Background and Importance Ustekinumab is a monoclonal antibody used in inflammatory diseases like Crohn´s disease(CD) and ulcerative colitis(UC). Sometimes, an intensification of its dosage is necessary to achieve the goal.

Aim and Objectives The objective is to know the dosage usually used in our patients compared to that indicated in the label, and the economic impact when an intensified dosage is used.

Material and Methods Retrospective, observational study. Patients with inflammatory bowel disease(IBD) treated with Ustekinumab from January 2022 to March 2023. The variables collected were age, sex, weight, indication, dosage(induction and maintenance regimen) and prior biological treatments. The data was obtained through Orion Clinic® and FarmisOncofarm®. The economic data were obtained using Orion Logis®.

Results 39 patients treated with Ustekinumab were analysed, being 59%(23) men. The median age was 54 years and the average weight was 67 kg. The indication for which Ustekinumab was prescribed: CD in 82%(32) and UC in 18%(7). Regarding previous treatments with biological drugs, 82%(32) had been treated with a single biological drug, while 18%(7) had used two previous lines of treatment. In all cases, the intravenous induction regimen was in accordance with the label according to weight range: 9 patients were 260 mg(≤ 55 kg), 24 received 390 mg(>55 kg to ≤ 85 kg), and 6 patients 520 mg(>85 kg). Regarding the maintenance regimen, 49% (19) of the patients continued with the dosage established in the label(90 mg subcutaneous (sc) every 8 weeks). In the remainder, corresponding to 51%(20), the dosage regimen was intensified mainly due to clinical criteria: 3%(1) continued with 90 mg sc/6 weeks, 3%(1) with 40 mg sc/4 weeks, 41%(16) in treatment with 130 mg IV/monthly, and 5%(2) with 130 mg IV/15 days. The average cost of the treatment the first year in patients who use the dosage of the label is 20148€, whereas the average cost in intensified dosage is 38533€.

Conclusion and Relevance In half of the patients, the maintenance dosage was off label, requiring changes in both the dosage regimen and the route of administration to achieve the clinical objectives, highlighting the need of individualisation. In addition, the intensification dosage involves a financial cost of almost twice as much.

Conflict of Interest No conflict of interest.