Azithromycin: Uses, dosage, side effects, warnings & patient reviews

What is Azithromycin?

Azithromycin is a prescription antibiotic belonging to the macrolide class. It is the active ingredient in the brand-name medication Zithromax and its generic equivalents. The medication works by inhibiting bacterial protein synthesis, thereby stopping the growth of susceptible bacteria.

Azithromycin is distinguished by its pharmacokinetic profile, which allows it to achieve high concentrations in infected tissues and remain active for several days after the last dose. This property enables shorter treatment courses, typically 3 to 5 days, compared to many other antibiotics.

It is important to understand that azithromycin, like all antibiotics, is only effective against bacterial infections and has no activity against viral illnesses such as the common cold or influenza.

How to Take Azithromycin

Follow your healthcare provider’s instructions precisely. The dosing schedule varies significantly depending on the type of infection being treated.

Administration

Azithromycin tablets should be swallowed whole with a full glass of water. It can be taken with or without food. However, if stomach upset occurs, taking it with food may help. Do not crush or chew the tablets.

For the oral suspension, shake the bottle well before each use. Measure the dose carefully using the provided measuring device (spoon or syringe), not a household spoon.

Timing and Missed Doses

Take doses at evenly spaced intervals as prescribed, typically once daily. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not double the dose to make up for a missed one.

Course Completion

It is critical to complete the entire prescribed course of azithromycin, even if you start to feel better after a few days. Stopping the medication early can lead to a resurgence of the infection and contribute to antibiotic resistance.

Side Effects of Azithromycin

As with any medication, azithromycin can cause side effects. Gastrointestinal symptoms are among the most common, which can include diarrhea.

What is Azithromycin Used For?

Azithromycin is prescribed for a variety of bacterial infections caused by susceptible organisms.

Respiratory Tract Infections

It is commonly used for bacterial respiratory tract infections such as acute bacterial exacerbations of chronic bronchitis, community-acquired pneumonia (often caused by Streptococcus pneumoniae), and acute bacterial sinusitis. For pneumonia, it is a standard treatment option for pneumococcal disease.

Skin and Soft Tissue Infections

Azithromycin is effective for uncomplicated skin infections like cellulitis and erysipelas.

Sexually Transmitted Infections (STIs)

A single 1-gram dose is the first-line treatment for uncomplicated chlamydia infections. It is also used for non-gonococcal urethritis and cervicitis.

Other Infections

It may be prescribed for otitis media (middle ear infection) in children and, in specific cases, for certain gastrointestinal infections.

Important Limitations

Azithromycin is not effective against viral infections. Its use for viral upper respiratory infections, including COVID-19, is not recommended unless a secondary bacterial infection is present and diagnosed by a physician.

Important Safety Concerns and Considerations

Cardiac Risk: QT Prolongation

Azithromycin can cause a change in the heart’s electrical activity known as QT interval prolongation, which may lead to a potentially fatal irregular heartbeat (torsades de pointes). The U.S. FDA has issued warnings about this risk. It is highest in patients with:

• Pre-existing heart disease (e.g., heart failure, arrhythmia).
• Low blood levels of potassium or magnesium.
• History of long QT syndrome or ventricular arrhythmia.
• Concurrent use of other drugs known to prolong the QT interval.

Patients should report any symptoms of palpitations, dizziness, or fainting immediately.

Exacerbation of Myasthenia Gravis

Azithromycin can worsen muscle weakness in patients with the neurological disorder myasthenia gravis, potentially leading to life-threatening respiratory failure. It is generally avoided in this population.

Clostridioides difficile-Associated Diarrhea (CDAD)

Antibiotic use, including azithromycin, can disrupt the normal bacteria in the colon, allowing overgrowth of C. difficile. This can cause mild diarrhea to severe, life-threatening colitis. CDAD can occur even weeks after finishing antibiotics. Report severe, persistent, or bloody diarrhea to your doctor.

Hepatotoxicity (Liver Injury)

Although rare, azithromycin can cause serious liver injury, including hepatitis and cholestatic jaundice. Symptoms include fatigue, abdominal pain, jaundice (yellowing of skin and eyes), and dark urine. The drug should be discontinued if signs of liver dysfunction appear.

