ABACAVIR

MEDICINE

Pharmacologic class:

Carbocyclic nucleoside reverse transcriptase
Therapeutic class: Antiretroviral
Pregnancy risk category C.

● Drug may cause serious and potentially fatal hypersensitivity reactions, including multi-organ syndrome marked by fever, rash, GI distress, malaise, fatigue, achiness, dyspnea, cough, and pharyngitis. Discontinue immediately if you suspect such a reaction. If hypersensitivity can’t be ruled out, discontinue permanently, even if other diagnoses are possible.
● After hypersensitivity reaction, never restart drug or other agents containing it, because more severe symptoms (including severe hypotension and death) may arise within hours.

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.
Be aware that drug may cause fatal hypersensitivity reactions.
● Give with food if GI upset occurs.

Route Onset Peak Duration
P.O. Unknown 0.5-1.7 hr Unknown

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, gammaglutamyltransferase, glucose, triglycerides: increased levels.
● Drug-behaviors. Alcohol use: increased drug half-life and concentration.

Patient monitoring

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

  • 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 to take drug with food to minimize GI upset.
  • Instruct to refrigerate drug but not to freeze it.
  • Teach patient how to recognize hypersensitivity reaction.
  • Instruct him to stop taking drug and contact prescriber immediately if signs or symptoms of such a reaction occur.
  • Tell to contact prescriber if he develops a rash (possible sign of Stevens-Johnson syndrome).
  • Instruct 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 that drug doesn’t cure HIV but lowers viral count.
  • Instruct to obtain medication guide and warning card with each refill.
  • Tell patient he’ll undergo frequent blood and urine testing during therapy.
  • Advise 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.