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Allopurinol tablets are indicated for: • The management of adults with signs and symptoms of primary or secondary gout (acute attacks, tophi, joint destruction, uric acid lithiasis, and/or nephropathy) • The management of adult and pediatric patients with leukemia, lymphoma and solid tumor malignancies who are receiving cancer therapy which causes elevations of serum and urinary uric acid levels • The management of adult patients with recurrent calcium oxalate calculi whose daily uric acid excretion exceeds 800 mg/day in male patients and 750 mg/day in female patients, despite lifestyle changes (such as reduction of dietary sodium, non-dairy animal protein, oxylate rich foods, refined sugars and increases in oral fluids and fruits and vegetables) Limitations of Use Allopurinol tablets are not recommended for the treatment of asymptomatic hyperuricemia.

• Gout : Prior to initiating treatment assess serum uric acid level, complete blood count, chemistry panel, liver and kidney function tests. Prophylactic treatment for gout flares is recommended. ( 2.1 , 2.2 ) o Patients with normal kidney function: Initial dosage is 100 mg orally daily. Increase by 100 mg weekly increments until serum uric acid of 6 mg/dl or less is reached (maximum 800 mg daily). ( 2.3 ) o Patients with impaired kidney function:  The initial dosage is 50 mg orally daily. Follow recommendations for titration in patients with renal impairment until target serum uric acid level is reached. ( 2.6 ) o See complete information in the Full Prescribing Information (FPI). • Hyperuricemia Associated with Cancer Therapy : The recommended dosage is: o Adults: 300 mg to 800 mg orally daily. o Pediatric patients: 100 mg/m 2 orally every 8 hours to 12 hours (10 mg/kg/day, maximum 800 mg/day) o See complete information in the FPI. ( 2.4 , 2.6 ) • Recurrent Calcium Oxalate Calculi : The recommended initial dosage in patients with normal kidney function is 200 mg to 300 mg orally daily. ( 2.5 ) • Dosage in Patients with Renal Impairment: See FPI for dosage modifications in patients with renal impairment. ( 2.6 )

How Supplied Allopurinol Tablets, USP Presentations 100-mg (white to off white) round, biconvex, uncoated tablet with inscription "AW" on one side and breakline on the other side, in bottles of; 30 (NDC 68788-7383-3) and 60 (NDC 68788-7383-6), Bottles of 90 (NDC 68788-7383-9).). Storage and Handling Store at 20°C to 25°C (USP Controlled Room Temperature) (68°F to 77°F) in a dry place. Dispense in a tight container as defined in the USP.

Allopurinol tablets are contraindicated in patients with a history of hypersensitivity reaction to allopurinol or to any of the ingredients of allopurinol tablets.

Allopurinol is a xanthine oxidase inhibitor. It has the following structural formula: Allopurinol is known chemically as 1, 5-dihydro-4 H -pyrazolo [3, 4- d ]pyrimidin-4-one and it has a molecular weight of 136.11 g/mol. Its solubility in water at 37°C is 80.0 mg/dL and is greater in an alkaline solution. It is a xanthine oxidase inhibitor which is administered orally. Each white to off white tablet contains 100 mg or 300 mg of allopurinol and the inactive ingredients lactose, crospovidone, magnesium stearate, maize starch, and povidone.

• The following drugs may increase the risk of serious skin reactions: bendamustine, thiazide diuretics, ampicillin and amoxicillin. ( 7.1 ) • Capecitabine: Avoid concomitant use. ( 7.2 ) • Mercaptopurine or Azathioprine: Reduce mercaptopurine or azathioprine dose as recommended in the respective prescribing information. ( 7.2 ) • Pegloticase: Discontinue and refrain from initiating treatment with allopurinol tablets. ( 7.2 ) • See FPI for complete list of significant drug interactions. ( 7.2 )

