A patient is taking the cancer drug, 6-mercaptopurine, and develops a recurrent problem (see image). He was asked to increase his fluid intake and started on allopurinol. The next step in his management is:
a. Inject corticosteroids into the joint
b. Decrease the dose of mercaptopurine
c. Start colchicine
d. Gradually increase the dose of allopurinol
e. Stop 6-mercaptopurine
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6-mercaptopurine is broken down by the enzyme xanthine oxidase.
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If this enzyme is inhibited, then the metabolism of 6-mercaptopurine is decreased and the levels increase. This can lead to significant toxicity due to the increased breakdown of cells leading to excess uric acid production.
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The image shows the presence of gout and the microscopy reveals the urate crystals- you must know this slide
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Therefore, to decrease the gouty episodes, the dose of 6 MP has to be decreased.
