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Drug Info

Azithromycin side effects and how to avoid them

Azithromycin side effects include stomach pain, heart palpitations, and diarrhea
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By | Updated on Sep. 7, 2023 Medically reviewed by Kristi C. Torres, Pharm.D.
Hand holding Rx pill: Azithromycin side effects and how to avoid them

Key takeaways

  • Azithromycin is an antibiotic used to treat various bacterial infections, with common side effects including diarrhea, nausea, stomach pain, and vomiting.

  • Rare but serious azithromycin side effects include liver problems, heart rhythm changes, and severe allergic reactions, necessitating immediate medical attention.

  • Azithromycin side effects usually start on the same day as the first dose. They can last for a week or more after stopping the drug, with severe effects like C. difficile-associated diarrhea occurring days after treatment ends.

  • Avoiding azithromycin side effects involves informing the prescriber about all medical conditions and medications and following the dosing schedule precisely. You can manage side effects by staying hydrated and avoiding antacids close to dosing times.

Common azithromycin side effects | Serious side effects | Stomach pain | Heart palpitations | Diarrhea | Side effects timeline | Contraindications | Warnings | Interactions | How to avoid side effects | How to treat side effects

Azithromycin is a generic prescription antibiotic used to treat a wide variety of mild to moderate bacterial infections. Also prescribed as brand-name Zithromax or Zithromax Z-Pak, azithromycin treats respiratory infections such as bacterial pneumonia, upper respiratory infections like sinusitis and tonsillitis, infections of the eyes and ears, skin infections, genital ulcers in men, and chlamydia infections of the vagina or urethra (urethritis). Macrolide antibiotics like azithromycin, clarithromycin, and erythromycin have some side effects, but fortunately, most people don’t have too many problems. Treatment typically ends in a few days. Still, it’s always important to know the potential downsides when given a prescription drug.

Common side effects of azithromycin

The most common side effects of azithromycin are digestive system problems: diarrhea, nausea, stomach pain, and vomiting. Azithromycin’s common side effects include:

  • Diarrhea
  • Nausea
  • Stomach pain
  • Vomiting
  • Indigestion
  • Redness
  • Vaginitis
  • Skin rash
  • Flatulence
  • Headache
  • Fatigue
  • Dizziness
  • Itching
  • Decreased appetite

Injection site reactions are among the most common side effects for people who get an azithromycin shot.

Serious side effects of azithromycin

Though rare, some azithromycin side effects can be very serious. The most common of these include:

Stomach pain

Gastrointestinal problems are hands-down the most common issues patients experience with azithromycin. The original manufacturer, Pfizer, reported that 7% to 14% of participants had problems with diarrhea or loose stools, 5% to 18% felt queasy, and 5% to 7% complained of stomach pain. The effects are dose-related. The higher the dose, the more likely a person will have digestive system problems. Fortunately, abdominal pain and other gastrointestinal issues usually go away after the drug has been stopped after three to five days of treatment. Meanwhile, the prescriber may have medical advice on handling the problem during treatment.

Heart palpitations

One of the more serious problems with azithromycin is heart rhythm changes. For this reason, azithromycin is used cautiously in any person with a heart rate abnormality. The exact incidence of heart rate problems caused by azithromycin is unknown. One severe, yet rare side effect is ventricular tachycardia, or the speeding up of the lower chambers of the heart This means the body may not get enough blood even though the heart is beating fast. Immediately report racing heartbeats or palpitations to a healthcare professional when taking azithromycin.

Diarrhea

Diarrhea or loose stools are by far the most common adverse effect of azithromycin. In clinical trials, 4% to 5% of participants taking small doses over several days had problems with diarrhea. 7% of people given a 1 g single dose reported diarrhea and 14% given a 2 g single dose had diarrhea. The problem is time-limited, however. Once the drug is stopped, diarrhea eventually clears up. Unfortunately, azithromycin can cause an overgrowth of C. difficile bacteria in the colon which causes serious and even life-threatening diarrhea in the days or weeks after azithromycin treatment. Always get medical treatment if diarrhea is persistent, watery, or bloody.

