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Zyflo zileuton 600 mg Tablet, 120-count — NDC 10122-0901-12 package photo
Label image from the product's FDA listing (DailyMed) — may show a different pack size or an older label revision.

Zyflo zileuton 600 mg Tablet, 120-count — NDC 10122-901-12 (Billing 10122-0901-12)

by Chiesi USA, Inc. · 120 TABLET in 1 BOTTLE

This is a package of 120 tablets of Zyflo zileuton 600 mg Tablet from Chiesi USA, Inc., marketed since Dec 1996 and currently FDA-listed, this package's marketing is listed to end Nov 2027. It is this product's only package size.

NDC 10122-0901-12
🏷️ FDA NDC (as labeled) 10122-901-12 billing pads the product segment with a zero
Rx only Brand On market Non-controlled ⇄ Compare with another NDC
🗂️ FDA directory synced Oct 1, 2026 · this listing last changed Jul 24, 2026 · sources: openFDA · FDA label (DailyMed) · FDA Orange & Purple Book · First Databank · CMS NADAC, ASP, Medicare & Medicaid · RxNorm
📋 All sources & update times →

This page is curated, coded, and maintained by

Compiled from public FDA, CMS, DailyMed, NADAC, and related drug data sources. Editorial policy

NDC database record

One package, one record: these facts belong to NDC 10122-901-12 alone.

Record
FDA NDC Directory package listing · Human prescription drug
Code segments
10122 labeler · 901 product · 12 package
Package marketed since
Dec 6, 1996
Package marketing ended
Nov 30, 2027
Sample package
No — commercial package
Billing quantity
120 EA per package
Barcode (UPC-A, from the NDC)
3 1012290112 4
FDA record last changed
Jul 24, 2026

Identity & classification

Regulatory identifiers FDA, NLM and CMS codes for this package

FDA NDC (as labeled) 10122-901-12
Product NDC 10122-901
11-digit billing NDC 10122090112
NCPDP billing unit EA — each (per item)
RxCUI 199904, 211777
UNII V1L22WVE2S
Application # NDA020471
SPL Set ID aee65202-fddb-497f-9f11-17cc727cb157
Established class (EPC) 5-Lipoxygenase Inhibitor
Mechanism of action 5-Lipoxygenase Inhibitors
Physiologic effect Decreased Leukotriene Production
DEA schedule Non-controlled
Marketing category NDA
Marketing status On market
FDA listing status Listed (active directory)
Marketing start 1996-12-06
Marketing end 2027-11-30
Route ORAL
Dosage form TABLET
Substance ZILEUTON

Drug-database identifiers Medi-Span GPI and First Databank GCN / HICL / AHFS classification

GPI-14 44504085000330
GPI class Zyflo
GCN Seq No 029803
GCN 40321
HICL code 012321
Ingredient (HICL) Zileuton
HIC1 code Z
Therapeutic class — broad (HIC1) Body As A Whole
HIC2 code Z4
Therapeutic class — intermediate (HIC2) Eicosanoids
HIC3 code Z4E
Therapeutic class — specific (HIC3) 5-Lipoxygenase Inhibitors
AHFS code 48:10.24.00
AHFS class Leukotriene Modifiers
FDB label name ZYFLO 600 MG TABLET
FDB brand name Zyflo
Legend status F — Federal legend — prescription drug or device
Quick answers
  • GSN (GCN sequence number): 029803
  • GCN: 40321
  • GPI-14 (Medi-Span): 44504085000330
  • HICL (First Databank): 012321
  • AHFS class code: 48:10.24.00
  • RxCUI (RxNorm): 199904
Why two NDCs? The FDA registers this code as 10122-901-12 — a 5-3-2 layout, and that's what's printed on the package and shown on DailyMed. For insurance claims, every NDC is standardized to a uniform 11-digit 5-4-2 format by adding a zero to the product segment → 10122-0901-12. Same drug, same package — only the format differs.
Where does this data come from?
Identifiers from the FDA openFDA NDC Directory and Structured Product Labeling; RxCUI from RxNorm (NLM); GPI from Medi-Span; GCN / HIC / AHFS / legend from First Databank.

RxNorm drug class

This medicine belongs to the 5-Lipoxygenase Inhibitor class.

Pharmacologic class 5-Lipoxygenase Inhibitor
How it works 5-Lipoxygenase Inhibitors
Where does this data come from?
Therapeutic classes from RxNorm RxClass (U.S. National Library of Medicine) — Established Pharmacologic Class (FDA), ATC drug family (WHO) and mechanism of action, matched by this product’s RxCUI.

