Abacavir is an effective medicine but stop using it and call your doctor at once if you have symptoms of an allergic reactions such as the reported side effects groups listed below.
Group 1 – fever;
Group 2 – rash;
Group 3 – nausea, vomiting, diarrhea, stomach pain;
Group 4 – general ill feeling, extreme tiredness, body aches;
Group 5 – shortness of breath, cough, sore throat.
Once you have had an allergic reaction to abacavir, you must never use it again. If you stop taking abacavir for any reason, talk to your doctor before you start taking the medication again.
Abacavir may cause lactic acidosis (a build-up of lactic acid in the body, which can be fatal). Lactic acidosis can start slowly and get worse over time. Get emergency medical help if you have even mild symptoms of lactic acidosis, such as: muscle pain or weakness, numb or cold feeling in your arms and legs, trouble breathing, stomach pain, nausea with vomiting, fast or uneven heart rate, dizziness, or feeling very weak or tired.
Abacavir can cause other serious side effects that may not be signs of an allergic reaction. Call your doctor at once if you have:
the first sign of any skin rash, no matter how mild;
signs of a new infection such as flu symptoms, chills, easy bruising or unusual bleeding, loss of appetite, mouth sores;
severe pain in your upper stomach spreading to your back;
itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
increased sweating, tremors in your hands, anxiety, feeling irritable, sleep problems (insomnia);
diarrhea, unexplained weight loss, menstrual changes, impotence, loss of interest in sex;
swelling in your neck or throat (enlarged thyroid);
weakness or prickly feeling in your fingers or toes;
problems with walking, breathing, speech, swallowing, or eye movement; or
severe lower back pain, loss of bladder or bowel control.
Less serious side effects of abacavir may include:
headache, ear pain;
cold symptoms such as stuffy nose, sneezing, sinus pain; or
changes in the shape or location of body fat (especially in your arms, legs, face, neck, breasts, and trunk).
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.
Side Effects Common To Healthcare Professionals
Patients receiving once-daily abacavir had a significantly higher incidence of severe hypersensitivity reactions and severe diarrhea than patients on the twice-daily regimen.
Common (1% to 10%): Drug hypersensitivity (Grades 2 to 4; 9%), hypersensitivity reaction (Grades 2 to 4; 8%)
Rare (less than 0.1%): Abacavir hypersensitivity reaction presenting as acute fibrinous and organizing pneumonia (at least 1 case)
Frequency not reported: Serious and sometimes fatal hypersensitivity reactions (including fever, skin rash [maculopapular, urticarial, or variable appearance], malaise, fatigue, achiness, nausea, vomiting, diarrhea, abdominal pain, pharyngitis, dyspnea, cough, lethargy, myolysis, edema, abnormal chest X-ray [infiltrates], paresthesia, anaphylaxis, liver failure, renal failure, hypotension, adult respiratory distress syndrome, respiratory failure, death, lymphadenopathy, mucous membrane lesions [conjunctivitis and stomatitis], elevated liver function tests, elevated creatine phosphokinase, elevated creatinine, lymphopenia)
Serious and sometimes fatal hypersensitivity reactions have been reported. Frequently observed signs and symptoms have included, but were not limited to, fever, skin rash (maculopapular, urticarial, or variable appearance), malaise, fatigue, achiness, nausea, vomiting, diarrhea, abdominal pain, pharyngitis, dyspnea, and cough. Other symptoms of abacavir hypersensitivity have included lethargy, myolysis, edema, abnormal chest X-ray (infiltrates), paresthesia, anaphylaxis, liver failure, renal failure, hypotension, adult respiratory distress syndrome, respiratory failure, death, lymphadenopathy, mucous membrane lesions (conjunctivitis and stomatitis), elevated liver function tests, elevated creatine phosphokinase, elevated creatinine, and lymphopenia.
In one 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 abacavir. 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 abacavir was discontinued due to suspicion of a hypersensitivity reaction. Three days following discontinuation of abacavir the patient’s status improved and chest films showed resolution of infiltrates.
Abacavir hypersensitivity is a clinical syndrome affecting multiple organs generally characterized by a sign or symptom in two or more of the following groups:
(3) Gastrointestinal (including nausea, vomiting, diarrhea, or abdominal pain)
(4) Constitutional (including generalized malaise, fatigue, or achiness)
(5) Respiratory (including dyspnea, cough, or pharyngitis)
A strong predictor of hypersensitivity reaction may be the presence of human leukocyte antigen subtype B*5701 (HLA-B*5701). Analyzing past studies, patients testing positive for the HLA-B*5701 allele had a greater risk (61% to about 70%) of developing hypersensitivity reactions with abacavir, while patients without the HLA-B*5701 allele had a low risk (less than 1% to 4%); therefore, screening for the HLA-B*5701 allele is recommended prior to starting abacavir treatment. Therapy with an abacavir-containing regimen is not recommended for HLA-B*5701-positive patients and should be considered only with close medical supervision under exceptional conditions where potential benefit outweighs the risk. Considerably less frequently, HLA-B*5701-negative patients may experience hypersensitivity reaction with abacavir.
Abacavir should be permanently discontinued as soon as a hypersensitivity reaction is suspected. Severe or fatal hypersensitivity reactions can also occur within hours after restarting abacavir in patients who have no identified history or unrecognized symptoms of this reaction. It should be permanently discontinued if hypersensitivity cannot be ruled out, even when other diagnoses are possible, to minimize the risk of a life-threatening hypersensitivity reaction.
