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Therapeutic Classification: antiretrovirals

Pharmacologic Classification: nucleoside reverse transcriptase inhibitors

• Treatment of HIV-1 infection.

• Converted inside cells to carbovir triphosphate, its active metabolite. Carbovir triphosphate inhibits the activity of HIV-1 reverse transcriptase, which in turn terminates viral DNA growth.

• Slows the progression of HIV infection and decreases the occurrence of its sequelae.
• Increases CD4 cell counts and decreases viral load.

Absorption: Rapidly and extensively (83%) absorbed.

Distribution: Distributes into extravascular space and readily distributes into erythrocytes.

Metabolism/Excretion: Mostly metabolized by the liver; 1.2% excreted unchanged in urine.

Half-life: 1.5 hr.

(blood levels)

Contraindicated in:

• Hypersensitivity (rechallenge may be fatal)
• Presence of HLA-B*5701 allele
• Moderate to severe hepatic impairment
• Concurrent use of antiretroviral combination products containing abacavir
• Lactation: Breastfeeding not recommended for women with HIV.

Use Cautiously in:

• Coronary heart disease
• Women and obesity (↑ risk of lactic acidosis and severe hepatomegaly with steatosis)
• OB: Considered a preferred NRTI for pregnant females who are antiretroviral-naive, who have had antiretroviral therapy in the past but are restarting, or who require a new antiretroviral regimen (due to poor tolerance or poor virologic response of current regimen)
• Pedi: Children <3 mo (safety and effectiveness not established).

CV: MYOCARDIAL INFARCTION.

Derm: rash.

F and E: LACTIC ACIDOSIS.

GI: diarrhea, nausea, vomiting, anorexia, HEPATOMEGALY (WITH STEATOSIS).

Neuro: headache, insomnia.
Misc: HYPERSENSITIVITY REACTIONS, immune reconstitution syndrome.

Drug-Drug:

• Alcohol↑ blood levels.
• May ↓ methadone levels; slight ↑ in methadone dosing may be needed.
• Use of fixed-dose abacavir/dolutegravir/lamivudine may ↑ riociguat levels and risk of toxicity; may need to ↓ riociguat dose.

• PO (Adults): 300 mg twice daily.
• PO (Children 3 mo): Oral solution: 8 mg/kg twice daily or 16 mg/kg once daily (not to exceed 600 mg/day); Tablets: 14–19 kg: 150 mg twice daily or 300 mg once daily; 20–24 kg: 150 mg in AM and 300 mg in PM or 450 mg once daily; 25 kg: 300 mg twice daily or 600 mg once daily.

(Generic available)

• Oral solution (strawberry/banana flavor): 20 mg/mL;
• Tablets: 300 mg;
• In combination with: lamivudine (generic only); lamivudine and zidovudine (generic only); lamivudine and dolutegravir (Triumeq). See Appendix [not included in this PDA edition].

• Assess patient for change in severity of HIV symptoms and for symptoms of opportunistic infections throughout therapy.
• Assess for signs of hypersensitivity reactions (fever; rash; gastrointestinal — nausea, vomiting, diarrhea, abdominal pain; constitutional — malaise, fatigue, achiness; respiratory — dyspnea, cough, pharyngitis). May also cause ↑ liver function tests, ↑ creatine kinase or serum creatinine, and lymphopenia. Patients who carry the HLA-B*5701 allele are at high risk for hypersensitivity reaction. Reactions usually occurred during first 6 wk of therapy. Discontinue promptly if hypersensitivity reaction is suspected. Regardless of HLA-B*5701 status, permanently discontinue abacavir if hypersensitivity cannot be ruled out, even when other diagnoses are possible. Following a hypersensitivity reaction, never restart abacavir or abacavir-containing products. More severe symptoms may occur within hours and may include life-threatening hypotension and death. Symptoms usually resolve upon discontinuation.
• May cause lactic acidosis and severe hepatomegaly with steatosis. Monitor patient for signs (↑ serum lactate levels, ↑ liver enzymes, liver enlargement on palpation). Therapy should be suspended if clinical or laboratory signs occur.

• Monitor viral load and CD4 cell count regularly during therapy.
  • Screen for HLA-B*5701 allele prior to initiation of therapy to decrease risk of hypersensitivity reaction. Screening is also recommended prior to reinitiation of abacavir in patients of unknown HLA-B*5701 status who have previously tolerated abacavir.
  • Monitor liver function. May cause ↑ AST, ALT, and alkaline phosphatase levels, which usually resolve after interruption of therapy. Lactic acidosis may occur with hepatic toxicity, causing hepatic steatosis; may be fatal, especially in women.
  • May cause ↑ serum glucose and triglyceride levels.

• PO: May be administered with or without food. Oral solution is clear to opalescent and yellow, may turn brown over time. Store at room temperature or refrigerated; do not freeze. Tablet may be used with children if able to swallow and dose is correctly calculated.

• Emphasize the importance of taking abacavir as directed. Must always be used in combination with other antiretroviral drugs. Do not take more than prescribed amount, and do not stop taking without consulting health care professional. Take missed doses as soon as remembered; do not double doses. Advise patient to read the Medication Guide prior to starting therapy and with each Rx refill in case of changes.
• Instruct patient not to share abacavir with others.
• Inform patient that abacavir does not cure AIDS or prevent associated or opportunistic infections. Abacavir may reduce risk of transmission of HIV to others through sexual contact or blood contamination. Caution patient to use a condom, and avoid sharing needles or donating blood to prevent spreading the AIDS virus to others. Advise patient that long-term effects of abacavir are unknown.
• Advise patient of potential for hypersensitivity reactions that may result in death. Instruct patient to discontinue abacavir and notify health care professional immediately if symptoms of hypersensitivity or signs of Immune Reconstitution Syndrome (signs and symptoms of an infection) occur. A warning card summarizing symptoms of abacavir hypersensitivity is provided with each prescription; instruct patient to carry card at all times.
• Instruct patient to notify health care professional immediately if symptoms of lactic acidosis (tiredness or weakness, unusual muscle pain, trouble breathing, stomach pain with nausea and vomiting, cold especially in arms or legs, dizziness, fast or irregular heartbeat) or if signs of hepatotoxicity (yellow skin or whites of eyes, dark urine, light-colored stools, lack of appetite for several days or longer, nausea, abdominal pain) occur. These symptoms may occur more frequently in patients that are female, obese, or have been taking medications like abacavir for a long time.
• Inform patient that redistribution and accumulation of body fat may occur, causing central obesity, dorsocervical fat enlargement (buffalo hump), peripheral wasting, breast enlargement, and cushingoid appearance.
• Advise patient to notify health care professional of all Rx or OTC medications, vitamins, or herbal products being taken and to consult with health care professional before taking other medications, especially methadone and other antiretrovirals.
• Advise females of reproductive potential to avoid breastfeeding during therapy and to notify health care professional if pregnancy is planned or suspected. Encourage women who become pregnant while taking abacavir to enroll in the Antiretroviral Pregnancy Registry by calling 1-800-258-4263.
• Emphasize the importance of regular follow-up exams and blood counts to determine progress and monitor for side effects.

• Delayed progression of AIDS, and decreased opportunistic infections in patients with HIV.
• Decrease in viral load and increase in CD4 cell counts.

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