Administration Advise patients to take allopurinol tablets after meals to minimize gastric irritation. If a single dose of allopurinol tablet is occasionally forgotten, there is no need to double the dose at the next scheduled time. Skin Rash and Hypersensitivity Inform patients that allopurinol tablets may increase the risk of serious and sometimes fatal dermatologic reactions. Instruct patients to discontinue allopurinol tablets and to seek medical attention immediately, at the first sign of a skin rash, blisters, fever, painful urination, blood in the urine, irritation of the eyes, swelling of the lips or mouth, or other signs and symptoms of hypersensitivity reactions [ see Warnings and Precautions (5.1) ]. Gout Flares During Treatment With Allopurinol Tablets Inform patients that gout flares may occur during initiation of treatment with allopurinol tablets, even when their serum uric acid is normal. Concurrent use of additional medications such as colchicine or other anti-inflammatory agents can prevent gout flares. Advise patients to continue treatment with both, allopurinol tablets and the prophylactic therapy as prescribed, even if gout flares occur. Reassure them that it may take months to achieve control of the flares but the flares typically become shorter and less severe after several months of therapy [ see Warnings and Precautions (5.2) ]. Nephrotoxicity Inform patients that allopurinol tablets may affect kidney function. Advise them to increase fluid intake during therapy (i.e., for adults, at least 2 liters of liquids per day) and to stay well hydrated to prevent kidney stones [ see Warnings and Precautions (5.3) ]. Hepatotoxicity Inform patients of the risk of hepatotoxicity and to report to their healthcare provider any signs and symptoms of liver failure, including jaundice, pruritus, bleeding, bruising, or anorexia [ see Warnings and Precautions (5.4) ]. Myelosuppression Advise patients of the risk of myelosuppression and to report any signs and symptoms of infection, fever, bleeding, shortness of breath, or significant fatigue to their healthcare provider [ see Warnings and Precautions (5.5) ]. Potential Effect on Driving and Use of Machinery Inform patients that drowsiness, somnolence and dizziness have been reported in patients taking allopurinol tablets. Inform also that the central nervous system depressant effects of allopurinol tablets may be additive to those of alcohol and other CNS depressants. Advise patients to avoid operation of automobiles or other dangerous machinery and activities made hazardous by decreased alertness when starting allopurinol tablets or increasing the dose, until they know how the drug affects them [ see Warnings and Precautions (5.6) ]. Risks Associated with Use of Concomitant Medications Inform patients that there are risks of adverse effects when allopurinol tablets are used with the following drugs: dicumarol, warfarin, sulfinpyrazone, mercaptopurine, azathioprine, ampicillin, amoxicillin, pegloticase, theophylline, and thiazide diuretics. Advise patients to disclose all medications in use and they should follow the instructions of their physician [ see Drug Interactions (7.2) ]. Pregnancy Advise pregnant women of the potential risk to a fetus. Advise women to notify their healthcare provider if they become pregnant or intend to become pregnant during treatment with allopurinol tablets [ see Use in Specific Populations (8.1) ]. Lactation Advise women not to breastfeed during treatment with allopurinol tablets and for one week after the last dose [ see Use in Specific Populations (8.2) ]. For more information, go to www.accordhealthcare.us or call Accord Healthcare Inc. at 1-866-941-7875. Manufactured For: Accord Healthcare, Inc., 8041 Arco Corporate Drive, Suite 200, Raleigh, NC 27617, USA. Manufactured By: Intas Pharmaceuticals Limited, Ahmedabad-380 054, India. 10 0258 2 6027034 Issued December 2023 Repackaged By: Preferred Pharmaceuticals Inc.

Risk Summary Allopurinol and oxypurinol are present in human milk. Based on information from a single case report, allopurinol and its active metabolite, oxypurinol, were detected in the milk of a mother receiving 300 mg of allopurinol daily at 5 weeks postpartum. The estimated relative infant dose were 0.14 mg/kg and 0.2 mg/kg of allopurinol and between 7.2 mg/kg to 8 mg/kg of oxypurinol daily. There was no report of effects of allopurinol on the breastfed infant or on milk production. Because of the potential for serious adverse reactions in a breastfed child, advise women not to breastfeed during treatments with allopurinol and for one week after the last dose.

Hyperuricemia Associated with Cancer Therapy The safety and effectiveness of allopurinol for the management of pediatric patients with leukemia, lymphoma and solid tumor malignancies who are receiving cancer therapy which causes elevations of serum and urinary uric acid levels have been established in approximately 200 pediatric patients. The efficacy and safety profile observed in this patient population were similar to that observed in adults. Primary or Secondary Gout The safety and effectiveness of allopurinol have not been established for the treatment of signs and symptoms of primary or secondary gout in pediatric patients. Recurrent Calcium Oxalate Calculi The safety and effectiveness of allopurinol have not been established for the management of pediatric patients with recurrent calcium oxalate calculi. Inborn Errors of Metabolism The safety and effectiveness of allopurinol have not been established in pediatric patients with rare inborn errors of purine metabolism.

No evidence of tumorigenicity was observed in male or female mice or rats that received oral allopurinol for the majority of their life spans (greater than 88 weeks) at doses up to 20 mg/kg/day (0.1 and 0.2 times the MRHD on a mg/m 2 basis in mice and rats, respectively). Allopurinol tested negative in the following genotoxicity assays: the in vitro Ames assay, in vitro mouse lymphoma assay, and in vivo rat bone marrow micronucleus assay. Allopurinol administered intravenously to rats (50 mg/kg) was not incorporated into rapidly replicating intestinal DNA. No evidence of clastogenicity was observed in lymphocytes taken from patients treated with allopurinol (mean duration of treatment 40 months), or in an in vitro assay with human lymphocytes. Allopurinol oral doses of 20 mg/kg/day had no effect on male or female fertility in rats or rabbits (approximately 0.2 or 0.5 times the MRHD on a mg/m 2 basis, respectively).

