abacavir + lamivudine: clinical use

Prescribing considerations

• Confirm documented negative HLA-B*5701 status and exclude previous suspected abacavir hypersensitivity.
• Use only when both components and the fixed-strength formulation are appropriate; individual component adjustment is not possible.
• Review resistance history and ensure an effective combination regimen.
• Assess renal and hepatic function, hepatitis B or C coinfection and cardiovascular risk.
• Consider alternatives in people with high cardiovascular risk because evidence concerning abacavir-associated cardiovascular events is inconsistent.

Contraindications and cautions

• Hypersensitivity to abacavir, lamivudine or an excipient.
• Positive HLA-B*5701 status.
• Previous suspected hypersensitivity to any abacavir-containing product; rechallenge is contraindicated.
• The fixed combination is not recommended where renal impairment requires lamivudine adjustment or in moderate to severe hepatic impairment.

Monitoring

• HIV viral load, treatment response, adherence and resistance where indicated.
• Renal function and lamivudine-related haematological or gastrointestinal toxicity when renal clearance is reduced.
• Liver function in people with pre-existing liver disease or viral hepatitis.
• Hepatitis B markers and liver function after discontinuation in people with HBV coinfection.
• Weight, blood lipids and glucose during antiretroviral treatment.
• Prompt clinical assessment of symptoms compatible with abacavir hypersensitivity.

Clinical pharmacology

Both components are NRTIs activated by intracellular phosphorylation. Carbovir triphosphate and lamivudine triphosphate inhibit HIV reverse transcriptase and terminate viral DNA chains. Abacavir is mainly metabolised hepatically by alcohol dehydrogenase and glucuronidation; lamivudine is predominantly eliminated unchanged by the kidneys.

Formulation and product differences

• The selected product is a fixed-strength, orange, modified capsule-shaped film-coated tablet.
• Separate abacavir and lamivudine preparations are needed if either component requires adjustment or discontinuation.
• The tablet contains Sunset Yellow FCF Aluminium Lake, which may cause allergic reactions.
• The selected product is essentially sodium-free and requires no special storage conditions.

Tablet

Route: Oral

Strengths: 600 mg + 300 mg