Ongoing Abacavir Safety Review Finds No Increased Risk of Heart Attack

Safety Announcement

The Food and Drug Administration (FDA) is updating the public about its ongoing safety review of abacavir and a possible increased risk of heart attack. Abacavir is an antiviral medication used in combination with other antiretroviral drugs for the treatment of HIV-1 infection. Available medications that contain abacavir include Ziagen, Trizivir, and Epzicom.

There has been conflicting information on the potential increased risk of heart attack with abacavir treatment. An increased risk of heart attack (myocardial infarction or MI) has been seen in several observational studies and one randomized controlled trial (RCT) with abacavir. However, an increased risk of heart attack has not been seen in other RCTs and the safety database maintained by the drug manufacturer.

FDA conducted a meta-analysis of 26 randomized clinical trials that evaluated abacavir. This meta-analysis did not show an increased risk of MI associated with the use of abacavir. Healthcare professionals should continue to prescribe abacavir according to the professional label. Patients should not stop taking their abacavir without first talking to their healthcare professional.

FDA will continue to communicate any new safety information to the public as it becomes available.

Additional Information for Patients

• Do not stop taking abacavir without talking to your healthcare professional.
• Discuss any questions or concerns about abacavir with your healthcare professional.
• Report any side effects you experience to the FDA MedWatch program using the information in the "Contact Us" box at the bottom of the page.

Additional Information for Healthcare Professionals

• Continue to prescribe abacavir according to the professional label.
• Be aware there are conflicting data on whether abacavir treatment increases the risk of MI. However, the FDA's recent meta-analysis of 26 RCTs found no statistically significant difference in MI events between patients who received abacavir and those who did not.
• Report adverse events involving abacavir to the FDA MedWatch program, using the information in the "Contact Us" box at the bottom of the page.

Data Summary

FDA's primary objective was to explore the association of abacavir with MI. A literature search was conducted among four databases (International Pharmaceutical Abstracts [IPA], Intelos, Embase and Scopus) for all clinical trials that included a randomized abacavir treatment arm. The FDA manually reviewed the results of the search to identify RCTs that met the following criteria: conducted in adults, sample size greater than 50 subjects, trial status completed, not a pharmacokinetic trial, and not conducted in Africa. The Mantel-Haenszel method, with risk difference, odds ratio (OR), and a 95% confidence interval (CI), was used for the primary analysis based on trial-level summaries; the unit of analysis was the subject, and the stratification factor was the trial. For trials with more than two arms, abacavir versus non-abacavir arms were compared.

Data from 26 RCTs conducted from 1996 to 2010 (16 trials from the drug manufacturer database, 5 from the AIDS Clinical Trials Group (ACTG), and 5 from academic centers were included in the meta-analysis conducted by FDA. The MI outcomes were reported for 9868 subjects randomized to receive either an antiretroviral regimen that included abacavir or a non-abacavir containing comparison drug regimen. A total of 46 MI events were reported, including 24 MI events from 5028 subjects randomized to an abacavir-containing regimen and 22 MI events from 4840 subjects randomized to a non-abacavir regimen. No statistically significant association between MI and the abacavir-containing regimen was detected (Mantel-Haenszel OR 1.02, 95% CI 0.56-1.84). For a review of this meta-analysis, see www.retroconference.org/2011/Abstracts/42436.htm.