Home Zithromax Side Effects

Zithromax Side Effects

The drug’s active ingredient, azithromycin, can cause rare and serious side effects such as severe or life-threatening allergic reactions, irregular heartbeats, Clostridium difficile-associated diarrhea and liver damage. More common side effects include nausea, vomiting, diarrhea and abdominal pain.

Last Modified: September 5, 2023
Fact Checked
Medically Reviewed

Board-certified physicians medically review Drugwatch.com content to ensure its accuracy and quality.

Drugwatch.com partners with Physicians’ Review Network Inc. to enlist specialists. PRN is a nationally recognized leader in providing independent medical reviews.

Reviewer specialties include internal medicine, gastroenterology, oncology, orthopedic surgery and psychiatry.

Why Trust DrugWatch?

Drugwatch.com has been empowering patients for more than a decade

Drugwatch.com has provided reliable, trusted information about medications, medical devices and general health since 2008. We’ve also connected thousands of people injured by drugs and medical devices with top-ranked national law firms to take action against negligent corporations.

Our team includes experienced medical writers, award-winning journalists, researchers and certified medical and legal experts. Drugwatch.com is HONCode (Health On the Net Foundation) certified. This means the high-quality information we provide comes from credible sources, such as peer-reviewed medical journals and expert interviews.

The information on Drugwatch.com has been medically and legally reviewed by more than 30 expert contributors, including doctors, pharmacists, lawyers, patient advocates and other health care professionals. Our writers are members of professional associations, including American Medical Writers Association, American Bar Association, The Alliance of Professional Health Advocates and International Society for Medical Publication Professionals.

About Drugwatch.com

  • Assisting patients and their families since 2008.
  • Helped more than 12,000 people find legal help.
  • A+ rating from the Better Business Bureau.
  • 5-star reviewed medical and legal information site.
Learn More About Us


"Drugwatch opened my eyes to the realities of big pharmacy. Having a family member with major depression and anxiety, I was looking for information on her medications. I found information that was very helpful, that her psychiatrist never told her."
Marianne Zahren Patient’s Family Member
  • Google Business Rating
  • BBB A+ Rating Logo

Common Z-Pak Side Effects

Most people who take Zithromax, better known as Z-Pak, tolerate it with few significant negative side effects. However, about 20% of people who take the drug report having some side effects. The medication is commonly prescribed to treat bacterial infections.

Among the common side effects of Z-Pak are abdominal pain, nausea and vomiting. Pregnant women and children younger than 6 months should not take the medication.

Z-Pak side effects may include:
  • Abdominal pain
  • Blurred vision
  • Headache
  • Liver issues
  • Nausea or vomiting
  • Nervousness or anxiety
  • Ringing ears
  • Skin rash
  • Yeast overgrowth leading to vaginal itchiness

These common side effects of azithromycin, the active ingredient in Z-Pak, are usually temporary. However, if you notice any of them while taking the drug, alert your health care provider.

What Are the Serious Side Effects of Azithromycin?

Azithromycin can also cause serious side effects, some of which are potentially life-threatening. They include allergic reactions and skin reactions, liver damage, heart problems and Clostridium difficile-associated diarrhea.

Z-Pak can also cause worsening or new onset of myasthenia gravis, a disease that causes muscle weakness.

Seek medical help if you notice the following side effects:
  • Anxiety
  • Dark urine, or blood in the urine or stools
  • Decreased feeling or sensitivity, especially in the skin
  • Fast or irregular heartbeat
  • Fast-developing sunburn
  • Fever, chills or sore throat
  • Hives
  • Jaundice
  • Oral candidiasis (yeast infection)
  • Severe bruising
  • Skin rash or body rash
  • Swollen lymph nodes

Infants taking Z-Pak could develop infantile hypertrophic pyloric stenosis, or IHPS, a serious intestinal condition.

Zithromax and Allergic Reactions

Zithromax is associated with allergic reactions, some of them severe or even fatal. The medication’s label warns that allergic reactions to azithromycin can happen even after only one dose.

Serious allergic reactions are angioedema (swelling), anaphylaxis and toxic epidermal necrolysis, a serious skin reaction. Anaphylaxis causes you to go into shock, develop sudden low blood pressure, or have a narrowing of breathing pathways.

