Allopurinol 315-30-0

Mechanism of action

Allopurinol is a structural isomer of hypoxanthine (a naturally occurring purine in the body) and is an enzyme inhibitor, inhibiting xanthine oxidase. and some patients will be hypersensitive to it. Therefore, use of this drug requires careful monitoring. A recent study has suggested that allopurinol can help reduce the effects of angina in ischaemic heart disease by reducing the workload on the heart.

Metabolism

Allopurinol is rapidly metabolized by its target, xanthine oxidase, to its active metabolite oxypurinol, which is also an inhibitor of xanthine oxidase. Allopurinol is almost completely metabolized to oxypurinol within two hours of oral administration, whereas oxypurinol is slowly excreted by the kidneys over 18-30 hours. For this reason, oxypurinol is believed to be responsible for the majority of allopurinol's effect.

Side effects

Side effects of allopurinol are rare, though significant when they occur. A small percentage of people develop a rash and must discontinue this drug. The most serious adverse effect is a hypersensitivity syndrome consisting of fever, skin rash, eosinophilia, hepatitis, worsened renal function and, in some cases, allopurinol hypersensitivity syndrome. Allopurinol is one of the drugs commonly known to cause Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TENS), two life-threatening dermatological conditions. Allopurinol can cause severe pancytopenia if given with azathioprine or mercaptopurine, due to inhibition of xanthine oxidase which metabolizes these drugs. It can also cause breast enlargement in both males and females. Allopurinol can lower blood pressure in mild hypertension.

Brand names

Allopurinol has been marketed in the United States since 1964. Allopurinol is marketed by Prometheus in the United States as Zyloprim, while in other countries it continues to be marketed by GlaxoSmithKline. Other brand names are Allohexal, Allosig, Milurit, Alloril, Progout, and Zyloric. In South Africa, Allopurinol is marketed under the brand name Puricos. It also known as Zyrik 300 in India and Aluron in Venezuela.