Medically reviewed on August 12, 2018
(al oh PURE i nole)
- Allopurinol Sodium
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Solution Reconstituted, Intravenous, as sodium [strength expressed as base]:
Generic: 500 mg (1 ea)
Solution Reconstituted, Intravenous, as sodium [strength expressed as base, preservative free]:
Aloprim: 500 mg (1 ea)
Zyloprim: 100 mg, 300 mg [DSC] [scored]
Zyloprim: 300 mg [scored; contains corn starch, fd&c yellow #6 aluminum lake]
Generic: 100 mg, 300 mg
Brand Names: U.S.
- Antigout Agent
- Xanthine Oxidase Inhibitor
Allopurinol inhibits xanthine oxidase, the enzyme responsible for the conversion of hypoxanthine to xanthine to uric acid. Allopurinol is metabolized to oxypurinol which is also an inhibitor of xanthine oxidase; allopurinol acts on purine catabolism, reducing the production of uric acid without disrupting the biosynthesis of vital purines.
Oral: 90% from GI tract
Vss: IV: 0.84 to 0.87 L/kg
Rapidly oxidized to active metabolites, primarily oxypurinol
Urine (76% as oxypurinol, 12% as unchanged drug); feces (~20%)
Onset of Action
Gout: Decrease in serum and urine uric acid: 2 to 3 days; peak effect: 1 week or longer; normal serum urate levels achieved typically within 1 to 3 weeks
Cancer therapy-induced hyperuricemia: Median time to plasma uric acid control: 27 hours (Cortes 2010)
Time to Peak
Plasma: Oral: Allopurinol: 1.5 hours; Oxypurinol: 4.5 hours
Parent drug: ~1 to 2 hours; Oxypurinol: ~15 hours
Use: Labeled Indications
Gout, treatment: Management of primary or secondary gout (acute attack, tophi, joint destruction, uric acid lithiasis, and/or nephropathy)
EULAR guidelines: Urate-lowering therapy (ULT) (eg, allopurinol) is indicated in all patients with recurrent flares, tophi, urate arthropathy, and/or renal stones. ULT initiation is recommended close in time to first diagnosis in patients presenting at a young age (<40 years of age) or with very high serum uric acid levels (>8 mg/dL) and/or comorbidities (eg, renal impairment, hypertension, ischemic heart disease, heart failure) (EULAR [Richette 2017]).
Nephrolithiasis, prevention of recurrent calcium stones: Management in patients with hyperuricosuria (uric acid excretion >800 mg/day in men and >750 mg/day in women)
Tumor lysis syndrome, prevention: Management of hyperuricemia associated with cancer treatment for leukemia, lymphoma, and other malignancies
Limitations of use: Allopurinol is not recommended for the treatment of asymptomatic hyperuricemia. Allopurinol reduces serum and urinary uric acid concentrations; its use should be individualized for each patient and requires an understanding of its mode of action and pharmacokinetics.
IV: Tumor lysis syndrome, prevention: Management of hyperuricemia associated with cancer treatment for leukemia, lymphoma, or solid tumor malignancies in patients who cannot tolerate oral therapy.
Off Label Uses
Lesch-Nyhan syndrome-associated hyperuricemia (pediatrics)
Data from a small retrospective analysis of patients with hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency (the majority of patients had complete HPRT deficiency [Lesch-Nyhan syndrome] and some had partial deficiency) support the use of allopurinol in the treatment of uric acid overproduction associated with this rare disease [Torres 2007a]. Clinical experience also suggests the utility of allopurinol in managing Lesch-Nyhan syndrome [Torres 2007b].
Nephrolithiasis, prevention of recurrent uric acid stones
Clinical experience suggests the utility of allopurinol in the management of patients with recurrent nephrolithiasis due to uric acid stones [Curhan 2018b], [Heilberg 2016], [Kenny 2010], [Lipkin 2011].