The following clinically significant adverse reactions are described elsewhere in the labeling: • Skin Rash and Hypersensitivity [ see Warnings and Precautions (5.1) ] • Nephrotoxicity [ see Warnings and Precautions (5.3) ] • Hepatoxicity [ see Warnings and Precautions (5.4) ] • Myelosuppression [ see Warnings and Precautions (5.5) ] • Potential Effect on Driving and Use of Machinery [ see Warnings and Precautions (5.6) ] The following adverse reactions associated with the use of allopurinol were identified in literature, unpublished clinical trials or postmarketing reports.  Because some of these reactions were 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. The most frequent adverse reaction to allopurinol is skin rash.  Most Common Adverse Reactions (≥ 1%) Gastrointestinal : Diarrhea, nausea, alkaline phosphatase increase, AST/ALT increase. Metabolic and Nutritional : Acute attacks of gout. Skin and Appendages : Rash, maculopapular rash. Less Common Adverse Reactions ( < 1%) Body As a Whole : Ecchymosis, fever, headache, malaise. Cardiovascular : Necrotizing angiitis, vasculitis, pericarditis, peripheral vascular disease, thrombophlebitis, bradycardia, vasodilation. Gastrointestinal : Hepatic necrosis, granulomatous hepatitis, hepatomegaly, hyperbilirubinemia, cholestatic jaundice, vomiting, intermittent abdominal pain, gastritis, dyspepsia, hemorrhagic pancreatitis, gastrointestinal bleeding, stomatitis, salivary gland swelling, hyperlipidemia, tongue edema, anorexia. Hemic and Lymphatic : Thrombocytopenia, eosinophilia, leukocytosis, leukopenia, aplastic anemia, agranulocytosis, eosinophilic fibrohistiocytic lesion of bone marrow, pancytopenia, prothrombin decrease, anemia, hemolytic anemia, reticulocytosis, lymphadenopathy, lymphocytosis. Musculoskeletal : Myopathy, arthralgias, myalgia. Nervous : Peripheral neuropathy, neuritis, paresthesia, somnolence, optic neuritis, confusion, dizziness, vertigo, foot drop, decrease in libido, depression, amnesia, tinnitus, asthenia, insomnia. Respiratory : Epistaxis, bronchospasm, asthma, pharyngitis, rhinitis. Skin and Appendages : Erythema multiforme exudativum (Stevens-Johnson syndrome), toxic epidermal necrolysis (Lyell's syndrome), hypersensitivity vasculitis, purpura, vesicular bullous dermatitis, exfoliative dermatitis, eczematoid dermatitis, pruritus, urticaria, alopecia, onycholysis, lichen planus, furunculosis, facial edema, sweating, skin edema. Special Senses : Taste loss/perversion, cataracts, macular retinitis, iritis, conjunctivitis, amblyopia. Urogenital : Renal failure, uremia, nephritis, impotence, primary hematuria, albuminuria. Endocrine : Infertility (male), hypercalcemia, gynecomastia (male).

In the management of overdosage there is no specific antidote for allopurinol. Both allopurinol and oxipurinol are dialyzable; however, the usefulness of hemodialysis or peritoneal dialysis in the management of an overdose of allopurinol is unknown.

Risk Summary Based on findings in animals, allopurinol may cause fetal harm when administered to a pregnant woman. Adverse developmental outcomes have been described in exposed animals ( see Data ). Allopurinol and its metabolite oxypurinol have been shown to cross the placenta following administration of maternal allopurinol. Available limited published data on allopurinol use in pregnant women do not demonstrate a clear pattern or increase in frequency of adverse developmental outcomes. Among approximately 50 pregnancies described in published literature, 2 infants with major congenital malformations have been reported with following maternal allopurinol exposure. Advise pregnant women of the potential risk to a fetus. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Data Human Data Experience with allopurinol during human pregnancy has been limited partly because women of reproductive age rarely require treatment with allopurinol. A case report published in 2011 described the outcome of a full-term pregnancy in a 35-year-old woman who had recurrent kidney stones since age 18 who took allopurinol throughout the pregnancy. The child had multiple complex birth defects and died at 8 days of life. A second report in 2013 provided data on 31 prospectively ascertained pregnancies involving mothers exposed to allopurinol for varying durations during the first trimester. The overall rate of major fetal malformations and spontaneous abortions was reported to be within the normal expected range; however, one child had severe malformations similar to those described in the cited earlier case report. Animal Data There was no evidence of fetotoxicity or teratogenicity in rats or rabbits treated during the period of organogenesis with oral allopurinol at doses up to 200 mg/kg/day and up to 100 mg/kg/day, respectively (about 2.4 times the human dose on a mg/m 2 basis). However, there is a published report in pregnant mice that single intraperitoneal doses of 50 mg/kg or 100 mg/kg (about 0.3 or 0.6 times the human dose on a mg/m 2 basis) of allopurinol on gestation days 10 or 13 produced significant increases in fetal deaths and teratogenic effects (cleft palate, harelip, and digital defects). It is uncertain whether these findings represented a fetal effect or an effect secondary to maternal toxicity.

Prior to initiating treatment with allopurinol tablets in patients with gout, assess the following baseline tests: serum uric acid level, complete blood count, chemistry panel, liver function tests (serum alanine aminotransferase [ALT], aspartate aminotransferase [AST] , alkaline phosphatase, and total bilirubin), kidney function tests (serum creatinine and eGFR).

Allopurinol tablets, USP have functional scoring and are available in the following strengths: • 100 mg: White to off white round, biconvex, uncoated tablet with inscription "AW" on one side and breakline on the other side. • 300 mg: White to off white round, biconvex with beveled edge, uncoated tablet with inscription "AX" on one side and breakline on the other side.

Allopurinol is a structural analogue of the natural purine base, hypoxanthine. Allopurinol acts on purine catabolism, without disrupting the biosynthesis of purines. It reduces the production of uric acid by inhibiting the biochemical reactions immediately preceding its formation. It is an inhibitor of xanthine oxidase, the enzyme responsible for the conversion of hypoxanthine to xanthine and of xanthine to uric acid, the end product of purine metabolism in humans. Allopurinol is metabolized to the corresponding xanthine analogue, oxypurinol (alloxanthine), which also is an inhibitor of xanthine oxidase.