Clinical

Label name ZYFLO 600 MG TABLET Ingredient Zileuton
📖 What it is MedlinePlus · NLM

Zileuton is used to prevent wheezing, shortness of breath, coughing, and chest tightness due to asthma. Zileuton is not used to treat an asthma attack (sudden episode of shortness of breath, wheezing, and coughing) that has already started. Zileuton belongs to a class of medications called leukotriene synthesis inhibitors. It works by stopping the formation of certain natural substances that cause swelling, tightening, and mucus production in the airways.

Read the full MedlinePlus article ↗
📗 Our plain-language guide HelloPharmacist
  • No — zileuton is a controller medicine, not a rescue medicine. It works slowly over time to reduce airway inflammation and prevent attacks, but it won't open your airways quickly d...
  • Can I use zileuton to stop an asthma attack that's already happening?
  • Zileuton can raise liver enzyme levels, and in some people this can lead to real liver injury. Regular blood tests — especially a liver enzyme called ALT — let your doctor catch an...
  • Why do I need blood tests while taking zileuton?
📖 Read our full Zileuton guide →
Where does this data come from?
Plain-language summary from MedlinePlus (U.S. National Library of Medicine); supplement & herbal interactions and nutrient depletion data from the Natural Medicines database; our full guide is HelloPharmacist editorial content.

Pricing

A drug doesn't have one price. Each row is a different public payment system, and none is what you'd pay at the counter — that depends on your insurance. The ⓘ on each row explains what it measures.

Price systemPer eachPer package
Retail pharmacies payNADAC · weekly Not in the retail survey — common for institutional, discontinued, or low-volume packs.
Medicaid paysCMS SDUD · 12 mo No recent Medicaid claims on file for this NDC — rare and low-volume NDCs are suppressed in the public data.
Medicare drug plans payPart D · quarterly No Part D plan price is available for this NDC in our data.
ℹ️
No price is published for this exact package yet. CMS surveys NADAC per package size, so a different pack of the same drug often has one.
Where does this data come from?
NADAC (National Average Drug Acquisition Cost) is the CMS weekly pharmacy-acquisition-cost survey — what pharmacies pay. ASP (Average Sales Price) is the CMS Medicare Part B drug-payment file, published quarterly. Medicaid pays is computed by us from CMS State Drug Utilization Data (total reimbursed ÷ units, trailing 12 months) — gross of rebates and inclusive of dispensing fees, so it reflects what Medicaid paid, not an acquisition cost. Medicare drug plans pay is the median negotiated point-of-sale unit cost across plans listing this NDC in the CMS quarterly Prescription Drug Plan pricing files, before rebates. The VA pays is the federal contract price (FSS, and the statutory Big 4 ceiling where listed) from the VA National Acquisition Center pharmaceutical price file. All are free public government data; each measures a different payer, so the figures are not directly comparable.

Packaging — all sizes for this product

Package NDCDescription Marketing startMarketing endStatus
10122-0901-12 You're viewing this Main listing 120 TABLET in 1 BOTTLE 1996-12-06 Nov 30, 2027 Active

Therapeutic equivalents

ProductLabelerPackNADAC/unitTEStatusPrice vs. this
Zyflo 600 mgthis 10122-0901-12 Chiesi 120 tablets — — FDA listed —
About this product: this is the brand-name version. We did not find an FDA-approved generic match for this exact strength, form and route.
Where does this data come from?
Equivalents are other NDCs of the same ingredient, form and route from the openFDA NDC Directory, ranked least-expensive-first by NADAC. Therapeutic-equivalence (AB) ratings come from the FDA Orange Book; biologics use the FDA Purple Book for biosimilar & interchangeable status.

Availability & generic status

🏛️
1996
On the market since
Dec 1996
📍
2026
Currently FDA-listed
30 years listed
🔒
·
No generic listed yet
brand only
ℹ️No FDA-approved generic found

We did not find an FDA-approved generic match for this exact strength, form and route.

Where does this data come from?
Patents and exclusivity from the FDA Orange Book (small-molecule drugs), refreshed from public FDA data. Generic launch timing is an estimate, not a guarantee.

What it looks like

Color white
ShapeOval
ImprintCT1
Size19 mm
ScoringNot scored
One label can cover several strengths, so colors may be combined — always confirm a loose pill against the dispensed prescription label or a pharmacist.
Where does this data come from?
Physical description (imprint, shape, color, scoring, coating) from this product’s FDA Structured Product Labeling (SPL), mirrored from DailyMed / openFDA.