Combining Zithromax with other medications can also increase the chance of an allergic reaction. Some drugs that should not be taken with azithromycin include:

  • Rifabutin, an antibiotic
  • Statins, such as Atorvastatin and Lovastatin
  • Theophylline, a bronchodilator

Cancer Relapse from Long-Term Azithromycin Use

A 2018 report from the U.S. Food and Drug Administration warned that prolonged use of Z-Pak can increase the risk of a cancer relapse in people with cancer of the lymph nodes or blood. A more recent study showed that Z-Pak did not cause cancer recurrence for pediatric stem cell transplant recipients. In addition, three other studies of adults showed no link between typical azithromycin use and a cancer recurrence.

Prior to the more recent research findings, the FDA warned against prescribing Z-Pak for people who previously had a stem cell transplant. Some physicians had recommended the drug to treat bronchiolitis obliterans syndrome, a major complication from a lung transplant.

Zithromax Linked to Heart Problems

A 2020 study reported that Zithromax, when combined with medications that affect heart rhythm, can cause irregular heartbeat and a higher risk of cardiac arrest.

Z-Pak’s label includes a warning about torsades de pointes (TdP), a potentially fatal condition that involves rapid heartbeats that start in the ventricles of the heart.

A 14-year study published in 2012 found that people who take Z-Pak are 2.5 times more likely to suffer a heart-related death within five days of starting the medication. The FDA issued a warning following the release of the study’s results, but more recent studies came to mixed conclusions.

Clostridium Difficile-Associated Diarrhea (CDAD)

Like many antibiotics, azithromycin changes gut flora and may cause Clostridium difficile-associated diarrhea. This side effect ranges from mild diarrhea to colitis, a fatal inflammation of the colon.

C. difficile is an antibiotic-resistant bacterium. Quick treatment is crucial to managing the infection. Symptoms of CDAD show up about five to 10 days after you begin the medication, although sometimes they take up to two months to appear.

Age, underlying diseases and prolonged hospital stays increase the risk of CDAD. Call your doctor if you notice C. difficile symptoms.

Azithromycin and Liver Damage

Azithromycin can also be a common cause of drug-induced liver damage. Cholestatic hepatitis is a typical development, occurring within one to three weeks of starting the medication. The condition is usually temporary and benign, although sometimes people experience jaundice and liver issues for six months or longer.

Other liver issues include liver failure, hepatic necrosis and abnormal liver function. Most people recover from Z-Pak-related liver problems in four to eight weeks. Severe cases of liver failure can lead to an emergency liver transplant or death.

Anyone who has existing liver issues should consult their doctor before using azithromycin long-term.

Zithromax and Myasthenia Gravis

Myasthenia gravis, or MG, is an autoimmune condition that leads to weak muscles. Several medications cause MG, and Zithromax is the most common one. Z-Pak halts the neuromuscular transmission process within a short time of the start of a course of the antibiotic. The condition is more severe if someone takes Zithromax through an IV.

Symptoms of MG include breathing and swallowing difficulties, double or blurred vision, drooping eyelids and weakness in the arms and legs.

How to Reduce the Side Effects of Azithromycin

There are several ways to minimize Z-Pak’s side effects. Be sure to drink plenty of water, eat more nutritiously and abstain from alcohol. Water helps with headaches, and food in your stomach helps with nausea. Because Zithromax hinders the appetite, counter that by eating smaller meals more often.

Antibiotics may cause diarrhea or ultra-soft stools, so taking a probiotic may help. People who take probiotics are 42% less likely to have diarrhea than people who don’t take them, according to research from the University of Pittsburgh Medical Center.

Common Questions About Z-Pak Side Effects

How long do Z-Pak side effects last?
Unwanted side effects usually disappear once your body adjusts to the medication. But some side effects can last up to two months after you stop taking the drug.
Can you take azithromycin if you’re allergic to penicillin?
Yes. Z-Pak does not contain penicillin, making it a suitable antibiotic medicine for those allergic to penicillin.
Can you drink alcohol if you’re taking a Z-Pak?
Medical providers (and the drug label) recommend not drinking alcohol while taking azithromycin. If you experience dizziness because of the drug, alcohol will worsen the situation.
What should you avoid while taking azithromycin?
If you take Z-Pak, avoid extreme exposure to sunlight or tanning beds. The medication can make sunburns severe. Also, don’t start a Z-Pak prescription if you’re allergic to telithromycin or clarithromycin.
Please seek the advice of a medical professional before making health care decisions.