Abacavir + Lamivudine

Oral
HIV infection

CrCl <50 mL/min: Not recommended.

Contraindicated.

May be taken with or without food.

Hypersensitivity. Hepatic impairment. Lactation.

Patients w/ coronary heart disease, chronic hepatitis B or C, renal impairment CrCl <50 mL/min. May exacerbate hepatitis B. Prior to treatment, screening for carriage of HLA-B*5701 should be done. Pregnancy.

Lipodystrophy, immune reactivation syndrome, osteonecrosis. Anorexia, headache, insomnia, nausea, vomiting, abdominal pain or cramps, diarrhoea, rash, urticaria, alopecia, arthralgia, peripheral neuropathy, muscle disorders, fever, fatigue, lethargy, cough, nasal symptoms, increased CPK.
Potentially Fatal: Severe hypersensitivity reactions, lactic acidosis, hepatic impairment (e.g. hepatomegaly), severe acute exacerbation of hepatitis B.

PO: C

Advise patient to continue to practice safe sex.

Monitor hepatic function, amylase bilirubin, blood glucose, serum creatinine kinase, haematologic parameters and triglycerides. Closely monitor for hypersensitivity reactions. Periodic LFT and markers for HBV is recommended in patients co-infected w/ hepatitis B as withdrawal of treatment may result in acute exacerbation of hepatitis.

Symptoms: Same as mentioned in the Adverse Reaction section. Management: Symptomatic and supportive treatment. May perform haemodialysis since lamivudine is dialysable.

Increased hepatic decompensation w/ interferon alfa. May increase the adverse effects of emtricitabine or emtricitabine-containing products. Bioavailability may decrease w/ methadone. Co-trimoxazole may increase the serum levels of lamivudine. Ribavirin may increase the risk of hepatotoxicity.

Ethanol may increase abacavir serum levels and risk of toxicity.

Description:
Mechanism of Action: Abacavir and lamivudine are both nucleoside reverse transcriptase inhibitors. Converted to their respective active triphosphate form, they have additive effect in inhibiting replication of retroviruses by interfering w/ viral RNA-directed DNA polymerase (reverse transcriptase).
Pharmacokinetics:
Absorption: Rapidly absorbed from GI tract. Bioavailability: Approx 80% (abacavir); 80-87% (lamivudine). Time to peak plasma concentration: Approx 1.5 hr (abacavir); approx 1 hr (lamivudine).
Distribution: Crosses blood-brain barrier. Lamivudine crosses the placenta and is distributed into breast milk. Plasma protein binding: Approx 50% (abacavir); up to 36% (lamivudine).
Metabolism: Abacavir and lamivudine are metabolised by intracellular kinase to carbovir triphosphate (active triphosphate form of abacavir) and lamivudine triphosphate, respectively.
Excretion: Mainly via urine as metabolites. Elimination half-life: Approx 1.5 hr (abacavir); 5-7 hr (lamivudine).

Store below 30°C.

Antivirals

J05AR02 - lamivudine and abacavir ; Belongs to the class of antivirals for treatment of HIV infections, combinations.

Anon. Abacavir and Lamivudine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 24/07/2014.

Buckingham R (ed). Abacavir. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com.

Buckingham R (ed). Lamivudine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 24/07/2014.

Wickersham RM. Abacavir/Lamivudine. Facts and Comparisons [online]. St. Louis, MO. Wolters Kluwer Clinical Drug Information, Inc. https://www.wolterskluwercdi.com/facts-comparisons-online/. Accessed 24/07/2014.