Inactive Ingredients / Excipients

Inactive ingredients, also called excipients, are components of the drug product other than the active ingredient. They may include fillers, dyes, coatings, preservatives, flavors, or other formulation ingredients.

🧪 Avoiding an ingredient? See Zileuton inactive ingredients by manufacturer: every current product's list side by side, so you can ask your pharmacy for the version that does not list it.

💡 Tap an ingredient (hover on desktop) to see what it is and why it’s used.

  • UNII OP1R32D61U
    Microcrystalline cellulose is a purified form of cellulose, a natural fiber from plant sources. It acts as a binder and filler in tablets and capsules, helping hold ingredients together and give the medicine its shape and size.
  • UNII 2S7830E561
    Crospovidone is a synthetic polymer derived from povidone. It acts as a disintegrant, helping the tablet or capsule break apart quickly in the stomach so the active ingredient can be absorbed.
  • UNII RFW2ET671P
    Hydroxypropyl cellulose is a plant-derived thickening agent made from cellulose. It acts as a binder to hold tablet ingredients together and as a film-former to coat tablets or control how fast the medicine releases.
  • UNII 3NXW29V3WO
    Hypromellose is a plant-based thickener made from cellulose. It's used in medicines as a binder to hold ingredients together, a coating for tablets, and a thickener for liquids.
  • UNII 70097M6I30
    Magnesium stearate is a salt made from magnesium and stearic acid, a fatty substance. It's used in tablets and capsules as a lubricant and glidant to help ingredients flow smoothly during manufacturing and prevent sticking.
  • UNII 6DC9Q167V3
    Propylene glycol is a clear liquid derived from petroleum or vegetable sources. It acts as a solvent, humectant, and preservative in medicines, helping dissolve active ingredients and maintain product stability.
  • UNII 5856J3G2A2
    A starch-based powder made from potatoes and processed with sodium. It acts as a disintegrant, helping the tablet or capsule break apart quickly in the stomach so the medicine can be absorbed.
  • UNII O8232NY3SJ
    A plant-based carbohydrate derived from corn kernels. It acts as a filler to add bulk, a binder to hold ingredients together, and a disintegrant to help the tablet break apart in your stomach for absorption.
  • UNII 7SEV7J4R1U
    A powder made from a naturally occurring mineral. In medicines, talc works as a glidant and anti-caking agent, helping tablets and capsules flow smoothly during manufacturing and preventing clumping.
  • UNII 15FIX9V2JP
    Titanium dioxide is a bright white mineral powder commonly used as a colorant and opacifying agent. It makes pills and tablets white or lighter in color and helps make coatings non-transparent.

10 inactive ingredients listed in the exact product block matched to this NDC.

Where does this data come from?
Data sourced from official FDA Structured Product Labeling (SPL) via DailyMed — ingredient classCode="IACT" elements from the exact product block matched by this NDC. Label-section narrative from DailyMed / the openFDA label index is shown separately when available.

Inactive ingredient FAQ

Are inactive ingredients the same for every manufacturer?
No. Inactive ingredients can differ by manufacturer, dosage form, strength, and package / product version.
Why might an inactive ingredient be missing?
Some SPLs do not provide a complete structured inactive-ingredient list, and older or unusual labels may only include the information in narrative text.
Can inactive ingredients matter?
Yes. They can matter for allergies, intolerances, dyes, gluten / lactose concerns, preservatives, and formulation differences — but confirm with a pharmacist or the manufacturer when it’s clinically important.

Manufacturer & labeler

LabelerChiesi USA, Inc.
Application holderCHIESI USA INC
FDA applicationNDA020471 (NDA)
Labeler code10122
First marketedDec 1996
Product typeHuman Prescription Drug
Portfolio25 products on file

More NDCs from Chiesi USA, Inc. labeler code 10122

The labeler markets the product; the application holder owns the FDA approval. They’re often the same company but can differ (e.g. a repackager or an authorized generic). A mailing address / phone appears here when the manufacturer includes it in the product’s FDA label (not all do).
Where does this data come from?
Labeler, application holder and registered establishment from the FDA openFDA NDC Directory and Drugs@FDA; address/contact from the product’s FDA label.