Severe hypersensitivity reaction to allopurinol or any component of the formulation
Canadian labeling: Additional contraindications (not in US labeling): Breastfeeding mothers and children (except those with cancer therapy-induced hyperuricemia or Lesch-Nyhan syndrome)
Note: While not an absolute contraindication, the American College of Rheumatology suggests avoiding the use of allopurinol in patients with the HLA-B*5801 genotype due to the increased risk of allopurinol hypersensitivity syndrome (AHS). The guidelines suggest HLA-B*5801 screening in patients with a high incidence of this genotype; this includes patients of Korean descent who have stage 3 or worse chronic kidney disease, as well as patients of Han Chinese or Thai descent regardless of kidney function (ACR [Khanna 2012a]).
Note: Before prescribing allopurinol, consider testing for the HLA-B*58:01 allele in patients at risk for severe cutaneous adverse reactions (SCAR) (ie, Koreans with CKD ≥ stage 3 and all patients of Han Chinese or Thai descent) (ACR [Khanna 2012a]). A negative HLA-B*58:01 genetic test, however, does not absolutely rule out the possibility of allopurinol-associated SCAR, so patients should still be appropriately monitored for SCAR (Hershfield 2013).
Gout, treatment (chronic urate-lowering therapy): Oral: Note: Starting urate-lowering therapy (ULT) can precipitate acute gout flares. Pharmacologic prophylaxis with colchicine or an NSAID is generally recommended for the first 3 to 6 months once serum urate goal is achieved with ULT (ACR [Khanna 2012b]; Becker 2018).
Initial: 100 mg once daily (ACR [Khanna 2012a]; EULAR [Richette 2017])
Dosage adjustments: Titrate in 100 mg increments every 2 to 4 weeks to achieve the desired serum uric acid level (EULAR [Richette 2017]; Jennings 2014).
Maintenance: Doses ≥300 mg/day are usually needed to reach the desired uric acid target; doses up to 800 mg/day may be required (EULAR [Richette 2017]; Jennings 2014).
Maximum: 800 mg/day
Frequency of administration: Once daily in a single dose or in 2 or 3 divided doses. Note: The manufacturer's labeling recommends doses >300 mg be given in divided doses; however, most experts prescribe a single daily dose, regardless of total dose administered, except during a brief period (eg, when initiating or titrating therapy) when divided doses may help improve GI tolerability (Becker 2018; Currie 1978).
Nephrolithiasis, prevention of recurrent calcium or uric acid stones:
Due to calcium oxalate stones: Patients with hyperuricosuria (who continue to have active disease despite attempted dietary modification): Oral: 300 mg/day, usually given in a single daily dose but may be given in 2 or 3 divided doses, if needed, to improve GI tolerability (Curhan 2018a; Ettinger 1986; Lipkin 2011).
Due to uric acid stones (off-label use): Oral: 300 mg/day, usually given in a single daily dose but may be given in 2 or 3 divided doses, if needed, to improve GI tolerability; use is reserved for patients who continue to have active disease despite urinary alkalinization therapy and increased hydration (Curhan 2018b; Heilberg 2016; Kenny 2010; Lipkin 2011).
Tumor lysis syndrome, prevention: Patients at intermediate risk for tumor lysis syndrome (TLS) and without preexisting hyperuricemia (serum uric acid ≥8 mg/dL [476 micromol/L]):
Note: Aggressive IV hydration should always be initiated prior to cytotoxic therapy in patients at elevated risk for TLS (Coiffier 2008).
Oral: 300 mg/m2/day or 10 mg/kg/day, given in 3 divided doses every 8 hours (maximum: 800 mg/day). Begin therapy 1 to 2 days before the start of induction chemotherapy and may continue for up to 3 to 7 days after chemotherapy until normalization of laboratory evidence of TLS (eg, serum uric acid, serum LDH) (Coiffier 2008; Larson 2018).
IV: 200 to 400 mg/m2/day, given in a single daily dose or in 2 or 3 divided doses (maximum: 600 mg/day). Begin therapy 1 to 2 days before the start of induction chemotherapy and may continue for 3 to 7 days after chemotherapy until normalization of laboratory evidence of TLS (eg, serum uric acid, serum LDH) (Coiffier 2008; Larson 2018).
