Side Effects of Uloric (febuxostat)

Uloric (febuxostat) is a xanthine oxidase inhibitor used to treat gout caused by excessive levels of uric acid in the blood (hyperuricemia). 

Uric acid is formed from the breakdown of certain chemicals (purines) in the body. Hyperuricemia occurs when the body produces more uric acid than it can eliminate. The uric acid forms crystals in joints (gouty arthritis) and tissues, causing inflammation and pain. 

Elevated blood uric acid levels also can cause kidney disease and kidney stones. Uloric prevents the production of uric acid by blocking the activity of the enzyme (xanthine oxidase) that converts purines to uric acid. Uric acid levels may fall to target treatment levels within two weeks. 

Uloric and allopurinol (Zyloprim) are similar in how they work, but the maximum dose of Uloric is more effective in reducing uric acid levels. 

Common side effects of Uloric include

• nausea,
• rash,
• joint pain,
• gout flares, and
• liver problems.

Serious side effects of Uloric include

• stroke,
• heart attack,
• anemia,
• hepatitis,
• hypersensitivity, and
• weight loss.

Drug interactions of Uloric include mercaptopurine, azathioprine, and theophylline because Uloric may increase blood levels of these drugs by reducing their breakdown in the body. 

There are no adequate studies of Uloric in pregnant women. It is unknown if Uloric is excreted in human milk. Consult your doctor before breastfeeding.

Common reactions to febuxostat include:

• nausea,
• rash,
• joint pain,
• gout flares, and
• liver problems.

Other important, but less common side effects include:

• stroke,
• heart attack,
• anemia,
• hepatitis,
• hypersensitivity, and
• weight loss.

The following serious adverse reactions are described elsewhere in the prescribing information:

• Cardiovascular Death
• Hepatic Effects
• Serious Skin Reactions

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

In Phase 2 and 3 clinical studies, a total of 2757 patients with hyperuricemia and gout were treated with Uloric 40 mg or 80 mg daily. For Uloric 40 mg, 559 patients were treated for =6 months. For Uloric 80 mg, 1377 patients were treated for =6 months, 674 patients were treated for =1 year and 515 patients were treated for =2 years. In the CARES study, a total of 3098 patients were treated with Uloric 40 mg or 80 mg daily; of these, 2155 patients were treated for =1 year and 1539 were treated for =2 years.

Most Common Adverse Reactions

In three randomized, controlled clinical studies (Studies 1, 2 and 3), which were six to 12 months in duration, the following adverse reactions were reported by the treating physician as related to study drug. Table 1 summarizes adverse reactions reported at a rate of at least 1% in Uloric treatment groups and at least 0.5% greater than placebo.

Table 1: Adverse Reactions Occurring in ≥1% of Patients Treated with Uloric and at Least 0.5% Greater than Seen in Patients Receiving Placebo in Controlled Studies

The most common adverse reaction leading to discontinuation from therapy was liver function abnormalities in 1.8% of Uloric 40 mg, 1.2% of Uloric 80 mg, and in 0.9% of patients treated with allopurinol.

In addition to the adverse reactions presented in Table 1, dizziness was reported in more than 1% of patients treated with Uloric although not at a rate more than 0.5% greater than placebo.

In the CARES study, liver function abnormalities and diarrhea were reported in more than 1% of patients treated with Uloric, although not at a rate more than 0.5% greater than allopurinol.

Less Common Adverse Reactions

In clinical studies the following adverse reactions occurred in less than 1% of patients and in more than one subject treated with doses ranging from 40 mg to 240 mg of Uloric. This list also includes adverse reactions (less than 1% of patients) associated with organ systems from Warnings and Precautions.