Full prescribing information FDA SPL

The complete FDA label for this product — the official prescribing information, verbatim, section by section. Very long sections are excerpted here and marked; the full text is on DailyMed (linked in the sources below). Jump with a chip, search within the label, or expand everything.
🎯 Indications and Usage ⏱️ Dosage and Administration ⛔ Contraindications ⚠️ Warnings 🤒 Adverse Reactions 🆘 Overdosage 🧬 Clinical Pharmacology 📦 How Supplied / Storage and Handling 📋 Description 💬 Information for Patients ⚠️ Precautions 🧬 Pharmacokinetics 🔬 Clinical Studies 📄 Package Label / Principal Display Panel
🎯 Indications and Usage 24 words ▾

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

⏱️ Dosage and Administration 63 words ▾

DOSAGE AND ADMINISTRATION The recommended dosage of ZYFLO for the symptomatic treatment of patients with asthma is one 600-mg tablet four times a day for a total daily dose of 2400 mg. For ease of administration, ZYFLO may be taken with meals and at bedtime. Hepatic transaminases should be evaluated prior to initiation of ZYFLO and periodically during treatment (see PRECAUTIONS, Hepatic ).

⛔ Contraindications 40 words ▾

CONTRAINDICATIONS ZYFLO tablets are contraindicated in patients with: Active liver disease or transaminase elevations greater than or equal to three times the upper limit of normal (≥3xULN) (see PRECAUTIONS, Hepatic ). Hypersensitivity to zileuton or any of its inactive ingredients.

⚠️ Warnings 143 words ▾

WARNINGS ZYFLO is not indicated for use in the reversal of bronchospasm in acute asthma attacks, including status asthmaticus. Therapy with ZYFLO can be continued during acute exacerbations of asthma. Co-administration of ZYFLO and theophylline results in, on average, an approximate doubling of serum theophylline concentrations.

Theophylline dosage in these patients should be reduced and serum theophylline concentrations monitored closely (see PRECAUTIONS, Drug Interactions ). Co-administration of ZYFLO and warfarin results in a clinically significant increase in prothrombin time (PT). Patients on oral warfarin therapy and ZYFLO should have their prothrombin times monitored closely and anticoagulant dose adjusted accordingly (see PRECAUTIONS, Drug Interactions ).

Co-administration of ZYFLO and propranolol results in doubling of propranolol AUC and consequent increased beta-blocker activity. Patients on ZYFLO and propranolol should be closely monitored and the dose of the propranolol reduced as necessary (see PRECAUTIONS, Drug Interactions ).

🤒 Adverse Reactions ~2 min read ▾

ADVERSE REACTIONS 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. 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 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 3xULN (see CONTRAINDICATIONS ).

It is recommended that hepatic transaminases be evaluated at initiation of and during therapy with ZYFLO (see P RECAUTIONS , Hepatic ). Occurrences of low white blood cell count (≤2.8 x 10 9 /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 : Cases of sleep disorders and behavior changes have been reported ( see PRECAUTIONS, Neuropsychiatric Events ). Rash and urticaria have been also reported with ZYFLO.

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

🆘 Overdosage 173 words ▾

OVERDOSAGE Human experience of acute overdose with zileuton is limited. A patient in a clinical trial took between 6.6 and 9.0 grams of zileuton 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. The oral minimum lethal doses in mice and rats were 500-4000 and 300-1000 mg/kg in various preparations, respectively (providing greater than 3 and 9 times the systemic exposure [AUC] achieved at the maximum recommended human daily oral dose, respectively). No deaths occurred, but nephritis was reported 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).

🧬 Clinical Pharmacology ~1 min read ▾

CLINICAL PHARMACOLOGY Mechanism of Action : Zileuton is a specific inhibitor of 5-lipoxygenase and thus inhibits leukotriene (LTB 4 , LTC 4 , LTD 4 , and LTE 4 ) formation. Both the R(+) and S(-) enantiomers are pharmacologically active as 5-lipoxygenase inhibitors in in vitro 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. Sulfido-peptide leukotrienes (LTC 4 , LTD 4 , LTE 4 , also known as the slow-releasing substances of anaphylaxis) and LTB 4 , a chemoattractant for neutrophils and eosinophils, can be measured in a number of biological fluids including bronchoalveolar lavage fluid (BALF) from asthmatic patients. Zileuton is an orally active inhibitor of ex vivo LTB 4 formation in several species, including dogs, monkeys, rats, sheep, and rabbits.

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. Zileuton inhibits leukotriene-dependent smooth muscle contractions in vitro 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. In humans, pretreatment with zileuton attenuated bronchoconstriction caused by cold air challenge in patients with asthma.

