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Abacavir Side Effects

Not all side effects for abacavir may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to abacavir: oral solution, oral tablet

In addition to its needed effects, some unwanted effects may be caused by abacavir. In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking abacavir:

Less common
  • Abdominal or stomach pain
  • cough
  • diarrhea
  • difficult or labored breathing
  • fever
  • headache
  • joint or muscle pain
  • nausea
  • numbness or tingling of the hands, feet, or face
  • redness and soreness of the eyes
  • skin rash
  • sore throat
  • sores in the mouth
  • swelling of the feet or lower legs
  • unusual feeling of discomfort or illness
  • unusual tiredness
  • vomiting
  • Abdominal or stomach swelling
  • decreased appetite
  • fast, shallow breathing
  • sleepiness
Incidence not known
  • Blistering, peeling, or loosening of the skin
  • chest pain or discomfort
  • chills
  • dark urine
  • itching
  • light-colored stools
  • pain or discomfort in the arms, jaw, back, or neck
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • sores, ulcers, or white spots in the mouth or on the lips
  • sweating
  • unusual weakness
  • upper right abdominal or stomach pain
  • yellow eyes and skin

Some of the side effects that can occur with abacavir may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Headache
Less common
  • Trouble sleeping
Incidence not known
  • Breast enlargement
  • buffalo hump
  • central obesity
  • facial wasting
  • gaining weight around your neck, upper back, breast, face, or waist
  • peripheral wasting

For Healthcare Professionals

Applies to abacavir: oral solution, oral tablet


In 1 study, patients receiving the once-daily regimen had a significantly higher incidence of severe drug hypersensitivity reactions and severe diarrhea than patients on the twice-daily regimen.[Ref]


Common (1% to 10%): Drug hypersensitivity, hypersensitivity reaction (including fever, rash [usually maculopapular or urticarial], nausea, vomiting, malaise, diarrhea, pruritus, headache, fatigue, myalgia, chills, mouth and throat involvement, achiness, abdominal pain, pharyngitis, dyspnea, cough, lethargy, myolysis, edema, elevated liver function tests, mouth ulceration, sore throat, adult respiratory distress syndrome, respiratory failure, lymphadenopathy, hypotension, conjunctivitis, anaphylaxis, paresthesia, lymphopenia, hepatitis, liver failure, arthralgia, elevated creatine phosphokinase, elevated creatinine, renal failure, abnormal chest x-ray findings [mainly infiltrates, which can be localized], death)
Frequency not reported: Serious and sometimes fatal hypersensitivity reactions, abacavir hypersensitivity reaction presenting as acute fibrinous and organizing pneumonia[Ref]

Serious and sometimes fatal hypersensitivity reactions have been associated with this drug. Hypersensitivity to this drug is a clinical syndrome affecting multiple organs generally characterized by a sign/symptom in 2 or more of the following groups: (1) Fever, (2) Rash, (3) Gastrointestinal (including nausea, vomiting, diarrhea, abdominal pain), (4) Constitutional (including generalized malaise, fatigue, achiness), (5) Respiratory (including dyspnea, cough, pharyngitis); infrequently reported after a single sign/symptom. Hypersensitivity was reported in up to 9% of patients during 9 clinical trials. Symptoms usually appeared within the first 6 weeks of therapy but the reaction may occur any time during therapy. Symptoms worsened with continued therapy and generally resolved when this drug was discontinued. Restarting this drug after a hypersensitivity reaction has resulted in more severe symptoms within hours and included life-threatening hypotension and death.

The symptoms reported most often in the first 406 patients with hypersensitivity reaction were fever (83%), rash (usually maculopapular or urticarial; 68%), nausea (38%), vomiting (25%), malaise (19%), diarrhea (18%), pruritus (17%), headache (17%), fatigue (15%), myalgia (13%), chills (12%), and mouth and throat involvement (11%). Abdominal pain, dyspnea, cough, lethargy, and elevated liver function tests were reported in at least 10% of patients. Other signs/symptoms of hypersensitivity have included mouth ulceration, sore throat, adult respiratory distress syndrome, respiratory failure, edema, lymphadenopathy, hypotension, conjunctivitis, anaphylaxis, paresthesia, lymphopenia, hepatitis, liver failure, myolysis, arthralgia, elevated creatine phosphokinase, elevated creatinine, renal failure, abnormal chest x-ray findings (mainly infiltrates, which can be localized), and death.

