INTERACTIONS Concomitant administration of febuxostat tablets with XO substrate drugs, azathioprine or mercaptopurine could increase plasma concentrations of these drugs resulting in severe toxicity. ( 7 )
7.1 Xanthine Oxidase Substrate Drugs Febuxostat tablet is an XO inhibitor. Based on a drug interaction study in healthy patients, febuxostat altered the metabolism of theophylline (a substrate of XO) in humans <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.3) ]</span>. Therefore, use with caution when coadministering febuxostat tablets with theophylline. A drug interaction study of febuxostat tablets and azathioprine, also metabolized by XO, showed an increase in exposure of 6-mercaptopurine which may lead to toxicity <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.3) ]</span> . Drug interaction studies of febuxostat tablets with other drugs that are metabolized by XO (e.g., mercaptopurine) have not been conducted. Febuxostat tablets are contraindicated in patients being treated with azathioprine or mercaptopurine <span class="opacity-50 text-xs">[see Contraindications (4) ]</span>.
7.2 Cytotoxic Chemotherapy Drugs Drug interaction studies of febuxostat tablets with cytotoxic chemotherapy have not been conducted. No data are available regarding the safety of febuxostat tablets during cytotoxic chemotherapy.
7.3 In Vivo Drug Interaction Studies Based on drug interaction studies in healthy patients, febuxostat tablets do not have clinically significant interactions with colchicine, naproxen, indomethacin, hydrochlorothiazide, warfarin or desipramine <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.3) ]</span>. Therefore, febuxostat tablets may be used concomitantly with these medications.
Febuxostat Tablets are contraindicated in patients being treated with azathioprine or mercaptopurine [see Drug Interactions ( 7 )] .
Febuxostat
Tablets are contraindicated in patients being treated with azathioprine or mercaptopurine. ( 4 )
AND PRECAUTIONS Cardiovascular Death: In a CV outcomes study, there was a higher rate of CV death in patients treated with febuxostat compared to allopurinol; in the same study febuxostat was non-inferior to allopurinol for the primary endpoint of major adverse cardiovascular events (MACE). Consider the risks and benefits of febuxostat when deciding to prescribe or continue patients on febuxostat. ( 1 , 5.1 )
Gout
Flares: An increase in gout flares is frequently observed during initiation of anti-hyperuricemic agents, including febuxostat. If a gout flare occurs during treatment, febuxostat need not be discontinued. Prophylactic therapy (i.e., non-steroidal anti-inflammatory drug [NSAID] or colchicine upon initiation of treatment) may be beneficial for up to six months. ( 2.4 , 5.2 )
Hepatic
Effects : Postmarketing reports of hepatic failure, sometimes fatal. Causality cannot be excluded. If liver injury is detected, promptly interrupt febuxostat and assess patient for probable cause, then treat cause if possible, to resolution or stabilization. Do not restart febuxostat if liver injury is confirmed and no alternate etiology can be found. ( 5.3 )
Serious Skin
Reactions: Postmarketing reports of serious skin and hypersensitivity reactions, including Stevens-Johnson Syndrome,drug reaction with eosinophilia and systemic symptoms (DRESS) and toxic epidermal necrolysis (TEN) have been reported in patients taking febuxostat. Discontinue febuxostat if serious skin reactions are suspected. ( 5.4 )
5.1 Cardiovascular Death In a cardiovascular (CV) outcome study (ClinicalTrials.gov identifier NCT01101035), gout patients with established CV disease treated with febuxostat had a higher rate of CV death compared to those treated cardiovascular events (MACE) in patients with gout who were treated with febuxostat. The study enrolled patients who had a history of major CV disease, cerebrovascular disease or diabetes mellitus with micro-and/or macrovascular disease. The primary endpoint was the time to first occurrence of MACE defined as the composite of CV death, nonfatal MI, nonfatal stroke, or unstable angina with urgent coronary revascularization. The study was designed to exclude a prespecified risk margin of 1.3 for the hazard ratio of MACE. Results showed that febuxostat was non-inferior to allopurinol for the primary endpoint of MACE [Hazard Ratio: 1.03, 95% Confidence Interval (CI): 0.89, 1.21]. However, there was a significant increase in CV deaths in patients treated with febuxostat (134 [1.5 per 100 patient-years]) compared to patients treated with allopurinol (100 [1.1 per 100 patient-years]) [Hazard Ratio: 1.34, 95% CI: 1.03, 1.73]. Sudden cardiac death was the most common cause of adjudicated CV deaths in the febuxostat group (83 of 3,098; 2.7%) as compared to the allopurinol group (56 of 3,092; 1.8%). Febuxostat was similar to allopurinol for nonfatal MI, nonfatal stroke and unstable angina with urgent coronary revascularization Because of the increased risk of CV death, febuxostat should only be used in patients who have an inadequate response to a maximally titrated dose of allopurinol, who are intolerant to allopurinol, or for whom treatment with allopurinol is not advisable Consider the risks and benefits of febuxostat when deciding to prescribe or continue patients on febuxostat Consider use of prophylactic