Allopurinol reduces the production of uric acid by inhibiting the biochemical reactions immediately preceding its formation in a dose dependent manner. The pharmacological action of allopurinol is generally believed to be mediated by its oxypurinol metabolite. Effect on Hypoxanthine and Xanthine Reutilization of both hypoxanthine and xanthine for nucleotide and nucleic acid synthesis is markedly enhanced when their oxidations are inhibited by allopurinol and oxipurinol. This reutilization does not disrupt normal nucleic acid anabolism, however, because feedback inhibition is an integral part of purine biosynthesis. As a result of xanthine oxidase inhibition, the serum concentration of hypoxanthine plus xanthine in patients receiving allopurinol for treatment of hyperuricemia is usually in the range of 0.3 mg/dL to 0.4 mg/dL compared to a normal level of approximately 0.15 mg/dL. A maximum of 0.9 mg/dL of these oxypurines has been reported when the serum urate was lowered to less than 2 mg/dL by high doses of allopurinol. These values are far below the saturation levels at which point their precipitation would be expected to occur (above 7 mg/dL). The increased xanthine and hypoxanthine in the urine in patients who were treated with oral allopurinol have not been accompanied by problems of nephrolithiasis; however, there are isolated case reports of xanthine crystalluria. Drug Interaction Studies Fluorouracil : Based on non-clinical data, allopurinol may decrease anti-tumor activity due to suppression of phosphorylation of 5-fluorouracil. Pegloticase : Concomitant use of allopurinol and pegloticase may potentially blunt the rise of serum uric acid levels required for monitoring the safe use of pegloticase. Cytotoxic Agents : Enhanced bone marrow suppression by cyclophosphamide and other cytotoxic agents has been reported among patients with neoplastic disease, except leukemia, in the presence of allopurinol. Thiazide Diuretics : Reports that the concomitant administration of allopurinol and thiazide diuretics contributed to increased allopurinol toxicity were reviewed; however, a causal mechanism or cause-and-effect relationship was not found.

Absorption Allopurinol is approximately 90% absorbed from the gastrointestinal tract. Peak plasma levels generally occur at 1.5 hours and 4.5 hours for allopurinol and oxipurinol respectively. After a single oral dose of 300 mg allopurinol, maximum plasma levels of about 3 mcg/mL of allopurinol and 6.5 mcg/mL of oxipurinol are produced. Elimination The half-life of allopurinol and oxipurinol are approximately 1 hour to 2 hours and 15 hours following oral dose of allopurinol, respectively. Metabolism Allopurinol is metabolized to the corresponding xanthine analogue, oxypurinol (alloxanthine), which also is an inhibitor of xanthine oxidase. Excretion Allopurinol and its primary active metabolite, oxipurinol, are eliminated by the kidneys. Approximately 20% of the ingested allopurinol is excreted in the feces. Oxipurinol is primarily eliminated unchanged in urine by glomerular filtration and tubular reabsorption. Drug Interaction Studies Capecitabine : Concomitant use with allopurinol may decrease concentration of capecitabine’s active metabolites, which may decrease capecitabine efficacy. Cyclosporine : Concomitant use of allopurinol increases cyclosporine concentrations which may increase the risk of adverse reactions. Mercaptopurine or Azathioprine : Allopurinol inhibits xanthine oxidase mediated metabolism of mercaptopurine and azathioprine. Concomitant use of allopurinol increases the exposure of either mercaptopurine or azathioprine which may increase the risk of their adverse reactions including myelosuppression. Theophylline : Concomitant use of allopurinol doses greater than or equal to 600 mg/day may decrease the clearance of theophylline. Uricosuric Agents : Uricosuric agents increase the excretion of the active allopurinol metabolite oxypurinol. Concomitant use with uricosuric agents decreases oxypurinol exposure which may reduce the inhibition of xanthine oxidase by oxypurinol and increases the urinary excretion of uric acid. Warfarin : Allopurinol may inhibit the metabolism of warfarin, possibly enhancing its anticoagulant effect.

• Pregnancy: May cause fetal harm. ( 8.1 ) • Lactation: Advise not to breastfeed. ( 8.2 )

• Skin Rash and Hypersensitivity: Allopurinol has been associated with serious and sometimes fatal dermatological reactions. Discontinue allopurinol tablets at the first appearance of skin rash or other signs of hypersensitivity reaction. ( 5.1 ) • Gout Flares: May occur during initiation of treatment. Concurrent prophylactic treatment with colchicine or anti-inflammatory agents is recommended.  ( 5.2 ) • Nephrotoxicity: Allopurinol may affect kidney function. Patients with decreased kidney function require lower doses of allopurinol tablets. ( 5.3 ) • Hepatoxicity: Cases of reversible hepatotoxicity have occurred. If signs and symptoms of hepatotoxicity develop, evaluate liver function. ( 5.4 ) • Myelosuppression: Bone marrow suppression has been reported with allopurinol. ( 5.5 ) • Potential Effect on Driving and Use of Machinery: Drowsiness, somnolence and dizziness have been reported in patients taking allopurinol. ( 5.6 )

100 mg

Allopurinol tablets are indicated for: • The management of adults with signs and symptoms of primary or secondary gout (acute attacks, tophi, joint destruction, uric acid lithiasis, and/or nephropathy) • The management of adult and pediatric patients with leukemia, lymphoma and solid tumor malignancies who are receiving cancer therapy which causes elevations of serum and urinary uric acid levels • The management of adult patients with recurrent calcium oxalate calculi whose daily uric acid excretion exceeds 800 mg/day in male patients and 750 mg/day in female patients, despite lifestyle changes (such as reduction of dietary sodium, non-dairy animal protein, oxylate rich foods, refined sugars and increases in oral fluids and fruits and vegetables) Limitations of Use Allopurinol tablets are not recommended for the treatment of asymptomatic hyperuricemia.

