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Z-Pak Side Effects

Generic name: azithromycin

Medically reviewed by Last updated on Apr 10, 2023.

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

Applies to azithromycin: oral powder for suspension, oral powder for suspension extended release, oral tablet. Other dosage forms:

Serious side effects of Z-Pak

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 immediately if any of the following side effects occur while taking azithromycin:

More common

  • Diarrhea
  • loose stools

Less common

  • Blistering, crusting, irritation, itching, or reddening of the skin
  • cracked, dry, or scaly skin
  • fever
  • swelling


  • Blistering, peeling, or loosening of the skin
  • bloody or cloudy urine
  • bloody, black, or tarry stools
  • body aches or pain
  • burning while urinating
  • chest pain or tightness
  • chills
  • congestion
  • cough increased
  • cough producing mucus
  • dark urine
  • difficult or labored breathing
  • difficult or painful urination
  • dizziness
  • drowsiness
  • dryness or soreness of the throat
  • earache
  • fainting
  • fast, irregular, pounding, or racing heartbeat or pulse
  • general feeling of discomfort or illness
  • headache
  • indigestion
  • irregular or slow heart rate
  • itching or rash
  • joint or muscle pain
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • loss of appetite
  • muscle aches and pains
  • nausea or vomiting
  • noisy breathing
  • passing of gas
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • redness or swelling in the ear
  • runny nose
  • shivering
  • sneezing
  • sores, ulcers, or white spots on the lips or in the mouth
  • stomach pain, continuing
  • stomach pain, fullness, or discomfort
  • stuffy nose
  • sweating
  • swelling of the face, ankles, hands, feet, or lower legs
  • tender, swollen glands in the neck
  • trouble with sleeping
  • trouble with swallowing
  • unpleasant breath odor
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • upper right abdominal or stomach pain
  • voice changes
  • vomiting of blood
  • yellow eyes or skin

Incidence not known

  • Bleeding gums
  • bloating
  • blood in the urine or stools
  • blurred vision
  • change in hearing
  • clay-colored stools
  • coma
  • confusion
  • constipation
  • continuing ringing or buzzing or other unexplained noise in the ears
  • decreased urine output
  • depression
  • diarrhea, watery and severe, which may also be bloody
  • dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
  • fainting
  • greatly decreased frequency of urination or amount of urine
  • hives
  • hostility
  • increased thirst
  • irritability
  • lethargy
  • loss of hearing
  • lower back or side pain
  • muscle twitching
  • no blood pressure or pulse
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • pale skin
  • pinpoint red spots on the skin
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • rapid weight gain
  • seizures
  • stomach cramps or tenderness
  • stopping of heart
  • stupor
  • unconsciousness
  • unusual weight loss

Other side effects of Z-Pak

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:


  • Acid or sour stomach
  • aggressive or angry
  • bad, unusual, or unpleasant (after) taste
  • belching
  • burning feeling in the chest or stomach
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • change in taste
  • changes in the color of the tongue
  • crying
  • depersonalization
  • dry mouth
  • dysphoria
  • euphoria
  • excess air or gas in the stomach or intestines
  • feeling of constant movement of self or surroundings
  • full feeling
  • heartburn
  • hyperventilation
  • increase in body movements
  • itching of the vagina or genital area
  • lack or loss of strength
  • mental depression
  • nervousness
  • pain during sexual intercourse
  • paranoia
  • quick to react or overreact emotionally
  • rapidly changing moods
  • rash with flat lesions or small raised lesions on the skin
  • redness of the skin
  • restlessness
  • sensation of spinning
  • shaking
  • sleepiness or unusual drowsiness
  • stomach upset
  • thick, white vaginal discharge with no odor or with a mild odor
  • white patches in the mouth, tongue, or throat

Incidence not known

  • Difficulty with moving
  • increased sensitivity of the skin to sunlight
  • muscle pain or stiffness
  • pain in the joints
  • redness or other discoloration of the skin
  • severe sunburn
  • 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 were diarrhea/loose stools, nausea, abdominal pain, and vomiting.[Ref]


Uncommon (0.1% to 1%): Palpitations, chest pain

Postmarketing reports: Torsades de pointes, arrhythmia (including ventricular tachycardia), ECG QT prolonged, hypotension, cardiovascular death


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

Uncommon (0.1% to 1%): Angioedema, photosensitivity reaction, Stevens-Johnson syndrome, urticaria, dermatitis, dry skin, hyperhidrosis/sweating

