6-TGN and 6-MMPN

Alternative names, keywords

Thioguanine nucleotides and methylmercaptopurine nucleotides, TGN, MeMP, 6 TGN, 6-MMPN, thiopurine metabolites.

Samples required

EDTA blood (purple cap/ yellow cap ring, 4 mL tube). Smaller tubes are available for paediatric samples.

4 weeks to steady state after starting/changing dose. No need to take sample at specific time relative to last dose.

Test indications

Monitoring patients on thiopurine drugs (azathioprine, mercaptopurine, tioguanine); may be helpful to check whether therapeutic concentrations are being achieved, especially in patients heterozygous for TPMT on reduced dose regimes.

Reference range

TGN therapeutic range: 235-450 pmol/8x10⁸ red blood cells.

MeMP concentrations over 5700 pmol/8x10⁸ red blood cells have been reported to confer an increased risk of hepatotoxicity.

Turnaround time

Referral lab quotes turnaround time of 5 days, however additional time must be allowed for packing, dispatch and delivery of sample, and return and processing of results.

Enquiries

Biochemistry (Referrals)