Value of 6-TGN and 6-MMP levels in optimising the dose of azathioprine/6-mercaptopurine
| Drug metabolites | Action |
|---|---|
| Very low 6-TGN and 6-MMP | Lack of compliance! Discuss with patient |
| Subtherapeutic 6-TGN<235 and low to normal 6-MMP | Increase dose if not enough efficacy |
| Therapeutic 6-TGN and 6-MMP | If in remission, keep therapy at same dose |
| If not in remission, stop therapy | |
| Subtherapeutic 6-TGN and high 6-MMP | Patient 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 remission | Reduce dose |
TPMT, thiopurine methyl transferase; 6-MMP, 6-methylmercaptopurine; 6-TGN, 6-thioguanine nucleotide.