Rare (0.01% to 0.1%): Acute generalized exanthematous pustulosis, drug reaction with eosinophilia and systemic symptoms (DRESS)

Frequency not reported: Eczema, fungal dermatitis, vesiculobullous rash

Postmarketing reports: Toxic epidermal necrolysis, erythema multiforme, serious skin reactions


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%), vomiting (up to 13%), flatulence (up to 10.7%), abdominal discomfort

Common (1% to 10%): Dyspepsia, stomatitis

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

Frequency not reported: Clostridioides difficile-associated diarrhea, melena, infantile hypertrophic pyloric stenosis, mucositis, enteritis

Postmarketing reports: Pyloric stenosis, pseudomembranous colitis, pancreatitis, tongue discoloration


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

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


Very common (10% or more): Decreased neutrophils (up to 29%)

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

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

Frequency not reported: Decreased white cell count, decreased platelet count, anemia

Postmarketing reports: Thrombocytopenia, hemolytic anemia


Hepatic failure has rarely resulted in death.

Common (1% to 10%): Increased AST, increased ALT, increased GGT, increased blood bilirubin

Uncommon (0.1% to 1%): Hepatitis, abnormal liver function tests

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

Frequency not reported: Liver enzyme abnormalities, increased transaminase levels, jaundice

Postmarketing reports: Hepatic failure, fulminant hepatitis, hepatic necrosis


Uncommon (0.1% to 1%): Hypersensitivity

Postmarketing reports: Anaphylactic reaction/anaphylaxis (e.g., anaphylactic shock), allergic reactions

Severe (rarely fatal) anaphylactic reaction has been reported.


Common (1% to 10%): IV site pain, injection site inflammation (with IV administration), IV site disorders (infection/inflammation/edema/pain reactions), local inflammation, infusion site reaction

Frequency not reported: Local inflammation at infusion site


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

Uncommon (0.1% to 1%): Increased bicarbonate

Postmarketing reports: Dehydration


Common (1% to 10%): Arthralgia, increased creatine phosphokinase

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

Nervous system

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

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

Frequency not reported: Hyperkinesia

Postmarketing reports: Syncope, convulsion, psychomotor hyperactivity, anosmia, ageusia, parosmia, myasthenia gravis, hyperactivity


Common (1% to 10%): Visual impairment, abnormal vision

Frequency not reported: Conjunctivitis, blurred vision


Very common (10% or more): Increased blood alkaline phosphatase (up to 20%)

Common (1% to 10%): Deafness, fatigue, increased potassium, increased lactate dehydrogenase, reversible hearing impairment

Uncommon (0.1% to 1%): Candidiasis/moniliasis, ear disorder, asthenia, malaise, chest pain, edema, hearing impaired, abnormal blood potassium, fungal infection, bacterial infection, hot flush, face edema, pyrexia/fever, pain, peripheral edema, increased chloride, abnormal sodium, postprocedural complications

Frequency not reported: Increased phosphate, decreased sodium, decreased potassium

Postmarketing reports: Hearing disturbances (including hearing loss, deafness, tinnitus)


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

Rare (0.01% to 0.1%): Agitation, depersonalization

Frequency not reported: Delirium, hallucination

Postmarketing reports: Aggression/aggressive reaction, anxiety


Common (1% to 10%): Increased blood urea/BUN, increased blood creatinine

Uncommon (0.1% to 1%): Renal pain

Frequency not reported: Nephritis, renal function abnormality

Postmarketing reports: Acute renal failure, interstitial nephritis


Common (1% to 10%): Dyspnea

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

Frequency not reported: Bronchospasm, cough, pleural effusion

Frequently asked questions


1. Product Information. Zithromax IV (azithromycin). Pfizer U.S. Pharmaceuticals Group. 2022.

2. Product Information. Zithromax (azithromycin). Pfizer U.S. Pharmaceuticals Group. 2021.

3. Product Information. Zithromax (aziTHROMYCIN). Pfizer Australia Pty Ltd. 2022.

4. Product Information. Zithromax IV (aziTHROMYCIN). Pfizer Australia Pty Ltd. 2019.

5. Product Information. AziTHROMYCIN (Mylan) (aziTHROMYCIN). Alphapharm Pty Ltd. 2022.

6. Product Information. Zedbac (azithromycin). Aspire Pharma Ltd. 2022.

7. Product Information. Zithromax (azithromycin). Pfizer Ltd. 2022.

8. Product Information. Azithromycin (azithromycin). Sandoz Ltd. 2022.

9. Product Information. Azithromycin (azithromycin). Accord-UK Ltd. 2022.

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.