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Abacavir Sulfate

Pronunciation

Pronunciation: a-BAK-a-vir SUL-fate
Class: Antiretroviral, Nucleoside reverse transcriptase inhibitor

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Trade Names

Ziagen
- Tablets 300 mg
- Solution, oral 20 mg/mL

Pharmacology

Converted by cellular enzymes to carbovir triphosphate, which inhibits HIV-1 reverse transcriptase and interferes with DNA synthesis.

Pharmacokinetics

Absorption

Rapidly and extensively absorbed. Bioavailability is 83% (tablets). C _max is approximately 3 mcg/mL and AUC _0-12 is approximately 6.02 mcg•h/mL.

Distribution

Vd after IV administration is approximately 0.86 L/kg. Plasma protein binding is approximately 50%.

Metabolism

Metabolized to inactive metabolites by alcohol dehydrogenase and glucuronyl transferase.

Elimination

1.2% is excreted in the urine as abacavir; 81% as inactive metabolites; 16% is excreted in the feces. The half-life is approximately 1.54 h and Cl is approximately 0.8 L/h/kg (after IV administration).

Special Populations

Renal Function Impairment

No data.

Hepatic Function Impairment

In mild hepatic function impairment (Child-Pugh score 5 to 6), AUC increased 89%, and half-life increased 58%.

Children

Steady-state C _max is 3.71 mcg/mL with a dosage of 8 mg/kg twice daily.

Indications and Usage

Treatment of HIV-1 in combination with other antiretroviral agents.

Contraindications

Moderate or severe hepatic function impairment; hypersensitivity to any component of the product.

Dosage and Administration

Adults

PO 600 mg once daily or 300 mg twice daily in combination with other antiretroviral agents.

Adolescents and Children 3 mo to 16 yr of age

PO 8 mg/kg twice daily (max, 300 mg twice daily) in combination with other antiretroviral agents.

Hepatic Function Impairment

PO 200 mg twice daily in patients with mild hepatic function impairment (Child-Pugh score 5 to 6).

General Advice

May take with or without food.
Tablets and oral solution may be used interchangeably.

Storage/Stability

Store at controlled room temperature (68° to 77°F). Solution may be refrigerated, but do not freeze.

Drug Interactions

Ethanol

Increases exposure to abacavir by decreasing the elimination and prolonging the half-life.

Methadone

Plasma levels of methadone may be decreased in some patients, reducing the therapeutic effect.

Laboratory Test Interactions

None well documented.

Adverse Reactions

The following adverse reactions have been reported with use of abacavir in combination with 1 or more antiretroviral agent.

Cardiovascular

MI (postmarketing).

CNS

Headache (13%); fatigue/malaise (12%); dreams/sleep disorders (10%); headache/migraine (7%); depressive disorders, dizziness (6%); anxiety (5%).

Dermatologic

Rashes (7%); erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis (postmarketing).

EENT

Ear/nose/throat infection (5%).

GI

Nausea (19%); nausea and vomiting (10%); diarrhea (7%); abdominal pain/gastritis/GI signs and symptoms (6%); vomiting (2%).

Hepatic

Hepatic steatosis, lactic acidosis (postmarketing).

Hematologic-Lymphatic

Neutropenia (5%); thrombocytopenia (1%).

Hypersensitivity

Drug hypersensitivity (9%); hypersensitivity reaction (8%).

Lab Tests

Elevated CPK (8%); elevated ALT, elevated AST, hypertriglyceridemia (6%); hyperamylasemia (4%).

Metabolic-Nutritional

Redistribution/accumulation of body fat (postmarketing).

Musculoskeletal

Musculoskeletal pain (6%).

Respiratory

Viral respiratory infection (5%); bronchitis, pneumonia (4%).

Miscellaneous

Fever and/or chills (9%).

Precautions

Warnings

Fatal hypersensitivity reaction

Serious and sometimes fatal hypersensitivity reactions have been associated with abacavir. The hypersensitivity is a multi-organ syndrome. Discontinue abacavir as soon as a hypersensitivity reaction is suspected. Persons carrying the HLA-B*5701 allele are at increased risk of experiencing abacavir hypersensitivity. Prior to starting therapy, screening for the allele is recommended. Regardless of HLA-B*5701 status, permanently discontinue abacavir if hypersensitivity cannot be ruled out. Never restart abacavir or any other form of abacavir-containing product because more severe symptoms can occur within hours and may include life-threatening hypertension and death.

Lactic acidosis and hepatomegaly

Lactic acidosis and severe hepatomegaly with steatosis, including death, have been reported with use of nucleoside analogues alone or in combination, including abacavir.

Pregnancy

Category C .

Lactation

Undetermined; however, HIV-infected mothers should not breast-feed.

Children

Safety and efficacy not established in children younger than 3 mo of age.

Elderly

Select dose with caution, reflecting greater frequency of decreased hepatic, renal, or cardiac function and comorbidity.

Fat redistribution

Redistribution/accumulation of body fat have been observed (eg, buffalo hump, peripheral/facial wasting, central obesity).

Immune reconstitution syndrome

Has been reported.

MI

Abacavir administration has been associated with an increased risk of MI.

Patient Information

Advise patient to review Medication Guide before starting therapy and with each refill of the medication.
Advise patient to review, and carry with them at all times, the Warning Card summarizing the symptoms of abacavir hypersensitivity reaction.
Instruct patient to take exactly as prescribed and not to change the dose or discontinue therapy unless advised by health care provider.
Advise patient to take drug twice daily without regard to meals but to take with food if GI upset occurs.
Advise patient, family, or caregiver to measure prescribed dose of solution using dosing spoon or dosing syringe.
Instruct patient that if a dose is missed, to take as soon as remembered, and to take the next dose at the usual scheduled time.
Instruct patient to continue to take other HIV medications as prescribed by health care provider.
Instruct patient to discontinue use and notify health care provider immediately if skin rash or 1 or more symptoms from at least 2 of the following groups are noted: abdominal pain, diarrhea, nausea, vomiting; cough, shortness of breath, sore throat; fatigue, malaise, muscle aches; fever.
Instruct patient to report the following symptoms immediately to health care provider: feeling cold, dizzy, or light-headed; muscle or joint pain; pain or tingling in the hands or feet; profound weakness or tiredness; slow or irregular heartbeat.
Inform patient that drug does not completely eliminate HIV virus and, therefore, does not reduce risk of transmitting HIV. Appropriate precautions must still be followed.
Advise patient that drug is not a cure for HIV infection. Illnesses associated with HIV infection, including opportunistic infections, may continue to be acquired, and patients should remain under a health care provider's care.
Inform patients that redistribution or accumulation of fat may occur and that the cause and long-term effects of these conditions are not known.
Caution breast-feeding mother to not breast-feed while receiving medication because of potential for adverse reactions from the medication in breast-feeding infants. Mothers with HIV should not breast-feed because HIV may be passed to the baby in breast milk.