low-dose aspirin therapy in patients with a history of CV disease. Physicians and patients should remain alert for the development of adverse CV event signs and symptoms. Patients should be informed about the symptoms of serious CV events and the steps to take if they occur. In a cardiovascular (CV) outcome study (ClinicalTrials.gov identifier NCT01101035), gout patients with established CV disease treated with febuxostat had a higher rate of CV death compared to those treated with allopurinol. The CV outcomes study in patients with gout (CARES) was a randomized, double-blinded, allopurinol-controlled, non-inferiority study conducted to evaluate the risk of major adverse cardiovascular events (MACE) in patients with gout who were treated with febuxostat. The study enrolled patients who had a history of major CV disease, cerebrovascular disease or diabetes mellitus with micro-and/or macrovascular disease. The primary endpoint was the time to first occurrence of MACE defined as the composite of CV death, nonfatal MI, nonfatal stroke, or unstable angina with urgent coronary revascularization. The study was designed to exclude a prespecified risk margin of 1.3 for the hazard ratio of MACE. Results showed that febuxostat was non-inferior to allopurinol for the primary endpoint of MACE [Hazard Ratio: 1.03, 95% Confidence Interval (CI): 0.89, 1.21]. However, there was a significant increase in CV deaths in patients treated with febuxostat (134 [1.5 per 100 patient-years]) compared to patients treated with allopurinol (100 [1.1 per 100 patient-years]) [Hazard Ratio: 1.34, 95% CI: 1.03, 1.73]. Sudden cardiac death was the most common cause of adjudicated CV deaths in the febuxostat group (83 of 3,098; 2.7%) as compared to the allopurinol group (56 of 3,092; 1.8%). Febuxostat was similar to allopurinol for nonfatal MI, nonfatal stroke and unstable angina with urgent coronary revascularization [ see Clinical Studies (14.2)]. Because of the increased risk of CV death, febuxostat should only be used in patients who have an inadequate response to a maximally titrated dose of allopurinol, who are intolerant to allopurinol, or for whom treatment with allopurinol is not advisable [ see Indications and Usage(1)]. Consider the risks and benefits of febuxostat when deciding to prescribe or continue patients on febuxostat [ see Indications and Usage (1)]. Consider use of prophylactic low-dose aspirin therapy in patients with a history of CV disease. Physicians and patients should remain alert for the development of adverse CV event signs and symptoms. Patients should be informed about the symptoms of serious CV events and the steps to take if they occur.
5.2 Gout Flares After initiation of febuxostat, an increase in gout flares is frequently observed. This increase is due to reduction in serum uric acid levels, resulting in mobilization of urate from tissue deposits. In order to prevent gout flares when febuxostat is initiated, concurrent prophylactic treatment with an NSAID or colchicine is recommended [ see Dosage and Administration (2.4)].
5.3 Hepatic Effects There have been postmarketing reports of fatal and nonfatal hepatic failure in patients taking febuxostat, although the reports contain insufficient information necessary to establish the probable cause. During randomized controlled studies, transaminase elevations greater than three times the upper limit of normal (ULN) were observed (AST: 2%, 2%, and ALT: 3%, 2% in febuxostat and allopurinol-treated patients, respectively). No dose-effect relationship for these transaminase elevations was noted <span class="opacity-50 text-xs">[see Clinical Pharmacology ( 12.3 )]</span> . Obtain a liver test panel (serum alanine aminotransferase [ALT], aspartate aminotransferase [AST], alkaline phosphatase, and total bilirubin) as a baseline before initiating febuxostat. Measure liver tests promptly in patients who report symptoms that may indicate liver injury, including fatigue, anorexia, right upper abdominal discomfort, dark urine or jaundice. In this clinical context, if the patient is found to have abnormal liver tests (ALT greater than three times the upper limit of the reference range), febuxostat treatment should be interrupted and investigation done to establish the probable cause. Febuxostat should not be restarted in these patients without another explanation for the liver test abnormalities. Patients who have serum ALT greater than three times the reference range with serum total bilirubin greater than two times the reference range without alternative etiologies are at risk for severe drug-induced liver injury and should not be restarted on febuxostat. For patients with lesser elevations of serum ALT or bilirubin and with an alternate probable cause, treatment with febuxostat can be used with caution.
5.4 Serious Skin Reactions Postmarketing reports of serious skin and hypersensitivity reactions, including Stevens-Johnson Syndrome, drug reaction with eosinophilia and systemic symptoms (DRESS) and toxic epidermal necrolysis (TEN) have been reported in patients taking febuxostat. Discontinue febuxostat if serious skin reactions are suspected [ see Patient Counseling Information (17)]. Many of these patients had reported previous similar skin reactions to allopurinol. Febuxostat should be used with caution in these patients.