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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice.
Other
Azithromycin is a potent macrolide antibiotic used to treat a wide range of bacterial infections. It works by inhibiting bacterial protein synthesis, effectively stopping the growth of bacteria in the respiratory tract, skin, and other systems.
Name
Azithromycin
Raw Name
AZITHROMYCIN MONOHYDRATE
Category
Other
Salt Form
Monohydrate
Drug Count
7
Variant Count
208
Last Verified
February 17, 2026
RxCUI
308460, 749783, 248656, 141963, 308459, 749780, 204844, 861416, 1668238, 706868, 706872, 105260, 211307, 212446, 226827, 750149, 750157, 1668240
UNII
JTE4MNN1MD, 5FD1131I7S
About Azithromycin
Azithromycin is a potent macrolide antibiotic used to treat a wide range of bacterial infections. It works by inhibiting bacterial protein synthesis, effectively stopping the growth of bacteria in the respiratory tract, skin, and other systems.
Detailed information about Azithromycin
This page is for informational purposes only and does not replace medical advice. Consult a qualified healthcare professional before using any medication containing Azithromycin.
Azithromycin is a broad-spectrum antibiotic belonging to the macrolide class, specifically a sub-class known as azalides. It is chemically derived from erythromycin but features a structural modification (the insertion of a methyl-substituted nitrogen atom into the lactone ring) that significantly enhances its acid stability, tissue penetration, and spectrum of activity. Since its initial FDA approval in 1991 under the brand name Zithromax, azithromycin has become one of the most frequently prescribed antibiotics globally due to its convenient dosing schedules and high efficacy against both Gram-positive and Gram-negative pathogens.
In clinical practice, azithromycin is utilized to combat various bacterial infections, including those of the respiratory tract, skin, and certain sexually transmitted infections (STIs). Unlike many other antibiotics that require multiple daily doses over a week or more, azithromycin’s unique chemical structure allows for shorter courses—often three to five days—because the medication remains in the body's tissues at therapeutic levels long after the final dose is consumed. It is important to note that azithromycin is effective only against bacterial infections; it does not treat viral infections such as the common cold, influenza, or COVID-19.
Azithromycin exerts its antibacterial effect by interfering with the protein synthesis process within the bacterial cell. At the molecular level, it binds reversibly to the 50S ribosomal subunit of susceptible microorganisms. By binding to this specific site, azithromycin inhibits the transpeptidation/translocation step of protein synthesis, effectively preventing the assembly of essential proteins required for the bacteria to grow, replicate, and maintain cellular function.
While azithromycin is primarily bacteriostatic (meaning it inhibits growth rather than killing bacteria directly), it can be bactericidal (killing the bacteria) against certain species or when present in high concentrations. A unique feature of azithromycin is its ability to accumulate within human white blood cells, specifically phagocytes (cells that protect the body by ingesting harmful foreign particles). These phagocytes then transport the drug directly to the site of infection, where it is released in high concentrations. This "targeted delivery" mechanism explains why the drug is so effective even with short treatment durations.
Understanding the pharmacokinetics (how the body processes the drug) of azithromycin is crucial for optimizing its clinical use.
Azithromycin is FDA-approved for a variety of clinical indications in both adults and children. These include:
Off-label uses may include the treatment of acne vulgaris, gastroparesis (due to its prokinetic effects), and certain types of traveler's diarrhea, though these should only be pursued under strict medical supervision.
Azithromycin is available in several formulations to accommodate different patient needs:
> Important: Only your healthcare provider can determine if Azithromycin is right for your specific condition. Misuse of antibiotics can lead to antibiotic resistance, making future infections harder to treat.
The dosage of azithromycin varies significantly depending on the type and severity of the infection being treated. Typical adult regimens include:
Azithromycin is approved for use in children aged 6 months and older for most indications. Dosing is strictly based on the child's weight (mg/kg):
It is critical to use a calibrated measuring device (not a household spoon) when administering the oral suspension to ensure accurate dosing.
For patients with mild to moderate kidney dysfunction (GFR 10-80 mL/min), no dosage adjustment is typically required. However, caution should be exercised in patients with severe renal impairment (GFR < 10 mL/min), as data in this population are limited.
