Therapeutic Classification: antiretrovirals (combination)
Pharmacologic Classification: integrase strand transfer inhibitors (INSTI) (dolutegravir), nucleoside reverse transcriptase inhibitors (abacavir, lamivudine)
Abacavir
Absorption: Rapidly and extensively (83%) absorbed.
Distribution: Distributes into extravascular space and readily distributes into erythrocytes.
Half-Life: 1.5 hr.
Dolutegravir
Absorption: Absorption follows oral administration; bioavailability is unknown.
Distribution: Enters CSF.
Protein Binding: >98.9%.
Half-Life: 14 hr.
Lamivudine
Absorption: Well absorbed after oral administration (86% in adults, 66% in infants and children).
Distribution: Distributes into the extravascular space. Some penetration into CSF; remainder of distribution unknown.
Half-Life: 1319 hr.
Contraindicated in:
Hypersensitivity to any component (especially abacavir; rechallenge may be fatal)
;Presence of HLA-B*5701 allele (↑ risk of potentially fatal hypersensitivity reaction)
;Use Cautiously in:
Coinfected with hepatitis B virus (HBV) (severe acute exacerbations of HBV may recur after discontinuation of lamivudine)
;CV: MI
F and E: LACTIC ACIDOSIS
GI: exacerbation of hepatitis B, HEPATOMEGALY (WITH STEATOSIS), HEPATOTOXICITY ( WITH HEPATITIS B OR C)↑ with hepatitis B or C)
Neuro: fatigue, headache, insomnia
Misc: HYPERSENSITIVITY REACTIONS, immune reconstitution syndrome
Drug-drug:
Drug-Natural Products:
Tablets and tablets for oral suspension are NOT interchangeable on a milligram-per-milligram basis.
Assess for signs of hypersensitivity reactions (fever, rash, nausea, vomiting, diarrhea, abdominal pain, malaise, fatigue, achiness, dyspnea, cough, pharyngitis). May also cause ↑ liver function tests, ↑ CK,↑ 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.
Lab Test Considerations:
Screen for HLA-B*5701 allele prior to initiation of therapy to ↓ 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.
Test for presence of hepatitis B virus (HBV) prior to or when starting therapy. Emergence of lamivudine-resistant HBV variants associated with lamivudine-containing antiretroviral regimens have been reported. Consider additional treatment for chronic HBV if used in patients coinfected with HIV-1 and HBV; or consider an alternative regimen.
Monitor liver function periodically. May cause ↑ levels of AST, ALT, and alkaline phosphatase, which usually resolve after interruption of therapy. Patients with concurrent hepatitis B or C should be followed for at least several months after stopping therapy. Lactic acidosis may occur with hepatic toxicity, causing hepatic steatosis; may be fatal, especially in women.
Advise patient that discontinuing therapy may lead to severe exacerbations of HBV.
Advise patient of potential for hypersensitivity reactions that may result in death. Instruct patient to discontinue medication and notify health care provider immediately if symptoms of hypersensitivity or signs of immune reconstitution syndrome (signs and symptoms of inflammation from previous infections) occur. A warning card summarizing symptoms of hypersensitivity is provided with each prescription; instruct patient to carry card at all times.