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Z-Pak Side Effects

Generic Name: azithromycin

Note: This document contains side effect information about azithromycin. Some of the dosage forms listed on this page may not apply to the brand name Z-Pak.

For the Consumer

Applies to azithromycin: intravenous powder for solution

Other dosage forms:

Side effects requiring immediate medical attention

Along with its needed effects, azithromycin (the active ingredient contained in Z-Pak) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking azithromycin:

More common

  • Pain, redness, and swelling at the injection site

Less common

  • Difficult or labored breathing
  • loose stools
  • tightness in the chest


  • Abdominal or stomach cramps or pain (severe)
  • abdominal or stomach tenderness
  • diarrhea (watery and severe, which may be bloody)
  • fever
  • joint pain
  • skin rash
  • swelling of the face, mouth, neck, hands, and feet

Incidence not known

  • Agitation
  • black, tarry stools
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • bloating
  • blood in the urine or stools
  • bloody or cloudy urine
  • blurred vision
  • chest pain or discomfort
  • chills
  • coma
  • confusion
  • constipation
  • convulsions
  • cough
  • darkened urine
  • decreased urine output
  • depression
  • difficulty with swallowing
  • dizziness
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fainting
  • fast, pounding, or irregular heartbeat or pulse
  • fever with or without chills
  • general feeling of discomfort or illness
  • greatly decreased frequency of urination or amount of urine
  • headache
  • hives or itching
  • hostility
  • increased thirst
  • indigestion
  • irregular heartbeat recurrent
  • irregular or slow heart rate
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • lethargy
  • light-colored stools
  • loss of appetite
  • muscle pain
  • muscle twitching
  • nausea or vomiting
  • pain
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • rapid weight gain
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • sore throat
  • sores, ulcers, or white spots in the mouth or on the lips
  • stupor
  • sweating
  • swelling of the hands, ankles, feet, or lower legs
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • yellow eyes or skin

Side effects not requiring immediate medical attention

Some side effects of azithromycin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

  • Diarrhea (mild)
  • nausea
  • stomach pain or discomfort (mild)
  • weight loss

Less common or rare

  • Acid or sour stomach
  • belching
  • burning feeling in the chest or stomach
  • cracked lips
  • excess air or gas in the stomach or intestines
  • full feeling
  • heartburn
  • passing gas
  • sleepiness or unusual drowsiness
  • sore mouth or tongue
  • stomach discomfort, upset, or pain
  • white patches in the mouth, tongue, or throat

Incidence not known

  • Attack, assault, or force
  • bad, unusual, or unpleasant (after) taste
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • change in taste
  • continuing ringing or buzzing or other unexplained noise in the ears
  • difficulty with moving
  • discoloration of the tongue
  • dizziness or lightheadedness
  • feeling of constant movement of self or surroundings
  • hearing loss
  • itching of the vagina or genital area
  • lack or loss of strength
  • loss of sense of smell
  • muscle pain or stiffness
  • pain during sexual intercourse
  • sensation of spinning
  • thick, white vaginal discharge with no odor or with a mild odor
  • trouble sitting still

For Healthcare Professionals

Applies to azithromycin: intravenous powder for injection, oral capsule, oral powder for reconstitution, oral powder for reconstitution extended release, oral tablet


The most commonly reported side effects include diarrhea/loose stools, abdominal pain, and nausea.[Ref]


Very common (10% or more): Diarrhea (up to 52.8%), nausea (up to 32.6%), abdominal pain (up to 32.2%), loose stools (up to 19.1%), flatulence (up to 10.7%)

Common (1% to 10%): Vomiting, dyspepsia, stomatitis

Uncommon (0.1% to 1%): Gastroenteritis, oral candidiasis, constipation, dysphagia/oral dysphagia, abdominal distension, dry mouth, eructation, mouth ulceration, salivary hypersecretion

Frequency not reported: Pseudomembranous colitis, pancreatitis, tongue discoloration, melena, enteritis, abnormal stools, gastrointestinal disorder

Postmarketing reports: Pyloric stenosis[Ref]


Common (1% to 10%): Decreased lymphocyte, hematocrit, hemoglobin, or neutrophil count, increased eosinophil count, increased platelets, hematocrit, lymphocytes, basophils, monocytes, or neutrophils