Since the liver is a primary route of elimination for azithromycin, it should be used with caution in patients with significant hepatic disease. If signs of liver dysfunction (such as jaundice or dark urine) appear, the medication should be discontinued immediately.
No specific dosage adjustments are generally required for geriatric patients based solely on age. However, older adults may be more susceptible to developing the "Torsades de Pointes" arrhythmia (a dangerous heart rhythm) associated with QT prolongation, so cardiovascular monitoring may be necessary.
If you miss a dose, take it as soon as you remember. If it is almost time for your next scheduled dose, skip the missed dose and continue with your regular schedule. Do not take a double dose to make up for a missed one.
Symptoms of an azithromycin overdose may include severe nausea, vomiting, diarrhea, and hearing loss. In the event of a suspected overdose, contact your local poison control center or seek emergency medical attention immediately.
> Important: Follow your healthcare provider's dosing instructions precisely. Do not adjust your dose or share your medication with others without medical guidance.
Azithromycin is generally well-tolerated, but gastrointestinal issues are the most frequently reported side effects. These occur because the medication can stimulate the motilin receptors in the gut, increasing motility. Common symptoms include:
These side effects are usually mild to moderate. If they become severe or persistent, you should contact your healthcare provider.
While rare, some side effects of azithromycin can be life-threatening. Stop taking the medication and seek emergency care if you experience:
> Warning: Stop taking Azithromycin and call your doctor immediately if you experience any of these serious symptoms.
Azithromycin is rarely used long-term, but in cases where it is (such as for MAC prevention or cystic fibrosis management), patients must be monitored for:
There are currently no FDA Black Box Warnings for azithromycin. However, the FDA has issued several Safety Communications regarding the risk of potentially fatal heart rhythms (QT prolongation) and the risk of relapse in patients who have undergone blood or marrow stem cell transplants.
Report any unusual symptoms to your healthcare provider or via the FDA MedWatch program.
Azithromycin is a powerful medication that requires careful screening by a healthcare professional. It is not suitable for everyone, particularly those with certain underlying heart or liver conditions. Patients must be honest with their providers regarding their full medical history, including any history of "long QT syndrome" or low levels of potassium or magnesium in the blood.
No FDA black box warnings for Azithromycin. However, the FDA has issued a specific safety alert regarding its use in patients who have received a lung or blood/marrow transplant, as long-term use in these patients may increase the risk of cancer relapse or death.
Azithromycin can cause serious allergic reactions, including angioedema (deep tissue swelling) and anaphylaxis. Unlike some other drugs, the allergic symptoms can disappear and then reappear days later without further exposure to the drug. This requires prolonged observation and potentially multiple rounds of treatment for the allergy.
Abnormal liver function, hepatitis, cholestatic jaundice, and hepatic necrosis have been reported. Some of these cases have resulted in death. If you develop symptoms of liver dysfunction, the drug must be stopped immediately and liver function tests (LFTs) should be performed.
Azithromycin can prolong the QT interval (the time it takes for the heart muscle to recharge between beats). This can lead to Torsades de Pointes, a life-threatening ventricular tachycardia. The risk is highest in:
Azithromycin may worsen symptoms of myasthenia gravis (a chronic autoimmune neuromuscular disease) or trigger a new onset of the condition. Patients with this condition should use azithromycin only if no other options are available.
For short-term use (3-5 days), intensive lab monitoring is usually unnecessary. However, for longer courses or in high-risk patients, doctors may monitor:
Azithromycin generally does not interfere with the ability to drive or operate machinery. However, if you experience side effects like dizziness, blurred vision, or fainting, you should avoid these activities until you know how the medication affects you.
There is no direct chemical interaction between alcohol and azithromycin that reduces the antibiotic's efficacy. However, alcohol can cause dehydration and stomach upset, which may worsen the side effects of the medication and slow your recovery from infection. It is generally advised to avoid alcohol while fighting an infection.