Common (1% to 10%): Elevated ALT (greater than 5 times ULN; 6%), elevated AST (greater than 5 times ULN; up to 6%)
Frequency not reported: Increased gamma-glutamyltransferase, severe hepatomegaly with steatosis
Postmarketing reports: Lactic acidosis, hepatic steatosis
The reported frequencies were similar to those observed during clinical trials with zidovudine and lamivudine administration.
Increased gamma-glutamyltransferase 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 alone or in combination with other antiretroviral agents.
Pancreatitis was observed in the expanded access program.
Very common (10% or more): Nausea (at least moderate intensity: up to 19%), nausea and vomiting (at least moderate intensity: 10%)
Common (1% to 10%): Diarrhea (at least moderate intensity: 7%), abdominal pain/gastritis/gastrointestinal signs and symptoms (at least moderate intensity: 6%), vomiting (at least moderate intensity: 2%)
Frequency not reported: Loss of appetite/anorexia, pancreatitis
Very common (10% or more): Headache (at least moderate intensity: 13%)
Common (1% to 10%): Headaches/migraine (at least moderate intensity: 7%), dizziness (at least moderate intensity: 6%)
Frequency not reported: Insomnia, other sleep disorders
In one case report, a 31-year-old HIV-infected male patient switched to abacavir and experienced a disulfiram-like reaction with nausea, facial flushing, and tachycardia following 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 abacavir and noticed reduced alcohol tolerance. The patient reported that he felt as if he had ingested 1.5 bottles of wine following 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.
Very common (10% or more): Malaise and fatigue (at least moderate intensity: 12%)
Common (1% to 10%): Fatigue/malaise (at least moderate intensity: 7%), fever and/or chills (at least moderate intensity: 6%), ear/nose/throat infections (at least moderate intensity: 5%)
Uncommon (0.1% to 1%): Non-site-specific pain (at least moderate intensity: less than 1%)
Frequency not reported: Asthenia, reduced alcohol tolerance, disulfiram-like reaction
Very common (10% or more): Dreams/sleep disorders (at least moderate intensity: 10%)
Common (1% to 10%): Depressive disorders (at least moderate intensity: 6%), anxiety (at least moderate intensity: 5%)
Frequency not reported: Mania, worsening of preexisting depression, lethargy
Common (1% to 10%): Rashes (at least moderate intensity: 6%), skin rashes (at least moderate intensity: 5%)
Frequency not reported: Sweet’s syndrome
Postmarketing reports: Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema multiforme
Suspected Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been reported in patients receiving abacavir primarily in combination with medications known to be associated with SJS and TEN, respectively. Due to overlap of clinical signs and symptoms between abacavir hypersensitivity and SJS and TEN, and the possibility of multiple drug sensitivities in some patients, abacavir should be permanently discontinued in such cases.
Common (1% to 10%): Elevated creatine phosphokinase (greater than 4 times ULN; up to 8%), hypertriglyceridemia (greater than 750 mg/dL; up to 6%), hyperamylasemia (greater than 2 times ULN; up to 4%)
Uncommon (0.1% to 1%): Hyperglycemia (greater than 13.9 mmol/L; less than 1%)
Rare (less than 0.1%): Hypoglycemia (at least 1 case)
Frequency not reported: Mild elevations of blood glucose
Postmarketing reports: Redistribution/accumulation of body fat (including central obesity, dorsocervical fat enlargement, peripheral wasting, facial wasting, breast enlargement, “cushingoid appearance”)
Common (1% to 10%): Neutropenia (ANC less than 750/mm3; up to 5%), thrombocytopenia (platelets less than 50,000/mm3; 1%)
Uncommon (0.1% to 1%): Anemia (Hgb 6.9 g/dL or less; less than 1%), leukopenia (WBC 1500/mm3 or less; less than 1%)
Rare (less than 0.1%): Eosinophilia
Frequency not reported: Agranulocytosis, increased platelet reactivity
The reported frequencies were similar to those observed during clinical trials with zidovudine and lamivudine administration.
Agranulocytosis has been reported after the addition of abacavir to a multi-drug regimen.
Common (1% to 10%): Musculoskeletal pain (at least moderate intensity: up to 6%)
Frequency not reported: Immune reconstitution syndrome, autoimmune disorders in the setting of immune reconstitution (e.g., Graves’ disease, polymyositis, and Guillain-Barre syndrome)
Common (1% to 10%): Viral respiratory infections (at least moderate intensity: 5%), bronchitis (at least moderate intensity: 4%)
Frequency not reported: Tachypnea, cough, pharyngitis
Rare (less than 0.1%): Peripheral arterial disease (at least 2 cases), coronary bypass surgery (at least 1 case), ischemic stroke (at least 1 case), deep venous thrombosis (at least 1 case), angina (at least 1 case), transient ischemic attack (at least 1 case)
Frequency not reported: Endothelial dysfunction
Postmarketing reports: Myocardial infarction
A study investigating the frequency of myocardial infarction (MI) in patients taking combination antiretroviral treatment showed an increased risk of MI with the use of abacavir within the previous 6 months; however, these results are not conclusive. The manufacturer reviewed its own clinical study databases and although the results of the analysis are inconclusive, they did not show an excess risk of MI. A meta-analysis conducted by the FDA showed no statistically significant difference in MI events between patients who received abacavir and those who did not.
Uncommon (0.1% to 1%): Renal signs/symptoms (at least moderate intensity: less than 1%)
Frequency not reported: Acute renal failure, interstitial nephritis
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