Background/Purpose: There is a well-known risk of developing adverse drug reactions (ADR) in rheumatic patients due, mainly, to the Disease Modifying Drugs (DMARD) widely used. It is mandatory to increase our knowledge of ADR outside of clinical trials; especially those that put the patient live at risk. The purpose of our study was to describe the incidence and characteristics of severe ADR (SADR) to DMARD in patients with incident RA as well as the factors associated to their development.

Methods: We conducted an observational longitudinal study. Patients: all recent onset RA diagnosed between April 15^th 2007 and December 31^st 2014 followed in outpatient clinic at Hospital Clinico San Carlos until December 31^st 2016, which used any DMARD treatment (synthetic and biologic). Primary outcome: development of a SADR (discontinuation and hospitalization or death due to the ADR). Incidence rates of discontinuation (IR) per 100 patient-years were estimated using survival techniques with their respective 95% confidence interval [CI]. Comparisons between associated factors were run by Cox bivariate and multivariate regression models. Results were expressed by hazard ratio (HR) and [CI].

Results: We included 2388 courses of DMARD treatment in 814 patients (3706.14 patient-years). Of these, 77.52% were women with a mean age at diagnosis of 57.53±15.50 years. 72.85% of patients were diagnosed at first visit and the median value of ESR at diagnose was 35.6±26.9 mm/h. From the courses of DMARD, 13.74% were biologicals (72.04% anti-TNF) and 60% were used in monotherapy. There were 56 SADRs in 47 patients (IR: 1.51[1.16-1.96]). Infection was the most frequent cause of SADR (n=31, 55.36%), followed by cancer (n=8, 8.93%); 12 patients died due to an ADR (IR: 0.32 [0.18-0.57]), mostly because of sepsis. IR are shown in table 1. We performed a multivariate analysis (table 2). We repeated the model changing the reference category of DMARD and found a higher risk to develop SADR also for Abatacept (HR: 15.38 [1.93-122.75]) and Gold (HR: 2.31 [1.06-5.03]) compared to the other drugs; the rest of DMARD did not achieve statistical significance in the models performed.

Conclusion: The IR of SADR in our cohort was 1.51% patient-years, being infection the main cause. We found differences in discontinuation rates among DMARD due to SADR, with Abatacept, Tocilizumab and Gold being the drugs with the highest risk. Caution should be taken regarding severe ADR in older patients, male sex, patients living alone or institutionalized, with higher values of ESR at the beginning of DMARD and those using combined therapy or with concomitant corticoids.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/analysis-of-severe-adverse-drug-reactions-to-disease-modifying-drugs-in-an-inception-rheumatoid-arthritis-cohort/