Abacavir not linked to increased risk of heart attack, reports US FDA

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The US Food and Drug Administration has found no evidence of an association between abacavir treatment and increased risk of myocardial infarction (heart attack) in a meta-analysis of 26 randomised trials of the drug, the agency reported this week.

The findings were presented as a poster at the Eighteenth Conference on Retroviruses and Opportunistic Infections (CROI) in Boston.

Abacavir (Ziagen) is one of the recommended alternatives for first-line antiretroviral treatment in the United Kingdom and United States, and is marketed as part of the combination pill Kivexa (Epzicom in the US).

Glossary

meta-analysis

When the statistical data from all studies which relate to a particular research question and conform to a pre-determined selection criteria are pooled and analysed together.

myocardial infarction

Heart attack. Myocardial refers to the muscular tissue of the heart. An infarction is the obstruction of the blood supply to an organ or region of tissue.

Food and Drug Administration (FDA)

Regulatory agency that evaluates and approves medicines and medical devices for safety and efficacy in the United States. The FDA regulates over-the-counter and prescription drugs, including generic drugs. The European Medicines Agency performs a similar role in the European Union.

odds ratio

Comparing one group with another, expresses differences in the odds of something happening. An odds ratio above 1 means something is more likely to happen in the group of interest; an odds ratio below 1 means it is less likely to happen. Similar to ‘relative risk’. 

first-line therapy

The regimen used when starting treatment for the first time.

Questions about the potential increased risk of heart attack in patients taking abacavir were first raised after an analysis of cardiovascular events in the D:A:D cohort study found a 70% increased risk of heart attack in patients exposed to abacavir. That risk appeared to persist for six months after stopping the drug.

Subsequent analyses of other datasets have produced conflicting results. Danish investigators also found a doubling of risk in abacavir-treated patients, as did the investigators of the SMART study of treatment interruption. However a pooled analysis of all clinical trials carried out by manufacturer GlaxoSmithKline failed to find any increased risk.

A meta-analysis of randomised trials is one way of excluding possible biases, since randomisation will remove elements of bias.

The US FDA carried out its own meta-analysis, gathering data from 26 studies in which abacavir was used as part of a combination antiretroviral regimen in adults in which the trial population was greater than 50 persons and in which patients were randomly assigned to receive abacavir.

The meta-analysis covered data from 26 studies (16 manufacturer studies, five AIDS Clinical Trials Group studies and five independent studies) which included 5028 abacavir recipients and 4804 non-abacavir recipients with a mean follow-up per person of 1.62 years. The studies recorded 47 cases of myocardial infarction, occurring in 18 of the 26 studies.

The FDA calculated an odds ratio of 1.02 (95% CI 0.56 to 1.84) for abacavir, a non-significant difference.

The FDA concluded that there was insufficient evidence to support the view that abacavir increases the risk of myocardial infarction.

References

Ding X et al. No association of myocardial infarction with ABC use: an FDA meta-analysis. 18th Conference on Retroviruses and Opportunistic Infections, Boston, abstract 808, 2011.

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