ZILEUTON Drug Interactions: What You Need to Know

INTERACTIONS The following study results were obtained using zileuton immediate-release tablets but the conclusions also apply to Zileuton Extended-Release Tablets. Zileuton increases theophylline levels. Reduce theophylline dose and monitor levels. ( 7.1 ) Zileuton increases warfarin levels. Monitor prothrombin time and adjust warfarin dose accordingly. ( 7.2 ) Zileuton increases propranolol levels and beta-blocker activity. Monitor appropriately. ( 7.3 )

7.1 Theophylline In a drug-interaction study in 16 healthy subjects, co-administration of multiple doses of zileuton immediate-release tablets (800 mg every 12 hours) and theophylline (200 mg every 6 hours) for 5 days resulted in a significant decrease (approximately 50%) in steady-state clearance of theophylline, an approximate doubling of theophylline AUC, and an increase in theophylline C max (by 73%). The elimination half-life of theophylline was increased by 24%. Also, during co-administration, theophylline-related adverse reactions were observed more frequently than after theophylline alone. Upon initiation of Zileuton Extended-Release Tablets in patients receiving theophylline, the theophylline dosage should be reduced by approximately one-half and plasma theophylline concentrations monitored. Similarly, when initiating therapy with theophylline in a patient receiving Zileuton Extended-Release Tablets, the maintenance dose and/or dosing interval of theophylline should be adjusted accordingly and guided by serum theophylline determinations.

7.2 Warfarin Concomitant administration of multiple doses of zileuton immediate-release tablets (600 mg every 6 hours) and warfarin (fixed daily dose obtained by titration in each subject) to 30 healthy male subjects resulted in a 15% decrease in R-warfarin clearance and an increase in AUC of 22%. The pharmacokinetics of S-warfarin were not affected. These pharmacokinetic changes were accompanied by a clinically significant increase in prothrombin times. Monitoring of prothrombin time, or other suitable coagulation tests, with the appropriate dose titration of warfarin is recommended in patients receiving concomitant Zileuton Extended-Release Tablets and warfarin therapy.

7.3 Propranolol Co-administration of zileuton immediate-release tablets and propranolol results in a significant increase in propranolol concentrations. Administration of a single 80 mg dose of propranolol in 16 healthy male subjects who received zileuton immediate-release tablets 600 mg every 6 hours for 5 days resulted in a 42% decrease in propranolol clearance. This resulted in an increase in propranolol C max , AUC, and elimination half-life by 52%, 104%, and 25%, respectively. There was an increase in β-blockade as shown by a decrease in heart rate associated with the co-administration of these drugs. Patients concomitantly on Zileuton Extended-Release Tablets and propranolol should be closely monitored and the dose of propranolol reduced as necessary. No formal drug-drug interaction studies between zileuton and other beta-adrenergic blocking agents (i.e., β-blockers) have been conducted. It is reasonable to employ appropriate clinical monitoring when these drugs are co-administered with Zileuton Extended-Release Tablets.

7.4 Other Concomitant Drug Therapy Drug-drug interaction studies conducted in healthy subjects between zileuton immediate-release tablets and prednisone and ethinyl estradiol (oral contraceptive), drugs known to be metabolized by the CYP3A4 isoenzyme, have shown no significant interaction. However, no formal drug-drug interaction studies between zileuton and CYP3A4 inhibitors, such as ketaconazole, have been conducted. It is reasonable to employ appropriate clinical monitoring when these drugs are co-administered with Zileuton Extended-Release Tablets. Drug-drug interaction studies in healthy subjects have been conducted with zileuton immediate-release tablets and digoxin, phenytoin, sulfasalazine, and naproxen. There was no significant interaction between zileuton and any of these drugs.

7.1 Theophylline In a drug-interaction study in 16 healthy subjects, co-administration of multiple doses of zileuton immediate-release tablets (800 mg every 12 hours) and theophylline (200 mg every 6 hours) for 5 days resulted in a significant decrease (approximately 50%) in steady-state clearance of theophylline, an approximate doubling of theophylline AUC, and an increase in theophylline C max (by 73%). The elimination half-life of theophylline was increased by 24%. Also, during co-administration, theophylline-related adverse reactions were observed more frequently than after theophylline alone. Upon initiation of Zileuton Extended-Release Tablets in patients receiving theophylline, the theophylline dosage should be reduced by approximately one-half and plasma theophylline concentrations monitored. Similarly, when initiating therapy with theophylline in a patient receiving Zileuton Extended-Release Tablets, the maintenance dose and/or dosing interval of theophylline should be adjusted accordingly and guided by serum theophylline determinations.

7.2 Warfarin Concomitant administration of multiple doses of zileuton immediate-release tablets (600 mg every 6 hours) and warfarin (fixed daily dose obtained by titration in each subject) to 30 healthy male subjects resulted in a 15% decrease in R-warfarin clearance and an increase in AUC of 22%. The pharmacokinetics of S-warfarin were not affected. These pharmacokinetic changes were accompanied by a clinically significant increase in prothrombin times. Monitoring of prothrombin time, or other suitable coagulation tests, with the appropriate dose titration of warfarin is recommended in patients receiving concomitant Zileuton Extended-Release Tablets and warfarin therapy.

