Zyflo (Zileuton)

The following drug information is obtained from various newswires, published medical journal articles, and medical conference presentations.

Approval Status:

Approved January 1997

Specific Treatments:


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General Information

Zyflo has been approved for the prevention and chronic treatment of asthma in patients aged 12 years and older. The recommended dosage of Zyflo is one 600 mg tablet four times daily, even during symptom-free periods. Zyflo is available nationwide by prescription.

Clinical Results

In clinical trials involving patients with mild-to-moderate asthma who used daily inhaled beta-agonists, Zyflo decreased the percentage of patients requiring steroid rescues for worsening asthma compared to patients treated with placebo. Overall, the percentage of Zyflo patients requiring steroid rescue was 7 percent, compared with 18.7 percent of patients in the placebo group. This represents a reduction of 62 percent.

In addition, patients receiving Zyflo also were able to reduce their use of inhaled beta-agonists. At the end of the six-month study, the number of beta-agonist puffs needed per day was 1.77 puffs, or 31 percent lower than baseline in Zyflo-treated patients; there was a 0.22 puff decrease in the placebo group. The reduction in the use of these medications was accompanied by improvements in lung function.

Patients’ asthma symptoms improved by 36 percent, and night-time symptoms improved 31 percent in patients treated with Zyflo. For placebo-treated patients, improvements were 21 percent and 5 percent, respectively.

Side Effects

Zyflo should not be used to treat acute episodes of asthma. Safety data with Zyflo have been gathered from more than 5,500 patients. In asthma studies, the overall incidence of adverse events was similar between the Zyflo- and placebo-treated groups. Dyspepsia (upset stomach) was reported significantly more often by patients treated with Zyflo than with placebo.

Some patients treated with Zyflo experienced elevations in liver function tests. Patients taking Zyflo should have their liver function tested prior to taking, and periodically while taking the medication. Zyflo should not be taken by patients who have active liver disease or liver enzymes that are elevated. Although liver function test elevations were observed throughout the treatment period, the majority (61%) of these elevations developed during the first two months of treatment. Generally, these abnormalities resolved or decreased to acceptable levels while treatment continued or soon after it was stopped. some patients discontinued treatment with Zyflo because of these elevations.

Doses of theophylline, warfarin, and/or propranolol should be adjusted and patients monitored when taking Zyflo.

Mechanism of Action

Zyflo, developed by Abbott Laboratories, is a member of a new class of anti-leukotriene asthma medicines that acts as a leukotriene pathway inhibitor (LPI) by inhibiting the enzyme 5-lipoxygenase (5-LO). Zyflo inhibits the formation of leukotrienes. Leukotrienes are molecules that contribute to the inflammation, swelling (edema), bronchoconstriction (tightening of muscles wrapped around the outside of the airways) and mucus secretion seen in the airways of patients with asthma.

Additional Information

Approximately one in 20 Americans has asthma. The symptoms of asthma include wheezing, coughing, and shortness of breath. From 1982-1992, the annual prevalence of self-reported asthma increased 42 percent.