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What is ZYFLO CR?

Zileuton is an orally active inhibitor of 5-lipoxygenase, the enzyme that catalyzes the formation of leukotrienes from arachidonic acid. Zileuton has the chemical name (±)-1-(1-Benzo[b]thien-2-ylethyl)-1-hydroxyurea and the following chemical structure:

ZYFLO CR (zileuton) extended-release tablets for oral administration are triple-layer tablets comprised of an immediate-release layer, a middle (barrier) layer, and an extended-release layer. ZYFLO CR tablets are oblong, film-coated tablets with one red layer between two white layers, debossed on one side with "CT2". Each tablet contains 600 mg of zileuton and the following inactive ingredients: crospovidone, ferric oxide, glyceryl behenate, hydroxypropyl cellulose, hypromellose, magnesium stearate, mannitol, microcrystalline cellulose, povidone, pregelatinized starch, propylene glycol, sodium starch glycolate, and talc.

What does ZYFLO CR look like?

What are the available doses of ZYFLO CR?

Extended-release tablets: 600 mg. ()

What should I talk to my health care provider before I take ZYFLO CR?

Information on specific populations is based on studies conducted with zileuton immediate-release tablets and is applicable to ZYFLO CR.

How should I use ZYFLO CR?

ZYFLO CR is indicated for the prophylaxis and chronic treatment of asthma in adults and children 12 years of age and older.

ZYFLO CR is not indicated for use in the reversal of bronchospasm in acute asthma attacks.  Therapy with ZYFLO CR can be continued during acute exacerbations of asthma.

The recommended dosage of ZYFLO CR for the treatment of patients with asthma is two 600 mg extended-release tablets twice daily, within one hour after morning and evening meals, for a total daily dose of 2400 mg. Tablets should not be chewed, cut or crushed. If a dose is missed, the patient should take the next dose at the scheduled time and not double the dose. Assess hepatic function enzymes prior to initiation of ZYFLO CR and periodically during treatment [see and ].

What interacts with ZYFLO CR?

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What are the warnings of ZYFLO CR?

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What are the precautions of ZYFLO CR?

Sorry No Records found

What are the side effects of ZYFLO CR?

Sorry No records found

What should I look out for while using ZYFLO CR?

The use of ZYFLO CR is contraindicated in patients with:

What might happen if I take too much ZYFLO CR?

Human experience of acute overdose with zileuton is limited. A patient in a clinical study took between 6.6 and 9.0 grams of zileuton immediate-release tablets in a single dose. Vomiting was induced and the patient recovered without sequelae. Zileuton is not removed by dialysis. Should an overdose occur, the patient should be treated symptomatically and supportive measures instituted as required. If indicated, elimination of unabsorbed drug should be achieved by emesis or gastric lavage; usual precautions should be observed to maintain the airway. A Certified Poison Control Center should be consulted for up-to-date information on management of overdose with ZYFLO CR.

The oral minimum lethal doses in mice and rats were 500-4000 and 300-1000 mg/kg, respectively (providing greater than 3 and 9 times the systemic exposure [AUC] achieved at the maximum recommended human daily oral dose, respectively). In dogs, at an oral dose of 1000 mg/kg (providing in excess of 12 times the systemic exposure [AUC] achieved at the maximum recommended human daily oral dose) no deaths occurred but nephritis was reported.

How should I store and handle ZYFLO CR?

Dispense in a well-closed container as defined in the USP.Store at 20°-25°C (68°-77°F) [see USP Controlled Room Temperature].Dispense in a well-closed container as defined in the USP.Store at 20°-25°C (68°-77°F) [see USP Controlled Room Temperature].ZYFLO CR (zileuton) extended-release tablets are debossed on one side with "CT2"; they are available in bottles of 120 tablets (NDC 10122-902-12) and as samples in bottles of 20 tablets (NDC 10122-902-20).


