TableĀ 2

Value of 6-TGN and 6-MMP levels in optimising the dose of azathioprine/6-mercaptopurine

Drug metabolitesAction
Very low 6-TGN and 6-MMPLack of compliance! Discuss with patient
Subtherapeutic 6-TGN<235 and low to normal 6-MMPIncrease dose if not enough efficacy
Therapeutic 6-TGN and 6-MMPIf in remission, keep therapy at same dose
If not in remission, stop therapy
Subtherapeutic 6-TGN and high 6-MMPPatient is a TPMT shunter. Increasing dose of azathioprine may lead to hepatotoxicity with low likelihood of achieving therapeutic 6-TGN levels
High 6-TGN in patients in remissionReduce dose
  • TPMT, thiopurine methyl transferase; 6-MMP, 6-methylmercaptopurine; 6-TGN, 6-thioguanine nucleotide.