📦 How Supplied / Storage and Handling 63 words ▾

HOW SUPPLIED ZYFLO Tablets are available as 1 dosage strength: 600-mg white to off white, ovaloid, film coated tablets debossed “CT 1” on one side and bisect on the other side. High-density polyethylene bottles of: 120 Tablets.....................................................................................NDC 10122-901-12 Recommended storage: Store tablets at controlled room temperature between 20˚-25˚C, (68˚-77˚F). See USP.

Protect from light. CTZI-003-0314-01-SPL-3 Manufactured for: Chiesi USA, Inc. Cary, NC 27518

📋 Description 135 words ▾

DESCRIPTION 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: Zileuton Zileuton has the molecular formula C 11 H 12 N 2 O 2 S and a molecular weight of 236.29. It is a racemic mixture (50:50) of R(+) and S(-) enantiomers.

Zileuton is a practically odorless, white, crystalline powder that is soluble in methanol and ethanol, slightly soluble in acetonitrile, and practically insoluble in water and hexane. The melting point ranges from 144.2˚C to 145.2˚C. ZYFLO tablets for oral administration are supplied in one dosage strength containing 600 mg of zileuton.

Inactive Ingredients: crospovidone, hydroxypropyl cellulose, hypromellose, magnesium stearate, microcrystalline cellulose, pregelatinized starch, propylene glycol, sodium starch glycolate, talc, and titanium dioxide. Zileuton

💬 Information for Patients ~3 min read ▾

Patient Information Leaflet ZYFLO ® (zileuton tablets) Patient Information Leaflet ZYFLO ® Tablets Generic Name: zileuton Please read this leaflet carefully before you start taking ZYFLO ® tablets. Also, read it each time you get your ZYFLO prescription refilled. This leaflet provides important information about taking ZYFLO.

It is not meant to take the place of your doctor’s specific instructions. Talk to your doctor if you have any questions about ZYFLO. Your doctor or pharmacist can also provide you with additional information about ZYFLO.

What is the most important information I should know about ZYFLO? The most important things to remember are to take all your doses of ZYFLO every day and to make sure that you return to your doctor’s office for scheduled liver enzyme tests. You should also know that you should seek medical help immediately if you need more “puffs” of your bronchodilator inhaler than normal or if you use the maximum number of “puffs” prescribed for one 24-hour period.

These could be a sign of worsening asthma which means that your asthma therapy may need to be changed. What is ZYFLO? ZYFLO, which contains the active ingredient zileuton, blocks the formation of certain chemicals (leukotrienes) that may contribute to your asthma symptoms.

Who should not take ZYFLO? You should not take ZYFLO if you: have active liver disease or have liver enzymes that are elevated. have ever had an allergic reaction to this medicine. Your doctor will determine if it is safe for you to take ZYFLO.

What should I tell my doctor before I take the first dose of ZYFLO? You should tell your doctor if you: have ever had liver disease, hepatitis, jaundice (yellow eyes or skin), or dark urine. drink alcohol. are taking any prescription or nonprescription medicines. Your doctor may adjust the doses of some of your other medicines while you are taking ZYFLO. if you are taking theophylline for your asthma, the blood-thinning medication warfarin, or the blood-pressure medication propranolol, your doctor may need to change the doses of these drugs. are pregnant, planning to become pregnant, or are breast-feeding.

How should I take ZYFLO? ZYFLO is taken four times a day with or without food. It may be easier to remember to take ZYFLO if you make it part of your daily routine such as with meals and at bedtime.

For ZYFLO to help control your asthma symptoms, it must be taken everyday as prescribed by your doctor. ZYFLO WILL NOT relieve an asthma attack that has already started. While taking ZYFLO, it is important to keep taking your other asthma medicines as directed and to follow all of your doctor’s instructions.

Even if you have no asthma symptoms, do not decrease the dose of ZYFLO or stop taking the medicine without talking to your doctor first. Feeling good is a sign that the medicine is working. When you take your dose of ZYFLO, the tablets may be swallowed whole or split in half to make them easier to swallow.

What should I avoid while taking ZYFLO? Because ZYFLO may affect how other medications work, always talk to your doctor before you start or stop taking any medicines while taking ZYFLO. This includes all prescription and nonprescription medicines.

Never take a larger dose of ZYFLO or take it more often than your doctor has prescribed. It is also important for you to know that it may take several days or a few weeks to get the full benefit from ZYFLO and that you should not stop taking it if you do not feel better right away. What are the possible side effects of ZYFLO?

All medicines, including ZYFLO, cause side effects in some people. Some of the most common side effects are abdominal pain, upset stomach, and nausea. You should tell your doctor if you experience any new or unusual symptoms while taking ZYFLO.

