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Zidovudine Side Effects

In Summary

Commonly reported side effects of zidovudine include: headache, nausea, neutropenia, vomiting, anemia, anorexia, and malaise. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to zidovudine: oral capsule, oral syrup, oral tablet

Other dosage forms:

Along with its needed effects, zidovudine 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 zidovudine:

More common
  • Black, tarry stools
  • chills
  • cough
  • feeling of fullness
  • fever
  • lower back or side pain
  • painful or difficult urination
  • pale skin
  • right upper abdominal pain and fullness
  • sore throat
  • stomach pain
  • swelling or inflammation of the mouth
  • swollen lymph nodes
  • ulcers, sores, or white spots in the mouth
  • unusual bleeding or bruising
  • unusual tiredness or weakness
  • Confusion
  • diarrhea
  • fast, shallow breathing
  • general feeling of discomfort
  • loss of appetite
  • mood or mental changes
  • muscle pain, tenderness, weakness, or cramping
  • nausea
  • seizures
  • sleepiness
  • stomach discomfort
Incidence not known
  • Back or leg pain
  • bleeding gums
  • blistering, peeling, or loosening of the skin
  • bloating
  • blood in the urine
  • blurred vision or other change in vision
  • bone pain
  • burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
  • clay-colored stools
  • constipation
  • dark urine
  • decreased appetite
  • decreased urine output
  • difficult or labored breathing
  • difficulty in moving
  • difficulty in swallowing
  • dilated neck veins
  • dizziness
  • extreme fatigue
  • fainting
  • fast, irregular, or pounding heartbeat
  • general body swelling
  • general tiredness and weakness
  • headache
  • high fever
  • hives
  • hoarseness
  • increased need to urinate
  • indigestion
  • irregular breathing
  • irritation or soreness of the mouth
  • joint or muscle pain
  • lack of coordination
  • large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
  • light-colored stools
  • muscle pain, cramp, spasm, or stiffness
  • nosebleeds
  • pains in the stomach, side, or abdomen, possibly radiating to the back
  • passing urine more often
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • red skin lesions, often with a purple center
  • red, irritated eyes
  • redness, soreness, or itching skin
  • runny nose
  • shakiness in the legs, arms, hands, or feet
  • shivering
  • skin rash
  • sores, welts, or blisters
  • stabbing pain
  • sweating
  • swollen joints
  • swollen or painful glands
  • tightness in the chest
  • trouble sleeping
  • unexplained bleeding or bruising
  • unpleasant breath odor
  • vomiting
  • vomiting of blood
  • weight gain
  • yellow eyes or skin

Some side effects of zidovudine 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:

More common
  • Difficulty having a bowel movement
  • headache (severe)
  • lack or loss of strength
  • muscle soreness
  • weight loss
Less common
  • Bluish-brown colored bands on nails
  • changes in skin color
Incidence not known
  • Belching
  • burning, tingling, numbness, or pain in the hands, arms, feet, or legs
  • heartburn
  • muscle or bone pain
  • stomach cramps

For Healthcare Professionals

Applies to zidovudine: intravenous solution, oral capsule, oral syrup, oral tablet


The adverse effects of zidovudine are sometimes difficult to distinguish from the symptomatology observed during the clinical course of AIDS, as well as from the possible adverse effects of other drugs used in the treatment of HIV-1 infection. Many of the side effects associated with nucleoside reverse transcriptase inhibitor therapy (myopathy, pancreatitis, liver failure, lactic acidosis, etc.) are attributable to their direct toxic effect on mitochondria which causes decreased mitochondrial energy-generating capacity.[Ref]

Nervous system

Nervous system side effects have included headache (up to 63%), insomnia (5% or greater), neuropathy (5% or greater), and numbness. Status epilepticus and Wernicke's syndrome have been rarely reported. Seizures, confusion, dizziness, paresthesia, somnolence, vertigo, hearing loss, and loss of mental acuity have been reported during postmarketing experience.[Ref]


Bone marrow suppression, the most common reason for cessation of zidovudine therapy, appears to be dose-dependent and may be seen as early as 2 to 6 weeks after initiation of therapy. Recombinant GM-CSF (sargramostim), G-CSF (filgrastim), and erythropoietin (epoetin alfa) have been used to control the hematologic toxicity of zidovudine.

Zidovudine should be used with extreme caution in patients with bone marrow suppression indicated by a granulocyte count below 1000 cells/mm3 or hemoglobin less than 9.5 g/dL. Routine blood counts are recommended, and generally should occur more frequently in patients with advanced disease. If bone marrow toxicity occurs, an interruption or discontinuation of zidovudine therapy may be necessary.[Ref]

Hematologic side effects have included granulocytopenia (less than 750 cells/mm3; up to 2%), anemia (hemoglobin less than 8 g/dL; up to 1.1%), and increased hemoglobin A2 percentage. Hematologic toxicity, including neutropenia and severe anemia, has been reported, mostly in patients with advanced HIV-1 disease. Exacerbation of anemia due to ribavirin has been reported when zidovudine was part of the HIV-1 regimen. Aplastic anemia, hemolytic anemia, leukopenia, lymphadenopathy, pancytopenia with marrow hypoplasia, and pure red cell aplasia have been reported during postmarketing experience.[Ref]


