Background To analyse the cost of biological drugs in clinical practice is a useful tool in choosing a drug, especially when direct comparison studies are limited and systematic reviews report similar effectiveness for these medicines.

Purpose To describe the dispensing pattern and calculate, according to clinical practice, the annual median cost and percentage of dispensing median dose of tocilizumab, etanercept, adalimumab or infliximab in rheumatoid arthritis (RA), ankylosing spondylitis (AS) or psoriatic arthritis (PsA). Moreover, to compare these results with recommended doses and theoretical costs (annual cost of each drug according to Spanish official unitary price and official dispensing frequency).

Material and methods Observational retrospective study. From 1 January 2009 to 31 December 2013, all adults with RA, AS or PsA treated with tocilizumab, etanercept, adalimumab and/or infliximab for at least 1 year were included. They were attending the rheumatology and pharmacy services. The information was collected from the electronic medical history programme and pharmaceutical care database. Data were analysed with SPSS statistical.

Results 251 episodes of treatment were included: 106 of adalimumab, 89 of etanercept, 38 of infliximab and 18 of tocilizumab. These episodes corresponded to 236 patients. Adalimumab was the most usually dispensed drug in all pathologies (42.2%). 59.4% of drugs were dispensed to treat RA, 23.5% for AS and 17.1% for PsA. Change in dispensing frequency was the most common posology adjustment.

For all indications, statistical differences in real cost between two subcutaneous therapies were described: etanercept was 4.0% cheaper than adalimumab in RA (p = 0.012), 12.2% cheaper in AS (p = 0.002) and 18.2% more economical than adalimumab in PsA (p = 0.001). Otherwise, the real annual median cost was lower than the theoretical annual cost (statistically significant differences) for all therapies with indications, except for infliximab. Only in RA was the real annual median cost of infliximab higher than the theoretical annual cost (p = 0.140). In AS, statistically significant differences were described in the percentage of dispensed median real dose of tocilizumab (86.7%), infliximab (114.2%), etanercept (93.1%) and adalimumab (89.3%) compared with recommended doses.

Conclusion Real dosage of etanercept, adalimumab and tocilizumab is lower than the recommended dosage. Therefore, the real annual cost should be taken into account to choose one biological therapy.

No conflict of interest.