Objectives: In inflammatory bowel disease therapy, thiopurines have been essential. However, several reports have investigated factors affecting thiopurine metabolism to date. This study investigated factors affecting intracellular concentrations of 6-thioguanine nucleotide (6-TGN) and 6-methylmercaptopurine (6-MMP) in a real-world setting.
Methods: Between May 2013 and October 2021 in one institution, 44 patients (median age 44 years;male 35, female 9;ulcerative colitis 32, Crohn's disease 12) receiving thiopurines were reviewed. Intracellular 6-TGN/6-MMP concentrations were measured by high-performance liquid chromatography, and the initial measurement in each patient was used for the study.
Results: The 6-TGN level was significantly higher in females, with mild disease activity, absence of NUDT15 polymorphism, and allopurinol administration. A higher trend was observed with high thiopurine dosage (>50 mg). 6-MMP levels were significantly lower with concomitant use of time-dependent 5-aminosalicylic acid (5-ASA) and allopurinol, and higher with high thiopurine dosage. On multivariate analysis of variance, logarithmically transformed 6-TGN levels were significantly higher in females, with high thiopurine dosage, and allopurinol administration. Similarly, logarithmically transformed 6-MMP levels were significantly higher with time-dependent 5-ASA administration and high thiopurine dosage.
Conclusions: Patients who received allopurinol, a high dose of thiopurine, or were female showed higher 6-TGN levels.
Keywords: 6-MMP; 6-TGN; Thiopurine; inflammatory bowel disease.