Allopurinol is a white, powdery drug used to treat gout. Its
use in the United States was started in 1964.

It is an isomer of hypoxanthine and inhibits the production of uric acid,
the metabolite responsible for gout, by inhibiting the enzyme xanthine
oxidase.

Allopurinol can also be given with some cancer treatments
(e.g., CHOP) that increase uric acid (tumor lysis syndrome), as well as
for kidney stones. These treatments result in large numbers of cells being
disposed of by the body, which releases uric acid as part of the breakdown
of DNA.

Allopurinol is an analog of the natural purines in the body, and
is quickly metabolised to oxipurinol which is also a xanthine oxidase
inhibitor.

The side effects of high levels of precursors are usually minor. A small
percentage of people develop a rash and must discontinue this drug. The
most serious adverse event is a hypersensitivity syndrome consisting of
fever, skin rash, eosinophilia, hepatitis, and worsening renal function.
In some cases, allopurinol hypersensitivity syndrome.

Allopurinol is marketed by GlaxoSmithKline as Zyloprim, and by
Hexal Australia as the generic brand Allohexal. It is also available under
the brand name Progout.

Allopurinol is also marketed by The Wellcome Foundation as Zyloric.