• Gout : Prior to initiating treatment assess serum uric acid level, complete blood count, chemistry panel, liver and kidney function tests. Prophylactic treatment for gout flares is recommended. ( 2.1 , 2.2 ) o Patients with normal kidney function: Initial dosage is 100 mg orally daily. Increase by 100 mg weekly increments until serum uric acid of 6 mg/dl or less is reached (maximum 800 mg daily). ( 2.3 ) o Patients with impaired kidney function:  The initial dosage is 50 mg orally daily. Follow recommendations for titration in patients with renal impairment until target serum uric acid level is reached. ( 2.6 ) o See complete information in the Full Prescribing Information (FPI). • Hyperuricemia Associated with Cancer Therapy : The recommended dosage is: o Adults: 300 mg to 800 mg orally daily. o Pediatric patients: 100 mg/m 2 orally every 8 hours to 12 hours (10 mg/kg/day, maximum 800 mg/day) o See complete information in the FPI. ( 2.4 , 2.6 ) • Recurrent Calcium Oxalate Calculi : The recommended initial dosage in patients with normal kidney function is 200 mg to 300 mg orally daily. ( 2.5 ) • Dosage in Patients with Renal Impairment: See FPI for dosage modifications in patients with renal impairment. ( 2.6 )

How Supplied Allopurinol Tablets, USP Presentations 100-mg (white to off white) round, biconvex, uncoated tablet with inscription "AW" on one side and breakline on the other side, in bottles of; 30 (NDC 68788-7383-3) and 60 (NDC 68788-7383-6), Bottles of 90 (NDC 68788-7383-9).). Storage and Handling Store at 20°C to 25°C (USP Controlled Room Temperature) (68°F to 77°F) in a dry place. Dispense in a tight container as defined in the USP.

Allopurinol tablets are contraindicated in patients with a history of hypersensitivity reaction to allopurinol or to any of the ingredients of allopurinol tablets.

• The following drugs may increase the risk of serious skin reactions: bendamustine, thiazide diuretics, ampicillin and amoxicillin. ( 7.1 ) • Capecitabine: Avoid concomitant use. ( 7.2 ) • Mercaptopurine or Azathioprine: Reduce mercaptopurine or azathioprine dose as recommended in the respective prescribing information. ( 7.2 ) • Pegloticase: Discontinue and refrain from initiating treatment with allopurinol tablets. ( 7.2 ) • See FPI for complete list of significant drug interactions. ( 7.2 )

Administration Advise patients to take allopurinol tablets after meals to minimize gastric irritation. If a single dose of allopurinol tablet is occasionally forgotten, there is no need to double the dose at the next scheduled time. Skin Rash and Hypersensitivity Inform patients that allopurinol tablets may increase the risk of serious and sometimes fatal dermatologic reactions. Instruct patients to discontinue allopurinol tablets and to seek medical attention immediately, at the first sign of a skin rash, blisters, fever, painful urination, blood in the urine, irritation of the eyes, swelling of the lips or mouth, or other signs and symptoms of hypersensitivity reactions [ see Warnings and Precautions (5.1) ]. Gout Flares During Treatment With Allopurinol Tablets Inform patients that gout flares may occur during initiation of treatment with allopurinol tablets, even when their serum uric acid is normal. Concurrent use of additional medications such as colchicine or other anti-inflammatory agents can prevent gout flares. Advise patients to continue treatment with both, allopurinol tablets and the prophylactic therapy as prescribed, even if gout flares occur. Reassure them that it may take months to achieve control of the flares but the flares typically become shorter and less severe after several months of therapy [ see Warnings and Precautions (5.2) ]. Nephrotoxicity Inform patients that allopurinol tablets may affect kidney function. Advise them to increase fluid intake during therapy (i.e., for adults, at least 2 liters of liquids per day) and to stay well hydrated to prevent kidney stones [ see Warnings and Precautions (5.3) ]. Hepatotoxicity Inform patients of the risk of hepatotoxicity and to report to their healthcare provider any signs and symptoms of liver failure, including jaundice, pruritus, bleeding, bruising, or anorexia [ see Warnings and Precautions (5.4) ]. Myelosuppression Advise patients of the risk of myelosuppression and to report any signs and symptoms of infection, fever, bleeding, shortness of breath, or significant fatigue to their healthcare provider [ see Warnings and Precautions (5.5) ]. Potential Effect on Driving and Use of Machinery Inform patients that drowsiness, somnolence and dizziness have been reported in patients taking allopurinol tablets. Inform also that the central nervous system depressant effects of allopurinol tablets may be additive to those of alcohol and other CNS depressants. Advise patients to avoid operation of automobiles or other dangerous machinery and activities made hazardous by decreased alertness when starting allopurinol tablets or increasing the dose, until they know how the drug affects them [ see Warnings and Precautions (5.6) ]. Risks Associated with Use of Concomitant Medications Inform patients that there are risks of adverse effects when allopurinol tablets are used with the following drugs: dicumarol, warfarin, sulfinpyrazone, mercaptopurine, azathioprine, ampicillin, amoxicillin, pegloticase, theophylline, and thiazide diuretics. Advise patients to disclose all medications in use and they should follow the instructions of their physician [ see Drug Interactions (7.2) ]. Pregnancy Advise pregnant women of the potential risk to a fetus. Advise women to notify their healthcare provider if they become pregnant or intend to become pregnant during treatment with allopurinol tablets [ see Use in Specific Populations (8.1) ]. Lactation Advise women not to breastfeed during treatment with allopurinol tablets and for one week after the last dose [ see Use in Specific Populations (8.2) ]. For more information, go to www.accordhealthcare.us or call Accord Healthcare Inc. at 1-866-941-7875. Manufactured For: Accord Healthcare, Inc., 8041 Arco Corporate Drive, Suite 200, Raleigh, NC 27617, USA. Manufactured By: Intas Pharmaceuticals Limited, Ahmedabad-380 054, India. 10 0258 2 6027034 Issued December 2023 Repackaged By: Preferred Pharmaceuticals Inc.

