The U.S. Food and Drug Administration (FDA) has issued a series of statements about the risk of life-threatening Xolair side effects possibly linked to the asthma drug.

Xolair is a breathing medication designed to help quell severe, hard-to-treat asthma, approved for people aged 12 and up.

Once the drug hit the market in 2003, there were postmarket reports of brain and heart problems in Xolair patients. Since the largest clinical trials only have a few thousand individuals, it is a real possibility that once a drug hits the market, new Xolair side effects may become more apparent.

This is a function of statistics. A population selected for clinical trials may not be large or diverse enough to properly emulate the range of people who take the drug once it is approved for use. Postmarket reports fill this gap, giving researchers a second chance to evaluate risks.

In response, the FDA ran a long-term study called the Evaluating the Clinical Effectiveness and Long-Term Safety in Patients with Moderate to Severe Asthma Study, or EXCELS.

In the EXCELS study, researchers collected data regarding Xolair users’ health. Though the study ended in September, the FDA issued an early announcement based on preliminary data in 2009.

In 2009, the Early Communication on the EXCELS study stated that researchers had already found that patients taking the drug had an increased risk of developing a variety of cardiovascular diseases, including stroke, pulmonary hypertension (high blood pressure in the lungs), heart failure, and other serious problems.

Many of these disorders are related. For example, many involve a narrowing or stiffening of blood vessels throughout the body. At the time, the FDA stressed that the data was preliminary, but wanted to make patients and physicians aware of the situation as it developed. However, the FDA made no recommendations to change the drug’s label or restrict use of the drug through bans or new guidelines.

The follow-up Drug Safety Communications expanded on data gathered during the initial communications. At the end of the EXCELS study, the FDA had more data and performed a more in-depth analysis of the information. The FDA also included information from double-blind trials to augment their data.

The federal agency found that patients taking the drug did have an increased risk of heart attack and other Xolair side effects relating to the cardiopulmonary system. While the risk was not so great that the FDA would recommend banning the drug, the risk was sufficient enough to warrant changing the drug’s safety information to allow patients and doctors to make a more informed decision about how to treat asthma.

The FDA does not recommend patients stop taking their medication without speaking to a doctor.