Background Ustekinumab, whose marketing led to a significant reduction in the number of administered doses (1–2 injections every 12 weeks, depending on the weight), represents an alternative treatment in the management of severe psoriasis. In daily clinical practice, it has been observed that ustekinumab posology is modified depending on the patient’s response.

Purpose To calculate and evaluate the economic impact of the use of ustekinumab in a tertiary care hospital in daily clinical practice.

Materials and methods Observational retrospective study of patients treated with ustekinumab between January/2009 and January/2013. All patients treated for at least 28 weeks were selected. The patient’s weight, posology, duration of treatment and real and theoretical costs per patient/year in relation to the patient’s weight, were collected. The cost of one ustekinumab 45 mg syringe was set at 3,174.3 € (official data).

Results 83 patients were studied, 16 weighed more than 100 kg at the beginning of the treatment. The average cost per patient/year was 17,027.5 €, though with the recommended posology it would have been 18,168.8 €. This means a cost saving of 6.3% (1,141.3 €). Per weight, the cost per patient/year of the <100 kg patients was 16,941.7 €, instead of the theoretical 16,438.9 €, which means 3% (502.8 €) more. They received 102% of the recommended dose due to reductions in the dosage interval. On the other side, the average cost per patient/year of those weighing >100 kg was 21,621.8 € instead of the theoretical 29,522.1 €, which means a cost saving of 26.7% (7,900.3 €). Due to reducing the ustekinumab dose from 90 to 45 mg and shortening the dosage interval, the >100 kg patients received the 73.2% of the total theoretical dose.

Conclusions Over the period of time analysed, the cost of ustekinumab was lower than expected, mainly due to dose modifications in the >100 kg patients. It is necessary to evaluate if the changes introduced for these patients have a clinical impact on the efficacy of their psoriasis treatment.

No conflict of interest.