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  • Generic Name: zileutin
  • Brand Name: Zyflo
  • Drug Class: 5-Lipoxygenase Inhibitors
Last updated on MDtodate: 10/11/2022


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 1.

Table 1: Proportion of Patients Experiencing Adverse Events in Placebo-Controlled Studies in Asthma

BODY SYSTEM/Event ZYFLO 600mg 4 times daily % Occurrence
(N =475)
Placebo % Occurrance
  Headache 24.6 24.0
  Pain (unspecified) 7.8 5,3
  Abdominal Pain 4.6 2.4
  Asthenia 3.B 2.4
  Accidental Injury 5.4 2.0
  Dyspepsia 8.2* 2,9
  Nausea i.S 3.7
  Myalgia 3.2 2.9
*p ≤ 0.05 vs placebo


Proportion of Patients Experiencing Adverse Events in Placebo-Controlled Studies in Asthma

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 ≥ 3xULN was 1.9% for ZYFLOtreated 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 3xULN. 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 x 109/L) were observed in 1.0% 9 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

Cases of sleep disorders and behavior changes have been reported. Rash and urticaria have been also reported with ZYFLO.



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