Adult: 200-400 mg/m2 daily as a single infusion or in equally divided doses at 6-, 8- or 12-hour intervals at recommended final concentration of 6 mg/mL, starting 1-2 days before starting chemotherapy. Max: 600 mg daily. Child: Initially, 200 mg/m2 as a single infusion or in equally divided doses at 6-, 8- or 12-hour intervals at recommended final concentration of 6 mg/mL, starting 24-48 hours before starting chemotherapy.
Oral Gout, Hyperuricaemia
Adult: Initially, 100 mg daily, adjusted in increments of 100 mg every 2-4 weeks according to serum urate concentration. Maintenance: 100-200 mg daily (mild); 300-600 mg daily (moderately severe); 700-900 mg daily (severe). Max: 900 mg daily. Doses >300 mg daily should be taken in divided doses. Dosage recommendations may vary among different products or countries. Child: In hyperuricaemia associated with enzyme disorder: <15 years 10-20 mg/kg daily. Max: 400 mg daily. Dosage recommendations may vary among different products or countries.
Oral Cancer therapy-induced hyperuricaemia
Adult: 600-800 mg daily in divided doses for 2-3 days before cancer treatment. Child: <6 years 150 mg daily; 6-10 years 300 mg daily. Alternatively, <15 years 10-20 mg/kg daily. Max: 400 mg daily. Dosage recommendations may vary among different products or countries.
Oral Recurrent calcium oxalate stones
Adult: 200-300 mg daily as a single dose or in 2-3 divided doses.
Special Patient Group
Patients taking allopurinol 300-600 mg concomitantly with mercaptopurine or azathioprine: Reduce mercaptopurine or azathioprine dose to 1/3 to 1/4 of the usual dose. Subsequent dose adjustments should be made based on therapeutic response and the appearance of toxic effects.
Pharmacogenomics:
HLA-B*58:01 allele is associated with an increased risk of Severe Cutaneous Adverse Reactions (SCAR), including Stevens-Johnson Syndrome (SJS) and toxic epidermal necrolysis (TEN). Individuals with 1 or 2 copies of the HLA-B*58:01 allele who are taking allopurinol have an increased risk for these adverse effects as compared to patients with no HLA-B*58:01 alleles or negative for the HLA-B*58:01 test. Use should be avoided in any patient testing positive for HLA-B*58:01 allele. The prevalence of HLA-B*58:01 allele varies widely among different ethnic or racial origin. It has been estimated to be up to 20% in Han Chinese, 8-15% in Thai, approx 12% in Korean, and 1-2% in Japanese or European origin. Consider HLA-B*58:01 screening prior to initiation of therapy in these patients (including those of Korean descent who have chronic kidney disease ≥stage 3).
Renal Impairment
CrCl (mL/min)
Dosage
<3
≤100 mg/dose at extended intervals.
3 to <10
≤100 mg daily.
10-20
200 mg daily.
Hepatic Impairment
Oral:
Dose reduction may be needed.
Administration
Should be taken with food. Take immediately after meals.
Reconstitution
IV: Dissolve the contents of the 50 mL vial with 50 mL of sterile water for injection. Dilute further with NaCl 0.9% inj or dextrose 5% inj to a final concentration not exceeding 6 mg/mL.
Patient with abnormal Fe storage (including haemochromatosis), thyroid disorder. Not intended for the treatment of an acute gout attack. Renal and hepatic impairment. Children. Pregnancy and lactation. Patients taking allopurinol (300-600 mg) concomitantly with mercaptopurine or azathioprine.
Adverse Reactions
Significant: Bone marrow suppression (e.g. leucopenia, eosinophilia, thrombocytopenia), reversible hepatotoxicity, asymptomatic increase in serum alkaline phosphatase or transaminase levels, renal failure, acute attacks of gout, dissolution of large uric acid renal pelvic stones. Gastrointestinal disorders: Nausea, vomiting, diarrhoea, abdominal pain, dyspepsia, loss of taste, gastritis. General disorders and administration site conditions: Fever. Hepatobiliary disorders: Granulomatous hepatitis, hepatic necrosis, hepatomegaly, cholestatic jaundice, hyperbilirubinaemia. Investigations: Increased blood TSH. Musculoskeletal and connective tissue disorders: Arthralgia, myopathy. Nervous system disorders: Headache, paraesthesia, neuritis, peripheral neuropathy. Psychiatric disorders: Somnolence. Renal and urinary disorders: Uraemia. Respiratory, thoracic and mediastinal disorders: Epistaxis. Skin and subcutaneous tissue disorders: Ecchymosis, alopecia, pruritus, onycholysis, lichen planus, urticaria. Vascular disorders: Vasculitis, necrotizing angiitis. Potentially Fatal: Drug rash and eosinophilia (DRESS), Stevens-Johnson syndrome, toxic epidermal necrolysis, irreversible hepatotoxicity.
This drug may cause drowsiness or dizziness, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor uric acid levels, CBC, LFT and renal function tests. Observe for signs/symptoms of hypersensitivity or hepatotoxicity. Monitor hydration status, therapeutic response, frequency and severity of gouty attacks.
Overdosage
Symptoms: Nausea, vomiting, diarrhoea, dizziness. Management: General supportive treatment. Maintain optimum diuresis through adequate hydration to facilitate excretion of the drug.
Drug Interactions
Reduces the metabolism of azathioprine and mercaptopurine, thus increasing the risk of severe bone marrow toxicity. May prolong the half-life of dicoumarol, chlorpropamide and vidarabine. May increase ciclosporin levels. May increase the risk of hypersensitivity in patients with decreased renal function and receiving thiazide diuretics. May inhibit the metabolism of theophylline. Uricosuric agents (e.g. probenecid) and large doses of salicylate may accelerate the excretion of oxipurinol and may result in reduced efficacy of allopurinol. Increased frequency of skin rash with concomitant ampicillin or amoxicillin.
Action
Description: Mechanism of Action: Allopurinol inhibits xanthine oxidase, the enzyme that catalyses the conversion of hypoxanthine to xanthine then to uric acid. It acts on purine catabolism, reducing the production of uric acid without disrupting the biosynthesis of vital purines. Pharmacokinetics: Absorption: Rapidly absorbed from the gastrointestinal tract (up to 90%). Bioavailability: Approx 49-53%. Time to peak plasma concentration: 1.5 hours (allopurinol; 4.5 hours (oxipurinol). Distribution: Distributed uniformly in total tissue water except for the brain. Crosses the placenta and enters breast milk. Metabolism: Rapidly metabolised to oxipurinol (active metabolite). Excretion: Mainly via urine (approx 70% as oxipurinol, approx 10% as allopurinol); remainder via faeces (approx. 20%). Elimination half-life: Approx 1-2 hours (allopurinol); approx ≥15 hours (oxipurinol).
Chemical Structure
Allopurinol Source: National Center for Biotechnology Information. PubChem Database. Allopurinol, CID=135401907, https://pubchem.ncbi.nlm.nih.gov/compound/Allopurinol (accessed on Jan. 20, 2020)
Storage
Tab: Store between 15-30°C. Protect from light and moisture. Inj: Store between 20-25°C.
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