skip to main content

Thiopurine Metabolite Monitoring Azathioprine — ESENeph MCQ

Instant feedback + full explanation. One question, done properly.

HardRenal VasculitisThiopurine Metabolite Monitoring AzathioprineESENeph

A 48-year-old woman with ANCA vasculitis achieves remission. She is started on maintenance Azathioprine. Her nephrologist checks her thiopurine metabolites (6-TGN and 6-MMP) to guide dosing. What do these metabolites indicate?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — 6-TGN (6-thioguanine nucleotides) levels correlate with efficacy and myelotoxicity; 6-MMP (6-methylmercaptopurine) levels correlate with hepatotoxicity – metabolite monitoring enables dose optimisation particularly in patients with intermediate TPMT activity

Thiopurine metabolite monitoring (6-TGN and 6-MMP) provides precision dosing of Azathioprine. Target 6-TGN levels (235-450 pmol/8x10^8 RBC in IBD; similar principles apply in vasculitis) correlate with therapeutic efficacy and myelosuppression risk. Elevated 6-MMP (>5700 pmol/8x10^8 RBC) indicates preferential metabolism via TPMT pathway and predicts hepatotoxicity. In patients with skewed metabolism (high 6-MMP, low 6-TGN despite adequate dosing), adding Allopurinol at low dose with 75% Azathioprine dose reduction can redirect metabolism toward 6-TGN. This requires specialist monitoring.

Reference: Lennard et al 2006 – Thiopurine Metabolites; BSG 2019 – Thiopurine Monitoring