Allopurinol

Question	Answer
Indications for allopurinol.	Indication: • Gout • Renal stones (uric acid and calcium oxalate) • Hyperuricaemia and tumour lysis syndrome - a condition associated with chemotherapy
MOA of allopurinol.	Allopurinol is a xanthine oxidase inhibitor. Xanthine oxidase metabolises xanthine (produced from purines) to uric acid. Inhibition of xanthine oxidase lowers plasma uric acid concentrations and reduces precipitation of uric acid in the joints or kidneys.
SE's for allopurinol.	• Skin rash • Hypersensitivity reactions - Stevens-Johnson syndrome, toxic epidermal necrolysis, drug hypersensitivity syndrome (fever, eosinophilia, lymphadenopathy, may inc involvement of other organs such as the liver and skin) • Starting allopurinol can trigger or worsen an acute attack of gout
CI's, cautions, & important interactions of allopurinol.	CI's: • Acute attacks of gout • Recurrent skin rash or signs of more severe hypersensitivity reactions Cautions: • Renal impairment (reduce dose) • Hepatic impairment ( reduce dose) Important interactions: The cytotoxic drug mercaptopurine and its pro-drug azathioprine require xanthine oxidase for metabolism. When allopurinol is prescribed with these drugs, it inhibits their metabolism and increases the risk of toxicity. Co-prescription of allopurinol with amoxicillin increases the risk of skin rash and with ACE inhibitors or thiazides increases the risk of hypersensitivity reactions.

Resource summary

	Created by Andrew Street about 8 years ago