How soon do azithromycin side effects start?

Many azithromycin side effects, such as digestive system problems, rash, headache, itching, and injection site reactions, can occur on the same day as the first dose, particularly if given a single, large dose. More serious side effects, such as C. difficile-associated diarrhea, are often delayed, sometimes appearing days after treatment has stopped. 

How long do azithromycin side effects last?

Most azithromycin side effects go away after the drug has been stopped, but it may take a while. It takes the body 68 hours—three days—to clear out half a dose of azithromycin from the body, so that some side effects may linger for a week or more.

What are the long-term side effects of azithromycin?

Azithromycin is rarely given for more than a few days, so side effects due to long-term use are not well known. Most side effects that appear while taking azithromycin get better in the days after the drug has been stopped. Some, like C. diff diarrhea, may appear a week or more after treatment and take several days of antibiotic treatment to get better. Others, like heart problems, may have lifelong consequences.

Azithromycin contraindications

As with all drugs, azithromycin can be so risky in people with certain medical conditions that they can never safely take it.  These are:

  • Known allergies to azithromycin or other macrolide antibiotics
  • A history of liver problems (impairment or blockage) associated with azithromycin

Azithromycin use is not contraindicated for children 6 months and older, pregnant women, breastfeeding women, or seniors. However, a risk versus benefit analysis should be done and alternative therapies considered if the risk of taking azithromycin seems too great.

Azithromycin warnings

Some people with certain medical conditions can take azithromycin, but there will be risks that the prescriber will have to manage. 

Cautions

Some people may have medical conditions that get worse when taking azithromycin. These include: 

  • Heart rhythm problems (arrhythmias)
  • Other heart problems, such as congestive heart failure or a recent heart attack
  • Liver disease
  • Poor kidneys
  • Myasthenia gravis
  • Electrolyte imbalances
  • A history of colon swelling due to antibiotic use

Abuse and dependence

The FDA does not consider azithromycin or other antibiotics to have a risk for abuse or dependence. Azithromycin is used for only a few days and is not known to cause withdrawal symptoms. 

Overdose

Too much azithromycin increases the likelihood and intensity of common side effects, particularly digestive system problems like diarrhea and nausea. Call a poison helpline or get medical attention if too much azithromycin has been taken. 

Recalls

The use of Azithromycin and Zithromax is very common in the United States. Tens of millions of pills are taken each year. It makes sense that lots produced by individual manufacturers have been recalled for quality reasons. However, the drug, in general, has not been subject to a total recall. 

Azithromycin interactions

Many problems caused by azithromycin are not side effects but drug interactions. The most serious involve potentially life-threatening changes to the way the heart beats. For this reason, the following drugs are too risky ever to be taken with azithromycin:

Though not forbidden, other drugs can also cause heart rhythm problems when combined with azithromycin. Many of these drugs lengthen the amount of time it takes for the heart to “recharge” after beating; this time is called the QT interval. The prescriber will call this “QT prolongation,” and it’s not good. Azithromycin can cause this problem, so combining it with other drugs that cause the same problem may make matters worse:

Some drug interactions may cause other problems and require people taking azithromycin to be monitored carefully:

  • Live vaccines: if they’re bacterial vaccines, they may not produce a good immune response when combined with antibiotics like azithromycin
  • Antacids: azithromycin should not be taken within two hours before or after taking a magnesium or aluminum-containing antacid because the antacid will reduce the body’s absorption of azithromycin
  • Oral anticoagulants: azithromycin may increase the anticoagulant effects of warfarin and other oral anticoagulants, so healthcare providers will monitor blood clotting rates carefully while azithromycin is being administered

How to avoid azithromycin side effects

Side effects are not necessarily inevitable, even when taking antibiotics. Here are some ideas that can help minimize side effects and maximize the benefits of azithromycin treatment.

