Zyflo CR Side Effects

Generic Name: zileuton

Please note - some side effects for Zyflo CR may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Side Effects of Zyflo CR - for the Consumer

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 irritation; sinus pain; symptoms of upper respiratory tract infection (eg, cough, mild sore throat, runny or stuffy nose, sneezing); throat pain or irritation.

Seek medical attention right away if any of these SEVERE side effects occur when using Zyflo CR Extended-Release Tablets:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fever, chills, or persistent sore throat; mental or mood changes; sleep problems; symptoms of liver problems (eg, dark urine; flu-like symptoms; pale stools; persistent loss of appetite; right upper stomach pain; unusual nausea, sluggishness, or tiredness; yellowing of the skin or eyes); unusual changes in behavior.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

Top

Zyflo CR Side Effects - for the Professional

Zyflo CR

Hepatotoxicity: Elevations of one or more hepatic function enzymes and bilirubin may occur during Zyflo CR therapy [see Warnings and Precautions (5)].

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

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 600 mg 2 Tablets Twice Daily N=199 n (%)	Placebo 2 Tablets Twice Daily N=198 n (%)
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.

Hepatotoxicity

In the 12-week placebo-controlled trial, the incidence of ALT elevations (≥3×ULN) 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 <2×ULN or normal within 9 and 12 days, respectively. The ALT elevations in the other 3 patients were observed to return to <2×ULN 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 (≥3×ULN) 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 × 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.

Postmarketing Experience

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 >8×ULN.

Cases of sleep disorders and behavior changes have also been reported [see Warnings and Precautions (5.2)].

Top

Side Effects by Body System - for Healthcare Professionals

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.

Psychiatric

Psychiatric side effects have postmarketing reports of sleep disorders and behavior changes.

Top

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date, and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This information does not endorse drugs, diagnose patients, or recommend therapy. This drug information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug of drug combination is safe, effective, or appropriate for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of information provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse, or pharmacist.