- It functions as a xanthine oxidase inhibitor.
- Purines (degradation products of amino acid and nucleic acid) are converted to xanthines and hypoxanthines, before being oxidized to uric acid.
- Allopurinol inhibits the final step and increases the amount of xanthine and hypoxanthine, which are both more water soluble.
- Indications as follows:
- Used in between acute gout attacks. Should not be used in the acute phase because it may actually precipitate an acute gout attack.
- Used to prevent increased in uric acid following therapy of blood dyscrasias (this reduces the chance of formation of uric acid stones)
- May also be used as an anti-protozoal drug.
- Adverse effects
- Precipitate gout (use colchicine or NSAIDs as a bridge)
- Nausea, vomiting and diarrhea
- Bone marrow suppression.
- May increase the activity of oral anti-coagulants by inhibiting their metabolism.
- Given PO
- Well absorbed, good bioavailability.
- It is metabolized by xanthine oxidase, but its metabolic byproduct retains the ability to further inhibit xanthine oxidase.