Uncommon (0.1% to 1%): Leukopenia, neutropenia/mild neutropenia, eosinophilia

Frequency not reported: Thrombocytopenia, anemia/hemolytic anemia, decreased platelets[Ref]

Nervous system

Common (1% to 10%): Headache, dizziness, paresthesia, dysgeusia

Uncommon (0.1% to 1%): Somnolence, hypesthesia

Frequency not reported: Syncope, convulsion, anosmia, ageusia, parosmia, vertigo, myasthenia gravis, taste perversion, hyperkinesia

Postmarketing reports: Hyperactivity[Ref]


Common (1% to 10%): Injection site pain, infection, edema, reactions or inflammation[Ref]


Common (1% to 10%): Deafness, fatigue

Uncommon (0.1% to 1%): Candidiasis, ear disorder, asthenia, malaise, face edema, pyrexia, pain, post procedural complications, hearing disturbances/impairment, tinnitus, laboratory abnormalities, fungal or bacterial infection

Frequency not reported: Psychomotor hyperactivity, mucositis, fever, chills, otitis media

Postmarketing reports: Hearing loss, taste/smell perversion and/or loss[Ref]


Common (1% to 10%): Rash, pruritus

Uncommon (0.1% to 1%): Photosensitivity reaction, Stevens-Johnson syndrome, urticaria, dermatitis, dry skin, hyperhidrosis, eczema

Very rare (less than 0.01%): Drug reaction of eosinophilia and systemic symptoms (DRESS)

Frequency not reported: toxic epidermal necrolysis, erythema multiforme, fungal dermatitis, sweating, vesiculobullous rash, maculopapular rash[Ref]


Common (1% to 10%): Decreased blood bicarbonate, anorexia

Uncommon (0.1% to 1%): Abnormal sodium, increased blood alkaline phosphatase, bicarbonate, or chloride

Frequency not reported: Increased lactate dehydrogenase, decreased sodium or potassium

Postmarketing reports: Dehydration[Ref]


Common (1% to 10%): Dyspnea

Uncommon (0.1% to 1%): Pneumonia, pharyngitis, rhinitis, respiratory disorder, epistaxis

Frequency not reported: Bronchospasm, cough, pleural effusion, asthma, bronchitis[Ref]


Common (1% to 10%): Arthralgia

Uncommon (0.1% to 1%): Osteoarthritis, myalgia, back pain, neck pain

Frequency not reported: Increased creatine phosphokinase[Ref]


Common (1% to 10%): Vaginitis/vaginal infection

Uncommon (0.1% to 1%): Dysuria, metrorrhagia, testicular disorder[Ref]


Common (1% to 10%): Allergic reaction

Uncommon (0.1% to 1%): Angioedema, hypersensitivity

Frequency not reported: Anaphylactic reaction/anaphylaxis

Postmarketing reports: Fatal anaphylaxis[Ref]


Common (1% to 10%): Visual impairment

Frequency not reported: Conjunctivitis[Ref]


Uncommon (0.1% to 1%): Hepatitis, increased AST, ALT, GGT, or blood bilirubin

Rare (0.01% to 0.1%): Abnormal liver function tests, cholestatic jaundice

Frequency not reported: Hepatic failure/fatal hepatic failure, fulminant hepatitis, hepatic necrosis[Ref]


Uncommon (0.1% to 1%): Palpitations, hot flush, edema, chest pain, peripheral edema

Frequency not reported: Torsades de pointes, arrhythmia, ECG QT prolonged, hypotension, ventricular tachycardia[Ref]


Uncommon (0.1% to 1%): Nervousness, insomnia

Rare (0.01% to 0.1%): Agitation

Frequency not reported: Aggression/aggressive reaction, anxiety, delirium, hallucination, emotional lability, irritability, hostility[Ref]


Uncommon (0.1% to 1%): Renal pain, increased blood urea nitrogen and creatinine

Frequency not reported: Acute renal failure, interstitial nephritis/nephritis[Ref]


Frequency not reported: Moniliasis, flu syndrome[Ref]


1. "Product Information. Zithromax injection (azithromycin)" Pfizer US Pharmaceuticals, New York, NY.

2. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

3. "Product Information. Zithromax (azithromycin)." Pfizer US Pharmaceuticals, New York, NY.

4. "Product Information. Azithromycin Product Information (azithromycin)." Pfizer US Pharmaceuticals, New York, NY.

5. Cerner Multum, Inc. "Australian Product Information." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

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