One side effect that occurs in a small number of patients is an increased release of substances from the liver called “enzymes.” Liver enzymes can be measured by a simple blood test. It is important that your doctor makes sur… [Excerpted — this section continues on DailyMed.]

⚠️ Precautions ~3 min read ▾

PRECAUTIONS Hepatic : Elevations of one or more liver function tests may occur during ZYFLO therapy. These laboratory abnormalities may progress, remain unchanged, or resolve with continued therapy. In a few cases, initial transaminase elevations were first noted after discontinuing treatment, usually within 2 weeks.

The ALT (SGPT) test is considered the most sensitive indicator of liver injury. In placebo-controlled clinical trials, the frequency of ALT elevations greater than or equal to three times the upper limit of normal (3xULN) was 1.9% for ZYFLO-treated patients, compared with 0.2% for placebo-treated patients. In a long-term safety surveillance study, 2458 patients received ZYFLO in addition to their usual asthma care and 489 received their usual asthma care.

In patients treated for up to 12 months with ZYFLO in addition to their usual asthma care, 4.6% developed an ALT of at least 3xULN, compared with 1.1% of patients receiving only their usual asthma care. Sixty-one percent of these elevations occurred during the first two months of ZYFLO therapy. After two months of treatment, the rate of new ALT elevations ≥3xULN stabilized at a mean of 0.30% per month for patients receiving ZYFLO-plus-usual-asthma care compared with 0.11% per month for patients receiving usual asthma care alone.

Of the 61 ZYFLO plus-usual-asthma-care patients with ALT elevations between 3 to 5xULN, 32 patients (52%) had ALT values decrease to below 2xULN while continuing ZYFLO therapy. Twenty-one of the 61 patients (34%) had further increases in ALT levels to ≥5xULN and were withdrawn from the study in accordance with the study protocol. In patients who discontinued ZYFLO, elevated ALT levels returned to <2xULN in an average of 32 days (range 1-111 days).

In controlled and uncontrolled clinical trials involving more than 5000 patients treated with ZYFLO, the overall rate of ALT elevation ≥3xULN 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 three times the upper limit of normal.

There was no evidence of hypersensitivity or other alternative etiologies for these findings. In subset analyses, females over the age of 65 appeared to be at an increased risk for ALT elevations. Patients with pre-existing transaminase elevations may also be at an increased risk for ALT elevations (see CONTRAINDICATIONS ).

It is recommended that hepatic transaminases be evaluated at initiation of, and during therapy with, ZYFLO. Serum ALT should be monitored before treatment begins, once-a-month for the first 3 months, every two to three months for the remainder of the first year, and periodically thereafter for patients receiving long-term ZYFLO therapy. If clinical signs and/or symptoms of liver dysfunction (e.g., right upper quadrant pain, nausea, fatigue, lethargy, pruritus, jaundice, or “flu-like” symptoms) develop or transaminase elevations greater than 5 times the ULN occur, ZYFLO should be discontinued and transaminase levels followed until normal.

Since treatment with ZYFLO may result in increased hepatic transaminases, ZYFLO should be used with caution in patients who consume substantial quantities of alcohol and/or have a past history of liver disease. Neuropsychiatric Events : Neuropsychiatric events have been reported in adult and adolescent patients taking zileuton, the active ingredient in ZYFLO and zileuton extended-release tablets. Post-marketing reports with zileuton include sleep disorders and behavior changes.

The clinical details of some post-marketing reports involving ZYFLO appear consistent with a drug-induced effect. Patients and prescribers should be alert for neuropsychiatric events. Patients should be instructed to notify their prescriber if these changes occur.

Prescribers should carefully evaluate the risks and benefits of continuing treatment with ZY… [Excerpted — this section continues on DailyMed.]

🧬 Pharmacokinetics ~2 min read ▾

PHARMACOKINETICS Zileuton is rapidly absorbed upon oral administration with a mean time to peak plasma concentration (T max ) of 1.7 hours and a mean peak level (C max ) of 4.98 μg/mL. The absolute bioavailability of ZYFLO is unknown. Systemic exposure (mean AUC) following 600 mg ZYFLO administration is 19.2 μg.hr/mL.

Plasma concentrations of zileuton are proportional to dose, and steady-state levels are predictable from single-dose pharmacokinetic data. Administration of ZYFLO with food resulted in a small but statistically significant increase (27%) in zileuton C max without significant changes in the extent of absorption (AUC) or T max . Therefore, ZYFLO can be administered with or without food (see DOSAGE AND ADMINISTRATION ).

