Background Infliximab (IFX) and adalimumab (ADA) are two monoclonal antibodies (inhibitors of tumour necrosis factor alpha (anti-TNF)) that have revolutionised the management of patients with inflammatory bowel disease (IBD). However, there is a high rate of patients who show no initial clinical benefit for anti-TNF therapy or who lose the response over time. This fact, besides the high cost of these drugs, makes it necessary for an adequate individualisation of the therapy in order to optimize it.

Purpose To describe the pharmacokinetic determinations of serum levels of IFX and ADA in patients with IBD and to evaluate its impact on clinical decision-making.

Material and methods Retrospective, cross-sectional study, carried out in a general hospital. We analysed all anti-TNF determinations (ADA and IFX) performed during 1 year (2017) in patients with IBD. After the analytical determination, the pharmacy service performed a pharmacokinetic study (Bayesian adjustment) and recommended a new posology to the digestive specialist. Anthropometric data of the patients, diagnosis, reason for the request for monitoring, analytical result, pharmacokinetic recommendation and acceptance of this by the physician were collected.

Results A total of 71 determinations were obtained corresponding to 49 participants (60.2% males; 45.6±15.4 age; 63.3% Crohn’s disease and 36,7% ulcerative colitis; 57% treated with ADA). The main reason for monitoring was the presence of activity of the disease (65% ADA; 64% IFX), followed by periodic control (35% ADA; 32% IFX) and other reasons. The drug levels obtained in the monitoring were 5.0±4.0 mcg/mL (0.1–12.3) for ADA and 6.4±3.9 mcg/mL (1–18.5) for IFX. A large number of patients presented serum levels outside the target range (63% ADA and 32% IFX underdosed, 2% ADA and 46% IFX overdosed).

The main recommendation was the maintenance of the regimen and the intensification of the dose. The gastroenterologist acted following the suggestion of the pharmacist in more than 80% of the cases.

Conclusion Results obtained show a high percentage of patients with inadequate anti-TNF serum levels and support the use of anti-TNF pharmacokinetic monitoring as a useful tool in clinical decision-making.

References and/or acknowledgements To my workmates, thank you.

No conflict of interest.