Refer to adult dosing.
Tumor lysis syndrome, prevention:
Oral: Note: Oral doses >300 mg should be given in divided doses. Adjust dose as necessary after 48 hours.
Children <6 years of age: 150 mg daily
Children 6 to 10 years: 300 mg daily
Children >10 years of age: Refer to adult dosing.
Off-label dosing: Intermediate risk for tumor lysis syndrome: 10 mg/kg daily divided every 8 hours (maximum dose: 800 mg/day) or 50 to 100 mg/m2 every 8 hours (maximum: 300 mg/m2/day) beginning 12 to 24 hours before start of induction chemotherapy; may continue for 3 to 7 days after chemotherapy (Coiffier 2008)
IV: Note: Intravenous daily dose can be given as a single infusion or in equally divided doses at 6-, 8-, or 12-hour intervals.
Manufacturer's labeling: Starting dose: 200 mg/m2 daily beginning 1 to 2 days before chemotherapy
Off-label dosing: Intermediate risk for tumor lysis syndrome: 200 to 400 mg/m2 daily (maximum: 600 mg/day) in 1 to 3 divided doses beginning 12 to 24 hours before the start of induction chemotherapy; may continue for 3 to 7 days after chemotherapy (Coiffier 2008)
Lesch-Nyhan syndrome-associated hyperuricemia (off-label use): Infants, Children, and Adolescents: Oral: Initial: 5 to 10 mg/kg daily in 1 or 2 divided doses; adjust dose as necessary to maintain high-normal serum uric acid levels and a urinary uric acid/creatinine ration <1; doses ranged from 50 to 600 mg/day (Torres 2007a; Torres 2007b).
Dosing: Renal Impairment
Manufacturer’s labeling: Oral, IV: Lower doses are required in renal impairment due to potential for accumulation of allopurinol and metabolites.
CrCl 10 to 20 mL/minute: 200 mg/day
CrCl 3 to 10 mL/minute: Do not exceed 100 mg/day.
CrCl <3 mL/minute: The dosing interval may need to be extended; do not exceed 100 mg/day.
Allopurinol and oxypurinol are dialyzable.
Indication-specific renal dosing (off-label):
Cancer therapy-induced hyperuricemia: Dosage reduction of 50% is recommended in renal impairment (Coiffier 2008)
Initiate therapy with 50 to 100 mg daily, and gradually increase to a maintenance dose to achieve a serum uric acid level of ≤6 mg/dL (with close monitoring of serum uric acid levels and for hypersensitivity) (Dalbeth 2007).
In patients with stage 4 CKD or worse, initiate therapy at 50 mg/day, increasing the dose every 2 to 5 weeks to achieve desired uric acid levels; doses >300 mg/day are permitted so long as they are accompanied by appropriate patient education and monitoring for toxicity (eg, pruritus, rash, elevated hepatic transaminases) (ACR [Khanna 2012]).
Hemodialysis: Initial: 100 mg alternate days given postdialysis, increase cautiously to 300 mg based on response. If dialysis is on a daily basis, an additional 50% of the dose may be required postdialysis (Dalbeth 2007)
Dosing: Hepatic Impairment
There are no dosage adjustments provided in the manufacturer’s labeling.
Reconstitute powder for injection with 25 mL SWFI. Further dilution with NS or D5W to a final concentration of ≤6 mg/mL.
