abacavir sulfate

Action

Converts via intracellular enzymes to active metabolite carbovir triphosphate, which inhibits activity of human immunodeficiency virus-1 (HIV-1) reverse transcriptase. Inhibits viral reproduction by interfering with DNA and RNA synthesis.

Availability

Oral solution: 20 mg/ml

Tablets: 300 mg

Indications and dosages

➣ HIV-1 infection

Adults: 300 mg P.O. b.i.d. or 600 mg P.O. daily

Children ages 3 months to 16 years: 8 mg/kg P.O. b.i.d., to a maximum dosage of 300 mg b.i.d.

Contraindications

• Hypersensitivity to drug

• Hepatic disease, lactic acidosis

• Breastfeeding

• Children younger than age 3 months

Precautions

Use cautiously in:

• impaired renal function, bone marrow suppression

• risk factors for hepatic disease

• elderly patients

• pregnant patients.

Administration

• Always give in combination with other antiretrovirals.

See Be aware that drug may cause fatal hypersensitivity reactions.

• Give with food if GI upset occurs.

Adverse reactions

CNS: headache, weakness, insomnia

GI: nausea, vomiting, diarrhea, poor appetite, pancreatitis

Hematologic: neutropenia, severe anemia

Hepatic: hepatic failure

Metabolic: mild hyperglycemia, lactic acidosis

Skin: rash, erythema multiforme, toxic epidermal necrolysis

Other: body fat redistribution, Stevens-Johnson syndrome, fatal hypersensitivity reaction, immune reconstitution syndrome

Interactions

Drug-drug. Methadone: Increased oral methadone clearance

Drug-diagnostic tests. Alanine aminotransferase, aspartate aminotransferase, creatine phosphokinase, gamma-glutamyltransferase, glucose, triglycerides: increased levels

Drug-herbs. St. John's wort: decreased drug blood level and reduced drug effect

Drug-behaviors. Alcohol use: increased drug half-life and concentration

Patient monitoring

See Assess for severe lactic acidosis, especially in women and obese patients.

See Evaluate closely for signs and symptoms of hypersensitivity reaction, which can be fatal. These include fever, rash, fatigue, nausea, vomiting, diarrhea, abdominal pain, dyspnea, cough, and pharyngitis.

See Be aware that immune reconstitution syndrome may occur in patients receiving combination antiretroviral therapy. During initial phase of therapy, patient whose immune system responds may develop inflammatory response to indolent or residual opportunistic infections (such as Mycobacterium avium complex, cytomegalovirus, Pneumocystis jiroveci pneumonia, and tuberculosis), which may necessitate further evaluation and treatment.

See Never restart therapy if patient has experienced a previous hypersensitivity reaction to this drug.

• Check for liver enlargement.

• Monitor CBC, serum electrolytes, and liver and kidney function test results.

Patient teaching

• Advise patient to take drug with food to minimize GI upset.

• Instruct patient to refrigerate drug but not to freeze it.

See Teach patient how to recognize hypersensitivity reaction. Instruct him to stop taking drug and contact pre-scriber immediately if signs or symptoms of such a reaction occur.

See Tell patient to contact prescriber if he develops a rash (possible sign of Stevens-Johnson syndrome).

See Instruct patient to immediately report signs and symptoms of immune reconstitution syndrome (such as new signs and symptoms of a previously subclinical infection, worsening or progression of a known infection despite treatment, a new infection or illness, or failure of antiretroviral therapy).

• Inform patient that drug doesn't cure HIV but lowers viral count.

• Instruct patient to obtain medication guide and warning card with each refill.

• Tell patient he'll undergo frequent blood and urine testing during therapy.

• Advise patient to consult prescriber before drinking alcohol or using herbs.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.