3.4 Therapeutic drug monitoring
Mercaptopurine dose adjustments were required in 22 out of 29 [75.9%] patients. Out of seven patients in the mercaptopurine group who did not require dose adjustments, five [17.2%] discontinued mercaptopurine treatment before the first TDM measurement at week 6, and the other two [6.9%] patients continued mercaptopurine treatment at the initial dose throughout the study up to week 52 [Median 6-thioguaninenucleotide [6-TGN] and 6-methylmercaptopurine [6-MMP] serum concentrations in pmol/8 × 10