A 20 mg/mL oral suspension may be made with tablets and either a 1:1 mixture of Ora-Sweet® and Ora-Plus® or a 1:1 mixture of Ora-Sweet® SF and Ora-Plus® or a 1:4 mixture of cherry syrup concentrate and simple syrup, NF. Crush eight 300 mg tablets in a mortar and reduce to a fine powder. Add small portions of chosen vehicle and mix to a uniform paste; mix while adding the vehicle in incremental proportions to almost 120 mL; transfer to a calibrated bottle, rinse mortar with vehicle, and add quantity of vehicle sufficient to make 120 mL. Label “shake well”. Stable for 60 days refrigerated or at room temperature (Allen 1996; Nahata 2004).Allen LV Jr and Erickson MA 3rd, "Stability of Acetazolamide, Allopurinol, Azathioprine, Clonazepam, and Flucytosine in Extemporaneously Compounded Oral Liquids," Am J Health Syst Pharm, 1996, 53(16):1944-9.8862208Nahata MC, Pai VB, and Hipple TF, Pediatric Drug Formulations, 5th ed, Cincinnati, OH: Harvey Whitney Books Co, 2004.
Administer fluids sufficient to yield daily urinary output of at least 2 L and to maintain neutral or, preferably, slightly alkaline urine.
Oral: Administer after meals.
IV: The rate of infusion depends on the volume of the infusion; infuse maximum single daily doses (600 mg/day) over ≥30 minutes. Whenever possible, therapy should be initiated at 24 to 48 hours before the start of chemotherapy known to cause tumor lysis (including adrenocorticosteroids). IV daily dose can be administered as a single infusion or in equally divided doses at 6-, 8-, or 12-hour interval.
Fluid intake should be administered to yield neutral or slightly alkaline urine and an output of ~2 L (in adults).
Powder for injection: Store at 20°C to 25°C (68°F to 77°F). Following preparation, intravenous solutions in NS or D5W should be stored at 20°C to 25°C (68°F to 77°F). Do not refrigerate reconstituted and/or diluted product. Must be administered within 10 hours of solution preparation.
Tablet: Store at 15°C to 25°C (59°F to 77°F). Store in a dry place. Protect from light.
Amoxicillin: Allopurinol may enhance the potential for allergic or hypersensitivity reactions to Amoxicillin. Monitor therapy
Ampicillin: Allopurinol may enhance the potential for allergic or hypersensitivity reactions to Ampicillin. Monitor therapy
Angiotensin-Converting Enzyme Inhibitors: May enhance the potential for allergic or hypersensitivity reactions to Allopurinol. Consider therapy modification
Antacids: May decrease the absorption of Allopurinol. Exceptions: Sodium Bicarbonate. Consider therapy modification
AzaTHIOprine: Allopurinol may increase serum concentrations of the active metabolite(s) of AzaTHIOprine. More specifically, allopurinol may increase mercaptopurine serum concentrations and promote formation of active thioguanine nucleotides. Management: Reduce the azathioprine dose to one third to one quarter of the usual dose if used concomitantly with allopurinol, and monitor closely for systemic toxicity (particularly hematologic toxicity, nausea, and vomiting). Consider therapy modification
Bacampicillin: Allopurinol may enhance the potential for allergic or hypersensitivity reactions to Bacampicillin. Monitor therapy
Bendamustine: Allopurinol may enhance the adverse/toxic effect of Bendamustine. Specifically, the risk of severe skin reactions may be enhanced. Monitor therapy
CarBAMazepine: Allopurinol may increase the serum concentration of CarBAMazepine. Monitor therapy
Cyclophosphamide: Allopurinol may enhance the adverse/toxic effect of Cyclophosphamide. Specifically, bone marrow suppression. Monitor therapy
CycloSPORINE (Systemic): Allopurinol may increase the serum concentration of CycloSPORINE (Systemic). Monitor therapy
Didanosine: Allopurinol may increase the serum concentration of Didanosine. Avoid combination
Doxofylline: Allopurinol may increase the serum concentration of Doxofylline. Monitor therapy
Loop Diuretics: May enhance the adverse/toxic effect of Allopurinol. Loop Diuretics may increase the serum concentration of Allopurinol. Specifically, Loop Diuretics may increase the concentration of Oxypurinol, an active metabolite of Allopurinol. Monitor therapy
