Thiopurine metabolites (Thioguanine nucleotides) (THIOM)

Reference Range

For children and young adults with ALL, please refer to your protocol directed guidance. The guidelines below apply to azathioprine/6-mercaptopurine immunosuppression.

TGN therapeutic range 235-450 pmol/8x10E8 RBC

*(TGN <235). TGN below the therapeutic range. Question adherence. Consider dose incrementing if the patient is adherent. If the MeMP/TGN ratio is >11, consider changing therapy to 25% of the target thiopurine dose with 100 mg allopurinol.

*(TGN 235-450). TGN within the therapeutic range. The patient is appropriately dosed. If the patient is not responding to therapy, consider alternative immunosuppressant  therapies. Where MeMP > 5700, there is an increased risk of hepatotoxicity, in such patients consider changing therapy to 25% of the target thiopurine dose with 100mg allopurinol.

*{TGN >450). TGN above the therapeutic range. Dose reduction is advisable if TGN levels are above 550, depending on clinical situation. If patient is not responding to therapy, consider alternative immunosuppressant  therapies.

For 6MMP, therapeutic range is <5700 pmol/8x10E8 RBC

Repeat TGN measurement 4 - 6 weeks after any change in therapy.