• Blood and Lymphatic System Disorders: anemia, idiopathic thrombocytopenic purpura, leukocytosis/leukopenia, neutropenia, pancytopenia, splenomegaly, thrombocytopenia.
• Cardiac Disorders: angina pectoris, atrial fibrillation/flutter, cardiac murmur, ECG abnormal, palpitations, sinus bradycardia, tachycardia.
• Ear and Labyrinth Disorders: deafness, tinnitus, vertigo.
• Eye Disorders: vision blurred.
• Gastrointestinal Disorders: abdominal distention, abdominal pain, constipation, dry mouth, dyspepsia, flatulence, frequent stools, gastritis, gastroesophageal reflux disease, gastrointestinal discomfort, gingival pain, haematemesis, hyperchlorhydria, hematochezia, mouth ulceration, pancreatitis, peptic ulcer, vomiting.
• General Disorders and Administration Site Conditions: asthenia, chest pain/discomfort, edema, fatigue, feeling abnormal, gait disturbance, influenza-like symptoms, mass, pain, thirst.
• Hepatobiliary Disorders: cholelithiasis/cholecystitis, hepatic steatosis, hepatitis, hepatomegaly.
• Immune System Disorder: hypersensitivity.
• Infections and Infestations: herpes zoster.
• Procedural Complications: contusion.
• Metabolism and Nutrition Disorders: anorexia, appetite decreased/increased, dehydration, diabetes mellitus, hypercholesterolemia, hyperglycemia, hyperlipidemia, hypertriglyceridemia, hypokalemia, weight decreased/increased.
• Musculoskeletal and Connective Tissue Disorders: arthritis, joint stiffness, joint swelling, muscle spasms/twitching/tightness/weakness, musculoskeletal pain/stiffness, myalgia.
• Nervous System Disorders: altered taste, balance disorder, cerebrovascular accident, Guillain-Barre syndrome, headache, hemiparesis, hypoesthesia, hyposmia, lacunar infarction, lethargy, mental impairment, migraine, paresthesia, somnolence, transient ischemic attack, tremor.
• Psychiatric Disorders: agitation, anxiety, depression, insomnia, irritability, libido decreased, nervousness, panic attack, personality change.
• Renal and Urinary Disorders: hematuria, nephrolithiasis, pollakiuria, proteinuria, renal failure, renal insufficiency, urgency, incontinence.
• Reproductive System and Breast Changes: breast pain, erectile dysfunction, gynecomastia.
• Respiratory, Thoracic and Mediastinal Disorders: bronchitis, cough, dyspnea, epistaxis, nasal dryness, paranasal sinus hypersecretion, pharyngeal edema, respiratory tract congestion, sneezing, throat irritation, upper respiratory tract infection.
• Skin and Subcutaneous Tissue Disorders: alopecia, angio edema, dermatitis, dermographism, ecchymosis, eczema, hair color changes, hair growth abnormal, hyperhidrosis, peeling skin, petechiae, photosensitivity, pruritus, purpura, skin discoloration/altered pigmentation, skin lesion, skin odor abnormal, urticaria.
• Vascular Disorders: flushing, hot flush, hypertension, hypotension.
• Laboratory Parameters: activated partial thromboplastin time prolonged, creatine increased, bicarbonate decreased, sodium increased, EEG abnormal, glucose increased, cholesterol increased, triglycerides increased, amylase increased, potassium increased, TSH increased, platelet count decreased, hematocrit decreased, hemoglobin decreased, MCV increased, RBC decreased, creatinine increased, blood urea increased, BUN/creatinine ratio increased, creatine phosphokinase (CPK) increased, alkaline phosphatase increased, LDH increased, PSA increased, urine output increased/decreased, lymphocyte count decreased, neutrophil count decreased, WBC increased/decreased, coagulation test abnormal, low density lipoprotein (LDL) increased, prothrombin time prolonged, urinary casts, urine positive for white blood cells and protein.

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of Uloric. 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 to drug exposure.

• Blood and Lymphatic System Disorders: agranulocytosis, eosinophilia.
• Hepatobiliary Disorders: hepatic failure (some fatal), jaundice, serious cases of abnormal liver function test results, liver disorder.
• Immune System Disorders: anaphylaxis, anaphylactic reaction.
• Musculoskeletal and Connective Tissue Disorders: rhabdomyolysis.
• Psychiatric Disorders: psychotic behavior including aggressive thoughts.
• Renal and Urinary Disorders: tubulointerstitial nephritis.
• Skin and Subcutaneous Tissue Disorders: generalized rash, Stevens-Johnson Syndrome, hypersensitivity skin reactions, erythema multiforme, drug reaction with eosinophilia and systemic symptoms, toxic epidermal necrolysis.

Xanthine Oxidase Substrate Drugs

• Uloric 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. Therefore, use with caution when coadministering Uloric with theophylline.
• Drug interaction studies of Uloric with other drugs that are metabolized by XO (e.g., mercaptopurine and azathioprine) have not been conducted. Inhibition of XO by Uloric may cause increased plasma concentrations of these drugs leading to toxicity. Uloric is contraindicated in patients being treated with azathioprine or mercaptopurine.

Cytotoxic Chemotherapy Drugs

• Drug interaction studies of Uloric with cytotoxic chemotherapy have not been conducted.
• No data are available regarding the safety of Uloric during cytotoxic chemotherapy.

In Vivo Drug Interaction Studies

• Based on drug interaction studies in healthy patients, Uloric does not have clinically significant interactions with colchicine, naproxen, indomethacin, hydrochlorothiazide, warfarin or desipramine.
• Therefore, Uloric may be used concomitantly with these medications.