Zyflo Side Effects

Generic Name: zileuton

Please note - some side effects for Zyflo may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Zyflo - for the Consumer

Zyflo

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Zyflo:

Nausea; stomach pain or upset.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; dark urine; fever, chills, or persistent sore throat; flu-like symptoms; pale stools; right upper stomach pain; severe or persistent nausea or stomach pain; unusual tiredness or weakness; yellowing of the skin or eyes.

Zyflo CR Extended-Release Tablets

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Zyflo CR Extended-Release Tablets:

Diarrhea; headache; muscle aches; nausea; nose or throat irritation; sinus inflammation.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; dark urine; fever, chills, or persistent sore throat; flu-like symptoms; pale stools; right upper stomach pain; severe or persistent nausea or stomach pain; unusual tiredness or weakness; yellowing of the skin or eyes.

Zyflo Side Effects - for the Professional

Zyflo

Clinical Studies

A total of 5542 patients have been exposed to zileuton in clinical trials, 2252 of them for greater than 6 months and 742 for greater than 1 year.

Adverse events most frequently occurring (frequency ≥3%) in Zyflo-treated patients and at a frequency greater than placebo-treated patients are summarized in Table 2.

Less common adverse events occurring at a frequency of greater than 1% and more commonly in Zyflo-treated patients included: arthralgia, chest pain, conjunctivitis, constipation, dizziness, fever, flatulence, hypertonia, insomnia, lymphadenopathy, malaise, neck pain/rigidity, nervousness, pruritus, somnolence, urinary tract infection, vaginitis, and vomiting.

The frequency of discontinuation from the asthma clinical studies due to any adverse event was comparable between Zyflo (9.7%) and placebo-treated (8.4%) groups.

In placebo-controlled clinical trials, the frequency of ALT elevations ≥3×ULN was 1.9% for Zyflo-treated patients, compared with 0.2% for placebo-treated patients. In controlled and uncontrolled trials, one patient developed symptomatic hepatitis with jaundice, which resolved upon discontinuation of therapy. An additional 3 patients with transaminase elevations developed mild hyperbilirubinemia that was less than three times the upper limit of normal. There was no evidence of hypersensitivity or other alternative etiologies for these findings. Zyflo is contraindicated in patients with active liver disease or transaminase elevations greater than or equal to 3×ULN. It is recommended that hepatic transaminases be evaluated at initiation of and during therapy with Zyflo.

Occurrences of low white blood cell count (≤2.8 × 109/L) were observed in 1.0% of 1,678 patients taking Zyflo and 0.6% of 1,056 patients taking placebo in placebo-controlled studies. These findings were transient and the majority of cases returned toward normal or baseline with continued Zyflo dosing. All remaining cases returned toward normal or baseline after discontinuation of Zyflo. Similar findings were also noted in a long-term safety surveillance study of 2458 patients treated with Zyflo plus usual asthma care versus 489 patients treated only with usual asthma care for up to one year. The clinical significance of these observations is not known.

In the long-term safety surveillance trial of Zyflo plus usual asthma care versus usual asthma care alone, a similar adverse event profile was seen as in other clinical trials.

Post-Marketing Experience

Rash and urticaria have been reported with Zyflo.

Side Effects by Body System

Nervous system

Nervous system side effects have included headache in 24.6% and asthenia in 3.8% of patients. Other nervous system effects were dizziness, insomnia, nervousness, and somnolence in less than 1% of patients.

Gastrointestinal

Gastrointestinal side effects have most frequently included dyspepsia (8.2%), nausea (5.5%), and abdominal pain (4.6%). Constipation and flatulence were noted in less than 1% of patients.

Hepatic

Hepatic side effects have included elevation of liver transaminase ALT(SGPT) levels to greater than three times the upper normal limit in up to 3.2% of patients in clinical trials. One patient developed symptomatic hepatitis and three patients developed mild hyperbilirubinemia.

Females over the age of 65 appear to be at the greatest risk for zileuton-induced transaminase elevations. With continued zileuton therapy, 52% of patients with ALT elevations between 3 and 5 times the upper normal limit had ALT levels drop below two times the upper normal limit, while 21% continued to demonstrate rising levels to greater than five times the upper normal limit. In patients in whom zileuton was discontinued, ALT levels dropped below two times the upper normal limit in approximately one month.

Hematologic

Hematologic side effects have included reduced white blood cell counts in 1% of patients in clinical trials. Most cases were either transient or reversed upon discontinuation of zileuton.

Musculoskeletal

Musculoskeletal side effects have included myalgia and arthralgia.

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