Clinical Information

Chemical Structure

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Clinical Pharmacology

Zileuton is an inhibitor of 5-lipoxygenase and thus inhibits leukotriene (LTB, LTC, LTD and LTE) formation. Both the R(+) and S(-) enantiomers are pharmacologically active as 5-lipoxygenase inhibitors in and systems. Leukotrienes are substances that induce numerous biological effects including augmentation of neutrophil and eosinophil migration, neutrophil and monocyte aggregation, leukocyte adhesion, increased capillary permeability, and smooth muscle contraction. These effects contribute to inflammation, edema, mucus secretion, and bronchoconstriction in the airways of asthmatic patients. LTB, a chemoattractant for neutrophils and eosinophils, and cysteinyl leukotrienes (LTC, LTD, LTE) can be measured in a number of biological fluids including bronchoalveolar lavage fluid (BALF), blood, urine and sputum from asthmatic patients.

Zileuton is an orally active inhibitor of LTB formation in several species, including mice, rats, rabbits, dogs, sheep, and monkeys. Zileuton inhibits arachidonic acid-induced ear edema in mice, neutrophil migration in mice in response to polyacrylamide gel, and eosinophil migration into the lungs of antigen-challenged sheep. In a mouse model of allergic inflammation, zileuton inhibited neutrophil and eosinophil influx, reduced the levels of multiple cytokines in the BALF, and reduced serum IgE levels. Zileuton inhibits leukotriene-dependent smooth muscle contractions in guinea pig and human airways. The compound inhibits leukotriene-dependent bronchospasm in antigen and arachidonic acid-challenged guinea pigs. In antigen-challenged sheep, zileuton inhibits late-phase bronchoconstriction and airway hyperreactivity. The clinical relevance of these findings is unknown.

Non-Clinical Toxicology
The use of ZYFLO CR is contraindicated in patients with:

Because tetracyclines have been shown to depress plasma prothrombin activity, patients who are on anticoagulant therapy may require downward adjustment of their anticoagulant dosage.

Since bacteriostatic drugs may interfere with the bactericidal action of penicillin, it is advisable to avoid giving tetracycline-class drugs in conjunction with penicillin.

Absorption of tetracyclines is impaired by antacids containing aluminum, calcium, or magnesium, and iron-containing preparations.

The concurrent use of tetracycline and methoxyflurane has been reported to result in fatal renal toxicity.

Concurrent use of tetracyclines with oral contraceptives may render oral contraceptives less effective.

Administration of isotretinoin should be avoided shortly before, during, and shortly after minocycline therapy. Each drug alone has been associated with pseudotumor cerebri (see ).

Increased risk of ergotism when ergot alkaloids or their derivatives are given with tetracyclines.

Elevations of one or more hepatic function enzymes and bilirubin may occur during ZYFLO CR therapy. These laboratory abnormalities may progress to clinically significant liver injury, remain unchanged, or resolve with continued treatment, usually within three weeks. The ALT (SGPT) test is considered the most sensitive indicator of liver injury for ZYFLO CR.

Assess hepatic function enzymes prior to initiation of, and during therapy with, ZYFLO CR. Assess serum ALT before treatment begins, once a month for the first 3 months, every 2-3 months for the remainder of the first year, and periodically thereafter for patients receiving long-term ZYFLO CR therapy. If clinical signs and/or symptoms of liver dysfunction develop (e.g., right upper quadrant pain, nausea, fatigue, lethargy, pruritus, jaundice, or "flu-like" symptoms) or transaminase elevations ≥5×ULN occur, discontinue ZYFLO CR and follow hepatic function enzymes until normal.

In controlled and open-label clinical studies involving more than 5000 patients treated with zileuton immediate-release tablets, the overall rate of ALT elevation ≥3×ULN was 3.2%. In these 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 3×ULN. There was no evidence of hypersensitivity or other alternative etiologies for these findings.

Since treatment with ZYFLO CR may result in increased hepatic function enzymes and liver injury, ZYFLO CR should be used with caution in patients who consume substantial quantities of alcohol and/or have a past history of liver disease.

Hepatotoxicity: Elevations of one or more hepatic function enzymes and bilirubin may occur during ZYFLO CR therapy [see ].

The most commonly occurring adverse reactions (≥5%) with ZYFLO CR are sinusitis, nausea, and pharyngolaryngeal pain.



This information is obtained from the National Institute of Health's Standard Packaging Label drug database.

While we update our database periodically, we cannot guarantee it is always updated to the latest version.



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