Abacavir/lamivudine

Abacavir/lamivudine is a fixed-dose combination tablet combining 300mg lamivudine (3TC) and 600mg abacavir. Abacavir/lamivudine is available as Kivexa, manufactured by ViiV Healthcare, or in generic versions.

Abacavir and lamivudine are both nucleoside reverse transcriptase inhibitors (NRTIs). This class of antiretroviral disrupts the activity of the HIV enzyme reverse transcriptase, which is needed to copy the genetic code of HIV into a form that can be inserted into human cells.

It is licensed for use in adults and children over 12 years of age. Its European Union and US marketing licence were both granted in 2004, under the trade names Kivexa and Epzicom respectively.

Effectiveness

Abacavir/lamivudine was licensed following demonstration that it had similar anti-HIV effects to once-daily lamivudine (Epivir) and abacavir (Ziagen) taken separately when they were used in combination with the non-nucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (Sustiva).

A meta-analysis of six published studies comparing abacavir/lamivudine to tenofovir disoproxil fumarate (TDF)/emtricitabine as first-line treatment in combination with a third agent showed no difference in viral suppression rates, regardless of baseline viral load. (Cruciani)

However, a study in previously untreated people showed that a regimen containing abacavir/lamivudine was inferior to a regimen containing TDF/emtricitabine in people with baseline viral loads above 100,000 copies/ml. (Sax) The findings of this study, the largest single comparison of the two NRTI combinations, led the British HIV Association to recommend that abacavir/lamivudine should only be used as an alternative to TDF/emtricitabine in people with baseline viral loads below 100,000 copies/ml and should be avoided in people with higher viral loads. This restriction does not apply if abacavir/lamivudine is used with dolutegravir (see Triumeq for further information on this combination). (BHIVA 2016)

Abacavir/lamivudine has also been shown to be as effective as its constituent drugs taken separately in treatment-experienced people. The efficacy of lamivudine and abacavir had already been demonstrated in previous studies.

A 2008 study in patients looking at adherence found that switching from separate abacavir and lamivudine formulations to fixed-dose Kivexa significantly improved adherence to therapy, using MEMS cap monitoring and patient satisfaction surveys. (Maitland)

Taking it

The standard dose of abacavir/lamivudine is one tablet once a day, with or without food, in combination with at least one other anti-HIV drug.

Side effects

The most common side effects of abacavir/lamivudine are hypersensitivity (allergic) reaction, headache, nausea and vomiting, diarrhoea, stomach pains, loss of appetite, tiredness, lack of energy, fever, general feeling of being unwell, difficulty sleeping, muscle pain and discomfort, joint pain, cough, irritated or runny nose, skin rash, hair loss.

Abacavir causes a hypersensitivity reaction in approximately 5% of people starting the drug. People with the B*5701 allele (genetic variant) have a high risk of hypersensitivity to abacavir so it is recommended that people with HIV should be tested for B*5701 before starting treatment with abacavir. You should not start abacavir unless you test negative for B*5701.  See abacavir for further details of the hypersensitivity reaction.

Abacavir may be associated with an increased risk of cardiovascular disease so the British HIV Association recommends that the use of abacavir in people with a higher risk of cardiovascular disease should be avoided. See abacavir for further details.

Drug interactions

You should not take abacavir/lamivudine with any of the following drugs:

• emtricitabine
• lamivudine
• high doses of trimethoprim/sulfamethoxazole
• cladribine.

Resistance

See abacavir and lamivudine for further details of resistance.

Pregnancy

Studies of pregnancy outcomes in women taking abacavir/lamivudine during pregnancy do not show any harmful effects of these drugs. The British HIV Association recommends abacavir/lamivudine as an option for antiretroviral treatment during pregnancy. (BHIVA 2020)

Children

Abacavir/lamivudine is suitable for children weighing 25kg or over. The tablets should not be split. Abacavir and lamivudine should be dosed as separate tablets in children weighing less than 25kg. See abacavir and lamivudine for further details of weight-based dosing for children weighing less than 25kg.

Further information

For more information on lamivudine and abacavir, see lamivudine and abacavir,

Abacavir and lamivudine are also contained in the fixed-dose combination product Triumeq, combined with dolutegravir (see Triumeq for further information).