Table 1.

Summary of strategies to optimize thiopurine metabolite levels

Method	Effectiveness (%)	Side effect
AZA to 6-MP	48-73[45-48]	Nausea, vomiting, hepatotoxicity, neutropenia, pancreatitis
6-MP to AZA	Not effective[48,50,51]	Nausea, vomiting, hepatotoxicity, neutropenia, pancreatitis
Desensitization	25[51]	Hypersensitivity reaction
Combination infliximab/thiopurine	25[72,74]	Lymphoma, infection
6-TG	46-82[50,58]	NRH, veno-occlusive disease and possible tumor
Allopurinol supplementation	25-75[68,69]	Skin rash, renal impairment, leukopenia
Split-dosing	60[75]	Reduces 6-MP, AZA associated adverse effects

AZA: Azathioprine; 6-MP: 6-mercaptopurine; NRH: Nodular regenerative hyperplasia; 6-TG: 6-thioguanine.