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Background: Adalimumab is administered via a pre-filled syringe or spring-loaded pen. In a previous study in Crohn's disease, higher drug levels were observed in syringe users. The aim of this study was to evaluate the impact of delivery device on adalimumab drug levels in patients with Crohn's disease. Method(s): Consecutive Crohn's disease patients treated with maintenance adalimumab [40 mg fortnightly] were recruited from five centres. The first recorded drug level with matched clinical and biochemical markers of disease activity was compared between pen and syringe users. Result(s): Of 218 patients, 64% used pen, with a median faecal calprotectin 110 mug/g and serum C-reactive protein 4 mg/L. In comparison to pen, syringe users had higher albumin [39 vs 42 g/L; p = 0.016], lower Harvey-Bradshaw Index [2 vs 1; p = 0.017], and higher rates of concomitant immunomodulation [54% vs 71%; p = 0.014]. Drug levels were equivalent between pen and syringe users [median 5.3 vs 5.2 mug/ml; p = 0.584], even after controlling for disease activity and immunomodulation. Syringe users at Alfred Health had higher drug levels than pen [6.1 vs 4.5 mug/ml; p = 0.039]; a greater proportion achieved therapeutic levels [75% vs 44%; p = 0.045]. A higher proportion of pen users from Saint-Etienne had therapeutic levels [79% vs 42%; p = 0.027], yet no significant difference in drug levels [7.9 vs 4.5 mug/ml; p = 0.119]. Conclusion(s): Delivery device does not appear to significantly affect adalimumab drug levels. Given differences between study sites, studies evaluating administration education and technique are warranted.Copyright © 2019 European Crohn's and Colitis Organisation (ECCO). Published by Oxford University Press. All rights reserved.

Introduction: In an intensive pharmacokinetic study of adalimumab (ADA) in Crohn's disease (CD), trough drug levels were significantly higher in syringe compared with pen users. Further data addressing the impact of delivery device on ADA drug level are lacking. Aim(s): Our aim was to compare drug levels associated with the use of pen and syringe delivery in patients undergoing maintenance ADA therapy for CD. Method(s): This was a retrospective observational study of adult patients with CD receiving 40 mg ADA fortnightly (for >14 weeks) across five centers. Therapeutic drug monitoring (TDM) was performed with ELISA as per manufacturer's instructions. Data on the first recorded drug level (independent of indication); markers of disease activity, including Harvey Bradshaw Index (HBI), C-reactive protein (CRP), and fecal calprotectin (FCP); and patient and disease characteristics were collected. Drug levels >4.9 mug/mL were considered therapeutic, and active disease was defined as CRP >5 mg/L or FCP >150 mug/g. Result(s): A total of 218 patients were included; 52% were male, the mean age was 39 years, and 60% received concomitant immunomodulation. Mean FCP level was 283 mug/g, and CRP level was 10.2 mg/L at TDM. Pens were used by 64% of the cohort. Syringe users had a higher albumin level (40 vs 38 g/L; P = 0.016), lower HBI (2.2 vs 3.4; P = 0.017), and higher rates of concomitant immunomodulation (71% vs 54%; P = 0.014) than pen users. No significant differences in disease activity (CRP or FCP), duration, or patient demographics between delivery device were observed. Considering all patients, there was no difference in drug levels in pen versus syringe (5.3 vs 5.2 mug/mL; P = 0.442; Fig. 1a). Fur-thermore, drug levels did not differ between pen and syringe users when controlling for disease activity (CRP or FCP). On subgroup analyses by center, syringe users at Alfred Health had significantly higher drug levels than pen users (6.1 vs 4.5 mug/mL; P = 0.039; Fig. 1b), a