Guidelines for the treatment of rheumatoid arthritis (RA) recommend the use of conventional synthetic disease modifying anti-rheumatic drugs (cs-DMARDs) at the onset of the disease and only in the case of therapeutic failure, the addition of a biological drug (b-DMARD) is suggested.The study aimed to evaluate determinants for first-line biological treatment in patients with RA in clinical practice.A cohort of patients with RA, resident in Lazio, a central Italian Region, where Rome is located, and with at least one disease modifying anti-rheumatic drugs (DMARD) prescription between 2010 and 2016 was selected using health information systems linkable with each other by an individual unique anonymous identifier. In particular RA cohort was defined retrieving all patients with at least a RA disease code in regional data claims (hospital discharge, exemption code, emergency department access, or therapeutic plan). Only new users were included and the first-line treatment was identified: cs-DMARD or b-DMARD.Descriptive analysis according to type of DMARD treatment was performed. Through multivariate logistic regression models (odds ratio [OR]; confidence interval [CI95%]) determinants of therapy such as age, comorbidity, and comedication were investigated.Finally, switching during the first year of treatment from cs-DAMARDs to b-DMARDs was analyzed.DMARD-new users with RA were 5641; 7.1% of them with b-DMARD as first-line treatment. Considering the year of dispensing, this percentage ranged from 4.9% (2011) to 8.2% (2015). Among cs-DMARD the most prescribed active agent was methotrexate (59.3%), while among b-DMARD it was etarnecept (37.0%), followed by adalimumab (21.2%). The average age of the cohort was 54 years with 77% of women. Determinants of first-line b-DMARD use were: age (OR65 = 3.7; 2.6-5.2, OR[30-45)vs>65 = 1.7; 1.2-2.4, OR[45-55)vs>65 = 1.6; 1.1-2.4, OR[55-65)vs>65 = 1.2; 0.8-1.7), cancers (OR = 2.3; 1.3-4.2), cardio-cerebrovascular disease (OR = 1.4; 1.0-1.9), use of non-steroidal anti-inflammatory drugs (NSAIDs) (OR = 0.6; 0.4-0.7) and corticosteroids (OR = 0.6; 0.5-0.7) in the 6 months preceding diagnosis.In the first year of treatment, we observed a percentage of switch from cs-DMARDs to b-DMARDs of 7.9%.In clinical practice, about 7% of patients with RA are prescribed with a b-DMARD as first-line treatment. This therapeutic option, even if not supported by guide lines, is mostly link to younger age and clinical profile of the patients.Copyright © 2021 the Author(s). Published by Wolters Kluwer Health, Inc.