Mercaptopurine: Allopurinol may increase the serum concentration of Mercaptopurine. Allopurinol may also promote formation of active thioguanine nucleotides. Management: Reduce the mercaptopurine dose to one third to one quarter of the usual dose if used with allopurinol, and monitor closely for systemic toxicity. US labeling for mercaptopurine oral suspension (Purixan brand) recommends avoiding allopurinol. Consider therapy modification
Pegloticase: Allopurinol may enhance the adverse/toxic effect of Pegloticase. Specifically, Allopurinol may blunt increases in serum urate that would signal an increased risk of anaphylaxis and infusion reactions. Avoid combination
Tegafur: Allopurinol may diminish the therapeutic effect of Tegafur. Avoid combination
Theophylline Derivatives: Allopurinol may increase the serum concentration of Theophylline Derivatives. Exceptions: Dyphylline. Monitor therapy
Thiazide and Thiazide-Like Diuretics: May enhance the potential for allergic or hypersensitivity reactions to Allopurinol. Thiazide and Thiazide-Like Diuretics may increase the serum concentration of Allopurinol. Specifically, Thiazide Diuretics may increase the concentration of Oxypurinol, an active metabolite of Allopurinol. Monitor therapy
Vitamin K Antagonists (eg, warfarin): Allopurinol may enhance the anticoagulant effect of Vitamin K Antagonists. Consider therapy modification
Most commonly reported:
Dermatologic: Skin rash
Endocrine & metabolic: Gout (acute)
Gastrointestinal: Diarrhea, nausea
Hepatic: Increased liver enzymes, increased serum alkaline phosphatase
<1%, postmarketing, and/or case reports: Abdominal pain, ageusia, agranulocytosis, alopecia, angioedema, aplastic anemia, arthralgia, bronchospasm, cataract, cholestatic jaundice, drowsiness, dysgeusia, dyspepsia, ecchymoses, eczematoid dermatitis, eosinophilia, epistaxis, exfoliative dermatitis, fever, gastritis, gynecomastia, headache, hepatic necrosis, hepatitis, hepatomegaly, hepatotoxicity (idiosyncratic) (Chalasani, 2014), hyperbilirubinemia, hypersensitivity reaction, leukocytosis, leukopenia, lichen planus, macular retinitis, myopathy, necrotizing angiitis, nephritis, neuritis, neuropathy, onycholysis, pancreatitis, paresthesia, pruritus, purpura, renal failure, skin granuloma (annulare), Stevens-Johnson syndrome, thrombocytopenia, toxic epidermal necrolysis, toxic pustuloderma, uremia, vasculitis, vesicobullous dermatitis, vomiting
Concerns related to adverse effects:
• Bone marrow suppression: Bone marrow suppression has been reported in patients receiving allopurinol, most of whom received concomitant medications with a potential for hematologic toxicity. The onset occurs between 6 weeks to 6 years after allopurinol initiation. Varying degrees of bone marrow depression affecting one or more cell lines may occur (rare) in patients receiving allopurinol alone.
• CNS effects: May occasionally cause drowsiness; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery or driving).
• Hepatotoxicity: Cases of hepatotoxicity (reversible) have been reported. Asymptomatic elevations of serum alkaline phosphatase or serum transaminases have been observed. Monitor for signs/symptoms of hepatotoxicity and evaluate liver function if they occur. Periodic liver function tests are recommended during the early stages of therapy in patients with preexisting hepatic impairment.
• Hypersensitivity: Allopurinol has been associated with hypersensitivity reactions. In some instances, a skin rash may be followed by more severe hypersensitivity reactions, including exfoliative, urticarial, and purpuric lesions, Stevens-Johnson syndrome, generalized vasculitis, and/or hepatotoxicity (irreversible); some reactions have been fatal (rare). Discontinue at first sign of skin rash or other signs indicative of allergic reaction. Consider HLA-B*5801 testing in patients at a higher risk for allopurinol hypersensitivity syndrome (eg, Korean patients with stage 3 or worse CKD and Han Chinese and Thai descent regardless of renal function) prior to initiation of therapy (ACR [Khanna 2012a]).
