abacavir sulfate

abacavir sulfate

Ziagen

Pharmacologic class: Carbocyclic nucleoside reverse transcriptase

Therapeutic class: Antiretroviral

Pregnancy risk category C

FDA Boxed Warning

• 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.

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

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

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