7.3 Propranolol Co-administration of zileuton immediate-release tablets and propranolol results in a significant increase in propranolol concentrations. Administration of a single 80 mg dose of propranolol in 16 healthy male subjects who received zileuton immediate-release tablets 600 mg every 6 hours for 5 days resulted in a 42% decrease in propranolol clearance. This resulted in an increase in propranolol C max , AUC, and elimination half-life by 52%, 104%, and 25%, respectively. There was an increase in β-blockade as shown by a decrease in heart rate associated with the co-administration of these drugs. Patients concomitantly on Zileuton Extended-Release Tablets and propranolol should be closely monitored and the dose of propranolol reduced as necessary. No formal drug-drug interaction studies between zileuton and other beta-adrenergic blocking agents (i.e., β-blockers) have been conducted. It is reasonable to employ appropriate clinical monitoring when these drugs are co-administered with Zileuton Extended-Release Tablets.

7.4 Other Concomitant Drug Therapy Drug-drug interaction studies conducted in healthy subjects between zileuton immediate-release tablets and prednisone and ethinyl estradiol (oral contraceptive), drugs known to be metabolized by the CYP3A4 isoenzyme, have shown no significant interaction. However, no formal drug-drug interaction studies between zileuton and CYP3A4 inhibitors, such as ketaconazole, have been conducted. It is reasonable to employ appropriate clinical monitoring when these drugs are co-administered with Zileuton Extended-Release Tablets. Drug-drug interaction studies in healthy subjects have been conducted with zileuton immediate-release tablets and digoxin, phenytoin, sulfasalazine, and naproxen. There was no significant interaction between zileuton and any of these drugs.

The use of zileuton extended-release tablets are contraindicated in patients with:

• Active liver disease or persistent hepatic function enzyme elevations greater than or equal to 3 times the upper limit of normal (≥3xULN) [see Warnings and Precautions ( 5 ), and Use in Specific Populations ( 8.7 ) ].
• A history of allergic reaction to zileuton or any of the ingredients of zileuton extended-release tablets (e.g., rash, eosinophilia, etc.).
• Active liver disease or persistent hepatic function enzyme elevations ≥3 times the upper limit of normal. ( 4 , 5.1 )
• History of allergic reaction to zileuton or any of the ingredients of zileuton extended-release tablets. ( 4 )

AND PRECAUTIONS Hepatotoxicity: Elevations of one or more hepatic function enzymes and bilirubin may occur with Zileuton Extended-Release Tablets. Assess hepatic function enzymes prior to initiation of Zileuton Extended-Release Tablets, monthly for the first 3 months, every 2-3 months for the remainder of the first year, and periodically thereafter.

Use Zileuton

Extended-Release Tablets with caution in patients who consume substantial quantities of alcohol and/or have a history of liver disease. ( 5.1 )

Neuropsychiatric

Events: Neuropsychiatric events, including sleep disorders and behavior changes, may occur with Zileuton Extended-Release Tablets. Instruct patients to be alert for neuropsychiatric events. Evaluate the risks and benefits of continuing treatment with Zileuton Extended-Release Tablets if such events occur. ( 5.2 )

5.1 Hepatotoxicity Elevations of one or more hepatic function enzymes and bilirubin may occur during Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets. Assess hepatic function enzymes prior to initiation of, and during therapy with, Zileuton Extended-Release Tablets. 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 Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets may result in increased hepatic function enzymes and liver injury, Zileuton Extended-Release Tablets should be used with caution in patients who consume substantial quantities of alcohol and/or have a past history of liver disease.

5.2 Neuropsychiatric Events Neuropsychiatric events have been reported in adult and adolescent patients taking zileuton, the active ingredient in Zileuton Extended-Release Tablets and zileuton immediate-release tablets. Post-marketing reports with zileuton include sleep disorders and behavior changes. The clinical details of some post-marketing reports involving zileuton 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 Zileuton Extended-Release Tablets if such events occur <span class="opacity-50 text-xs">[see Adverse Reactions (6.3) ]</span>.

5.1 Hepatotoxicity Elevations of one or more hepatic function enzymes and bilirubin may occur during Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets. Assess hepatic function enzymes prior to initiation of, and during therapy with, Zileuton Extended-Release Tablets. 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 Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets 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 Zileuton Extended-Release Tablets may result in increased hepatic function enzymes and liver injury, Zileuton Extended-Release Tablets should be used with caution in patients who consume substantial quantities of alcohol and/or have a past history of liver disease.

5.2 Neuropsychiatric Events Neuropsychiatric events have been reported in adult and adolescent patients taking zileuton, the active ingredient in Zileuton Extended-Release Tablets and zileuton immediate-release tablets. Post-marketing reports with zileuton include sleep disorders and behavior changes. The clinical details of some post-marketing reports involving zileuton 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 Zileuton Extended-Release Tablets if such events occur <span class="opacity-50 text-xs">[see Adverse Reactions (6.3) ]</span>.