Risk Summary Allopurinol and oxypurinol are present in human milk. Based on information from a single case report, allopurinol and its active metabolite, oxypurinol, were detected in the milk of a mother receiving 300 mg of allopurinol daily at 5 weeks postpartum. The estimated relative infant dose were 0.14 mg/kg and 0.2 mg/kg of allopurinol and between 7.2 mg/kg to 8 mg/kg of oxypurinol daily. There was no report of effects of allopurinol on the breastfed infant or on milk production. Because of the potential for serious adverse reactions in a breastfed child, advise women not to breastfeed during treatments with allopurinol and for one week after the last dose.

Hyperuricemia Associated with Cancer Therapy The safety and effectiveness of allopurinol for the management of pediatric patients with leukemia, lymphoma and solid tumor malignancies who are receiving cancer therapy which causes elevations of serum and urinary uric acid levels have been established in approximately 200 pediatric patients. The efficacy and safety profile observed in this patient population were similar to that observed in adults. Primary or Secondary Gout The safety and effectiveness of allopurinol have not been established for the treatment of signs and symptoms of primary or secondary gout in pediatric patients. Recurrent Calcium Oxalate Calculi The safety and effectiveness of allopurinol have not been established for the management of pediatric patients with recurrent calcium oxalate calculi. Inborn Errors of Metabolism The safety and effectiveness of allopurinol have not been established in pediatric patients with rare inborn errors of purine metabolism.

No evidence of tumorigenicity was observed in male or female mice or rats that received oral allopurinol for the majority of their life spans (greater than 88 weeks) at doses up to 20 mg/kg/day (0.1 and 0.2 times the MRHD on a mg/m 2 basis in mice and rats, respectively). Allopurinol tested negative in the following genotoxicity assays: the in vitro Ames assay, in vitro mouse lymphoma assay, and in vivo rat bone marrow micronucleus assay. Allopurinol administered intravenously to rats (50 mg/kg) was not incorporated into rapidly replicating intestinal DNA. No evidence of clastogenicity was observed in lymphocytes taken from patients treated with allopurinol (mean duration of treatment 40 months), or in an in vitro assay with human lymphocytes. Allopurinol oral doses of 20 mg/kg/day had no effect on male or female fertility in rats or rabbits (approximately 0.2 or 0.5 times the MRHD on a mg/m 2 basis, respectively).

