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Cardiovascular disorders: In patients with pre-existing major cardiovascular diseases (e.g. myocardial infarction, stroke or unstable angina), during the development of the product and in one post registrational study (CARES), a higher number of fatal cardiovascular events were observed with febuxostat when compared to allopurinol. However, in a subsequent post registrational study (FAST), febuxostat was not inferior to allopurinol in the incidence of both fatal and non-fatal cardiovascular events.
Treatment of this patient group should be exercised cautiously and they should be monitored regularly.
Medicinal product allergy/hypersensitivity: Rare reports of serious allergic/hypersensitivity reactions, including life-threatening Stevens-Johnson syndrome, toxic epidermal necrolysis and acute anaphylactic reaction/shock, have been collected in the post-marketing experience. In most cases, these reactions occurred during the first month of therapy with febuxostat. Some, but not all of these patients reported renal impairment and/or previous hypersensitivity to allopurinol. Severe hypersensitivity reactions, including drug reaction with eosinophilia and systemic symptoms (DRESS) were associated with fever, haematological, renal or hepatic involvement in some cases.
Patients should be advised of the signs and symptoms and monitored closely for symptoms of allergic/hypersensitivity reactions. Febuxostat treatment should be immediately stopped if serious allergic/hypersensitivity reactions, including Stevens-Johnson syndrome, occur since early withdrawal is associated with a better prognosis. If patient has developed allergic/hypersensitivity reactions including Stevens-Johnson syndrome and acute anaphylactic reaction/shock, febuxostat must not be re-started in this patient at any time.
Acute gouty attacks (gout flare): Febuxostat treatment should not be started until an acute attack of gout has completely subsided. Gout flares may occur during initiation of treatment due to changing serum uric acid levels resulting in mobilisation of urate from tissue deposits. At treatment initiation with febuxostat, flare prophylaxis for at least 6 months with an NSAID or colchicine is recommended.
If a gout flare occurs during febuxostat treatment, it should not be discontinued. The gout flare should be managed concurrently as appropriate for the individual patient. Continuous treatment with febuxostat decreases frequency and intensity of gout flares.
Xanthine deposition: In patients in whom the rate of urate formation is greatly increased (e.g. malignant disease and its treatment, Lesch-Nyhan syndrome), the absolute concentration of xanthine in urine could, in rare cases, rise sufficiently to allow deposition in the urinary tract. As there has been no experience with febuxostat, its use in these populations is not recommended.
Mercaptopurine/azathioprine: Febuxostat use is not recommended in patients concomitantly treated with mercaptopurine/azathioprine as inhibition of xanthine oxidase by febuxostat may cause increased plasma concentrations of mercaptopurine/azathioprine that could result in severe toxicity.
Where the combination cannot be avoided, a reduction of the dose of mercaptopurine/azathioprine is recommended. Based on modelling and simulation analysis of data from a pre-clinical study in rats, when co-administered with febuxostat, the dose of mercaptopurine/azathioprine should be reduced to the 20% or less of the previously prescribed dose in order to avoid possible haematological effects.
The patients should be closely monitored and the dose of mercaptopurine/azathioprine should be subsequently adjusted based on the evaluation of the therapeutic response and the onset of eventual toxic effects.
Organ transplant recipients: As there has been no experience in organ transplant recipients, the use of febuxostat in such patients is not recommended.
Theophylline: Co-administration of febuxostat 80 mg and theophylline 400 mg single dose in healthy subjects showed absence of any pharmacokinetic interaction. Febuxostat 80 mg can be used in patients concomitantly treated with theophylline without risk of increasing theophylline plasma levels.
Liver disorders: During the combined phase 3 clinical studies, mild liver function test abnormalities were observed in patients treated with febuxostat (5.0%). Liver function test is recommended prior to the initiation of therapy with febuxostat and periodically thereafter based on clinical judgment.
Thyroid disorders: Increased TSH values (>5.5 μIU/ml) were observed in patients on long-term treatment with febuxostat (5.5%) in the long-term open label extension studies. Caution is required when febuxostat is used in patients with alteration of thyroid function.
Lactose: Febuxostat tablets contain lactose. Patients with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption should not take this medicine.
Sodium: This medicinal product contains less than 1 mmol sodium (23 mg) per tablet, that is to say essentially 'sodium-free'.
Effects on ability to drive and use machines: Somnolence, dizziness, paraesthesia and blurred vision have been reported with the use of febuxostat. Patients should exercise caution before driving, using machinery or participating in dangerous activities until they are reasonably certain that febuxostat does not adversely affect performance.
