Composition:
Each tablet contains 100 or 300mg Allopurinol
Pharmacological Classification: Drugs used to treat gout.
Mechanism of Action:
Allopurinol is a xanthine-oxidase inhibitor. Allopurinol and its main metabolite oxipurinol lower the level of uric acid in plasma and urine by inhibition of xanthine oxidase, the enzyme catalyzing the oxidation of hypoxanthine to xanthine and xanthine to uric acid. In addition to the inhibition of purine catabolism in some patients.
Pharmacokinetics:
Absorption: Allopurinol is rapidly absorbed from the upper gastrointestinal tract. The bioavailability vary from 67% to 90%. Peak plasma levels of allopurinol generally occur approximately 1.5 hours after oral administration of the drug. Peak plasma levels of oxipurinol generally occur after 3-5 hours after oral administration of the drug.
Distribution: Allopurinol is negligibly bound by plasma proteins. The volume of distribution is approximately 1.6 L/kg
Metabolism: The main metabolite of the drug is oxipurinol.
Elimination: Approximately 20% of the ingested allopurinol is excreted in the faeces, and less than 10% of the unchanged drug excreted in the urine. Allopurinol has a plasma half-life of about 0.5 to 1.5 hours.
Pharmacokinetics in patients with renal impairment: Allopurinol and oxipurinol clearance is greatly reduced in patients with poor renal function resulting in higher plasma levels in chronic therapy.
Indications:
Glorizyl is indicated for reducing urate/uric acid formation in conditions where urate/uric acid deposition has already occurred (e.g., gouty arthritis, skin tophi, nephrolithiasis). Glorizyl is indicated for idiopathic gout; uric acid lithiasis; acute uric acid nephropathy; neoplastic disease, myeloproliferative disease and certain enzyme disorders which lead to overproduction of urate. Glorizyl is indicated for the management of renal stones related to deficient activity of adenine phosphoribosyl transferase. Glorizyl is also indicated for the management of recurrent mixed calcium oxalate renal stones in the presence of hyperuricosuria.
Contraindications:
Glorizyl should not be administered to individuals known to be hypersensitive to allopurinol or to any of its components.
Warnings and precautions:
Side Effects:
Common: rash, vomiting, nausea, hypersensetivity including skin reactions associated with exfoliation, fever, lymphadenopathy, pseudo lymphoma, arthralgia, leucopenia and/or eosinophilia.
Rare: hepatitis (including hepatic necrosis and granulomatous hepatitis), Stevens-Johnson syndrome/toxic epidermal necrolysis.
Pregnancy and lactation:
Glorizyl can be used only when there is no safe alternative and when the disease itself is dangerous to the mother or the fetus. There are no studies on the effect of allopurinol or any of its metabolites on the infant through breast milk.
Drug Interactions:
Dosage and Administration:
Adults: 100 to 200mg daily in mild conditions, 300 to 600mg daily in moderately severe conditions,700 to 900mg daily in severe conditions.
Children under 15 years: 10 to 20 mg/kg bodyweight/day up to a maximum of 400 mg daily.
Older people: The lowest dosage which produces satisfactory urate reduction should be used.
Patients with renal impairment: In severe renal insufficiency, it may be advisable to use less than 100 mg per day or to use single doses of 100 mg at longer intervals than one day.
Patients with hepatic impairment: Reduced doses should be used in patients with hepatic impairment. Dosage should be at the lower end of the recommended dosage schedule.
Overdosage:
Symptoms: nausea, vomiting, diarrhoea and dizziness in a patient who ingested 20g allopurinol.
Treatment: Adequate hydration to maintain optimum diuresis facilitates excretion of allopurinol and its metabolites also, haemodialysis may be used.
Effects on ability to drive and use machines:
Since adverse reactions such as somnolence, vertigo and ataxia have been reported in patients receiving Glorizyl, patients should exercise caution before driving.