In a clinical trial, 3.4% of human leukocyte antigen subtype B*5701 (HLA-B*5701)-negative patients using this drug had a hypersensitivity reaction. Studies showed that patients testing positive for the HLA-B*5701 allele had a significantly greater risk of hypersensitivity reactions to this drug. Based on a prospective study, screening for the HLA-B*5701 allele prior to therapy and then avoiding this drug in HLA-B*5701-positive patients significantly lowered the incidence of abacavir hypersensitivity reactions. It has been estimated that 48% to 61% of HLA-B*5701-positive patients will develop a hypersensitivity reaction during use of this drug compared with 0% to 4% of HLA-B*5701-negative patients; such results were consistent with prior retrospective studies.

Hypersensitivity reactions with rapid onset (including life-threatening reactions) have occurred after restarting this drug in patients with only 1 key symptom of hypersensitivity before stopping therapy; very rarely, hypersensitivity reactions were reported with resumption of therapy in patients previously considered tolerant to this drug (i.e., had no prior hypersensitivity symptoms).

In 1 case report, a 57-year-old HIV-positive male presented to medical attention with a 2-day history of fever, malaise, and diarrhea related to initiation of this drug. Six days prior to the onset of symptoms, the patient's antiretroviral therapy was switched from efavirenz and lamivudine-zidovudine to zidovudine, abacavir, and lopinavir-ritonavir after a drop in his CD4 cell count. The patient developed acute dyspnea and severe hypoxemia, hemoptysis, and diffuse bilateral pulmonary infiltrates within 72 hours of admission and this drug was discontinued due to suspicion of a hypersensitivity reaction. Three days after drug discontinuation, the patient's status improved and chest films showed resolution of infiltrates.[Ref]


Pancreatitis was observed in the expanded access program.[Ref]

Very common (10% or more): Nausea (up to 47%), nausea and vomiting (up to 38%), diarrhea (up to 16%)
Common (1% to 10%): Abdominal pain/gastritis/gastrointestinal signs and symptoms, vomiting, abdominal discomfort and pain, abnormal amylase
Rare (0.01% to 0.1%): Pancreatitis[Ref]


Very common (10% or more): Malaise and fatigue (up to 34%), temperature regulation disturbance (up to 19%)
Common (1% to 10%): Fever/pyrexia, lethargy, fatigue, fatigue/malaise, fever and/or chills
Uncommon (0.1% to 1%): Non-site-specific pain
Frequency not reported: Asthenia, reduced alcohol tolerance, disulfiram-like reaction[Ref]

In 1 case report, a 31-year-old HIV-infected male patient switched to this drug and experienced a disulfiram-like reaction with nausea, facial flushing, and tachycardia after alcohol consumption. When the patient was rechallenged with a shot of vodka, the same reaction occurred.

In another case, a 27-year-old HIV-infected male patient switched to this drug and noticed reduced alcohol tolerance. The patient reported that he felt as if he had ingested 1.5 bottles of wine after 3 glasses, with loss of memory until the next morning and vomiting. The patient was able to tolerate small quantities of alcohol or alcohol consumed with food.[Ref]

Nervous system

Very common (10% or more): Headache (up to 31%)
Common (1% to 10%): Headaches/migraine, dizziness, neuropathy[Ref]


Very common (10% or more): Cough (up to 24%), ear/nose/throat infections (up to 19%), nasal signs/symptoms (up to 11%)
Common (1% to 10%): Viral respiratory infections (including viral ear, nose, and throat infection), bronchitis
Frequency not reported: Tachypnea, pharyngitis[Ref]


Elevated creatine phosphokinase (greater than 4 times the upper limit of normal [4 x ULN]) has been reported in up to 8% of patients.[Ref]

Very common (10% or more): Elevated creatine phosphokinase (up to 12%)
Common (1% to 10%): Musculoskeletal pain
Frequency not reported: Osteonecrosis[Ref]


Very common (10% or more): Skin rashes (maculopapular, urticarial, or variable appearance; up to 11%)
Common (1% to 10%): Rash (without systemic symptoms)
Frequency not reported: Sweet's syndrome
Very rare (less than 0.01%): Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme[Ref]