There is no withdrawal syndrome associated with stopping azithromycin. However, failing to complete the full course can lead to a relapse of the infection and the development of antibiotic-resistant bacteria. If you must stop the drug due to side effects, contact your doctor immediately to discuss an alternative treatment.
> Important: Discuss all your medical conditions with your healthcare provider before starting Azithromycin.
Certain drugs should never be used with azithromycin due to the extreme risk of fatal heart arrhythmias (QT prolongation). These include:
Azithromycin does not typically interfere with common laboratory tests, though it may cause false elevations in certain liver function tests or urinary protein measurements in rare instances.
For each major interaction, the mechanism usually involves either the inhibition of drug transporters (like P-glycoprotein) or additive pharmacodynamic effects (like both drugs prolonging the QT interval). The management strategy usually involves dose adjustment, increased monitoring, or choosing an alternative antibiotic.
> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking.
Azithromycin must NEVER be used in the following circumstances:
These are conditions where the risk-benefit ratio must be carefully weighed by a physician:
Patients allergic to azithromycin are likely allergic to all drugs in the macrolide class. There is no known cross-sensitivity between azithromycin and penicillins or cephalosporins, which makes it a common alternative for patients with "penicillin allergies." However, always confirm your specific allergy profile with an allergist or your primary physician.
> Important: Your healthcare provider will evaluate your complete medical history before prescribing Azithromycin. Never take an antibiotic that was prescribed for someone else.
Azithromycin is classified as Pregnancy Category B under the older FDA system. This means that animal reproduction studies have failed to demonstrate a risk to the fetus, but there are no adequate and well-controlled studies in pregnant women.
Azithromycin is excreted into human breast milk. While it is generally considered compatible with breastfeeding by the American Academy of Pediatrics, clinicians should monitor the nursing infant for:
Azithromycin is approved for children as young as 6 months for ear infections and pneumonia, and for children of all ages for pharyngitis.
Elderly patients (65 and older) may be more sensitive to the drug's effects on the heart.
Azithromycin is primarily eliminated through the liver and bile. In patients with mild-to-moderate hepatic impairment, the pharmacokinetics do not seem to change significantly. However, in patients with severe liver disease (Child-Pugh Class C), the drug should be used with extreme caution, and treatment should be stopped if any signs of worsening liver function occur.
> Important: Special populations require individualized medical assessment to ensure the safest possible treatment outcome.
Azithromycin is an azalide antibiotic, a subclass of the macrolide class. Its molecular mechanism involves binding to the 23S rRNA of the 50S ribosomal subunit of susceptible bacteria. This binding blocks the exit tunnel through which newly synthesized polypeptide chains pass, effectively halting bacterial protein synthesis. Because human ribosomes are structurally different from bacterial ribosomes, the drug does not typically interfere with human protein synthesis.
| Parameter | Value |
|---|---|
| Bioavailability | ~37% |
| Protein Binding | 7% to 51% (concentration-dependent) |
| Half-life | ~68 hours |
| Tmax | 2 to 3 hours |
| Metabolism | Minimal (Hepatic) |
| Excretion | Biliary (~70%), Renal (~6-12%) |
Azithromycin is a macrolide antibiotic of the azalide subclass. It is related to other macrolides such as erythromycin and clarithromycin, and the ketolide telithromycin. Its primary advantage over its predecessors is its superior tissue distribution and reduced potential for CYP450-mediated drug interactions.
Medications containing this ingredient
Common questions about Azithromycin
Azithromycin is a broad-spectrum antibiotic used to treat various bacterial infections, including respiratory tract infections like pneumonia, bronchitis, and sinusitis. It is also commonly prescribed for skin infections, ear infections (otitis media), and certain sexually transmitted diseases such as chlamydia. Your doctor may also use it to treat or prevent Mycobacterium avium complex (MAC) in patients with weakened immune systems. It is important to remember that it only works against bacteria and will not treat viral infections like the flu. Always consult your healthcare provider to ensure it is the correct treatment for your specific symptoms.
