Objective:

To analyze the activity developed by a multidisciplinary team of pharmacists, digestive specialists and clinical analysts for the therapeutic drug monitoring (TDM) of anti-TNFa therapies in inflammatory bowel disease (IBD).

Methods:

A prospective observational study (January-December 2019) was conducted of referrals from digestive specialists to the Clinical Pharmacokinetics Unit (CPU) of our general hospital for the TDM of anti-TNFa drugs (infliximab/adalimumab) in adults with IBD. Serum anti-TNFa concentrations were quantified in our Clinical Analysis Laboratory using lateral flow chromatography. When concentrations were undetectable, the presence of anti-drug antibodies (ADAs) was analyzed.

CPU recommendations were based on the correct interpretation of anti-TNFa concentrations, therapeutic algorithms, and populational pharmacokinetic models implemented using MW-Pharm++® software.

Results:

Referrals were received for 84 patients (81.0% with Crohn’s disease, 8.3% with ADAs) treated with infliximab (46.4%) or adalimumab (53.6%); 64.3% were also treated with concomitant immunomodulators (IMMs). Sixty-three referrals (75.0%) were for proactive monitoring (treatment optimization) and the remainder for reactive monitoring after therapeutic failure. Anti-TNFa concentrations were subtherapeutic in 36.9% of patients, therapeutic in 39.3%, and supratherapeutic in 23.8%. Subtherapeutic/undetectable concentrations were significantly more frequent (p≤0.004) in patients treated with infliximab versus adalimumab (64.1% vs.. 13.3%) and in concomitant IMM non-adherents versus adherents (85.7% vs. 25.5%).

Conclusions:

Anti-TNFa TDM is frequently proactive in patients with IBD. The wide variability in anti-TNFa concentrations is in part explained by the type of anti-TNFa drug and adherence to IMM.

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