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Zyflo CR Side Effects Center
Medical Editor: John P. Cunha, DO, FACOEP
Zyflo CR (zileuton) Extended-Release Tablets are used to prevent asthma symptoms and to decrease the number of asthma attacks. It is a leukotriene inhibitor. Common side effects include nausea, diarrhea or trouble sleeping.
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. Zyflo CR may interact with blood thinners, theophylline, or propranolol. Tell your doctor all medications and supplements you use. During pregnancy, Zyflo CR should be used only when prescribed. It is unknown if this medication passes into breast milk. Consult your doctor before breastfeeding.
Our Zyflo CR (zileuton) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
What is Patient Information in Detail?
Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.
Zyflo CR in Detail - Patient Information: Side Effects
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have a serious side effect such as:
- nausea, upper stomach pain, itching, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);
- skin rash, bruising, severe tingling, numbness, pain, muscle weakness;
- mood or behavior changes, anxiety, depression, or thoughts about suicide or hurting yourself; or
- worsening asthma symptoms.
Less serious side effects may include:
- cold symptoms such as stuffy nose, sinus pain, sneezing, sore throat;
- diarrhea, upset stomach;
- weakness; or
- muscle pain.
Read the entire detailed patient monograph for Zyflo CR (Zileuton Extended Release Tablets)
What is Patient Information Overview?
A concise overview of the drug for the patient or caregiver from First DataBank.
Zyflo CR Overview - Patient Information: Side Effects
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of these rare but very serious side effects occur: mental/mood changes (e.g., agitation, aggression, hallucinations, abnormal dreams, depression, suicidal thoughts/suicide), yellowing skin/eyes, dark urine, severe stomach/abdominal pain, unusual tiredness, persistent nausea/vomiting.
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US -
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.
Read the entire patient information overview for Zyflo CR (Zileuton Extended Release Tablets)
What is Prescribing information?
The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.
Zyflo CR FDA Prescribing Information: Side Effects
Short-Term Clinical Studies Experience
The safety data described below reflect exposure to ZYFLO CR in 199 patients for 12 weeks duration. In a 12-week, randomized, double-blind, placebo-controlled trial in adults and adolescents 12 years of age and older with asthma, patients received ZYFLO CR two 600 mg tablets (n=199) or placebo (n=198) twice daily by mouth. Eighty-three percent of patients were white, 48% were male, and the mean age was 34 years.
Because clinical studies are conducted under widely varying conditions, adverse reaction rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.
The most commonly reported adverse reactions (occurring at a frequency of ≥ 5%) in ZYFLO CR-treated patients and at a frequency greater than placebo-treated patients are reflected in Table 1.
Table 1. Adverse Reactions with ≥ 5% Incidence in a 12-Week
Placebo-Controlled Trial in Patients with Asthma.
|Adverse Reaction|| ZYFLO CR
N=199 n (%)
2 Tablets Twice
|Sinusitis||13 (6.5)||8 (4.0)|
|Nausea||10 (5.0)||3 (1.5)|
|Pharyngolaryngeal pain||10 (5.0)||8 (4.0)|
Less common adverse reactions occurring at a frequency ≥ 1% and more often in the ZYFLO CR group than in the placebo group included gastrointestinal disorders (upper abdominal pain, diarrhea, dyspepsia, vomiting), rash, hypersensitivity, and hepatotoxicity. There were no differences in the incidence of adverse reactions based upon gender. The clinical trials did not include sufficient numbers of patients < 18 years of age or non-Caucasians to determine whether there is any difference in adverse reactions based upon age or race.
In the 12-week placebo-controlled trial, the incidence of ALT elevations ( ≥ 3xULN) was 2.5% (5 of 199) in the ZYFLO CR group, compared to 0.5% (1 of 198) in the placebo group. In the ZYFLO CR group, the majority of ALT elevations (60%) occurred in the first month of treatment, and in 2 of the 5 patients in the ZYFLO CR group, ALT elevations were detected 14 days after completion of the 3-month study treatment. The levels returned to < 2xULN or normal within 9 and 12 days, respectively. The ALT elevations in the other 3 patients were observed to return to < 2xULN or normal within 15, 19, and 31 days after ZYFLO CR discontinuation. There appeared to be no clinically relevant relationship between the time of onset and the magnitude of the first elevation or the magnitude of first elevation and time to resolution. The hepatic function enzyme elevations attributed to ZYFLO CR did not result in any cases of jaundice, development of chronic liver disease, or death in this clinical trial.
Long-Term Clinical Studies Experience
The safety of ZYFLO CR was evaluated in one 6-month, randomized, double-blind, placebo-controlled clinical trial in adults and adolescents 12 years of age and older with asthma. Patients received two 600 mg ZYFLO CR tablets (n=619) or placebo (n=307) twice daily by mouth along with usual asthma care. Eighty-six percent of patients were white, 40% were male, and the overall mean age was 36.
The rate and type of adverse reactions observed in this study were comparable to the adverse reactions observed in the 12-week study. Other commonly reported adverse reactions (occurring at a frequency of ≥ 5%) in ZYFLO CR-treated patients and at a frequency greater than placebo-treated patients included the following: headache (23%), upper respiratory tract infection (9%), myalgia (7%), and diarrhea (5%) compared to 21%, 7%, 5% and 2%, respectively, in the placebo-treated group.
ALT elevations ( ≥ 3xULN) were observed in 1.8% of patients treated with ZYFLO CR compared to 0.7% in patients treated with placebo. The majority of elevations (82%) were reported within the first 3 months of treatment and resolved within 21 days for most of these patients after discontinuation of the drug. The hepatic function enzyme elevations attributed to ZYFLO CR did not result in any cases of jaundice, development of chronic liver disease, or death in this clinical trial.
Occurrences of low white blood cell (WBC) count ( < 3.0 x 109/L) were observed in 2.6% (15 of 619) of the ZYFLO CR-treated patients and in 1.7% (5 of 307) of the placebo-treated patients. The WBC counts returned to normal or baseline following discontinuation of ZYFLO CR. The clinical significance of these findings is not known.
The following adverse reactions have been identified during post-approval use of zileuton immediate-release tablets and may be applicable to ZYFLO CR. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship.
Cases of severe hepatic injury have been reported in patients taking zileuton immediate-release tablets. These cases included death, life-threatening liver injury with recovery, symptomatic jaundice, hyperbilirubinemia, and elevations of ALT > 8xULN.
Read the entire FDA prescribing information for Zyflo CR (Zileuton Extended Release Tablets)
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