Abacavir: Uses, Indications, Dosages, Precautions, Contraindications, Side Effects & Interactions

Abacavir

(a-bak-a-veer)
Classification 
Pharmacotherapeutic: Antiretroviral agent
Clinical: Antiviral

Ziagen

CATEGORY AND SCHEDULE

Pregnancy Risk Category: C

Do not confuse:

abacavir/amprenavir

General Information

Abacavir belongs to the group of antiretroviral agents of the antiviral drug group. They are effective for the treatment of HIV-1 infection, in combination with at least two other antiretroviral agents.

Abacavir can cause severe reactions such as: the hypersensitivity reaction can be life-threatening. Signs and symptoms include fever, rash, fatigue, intractable nausea and vomiting, severe diarrhea, abdominal pain, cough, pharyngitis, and dyspnoea. Life-threatening hypotension, lactic acidosis and severe hepatomegaly can occur

Action

An antiretroviral that inhibits HIV-1 reverse transcriptase activity by competing with the natural substrate deoxyguanosine-5'-triphosphate (dGTP) and incorporating it into viral DNA

Therapeutic Effect

Inhibits/prevents HIV replication in infected cells

Availability (Rx)

Tablets: 300 mg

Oral Solution: 20 mg/mL

Uses

In combination with other antiretroviral agents for HIV-1 infection (not to be used with lamivudine or tenofovir)

Unlabeled uses: HIV prophylaxis following occupational exposure

Precautions

Pregnancy C, breastfeeding, child ,3 mo, granulocyte count ,1000/mm3 or Hgb ,9.5 g/dl, severe renal disease, impaired hepatic function, HLA B5701 (Black, Caucasian, Asian patients), abrupt discontinuation; Guillain-Barré syndrome, immune reconstitution syndrome, MI, obesity, polymyositis

Black Box Warning: Lactic acidosis

Make sure to tell your doctor if:

• You have heart problems

• You have diabetes

• You have had hepatic disease

• You have long-term kidney problems

• You are taking other medicines

Indications and Dosages

‣ To Treat HIV infection (in combination with other antiretrovirals)

PO

• Adults. 300 mg twice a day or 600 mg once daily

• Children (3 mo and older). 8 mg/kg twice a day. Maximum: 300 mg twice a day

‣ Dosage in hepatic impairment

Mild impairment

• Adults: 200 mg twice a day

Moderate to Severe Impairment

• Contraindicated

Pharmacokinetics

Rapidly and extensively absorbed after PO administration. Protein binding: 50%. Widely distributed, including to CSF and erythrocytes. Metabolized in the liver to inactive metabolites. Excreted primarily in urine. Unknown whether removed by hemodialysis. Half-life: 1.5 h

Implementation

PO route

• May give without regard to food q12hr around the clock

• Give in combination with other antiretrovirals with or without food; do not use triple therapy as a beginning treatment, resistance may occur

• Store in cool environment; protect from light; do not freeze

Contraindications

Hypersensitivity to abacavir or its components. Moderate to severe hepatic impairment

Cautions: Mild hepatic disease. Pts at risk for coronary heart disease (e.g., hypertension, hyperlipidemia, diabetes, smoking). Pts at risk for hepatotoxicity (e.g., female gender, obesity), pts with plasma HIV RNA levels greater than 100,000 copies/mL

Interactions

Individual drugs

• Do not coadminister with abacavir-containing products

• Alcohol: increased abacavir levels; do not use with alcohol

• Ribavirin: possible lactic acidosis

• Methadone: decreased levels of methadone

• Tipranavir: decreased abacavir levels

Drug/laboratory tests

• May increase serum amylase, ALT, AST, CPK, GGT, blood glucose, triglycerides. May decrease Hgb, leukocytes, lymphocytes

Drugs/food

• None known

Herbal

• None significant

Side effects

• CNS: Anxiety, chills, depression, dizziness, fatigue, fever, headache, lethargy, malaise, migraines, paresthesia, sleep disorders 