• Acute gout attacks: Even when normal or subnormal serum uric acid levels have been attained, an increase in acute gout attacks has been reported during the early stages of allopurinol administration. When allopurinol is initiated, maintenance colchicine doses should generally be administered as prophylaxis. Additionally, it is recommended to initiate with a low allopurinol dose (100 mg daily) and increase at weekly intervals by 100 mg until a serum uric acid level of 6 mg/dL or less is attained (do not exceed the maximum recommended dose of 800 mg/day). In some cases, colchicine or anti-inflammatory agents may be required to suppress gouty attacks. After several months of therapy, attacks usually decrease in duration and severity. These episodes may be due to mobilization of urates from tissue deposits, causing fluctuations in the serum uric acid levels. Even with adequate allopurinol therapy, several months may be required to deplete the uric acid pool enough to achieve control of the acute attacks.
• Renal impairment: Dose reductions are recommended in patients with renal impairment; monitor closely. Patients with reduced renal function receiving thiazide diuretics in combination with allopurinol may be at increased risk for hypersensitivity reactions. Some patients with preexisting renal disease or poor urate clearance have shown a rise in BUN with allopurinol. Patients with renal impairment should be carefully monitored during the early stages of allopurinol treatment; reduce the dose or withdraw therapy if increased renal function abnormalities appear and persist. Renal failure associated with allopurinol has been observed in patients with hyperuricemia secondary to neoplastic diseases. Concurrent conditions including multiple myeloma and congestive myocardial disease were present among patients whose renal dysfunction increased after allopurinol was begun. Renal failure is also frequently associated with gouty nephropathy and rarely with hypersensitivity reactions associated with allopurinol. Albuminuria has been observed among patients who developed clinical gout following chronic glomerulonephritis and chronic pyelonephritis.
Concurrent drug therapy issues:
• Drug-drug interactions: Potentially significant drug interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.
• Concomitant medications: Concomitant use of allopurinol (at doses of 300 to 600 mg/day) with mercaptopurine or azathioprine will require a reduction in the mercaptopurine or azathioprine dose to approximately one-third to one-fourth of the usual dose. Subsequent dose adjustments may be necessary based on therapeutic response and toxicity.
• Appropriate use: Do not use to treat asymptomatic hyperuricemia.
• Hydration: Fluid intake sufficient to yield a daily urinary output of at least 2 L and maintenance of a neutral or (preferably) a slightly alkaline urine are desirable in order to avoid possible formation of xanthine calculi due to allopurinol therapy and to help prevent renal urate precipitation in patients receiving concomitant uricosuric agents.
CBC, serum uric acid levels every 2 to 5 weeks during dose titration until desired level is achieved and every 6 months thereafter (ACR [Khanna 2012a]), liver function tests (periodically in patients with preexisting hepatic disease), renal function (BUN, serum creatinine or creatinine clearance [prior to initiation and periodically]), prothrombin time (periodically in patients receiving warfarin); consider HLA-B*5801 testing prior to initiation of therapy in patients at a higher risk for allopurinol hypersensitivity syndrome (see Contraindications) (ACR [Khanna 2012a]). Monitor hydration status, for signs and symptoms of hypersensitivity, hepatotoxicity.
Adverse events were observed in some animal reproduction studies. Allopurinol crosses the placenta (Torrance 2009). An increased risk of adverse fetal events has not been observed (limited data) (Hoeltzenbein 2013).
• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)
• Patient may experience diarrhea, nausea, or injection site irritation. Have patient report immediately to prescriber signs of kidney problems (urinary retention, hematuria, change in amount of urine passed, or weight gain), signs of liver problems (dark urine, fatigue, lack of appetite, nausea, abdominal pain, light-colored stools, vomiting, or jaundice), painful urination, hematuria, chills, pharyngitis, eye irritation, joint pain, bruising, bleeding, severe loss of strength and energy, or signs of Stevens-Johnson syndrome/toxic epidermal necrolysis (red, swollen, blistered, or peeling skin [with or without fever]; red or irritated eyes; or sores in mouth, throat, nose, or eyes) (HCAHPS).
• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.
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- Drug class: antigout agents