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* = Presenting author

P632 Thiopurine metabolite (TM) monitoring in Adolescent IBD (aIBD): Non- and poor adherence is common adolescent practice

F. Kiparissi*1, 2, L. Whitley2, C. Murray3, A. Dawney2, S. McCartney2

1Great Ormond Street Hospital, Paediatric Gastroenterology, London, United Kingdom, 2University College London Hospitals NHS Foundation Trust, Department of Gastroenterology, London, United Kingdom, 3Royal Free London NHS Foundation Trust, Department of Gastroenterology, London, United Kingdom

Background

Azathioprine (AZA)/6-Mercaptopurine (6-MP) are established treatments in IBD. Adherence and dose optimisation can be monitored by measurement of serum 6-Thioguanine (6-TGN) levels (therapeutic range 245-450pmol/8x108 RBC. We aimed to identify if adolescent patients were both receiving and taking an optimal dose of Thiopurine

Methods

96 patients with 130 patient episodes were retrospectively identified over a 24 month period, 52 male; median age 19 years, range 14-23y, diagnosis of: Crohn's (n=68), Ulcerative Colitis (n=16), IBDU (n=2), OFG only (n=1, 82/93 (88%) were on AZA, 11/93 (12%) were on 6-MP

Results

TM were monitored for symptomatic patients 60/96 (63%), well patient/routine blood monitoring 19/96 (20%), adjustment of dose due to weight gain (9%), side effects 3/96 (3%), others 5/96 (5%).

Thiopurine doses varied between 0.4-1mg/kg, median 0.8mg/kg in 6-MP and 0.8-2.7mg/kg, median 1.8mg/kg in Azathioprine, the lower doses being in TPMT heterozygotes.

6-TGN levels were divided into 6 groups (G): G1: levels of 0 (8/96; 8.3%)G2: < 100 (8/96; 8.3%)G3: 101-150 (12/96; 12.5%)G4: 151-244 (18/96; 18.7%)G5: 245-450 (37/96; 38.5%)G6: >451 (11/96; 11.4%).

30/96 (28%) of adolescent patient either did not take their medication at all (n=8, 8.3%) or skipped doses (n=22, 22.9%. Of 8 patient with 0 levels 6/8(75%) were unwell, 2/8(25%) were asymptomatic/best ever. In G4 compliance was checked and dose escalation was instigated. In G6 dose was reduced. In G5 24/37 (54%) patients were symptomatic, 6/37 (16%) were well, 4/7(11%) had gained weight, 2/37(5%) had side effects. Overall 48% (46/96 patients) were inadequately dosed. TPMT levels had poor correlation to 6-TGN levels, even in G6.

Conclusion

TM monitoring is highly useful in adolescents with IBD as it unequivocally identifies lack of adherence and is vital in optimising dose tailoring in a challenging group of patients with complex disease and weight variability.