Gastrointestinal side effects have included nausea (up to 51.4%), anorexia (up to 20.1%), vomiting (up to 17.2%), constipation (up to 6.4%), dyspepsia (5% or greater), abdominal cramps (5% or greater), abdominal pain (5% or greater), diarrhea, stomatitis, and splenomegaly. Dysphagia, constipation, flatulence, oral mucosa pigmentation, mouth ulcer, and pancreatitis have been reported during postmarketing experience.[Ref]


Hepatic side effects have included increased ALT (greater than 5 times ULN; up to 3.1%) and AST (greater than 5 times ULN; up to 1%), hyperbilirubinemia (less than or equal to 0.8%), fulminate hepatitis, and hepatic failure. Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, have been reported with the use of nucleoside analogs alone or in combination, including zidovudine and other antiretrovirals. Hepatic decompensation (some fatal) has been reported in patients coinfected with HIV-1 and hepatitis C receiving combination antiretroviral therapy for HIV-1 and interferon alfa with or without ribavirin. Hepatitis, hepatomegaly with steatosis, lactic acidosis, and jaundice have been reported during postmarketing experience.[Ref]

One patient with preexisting hepatitis B developed acute hepatic failure two weeks after starting zidovudine therapy.

Patients with a history of liver disease should be monitored for further deterioration in liver function.[Ref]


In one case of zidovudine-associated fever, no source of infection was found after an extensive evaluation, but an anti-zidovudine immunoglobulin was isolated, indicating a possible hypersensitivity reaction.[Ref]

Other side effects have included malaise (up to 53.2%), asthenia (up to 9%), fatigue (5% or greater), chills (5% or greater), and fever. Zidovudine therapy has been associated with lower levels of vitamins B2 and C, folate, and zinc despite adequate dietary intake. Back pain, chest pain, influenza-like syndrome, generalized pain, syncope, and taste perversion have been reported during postmarketing experience.[Ref]


In one study, myalgias and elevated creatine kinase occurred in 8% of treated patients with a CD4 cell count less than 200/mm3, and in none of the patients with higher CD4 cell counts. Dosage reduction has not affected the course of myopathy, although drug discontinuation sometimes resulted in improvement of symptoms, generally within a month. Muscle biopsy has shown atrophic and sometimes necrotic fibers, ragged-red fibers, and large accumulations of mitochondrial and fibrillar sarcoplasmic inclusions.

Myopathy and myositis with pathological changes, similar to that produced by HIV-1 disease, have been associated with prolonged use of zidovudine.[Ref]

Musculoskeletal side effects have included arthralgia, myalgia, and musculoskeletal pain in greater than or equal to 5% of patients. Myopathy, myositis, muscle tenderness, and weakness in the arms and legs have been reported and were generally associated with an elevation in serum creatine kinase. Increased creatine phosphokinase, muscle spasm, myopathy and myositis with pathological changes (similar to that produced by HIV-1 disease), rhabdomyolysis, and tremor have been reported during postmarketing experience.[Ref]


Psychiatric side effects have included isolated cases of depression, mania, anxiety, and grandiosity. Anxiety, depression, and mania have been reported during postmarketing experience.[Ref]


Dermatologic side effects have included case reports of nailbed hyperpigmentation, particularly in black people. Rarely, nail hyperpigmentation has been accompanied by mucocutaneous pigmentation or hypertrichosis. Skin rashes and leukocytoclastic vasculitis with eosinophilia and fever have also been reported. Changes in skin and nail pigmentation, pruritus, rash, Stevens-Johnson syndrome, toxic epidermal necrolysis, sweat, and urticaria have been reported during postmarketing experience.[Ref]

Bluish or brownish-black discoloration of nails has developed during the first month or two of zidovudine therapy and usually disappeared within 2 months if the drug was discontinued. Discoloration has occurred as longitudinal streaks or transverse bands.[Ref]


Cardiovascular side effects have included rare cases of reversible congestive heart failure and vasodilation. Cardiomyopathy and vasculitis have been reported during postmarketing experience.[Ref]


Hypersensitivity side effects have included allergic skin rash. Sensitization reactions including anaphylaxis and angioedema have been reported during postmarketing experience.[Ref]


Metabolic side effects have included hyperlipidemia. Redistribution/accumulation of body fat including central obesity, dorsocervical fat enlargement, peripheral wasting, facial wasting, breast enlargement, and "cushingoid appearance" have been observed in patients receiving antiretroviral therapy. Increased lactate dehydrogenase and redistribution/accumulation of body fat have been reported during postmarketing experience.[Ref]


Respiratory side effects have included cough, dyspnea, rhinitis, and sinusitis during postmarketing experience.[Ref]


Immunologic side effects have included immune reconstitution syndrome. Autoimmune disorders (e.g., Graves' disease, polymyositis, and Guillain-Barre syndrome) have been reported in the setting of immune reconstitution.


A case of macular edema in a patient with a history of anterior uveitis secondary to syphilis has been reported.[Ref]

Ocular side effects have included amblyopia, macular edema, and photophobia during postmarketing experience.[Ref]


Genitourinary side effects have included gynecomastia, urinary frequency, and urinary hesitancy during postmarketing experience.[Ref]


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Some side effects of zidovudine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

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