1. Tell the prescriber about all medical conditions and medications

Since many azithromycin side effects are due to pre-existing problems or drug interactions, give the prescribing healthcare provider a complete medical history. This should include all drugs being taken, including over-the-counter drugs and supplements. Current medical problems are important, but so is a history of past medical conditions, especially:

  • Liver problems
  • Kidney problems
  • Heart rhythm abnormalities or other heart problems
  • Drug allergies or reactions to antibiotics
  • Any history of diarrhea when taking antibiotics
  • Myasthenia gravis
  • Cystic fibrosis
  • Bacterial infection of the blood
  • Pregnancy or plans on getting pregnant
  • Breastfeeding

2. Take azithromycin as directed

Follow the directions and dosing schedule given. The prescriber may advise taking the pill with a meal or on an empty stomach.

3. Do not miss doses

Use an app or alarm to ensure each dose is taken as scheduled and on time. Late or missed doses allow the bacteria colony to recover. That’s bad. Letting the bacteria recover increases the risk of growing an antibiotic-resistant strain, making treatment more difficult. If a dose is missed, take it as soon as it’s remembered. However, if it’s almost time for the next dose, skip the missed dose and take the next dose on schedule.

4. Take all the azithromycin doses

Take this medicine for as many days as instructed. It’s common to feel much better after a few days of antibiotics, but the infection isn’t completely gone. Even if the medicine makes you feel bad, take it faithfully until the very end to make sure the bacteria are gone for good. 

5. Do not use azithromycin for other infections

Azithromycin only works against bacterial infections. Using it against viral or fungal infections will only cause side effects without any benefit.

6. Eat plain foods

 Consider eating plain and simple foods while taking azithromycin to avoid nausea, vomiting, and upset stomach. Fatty, rich, or spicy foods may make the problem worse.

7. Don’t take azithromycin with antacids

Azithromycin can cause stomach pain and indigestion, but be careful about using antacids. Some antacids interfere with the digestive system’s ability to absorb azithromycin. This is equivalent to reducing the dose, which isn’t good. Don’t take antacids two hours before or two hours after taking an azithromycin tablet.

How to treat side effects of azithromycin

It’s possible to be smart and avoid side effects, but not always. Here are a few tips for managing azithromycin’s adverse effects if they rear up.

Diarrhea

Drink lots of fluids to keep from dehydrating. Talk to the prescribing healthcare provider if the diarrhea is watery, bloody, or doesn’t go away. Do this even if diarrhea occurs days or weeks after azithromycin has been stopped, as this could indicate a more serious problem.

Vomiting

As with diarrhea, drink clear liquids to avoid dehydration, but only in small amounts.

Loss of appetite

Eat meals as you normally would, even if not hungry.

Dizziness

Sit down when feeling dizzy and stay seated until the spinning stops. Then stand up slowly. Lying down can sometimes make the spinning worse, so sitting is best.

Palpitations

Changes in the way the heart beats are a potentially serious problem. Go to an emergency room at any sign of irregular heartbeats, including:

  • Fast heartbeats
  • Fluttering or palpitations
  • Chest pain or discomfort
  • Shortness of breath
  • Sudden dizziness

Liver problems

Liver problems caused by azithromycin can only be spotted indirectly through symptoms such as:

  • Nausea and vomiting
  • Dark urine
  • Discoloration of stools
  • Stomach pain
  • Loss of appetite
  • Yellow skin
  • Feeling tired

These problems require medical help, so start by calling the prescribing healthcare provider. If the skin or the whites of the eyes start turning yellow, stop taking azithromycin and get immediate medical help.

Allergic reactions

Reactions to azithromycin could quickly escalate into serious medical problems, so get emergency medical help at any sign of an allergic reaction, skin reaction, or drug reaction, including:

  • Swelling of the face, mouth, lips, or throat
  • Trouble breathing
  • Trouble swallowing
  • Skin rash
  • Hives
  • Blisters
  • Red or purple skin
  • Skin pain
  • Eye pain or burning
  • Muscle weakness or cramps
  • Bruising
  • Fever
  • Sore throat (pharyngitis) or hoarseness

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