Hearing Impairment

Cases of reversible hearing loss, tinnitus (ringing in the ears), and deafness have been reported, usually with high doses or prolonged use.

Critical Warnings for Azithromycin Use

Cardiovascular Death Risk

In addition to the QT prolongation risk, studies have shown a small but significant increase in the risk of cardiovascular death, particularly in patients with existing heart disease, compared to other antibiotics like amoxicillin. This risk must be carefully weighed against the benefits, especially for those with known cardiovascular risk factors.

Severe Skin Reactions

Rare but severe skin reactions, including Stevens-Johnson Syndrome and toxic epidermal necrolysis, have been reported with azithromycin use. These reactions can be life-threatening. Discontinue use at the first sign of a rash, skin peeling, blistering, or sores in the mouth.

Drug Interactions with Antacids

Antacids containing aluminum or magnesium (e.g., Maalox, Mylanta) can reduce the absorption of azithromycin if taken simultaneously. To avoid this interaction, take azithromycin at least 1 hour before or 2 hours after taking an antacid.

Use in Bacterial Infections Only

Azithromycin is not indicated for and will not work against viral infections. Prescribing it for viral upper respiratory tract infections increases the risk of adverse effects and fosters bacterial antibiotic resistance.

Azithromycin Dosage Information

Dosage is determined by the treating physician based on the type and severity of infection, patient weight, and renal function. The following table provides general guidelines; always follow your doctor’s specific prescription.

Important Administration Notes

• Renal Impairment: No dosage adjustment is typically needed for patients with mild to moderate renal impairment. Use with caution in severe renal impairment.
• Hepatic Impairment: No dosage adjustment is provided for patients with mild to moderate liver impairment. Use with caution in severe hepatic disease.
• Elderly: No routine dosage adjustment, but consider potential for increased side effects and concurrent conditions.

Drug Interactions with Azithromycin

Azithromycin interacts with several important medications. Inform your doctor about all prescription, over-the-counter, and herbal products you use.

Additional Information

Storage and Handling

Store azithromycin tablets at room temperature (between 15°C and 30°C or 59°F and 86°F), in a tightly closed container, away from light, excess heat, and moisture. Keep the oral suspension in the refrigerator after mixing and discard any unused portion after the time specified by your pharmacist (usually 10 days). Keep all medications out of the reach of children and pets.

Historical Fact

Azithromycin was discovered in 1980 by researchers at the pharmaceutical company Pliva in Croatia. It was specifically engineered from erythromycin to improve its acid stability, broaden its spectrum of activity, and, most notably, to achieve a much longer half-life. These improvements were revolutionary, as they allowed for the short-course therapy (often just 3-5 days) that made it one of the world’s most prescribed antibiotics after its global launch.

Reporting Side Effects

You are encouraged to report negative side effects of prescription drugs to the relevant national health authority (e.g., the FDA in the United States). Reporting helps health authorities monitor drug safety and identify new risks.

References and Medical Sources

The information on this page is compiled from reputable medical sources and prescribing information.

1. U.S. Food and Drug Administration (FDA). Zithromax (azithromycin) Prescribing Information. [Updated 2022]. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/050670s036,050710s051,050711s050,050784s037lbl.pdf
2. MedlinePlus. Azithromycin. U.S. National Library of Medicine; [Updated 2024]. https://medlineplus.gov/druginfo/meds/a697037.html
3. Centers for Disease Control and Prevention (CDC). Sexually Transmitted Infections Treatment Guidelines, 2021. [Updated 2021]. https://www.cdc.gov/std/treatment-guidelines/default.htm
4. Drugs.com. Azithromycin Professional Monograph. Drugs.com; [Updated 2024]. https://www.drugs.com/monograph/azithromycin.html

Disclaimer: The information on this site is provided for informational purposes only and is not medical advice. It does not replace professional medical consultation, diagnosis, or treatment. Do not self-medicate based on the information presented on this site. Always consult with a doctor or other qualified healthcare professional before making any decisions about your health.