Allopurinol

Its major metabolite alloxanthine is long acting and non competitive inhibitor-primarily responsible for uric acid synthesis inhibition. During allopurinol administration, plasma concentration of uric acid reduced and that of hypoxanthine and xanthine is increased.

Indications

Chronic gout. Secondary hyper-uricaemia, due to cancer chemotherapy, radiation & thiazides or drugs, prevention of uric acid nephro-pathy. Calcium renal lithiasis.

Dosage

-Adults: The typical starting dose is 100 mg daily, which may be increased by 100 mg weekly until the desired uric acid level is achieved. Maintenance doses usually range from 200 to 300 mg per day for mild conditions and 400 to 600 mg per day for severe conditions. -Children: The dosage is typically 10 to 20 mg/kg of body weight per day, up to a maximum of 400 mg daily.

Contra-Indications

Children, Acute gout.

Special Precautions

Both allopurinol and uricosurics should not be started during acute attack of gout. Iron therapy not advised with allopurinol. Renal or hepatic impairment. Maintain adequate fluid intake. Paediatrics: Reduced dose necessary. Pregnancy: Should not be used. Lactation: Use with caution. Elderly: Reduced dose may be necessary.

Side Effects

Rashes, Fever, malaise, muscle pain, gastric irritation, headache, nasea, liver damage.

Drug Interactions

-Dose of Azothioprine and mercaptopurine should be reduced when administered allupurinol . -Probenecid & Salicylates enhance urinary excretion of allopurinol. Enhanced activity of oral hypoglycaemic agents and anticoagulants.