The apparent volume of distribution (V/F) of zileuton is approximately

1.2L/kg. Zileuton is 93% bound to plasma proteins, primarily to albumin, with minor binding to αl-acid glycoprotein. Elimination of zileuton is predominantly via metabolism with a mean terminal half-life of 2.5 hours.

Apparent oral clearance of zileuton is 7.0 mL/min/kg. ZYFLO activity is primarily due to the parent drug. Studies with radiolabeled drug demonstrated that orally administered zileuton is well absorbed into the systemic circulation with 94.5% and 2.2% of the radiolabeled dose recovered in urine and feces, respectively.

Several zileuton metabolites have been identified in human plasma and urine. These include two diastereomeric O-glucuronide conjugates (major metabolites) and an N-dehydroxylated metabolite of zileuton. The urinary excretion of the inactive N-dehydroxylated metabolite and unchanged zileuton each accounted for less than 0.5% of the dose.

In vitro studies utilizing human liver microsomes have shown that zileuton and its N-dehydroxylated metabolite can be oxidatively metabolized by the cytochrome P450 isoenzymes 1A2, 2C9 and 3A4 (CYP1A2, CYP2C9 and CYP3A4). Special populations : Effect of age : The pharmacokinetics of zileuton were investigated in healthy elderly volunteers (ages 65 to 81 years, 9 males, 9 females) and healthy young volunteers (ages 20 to 40 years, 5 males and 4 females) after single and multiple oral doses of 600 mg every 6 hours of zileuton.

Zileuton pharmacokinetics were similar in healthy elderly subjects (≥65 years) compared to healthy younger adults (18 to 40 years). Effect of gender : Across several studies, no significant gender effects were observed on the pharmacokinetics of zileuton. Renal insufficiency : The pharmacokinetics of zileuton were similar in healthy subjects and in subjects with mild, moderate, and severe renal insufficiency.

In subjects with renal failure requiring hemodialysis, zileuton pharmacokinetics were not altered by hemodialysis and a very small percentage of the administered zileuton dose (<0.5%) was removed by hemodialysis. Hence, dosing adjustment in patients with renal dysfunction or undergoing hemodialysis is not necessary. Hepatic insufficiency : ZYFLO is contraindicated in patients with active liver disease (see CONTRAINDICATIONS and PRECAUTIONS , Hepatic ).

🔬 Clinical Studies ~2 min read ▾

CLINICAL STUDIES Two double-blind, parallel, placebo-controlled, multi-center studies have established the efficacy of ZYFLO in the treatment of asthma. Three hundred seventy-three (373) patients were enrolled in the 6-month, double-blind phase of Study 1, and 401 patients were enrolled in the 3-month double-blind phase of Study 2. In these studies, the patients were mild-to-moderate asthmatics who had a mean baseline FEV 1 of approximately 2.3 liters and who used inhaled beta-agonists as needed, the mean being approximately 6 puffs of albuterol per day from a metered-dose inhaler.

In each study, patients were randomized to receive either ZYFLO 400 mg four times daily, ZYFLO 600 mg four times daily, or placebo. Only the ZYFLO 600 mg four times daily dosage regimen was shown to be efficacious by demonstrating statistically significant improvement across several parameters. Efficacy endpoints measured in Study 1 are shown in Table 1 below as mean change from baseline to the end of the study (six months).

Statistically significant differences from placebo at the p<0.05 level are indicated by an asterisk(*). Similar results were observed after three months in Study 2. Mean Change from Baseline to End of Study Figure 1 shows the mean effect of ZYFLO versus placebo for the primary efficacy variable, trough FEV 1 , over the course of Study 1.

Mean Change From Baseline to Trough FEV1 (L) Of all the patients in Study 1 and Study 2, 7.0% of those administered ZYFLO 600 mg four times daily required systemic corticosteroid therapy for exacerbation of asthma, whereas 18.7% of the placebo group required corticosteroid treatment. This difference was statistically significant. In these trials, there was a statistically significant improvement from baseline in FEV 1 , which occurred 2 hours after initial administration of ZYFLO.

This mean increase was approximately

0.10L greater than that in placebo-treated patients. These studies evaluated patients receiving as-needed inhaled beta-agonist as their only asthma therapy. In this patient population, post-hoc analyses suggested that individuals with lower FEV 1 values at baseline showed a greater improvement.