The most common side effects of azithromycin involve the digestive system, including diarrhea, nausea, and abdominal pain. Some patients may also experience vomiting, headaches, or dizziness shortly after taking the medication. These symptoms are usually mild and tend to resolve once the treatment course is completed. However, if you experience severe watery or bloody diarrhea, you should contact your doctor immediately as this could indicate a serious colon infection. Most people tolerate the medication well, but it is important to report any persistent discomfort to your medical provider.
There is no known direct chemical interaction between alcohol and azithromycin that makes the antibiotic stop working. However, drinking alcohol while you have an active infection can slow your recovery by causing dehydration and disrupting your sleep. Additionally, both alcohol and azithromycin can cause stomach upset and nausea, so combining them may make these side effects much worse. To give your body the best chance to heal, most healthcare providers recommend avoiding alcohol until you have finished your medication and feel fully recovered. Always check with your doctor for personalized advice based on your health status.
Azithromycin is generally considered one of the safer antibiotics to use during pregnancy and is often the first-choice treatment for certain infections in pregnant women. It is classified as FDA Pregnancy Category B, meaning animal studies have shown no harm to the fetus, though human data is more limited. Many doctors prefer it over other antibiotics like doxycycline, which can cause permanent tooth discoloration in the developing baby. However, it should still only be used when the benefits clearly outweigh the risks. If you are pregnant or planning to become pregnant, discuss the potential risks and benefits with your OB/GYN before starting treatment.
Most patients begin to feel an improvement in their symptoms within 24 to 48 hours of taking the first dose of azithromycin. However, the medication continues to work in your body for several days after your last dose because it concentrates in your tissues and stays there for a long time. Even if you feel completely better after just one or two days, you must finish the entire prescribed course to ensure the infection is fully cleared. If your symptoms do not improve or if they get worse after three days of treatment, contact your healthcare provider. They may need to re-evaluate the diagnosis or the choice of antibiotic.
You should never stop taking azithromycin or any antibiotic suddenly without first consulting your healthcare provider. Stopping the medication early, even if you feel better, can allow the remaining bacteria to continue growing and potentially lead to a relapse of the infection. Furthermore, incomplete treatment contributes to the development of antibiotic resistance, which makes future infections much harder to treat. If you are experiencing severe side effects that make it difficult to continue the medication, call your doctor immediately. They can determine if you need to switch to a different antibiotic to complete your treatment safely.
If you miss a dose of azithromycin, take it as soon as you remember to maintain the necessary levels of the drug in your system. However, if it is almost time for your next scheduled dose, you should skip the missed dose and simply take your next one at the regular time. Never take two doses at once to make up for a missed one, as this can increase your risk of experiencing side effects like nausea or stomach pain. If you miss more than one dose, it is a good idea to contact your pharmacist or doctor for guidance. Consistency is key to ensuring the antibiotic successfully eliminates the bacteria.
Weight gain is not a typical or documented side effect of short-term azithromycin use. Most courses of this antibiotic last only three to five days, which is not long enough to cause significant changes in body weight. Some patients might experience temporary bloating or water retention due to gastrointestinal upset, but this is not actual fat gain. If you notice rapid or unusual weight gain while taking this medication, it could be a sign of a different medical issue or a rare reaction like kidney or heart problems. You should discuss any unexpected weight changes with your healthcare provider to determine the underlying cause.
Azithromycin can interact with several other medications, so it is vital to provide your doctor with a complete list of everything you are taking. It can interact with blood thinners like warfarin, increasing the risk of bleeding, and with heart medications like digoxin. It also should not be taken at the same time as antacids containing aluminum or magnesium, as these can prevent the antibiotic from being absorbed properly. Perhaps most importantly, it can interact with other drugs that affect your heart rhythm. Always consult your pharmacist or doctor before starting any new supplements or over-the-counter drugs while on azithromycin.
Yes, azithromycin is widely available as a generic medication and is typically much more affordable than the brand-name versions like Zithromax. Generic azithromycin is required by the FDA to have the same active ingredient, strength, dosage form, and route of administration as the brand-name drug. It must also prove bioequivalence, meaning it works in the body the same way and provides the same clinical benefit. Most insurance plans cover the generic version of azithromycin. If you have concerns about the cost or the specific manufacturer of your medication, speak with your pharmacist about the options available to you.