The following clinically significant adverse reactions are described elsewhere in the labeling: • Skin Rash and Hypersensitivity [ see Warnings and Precautions (5.1) ] • Nephrotoxicity [ see Warnings and Precautions (5.3) ] • Hepatoxicity [ see Warnings and Precautions (5.4) ] • Myelosuppression [ see Warnings and Precautions (5.5) ] • Potential Effect on Driving and Use of Machinery [ see Warnings and Precautions (5.6) ] The following adverse reactions associated with the use of allopurinol were identified in literature, unpublished clinical trials or postmarketing reports.  Because some of these reactions were 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. The most frequent adverse reaction to allopurinol is skin rash.  Most Common Adverse Reactions (≥ 1%) Gastrointestinal : Diarrhea, nausea, alkaline phosphatase increase, AST/ALT increase. Metabolic and Nutritional : Acute attacks of gout. Skin and Appendages : Rash, maculopapular rash. Less Common Adverse Reactions ( < 1%) Body As a Whole : Ecchymosis, fever, headache, malaise. Cardiovascular : Necrotizing angiitis, vasculitis, pericarditis, peripheral vascular disease, thrombophlebitis, bradycardia, vasodilation. Gastrointestinal : Hepatic necrosis, granulomatous hepatitis, hepatomegaly, hyperbilirubinemia, cholestatic jaundice, vomiting, intermittent abdominal pain, gastritis, dyspepsia, hemorrhagic pancreatitis, gastrointestinal bleeding, stomatitis, salivary gland swelling, hyperlipidemia, tongue edema, anorexia. Hemic and Lymphatic : Thrombocytopenia, eosinophilia, leukocytosis, leukopenia, aplastic anemia, agranulocytosis, eosinophilic fibrohistiocytic lesion of bone marrow, pancytopenia, prothrombin decrease, anemia, hemolytic anemia, reticulocytosis, lymphadenopathy, lymphocytosis. Musculoskeletal : Myopathy, arthralgias, myalgia. Nervous : Peripheral neuropathy, neuritis, paresthesia, somnolence, optic neuritis, confusion, dizziness, vertigo, foot drop, decrease in libido, depression, amnesia, tinnitus, asthenia, insomnia. Respiratory : Epistaxis, bronchospasm, asthma, pharyngitis, rhinitis. Skin and Appendages : Erythema multiforme exudativum (Stevens-Johnson syndrome), toxic epidermal necrolysis (Lyell's syndrome), hypersensitivity vasculitis, purpura, vesicular bullous dermatitis, exfoliative dermatitis, eczematoid dermatitis, pruritus, urticaria, alopecia, onycholysis, lichen planus, furunculosis, facial edema, sweating, skin edema. Special Senses : Taste loss/perversion, cataracts, macular retinitis, iritis, conjunctivitis, amblyopia. Urogenital : Renal failure, uremia, nephritis, impotence, primary hematuria, albuminuria. Endocrine : Infertility (male), hypercalcemia, gynecomastia (male).

In the management of overdosage there is no specific antidote for allopurinol. Both allopurinol and oxipurinol are dialyzable; however, the usefulness of hemodialysis or peritoneal dialysis in the management of an overdose of allopurinol is unknown.

Allopurinol is a xanthine oxidase inhibitor. It has the following structural formula: Allopurinol is known chemically as 1, 5-dihydro-4 H -pyrazolo [3, 4- d ]pyrimidin-4-one and it has a molecular weight of 136.11 g/mol. Its solubility in water at 37°C is 80.0 mg/dL and is greater in an alkaline solution. It is a xanthine oxidase inhibitor which is administered orally. Each white to off white tablet contains 100 mg or 300 mg of allopurinol and the inactive ingredients lactose, crospovidone, magnesium stearate, maize starch, and povidone.

Risk Summary Based on findings in animals, allopurinol may cause fetal harm when administered to a pregnant woman. Adverse developmental outcomes have been described in exposed animals ( see Data ). Allopurinol and its metabolite oxypurinol have been shown to cross the placenta following administration of maternal allopurinol. Available limited published data on allopurinol use in pregnant women do not demonstrate a clear pattern or increase in frequency of adverse developmental outcomes. Among approximately 50 pregnancies described in published literature, 2 infants with major congenital malformations have been reported with following maternal allopurinol exposure. Advise pregnant women of the potential risk to a fetus. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. Data Human Data Experience with allopurinol during human pregnancy has been limited partly because women of reproductive age rarely require treatment with allopurinol. A case report published in 2011 described the outcome of a full-term pregnancy in a 35-year-old woman who had recurrent kidney stones since age 18 who took allopurinol throughout the pregnancy. The child had multiple complex birth defects and died at 8 days of life. A second report in 2013 provided data on 31 prospectively ascertained pregnancies involving mothers exposed to allopurinol for varying durations during the first trimester. The overall rate of major fetal malformations and spontaneous abortions was reported to be within the normal expected range; however, one child had severe malformations similar to those described in the cited earlier case report. Animal Data There was no evidence of fetotoxicity or teratogenicity in rats or rabbits treated during the period of organogenesis with oral allopurinol at doses up to 200 mg/kg/day and up to 100 mg/kg/day, respectively (about 2.4 times the human dose on a mg/m 2 basis). However, there is a published report in pregnant mice that single intraperitoneal doses of 50 mg/kg or 100 mg/kg (about 0.3 or 0.6 times the human dose on a mg/m 2 basis) of allopurinol on gestation days 10 or 13 produced significant increases in fetal deaths and teratogenic effects (cleft palate, harelip, and digital defects). It is uncertain whether these findings represented a fetal effect or an effect secondary to maternal toxicity.

Prior to initiating treatment with allopurinol tablets in patients with gout, assess the following baseline tests: serum uric acid level, complete blood count, chemistry panel, liver function tests (serum alanine aminotransferase [ALT], aspartate aminotransferase [AST] , alkaline phosphatase, and total bilirubin), kidney function tests (serum creatinine and eGFR).

Allopurinol tablets, USP have functional scoring and are available in the following strengths: • 100 mg: White to off white round, biconvex, uncoated tablet with inscription "AW" on one side and breakline on the other side. • 300 mg: White to off white round, biconvex with beveled edge, uncoated tablet with inscription "AX" on one side and breakline on the other side.

Allopurinol is a structural analogue of the natural purine base, hypoxanthine. Allopurinol acts on purine catabolism, without disrupting the biosynthesis of purines. It reduces the production of uric acid by inhibiting the biochemical reactions immediately preceding its formation. It is an inhibitor of xanthine oxidase, the enzyme responsible for the conversion of hypoxanthine to xanthine and of xanthine to uric acid, the end product of purine metabolism in humans. Allopurinol is metabolized to the corresponding xanthine analogue, oxypurinol (alloxanthine), which also is an inhibitor of xanthine oxidase.