Suspected Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported during postmarketing experience in patients receiving this drug primarily in combination with medications known to be associated with SJS and TEN, respectively. Due to overlap of clinical signs/symptoms between abacavir hypersensitivity and SJS and TEN, and the possibility of multiple drug sensitivities in some patients, this drug should be permanently discontinued in such cases.[Ref]


Very common (10% or more): Feeding problems (up to 11%)
Common (1% to 10%): Hypertriglyceridemia, hyperamylasemia, anorexia, abnormal triglycerides, hyperlactatemia
Uncommon (0.1% to 1%): Hyperglycemia, abnormal alkaline phosphatase, abnormal glucose, abnormal sodium
Rare (0.01% to 0.1%): Lactic acidosis
Frequency not reported: Mild elevations of blood glucose, hypoglycemia, loss of appetite
Postmarketing reports: Redistribution/accumulation of body fat (including central obesity, dorsocervical fat enlargement, peripheral wasting, facial wasting, breast enlargement, "cushingoid appearance")

Combination antiretroviral therapy:
-Frequency not reported: Metabolic abnormalities (e.g., hypertriglyceridemia, hypercholesterolemia, insulin resistance, hyperglycemia, hyperlactatemia)[Ref]

Hypertriglyceridemia (greater than 750 mg/dL), hyperamylasemia (greater than 2 x ULN), and hyperglycemia (greater than 13.9 mmol/L) have been reported in up to 6%, up to 4%, and less than 1% of patients, respectively.

Lactic acidosis and severe hepatomegaly with steatosis (including fatal cases) have been reported with the use of nucleoside analogs.[Ref]


Very common (10% or more): Dreams/sleep disorders (10%)
Common (1% to 10%): Depression, anxiety, sleep disorders, insomnia, abnormal dreams
Frequency not reported: Mania, worsening of preexisting depression, lethargy[Ref]


Common (1% to 10%): Elevated ALT, elevated AST
Uncommon (0.1% to 1%): Abnormal bilirubin
Frequency not reported: Increased GGT, severe hepatomegaly with steatosis
Postmarketing reports: Lactic acidosis, hepatic steatosis[Ref]

Elevated ALT (greater than 5 x ULN) and AST (greater than 5 x ULN) have been reported in 6% and up to 6% of patients, respectively.

The reported frequencies were similar to those observed during clinical trials with zidovudine and lamivudine administration.

Increased GGT was observed in the expanded access program.

Lactic acidosis and severe hepatomegaly with steatosis (including fatal cases) have been reported with the use of nucleoside analogs.[Ref]


Neutropenia (absolute neutrophil count less than 750/mm3), thrombocytopenia (platelets less than 50,000/mm3), anemia (hemoglobin 6.9 g/dL or less), and leukopenia (WBC 1500/mm3 or less) have been reported in up to 5%, 1%, less than 1%, and less than 1% of patients, respectively.

The reported frequencies were similar to those observed during clinical trials with zidovudine and lamivudine administration.

Agranulocytosis has been reported after the addition of this drug to a multi-drug regimen.[Ref]

Common (1% to 10%): Neutropenia, thrombocytopenia, decreased white cells, abnormal absolute neutrophils
Uncommon (0.1% to 1%): Anemia, leukopenia, abnormal hemoglobin, abnormal platelets, abnormal WBC
Rare (less than 0.1%): Eosinophilia
Frequency not reported: Agranulocytosis, increased platelet reactivity[Ref]


Uncommon (0.1% to 1%): Renal signs/symptoms, abnormal creatinine
Frequency not reported: Acute renal failure, interstitial nephritis[Ref]


Frequency not reported: Immune reconstitution/reactivation syndrome, autoimmune disorders in the setting of immune reconstitution (e.g., Graves' disease, polymyositis, Guillain-Barre syndrome)


An observational study investigating the rate of MI in patients on combination antiretroviral therapy showed an increased risk of MI with the use of this drug within the previous 6 months. A sponsor-conducted pooled analysis of clinical trials showed no excess risk of MI in abacavir-treated patients as compared with control subjects. Overall, available data from the observational cohort and from clinical trials were inconclusive.[Ref]

Frequency not reported: Endothelial dysfunction, peripheral arterial disease, coronary bypass surgery, ischemic stroke, deep venous thrombosis, angina, transient ischemic attack
Postmarketing reports: Myocardial infarction (MI)[Ref]


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