• CV: Edema, elevated triglyceride levels, hypotension, 

• MI/EENT: Conjunctivitis, ENT infections, mouth ulcerations, pharyngitis 

• ENDO: Cushingoid appearance, fat redistribution, hyperglycemia 

• GI: Abdominal pain, diarrhea, elevated liver enzymes, gastritis, hyperamylasemia, liver failure, nausea, pancreatitis, severe hepatomegaly with steatosis, vomiting GU: Renal dysfunction, renal failure 

• HEME: Anemia, neutropenia, leukopenia, thrombocytopenia 

• MS: Achiness, arthralgia, elevated CPK levels, musculoskeletal pain, myalgia, myolysis 

• RESP: Adult respiratory distress syndrome, bronchitis, cough, dyspnea, pneumonia, respiratory failure, viral respiratory infections 

• SKIN: Erythema multiforme, rash, Stevens–Johnson syndrome, toxic epidermal necrolysis 

• Other: Anaphylaxis, lactic acidosis, lymphadenopathy, multiorgan failure, nonspecific pain

 

Nursing considerations

Baseline assessment

• Obtain CBC, LFT before beginning therapy and at periodic intervals during

therapy

• Question history of hypersensitivity reaction

• Question for possibility of pregnancy. Increased risk of sensitivity (cutaneous, GI, pulmonary) in those with positive HLA-B*5701 genotype status. Offer emotional support

Intervention/evaluation

• Stop abacavir if 3 or more of the following occur: rash, fever, GI disturbances

(diarrhea, nausea, vomiting), flu-like symptoms, respiratory difficulty

• Assess for nausea, vomiting. Monitor daily pattern of bowel activity, stool consistency

• Assess dietary pattern; monitor for weight loss. Monitor lab values, hepatic

function

Equipment must be available for anaphylaxis

• Assess for symptoms of HIV and possible infection, increased temp

• Assess for lactic acidosis (elevated lactate levels, increased liver function tests) and severe hepatomegaly with steatosis; discontinue treatment and do not restart, women are at greater risk for lactic acidosis

• Assess for fatal hypersensitivity reactions: fever, rash, nausea, vomiting, fatigue, cough, dyspnea, diarrhea, abdominal discomfort; treatment should be discontinued and not restarted

• Assess for pancreatitis: abdominal pain, nausea, vomiting, elevated liver enzymes; product should be discontinued because condition can be fatal

• Monitor CBC, differential, platelet count qmo; withhold product if WBC is ,4000/ mm3 or platelet count is ,75,000/mm3; notify prescriber of results; monitor viral load and CD4 counts during treatment, perform hepatitis B virus (HBr) screening to confirm correct treatment

• Monitor renal function studies; BUN, serum uric acid, urine CCr before, during therapy; these may be elevated throughout treatment

• Monitor temp q4hr; may indicate beginning of infection

• Monitor liver function tests before, during therapy (bilirubin, AST, ALT, amylase, alkaline phosphatase, creatine phosphokinase, creatinine prn or qmo)

Evaluation

Positive therapeutic result

• Increased CD4 count

• Decreased viral load

Patient/family teaching

• Advise patient to report signs of infection: increased temp, sore throat, flulike symptoms; to avoid crowds and those with known infections, to carry emergency ID with condition, products taken

• Instruct patient to report signs of anemia: fatigue, headache, faintness, shortness of breath, irritability

• Advise patient to report bleeding; avoid use of razors or commercial mouthwash

• Inform patient that product is not a cure but will control symptoms

• Inform patient that major toxicities may necessitate discontinuing product

• Instruct patient to use contraception during treatment, that body fat distribution may occur, not to share product

• Advise patient to notify prescriber if skin rash, fever, cough, shortness of breath, GI symptoms occur; advise all health care providers that allergic reactions have occurred with this product

• Do not take any medications, including OTC drugs, without consulting prescriber

• Give Medication Guide and Warning Card; discuss points on guide

• Caution patient not to have any sexual contact without use of a condom; needles should not be shared; blood from infected individual should not come in contact with another’s mucous membranes

• Instruct a mother not to breastfeed while she is receiving abacavir therapy

• Warn patient that fat distribution may occur with abacavir therapy

• Tell women of childbearing age to report a known or suspected pregnancy. Provide patient with information on pregnancy exposure registry, if pregnancy occurs