Allopurinol reduces the production of uric acid by inhibiting the biochemical reactions immediately preceding its formation in a dose dependent manner. The pharmacological action of allopurinol is generally believed to be mediated by its oxypurinol metabolite. Effect on Hypoxanthine and Xanthine Reutilization of both hypoxanthine and xanthine for nucleotide and nucleic acid synthesis is markedly enhanced when their oxidations are inhibited by allopurinol and oxipurinol. This reutilization does not disrupt normal nucleic acid anabolism, however, because feedback inhibition is an integral part of purine biosynthesis. As a result of xanthine oxidase inhibition, the serum concentration of hypoxanthine plus xanthine in patients receiving allopurinol for treatment of hyperuricemia is usually in the range of 0.3 mg/dL to 0.4 mg/dL compared to a normal level of approximately 0.15 mg/dL. A maximum of 0.9 mg/dL of these oxypurines has been reported when the serum urate was lowered to less than 2 mg/dL by high doses of allopurinol. These values are far below the saturation levels at which point their precipitation would be expected to occur (above 7 mg/dL). The increased xanthine and hypoxanthine in the urine in patients who were treated with oral allopurinol have not been accompanied by problems of nephrolithiasis; however, there are isolated case reports of xanthine crystalluria. Drug Interaction Studies Fluorouracil : Based on non-clinical data, allopurinol may decrease anti-tumor activity due to suppression of phosphorylation of 5-fluorouracil. Pegloticase : Concomitant use of allopurinol and pegloticase may potentially blunt the rise of serum uric acid levels required for monitoring the safe use of pegloticase. Cytotoxic Agents : Enhanced bone marrow suppression by cyclophosphamide and other cytotoxic agents has been reported among patients with neoplastic disease, except leukemia, in the presence of allopurinol. Thiazide Diuretics : Reports that the concomitant administration of allopurinol and thiazide diuretics contributed to increased allopurinol toxicity were reviewed; however, a causal mechanism or cause-and-effect relationship was not found.

Absorption Allopurinol is approximately 90% absorbed from the gastrointestinal tract. Peak plasma levels generally occur at 1.5 hours and 4.5 hours for allopurinol and oxipurinol respectively. After a single oral dose of 300 mg allopurinol, maximum plasma levels of about 3 mcg/mL of allopurinol and 6.5 mcg/mL of oxipurinol are produced. Elimination The half-life of allopurinol and oxipurinol are approximately 1 hour to 2 hours and 15 hours following oral dose of allopurinol, respectively. Metabolism Allopurinol is metabolized to the corresponding xanthine analogue, oxypurinol (alloxanthine), which also is an inhibitor of xanthine oxidase. Excretion Allopurinol and its primary active metabolite, oxipurinol, are eliminated by the kidneys. Approximately 20% of the ingested allopurinol is excreted in the feces. Oxipurinol is primarily eliminated unchanged in urine by glomerular filtration and tubular reabsorption. Drug Interaction Studies Capecitabine : Concomitant use with allopurinol may decrease concentration of capecitabine’s active metabolites, which may decrease capecitabine efficacy. Cyclosporine : Concomitant use of allopurinol increases cyclosporine concentrations which may increase the risk of adverse reactions. Mercaptopurine or Azathioprine : Allopurinol inhibits xanthine oxidase mediated metabolism of mercaptopurine and azathioprine. Concomitant use of allopurinol increases the exposure of either mercaptopurine or azathioprine which may increase the risk of their adverse reactions including myelosuppression. Theophylline : Concomitant use of allopurinol doses greater than or equal to 600 mg/day may decrease the clearance of theophylline. Uricosuric Agents : Uricosuric agents increase the excretion of the active allopurinol metabolite oxypurinol. Concomitant use with uricosuric agents decreases oxypurinol exposure which may reduce the inhibition of xanthine oxidase by oxypurinol and increases the urinary excretion of uric acid. Warfarin : Allopurinol may inhibit the metabolism of warfarin, possibly enhancing its anticoagulant effect.

• Pregnancy: May cause fetal harm. ( 8.1 ) • Lactation: Advise not to breastfeed. ( 8.2 )

• Skin Rash and Hypersensitivity: Allopurinol has been associated with serious and sometimes fatal dermatological reactions. Discontinue allopurinol tablets at the first appearance of skin rash or other signs of hypersensitivity reaction. ( 5.1 ) • Gout Flares: May occur during initiation of treatment. Concurrent prophylactic treatment with colchicine or anti-inflammatory agents is recommended.  ( 5.2 ) • Nephrotoxicity: Allopurinol may affect kidney function. Patients with decreased kidney function require lower doses of allopurinol tablets. ( 5.3 ) • Hepatoxicity: Cases of reversible hepatotoxicity have occurred. If signs and symptoms of hepatotoxicity develop, evaluate liver function. ( 5.4 ) • Myelosuppression: Bone marrow suppression has been reported with allopurinol. ( 5.5 ) • Potential Effect on Driving and Use of Machinery: Drowsiness, somnolence and dizziness have been reported in patients taking allopurinol. ( 5.6 )

100 mg