The role of ZYFLO in the management of patients with more severe asthma, patients receiving anti-asthma therapy other than as-needed, inhaled beta-agonists, or patients receiving it as an oral or inhaled corticosteroid-sparing agent remains to be fully characterized. Mean Change from Baseline to End of Study Mean Change From Baseline to Trough FEV1 (L)

📄 Package Label / Principal Display Panel 2 words ▾

Zyflo Bottle

Source: FDA Structured Product Labeling, mirrored from DailyMed / openFDA. Prefer the government’s original formatting? View this label on DailyMed ↗

Medicare Part D spend CMS · PART D · 2026 (Q1)

Medicare Part D (outpatient prescription) spending for Zyflo — the program that covers self-administered drugs. 1 manufacturer.
⚠️ Drug-level data: CMS publishes Part D spending by drug, not by NDC — these figures combine every manufacturer, strength and package size sold under the name Zyflo. That’s a different level of aggregation than the Medicaid card above, which is specific to this exact 11-digit NDC (pack size included), so the two aren’t directly comparable.
Period
Total Part D spend
$149.7K
Claims incl. refills
38
Beneficiaries
27
Spend / beneficiary
$5,543.57
Spend / claim
$3,938.85
Trend by period
💵 About the dollar figures: spending is what Part D plans paid before confidential manufacturer rebates, so the program’s real net cost is lower. A blank patient count means fewer than 11 people — CMS hides counts that small to protect privacy. Source: CMS Medicare Quarterly Part D Spending by Drug (data.cms.gov), updated quarterly.

About this NDC listing & data coverage

Finished prescription product
What data is (and isn’t) available for this NDC — tap to expand
NDC identity (package / product / labeler codes) ✓ Available
Labeler ✓ Available
Product & package description ✓ Available
Marketing category & status ✓ Available
Active ingredient / dosage form / route ✓ Available
FDA label (SPL via DailyMed) ✓ Available
Package photos ✓ Available
Inactive ingredients (structured) ✓ Available
NADAC pharmacy acquisition price (CMS) — Not published for this NDC CMS publishes NADAC only for NDCs reported in its retail-pharmacy survey.
Orange Book / therapeutic-equivalence data — Not published for this NDC Applies only to products approved under an NDA/ANDA; many listings are out of scope.
HCPCS J-code billing crosswalk — Not published for this NDC Most self-administered / retail products have no J-code — that is normal.
Medicaid utilization (CMS SDUD) — Not published for this NDC CMS reports utilization only for NDCs with Medicaid claims above its privacy threshold.
“Not published” reflects what the public FDA / CMS / NLM sources provide for this exact package code — it is a property of the data feeds, not a judgment about the product.

Questions about this listing

Why is there no price listed?
The pricing shown on our NDC pages comes from CMS NADAC, a voluntary survey of retail community pharmacy invoices. CMS does not publish a NADAC for every NDC — packages outside the retail survey (institutional and hospital products, bulk packages, discontinued items, and many OTC items) may never receive one. A missing price reflects the survey's scope, not this product's actual cost, and does not mean the product is free or unavailable.
Is the NDC printed on the package the same as the 11-digit billing NDC?
Yes, they identify this exact package in different formats. The form printed on the packaging and shown on DailyMed is the one the FDA registered. Insurance claims use a fixed 11-digit 5-4-2 format, so the short segment is padded with a leading zero and the dashes are dropped. The Identity section at the top of this page lists each form of this code.
Is this package still being marketed?
Yes, per the latest FDA NDC Directory data on this page it is currently marketed — but Chiesi USA, Inc. has reported a marketing end date of 2027-11-30, after which this package is expected to stop being marketed. The directory data on this page refreshes weekly.
Who lists this product with the FDA?
Chiesi USA, Inc. is the labeler of record for this NDC — the company under whose FDA-assigned code the package is listed. The labeler may be the manufacturer itself or a distributor marketing the product under its own code.
Do I need a prescription for this product?
This NDC is listed with FDA as a prescription product, so it is dispensed under a prescriber's order. Your pharmacist can tell you whether any over-the-counter forms of the same medication exist.
This page identifies an FDA-listed package (the NDC) and reports public regulatory and pricing data about the listing. It is reference information, not a medical recommendation — talk to your pharmacist or prescriber about your own medication.
Where does this data come from?
Listing facts (marketing category, packager status, marketing dates) from the FDA openFDA NDC Directory; label availability from DailyMed; pricing coverage from CMS NADAC; equivalence scope from the FDA Orange Book.
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For educational and professional reference only — not medical advice. Pricing reflects published NADAC and CMS ASP (free public data) and may differ from your acquisition cost; always verify before billing or dispensing.