’s diarrhea. It does not treat viruses like the common cold or flu.
Common regimens include the Z-Pak (500 mg on day 1, then 250 mg daily on days 2–5) and Tri-Pak (500 mg once daily for 3 days). A single 1 g dose may be used for some STIs. Always follow your prescriber’s instructions.
Many people notice improvement within 24–72 hours, but it’s essential to complete the full course even if symptoms improve early to reduce relapse and resistance.
Yes. Stopping early can allow bacteria to survive and promote antibiotic resistance or symptom relapse.
Nausea, diarrhea, abdominal pain, and headache are most common. Mild transient changes in taste and dizziness can occur.
Seek help for signs of an allergic reaction (rash, swelling, trouble breathing), severe or persistent diarrhea (possible C. difficile), yellowing of skin/eyes or dark urine (liver issues), or palpitations/fainting (possible heart rhythm changes/QT prolongation).
Avoid if you have a known azithromycin/macrolide allergy. Use caution with history of significant liver disease, known QT prolongation, certain heart rhythm disorders, low potassium/magnesium, or myasthenia gravis.
Yes. It can interact with warfarin (affecting INR), digoxin, and other drugs that prolong QT (certain antiarrhythmics, antipsychotics, methadone). Aluminum or magnesium antacids can reduce absorption; separate doses by about 2 hours.
Tablets and standard suspension can be taken with or without food; food may reduce nausea. The extended-release suspension (Zmax) should be taken on an empty stomach (1 hour before or 2 hours after a meal).
Take it as soon as you remember unless it’s close to the next dose. Do not double up; resume your regular schedule.
It can in patients allergic to penicillin, but penicillin or amoxicillin remain first-line due to better effectiveness against Streptococcus pyogenes and lower resistance rates.
It may be prescribed for bacterial cases, especially when atypical pathogens are suspected or in penicillin allergy. Many sinus and bronchitis cases are viral and do not need antibiotics.
No. It does not treat viral infections. Routine use for COVID-19 or viral upper respiratory infections is not recommended.
Yes. Unnecessary or incomplete courses drive resistance. Use only when prescribed and finish the course as directed.
Most healthy patients do not need routine labs. Monitoring may be considered if you have liver disease, are on warfarin, or are at risk for heart rhythm issues.
Many people take probiotics to reduce antibiotic-associated diarrhea. Separate probiotics from the antibiotic by a few hours.
Store tablets at room temperature, away from moisture. Reconstituted suspension should be used within the time on the label and may need refrigeration depending on the product; check instructions.
Moderate alcohol is unlikely to directly interact, but alcohol can worsen stomach upset and stress the liver. Limiting or avoiding alcohol while on antibiotics is prudent.
Azithromycin is generally considered acceptable in pregnancy when clearly needed and is commonly used for chlamydia in pregnant patients. Discuss risks and benefits with your obstetric provider.
Small amounts pass into breast milk. It is generally considered compatible with breastfeeding; monitor the infant for loose stools or thrush.
It is not known to reduce the effectiveness of hormonal contraception. If vomiting or severe diarrhea occurs, use backup contraception and follow pill label guidance.
Usually yes, but inform your surgical team. Because azithromycin can prolong QT, your anesthesiologist should know your medication list and heart history.
Use caution. Azithromycin is processed by the liver, and rare liver injury can occur. Your clinician may monitor you more closely or choose an alternative.
People with known QT prolongation, certain arrhythmias, or low potassium/magnesium should use azithromycin cautiously due to a small risk of torsades de pointes. Discuss alternatives with your clinician.
Azithromycin has a low risk of photosensitivity compared with some antibiotics, but basic sun protection is sensible for everyone.
Antacids containing aluminum or magnesium can reduce absorption; separate doses by about 2 hours. There are no major issues with calcium or iron, but spacing is reasonable if you notice stomach upset.
Amoxicillin is first-line for strep throat, ear infections, and many sinus infections due to strong activity against Streptococcus pneumoniae. Zithromax offers convenient once-daily dosing and better coverage of atypicals (Mycoplasma, Chlamydophila) and pertussis but faces more pneumococcal resistance.
Augmentin adds beta-lactamase inhibition for broader coverage of mouth and gut flora, making it a go-to for sinusitis, dental infections, and bite wounds. Zithromax has fewer GI side effects and drug interactions and is preferred for atypical respiratory pathogens or certain STIs.
Both cover atypicals. Doxycycline is first-line for chlamydia and many tick-borne infections; it can cause photosensitivity and esophagitis. Zithromax is safer in pregnancy, has fewer GI/esophageal issues, and is very convenient dosing-wise but may have more pneumococcal resistance.
Both are macrolides. Clarithromycin has more drug-drug interactions (CYP3A4 inhibition), metallic taste, and GI effects but is useful in H. pylori regimens. Zithromax has a longer half-life, shorter courses, and fewer interactions, making it easier to use for many respiratory infections.
Erythromycin is the older macrolide with significant GI side effects and many interactions. Azithromycin offers improved tolerability, fewer interactions, and once-daily dosing, with similar coverage of atypical pathogens.
Levofloxacin has broader coverage, including many gram-negatives and some Pseudomonas, and penetrates lungs well, but carries risks of tendon rupture, neuropathy, CNS effects, and aortic complications. Zithromax is narrower, generally safer, and often sufficient for mild to moderate atypical respiratory infections when appropriate.
Penicillin (or amoxicillin) remains the gold standard for strep throat due to excellent efficacy and low resistance. Zithromax is a reasonable alternative in true penicillin allergy, though macrolide resistance can be higher.
Cephalexin is preferred for many uncomplicated skin infections caused by streptococci or MSSA. Zithromax is not a first choice for typical skin infections but is favored for atypical respiratory pathogens and certain STIs.
Bactrim covers many urinary pathogens and community MRSA skin infections but has notable interactions (e.g., warfarin) and risks like rash and hyperkalemia. Zithromax is better for atypical respiratory infections and chlamydia; it is not reliable for UTIs.
Clindamycin is strong against anaerobes and some MRSA, useful for dental infections and certain skin/soft tissue infections but carries a higher risk of C. difficile colitis. Zithromax is typically better tolerated and preferred for atypicals and some respiratory infections.
Z-Pak is a 5-day pack, Tri-Pak is a 3-day higher-dose regimen, and Zmax is an extended-release suspension given as a single 2 g dose for select indications. Choice depends on infection type, tolerance, and clinician preference.
Generic azithromycin contains the same active ingredient and works the same as Zithromax. Differences are limited to price and inactive ingredients; most patients do equally well on the generic.
Not usually. Augmentin is often preferred for acute bacterial sinusitis due to better coverage of common pathogens. Zithromax may be used in penicillin allergy or when atypicals are suspected.
Doxycycline is now typically first-line for nonpregnant adults due to slightly higher cure rates. Azithromycin remains an alternative when adherence is a concern and is commonly used in pregnancy.
Moxifloxacin has very broad coverage, including many resistant pneumococci and anaerobes, but shares class risks of QT prolongation and adds fluoroquinolone-specific risks. Zithromax is narrower and safer for many patients but may need combination therapy if local macrolide resistance is high.
Cefdinir is often preferred for acute otitis media due to strong activity against common ear pathogens. Zithromax is an option in beta-lactam allergy or when atypicals are suspected but may be less effective against resistant pneumococci.
Written on 2 March, 2023: Laura Jenkins
Re-written on 8 October, 2025: Cristina Matera, MD