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

Methods: An observational longitudinal study was conducted. Patients: all recent onset RA patients diagnosed between April 15^th 2007 and 31^st June 2011 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 severe ADR (discontinuation and hospitalization or death as a result of the ADR) due to DMARD treatment. 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 1054 courses of DMARD treatment in 405 patients (2277.9 patient-years). Of these, 78.27% were women with a mean age at diagnosis of 57 ± 15 years. The median time to the start of the first DMARD was 0.3 [± 0.6] days and the median value of ESR at diagnose was 40 [± 27] mm/h. 16.3% of patients were taking biological DMARD, 73.3% were using monotherapy and 89% were taking corticoids. There were 369 ADRs in 212 patients, 41 of them (11.1%) severe (IR: 1.8 [1.3-2.4]). Infection was the most frequent cause of severe ADR (n=26, 63.4%), followed by cancer (n=3, 7.3%); 6 patients died during follow up. Incidence rates are shown in table 1. In the multivariate analysis after adjusting by age: female sex (HR: 2.7 [1.2-5.9]), the use of biological DMARD compared to synthetic DMARD (HR: 3.6 [1.03-12.6]), higher ERS at the beginning of the DMARD (HR: 1.01 [1-1.02]) and the presence at baseline of congestive heart failure (HR: 4.3 [2-9.2]), periphery arteriopathy (HR: 3.1 [1.02-9.2]) and cancer (HR: 3.2 [1.6-6.5]) achieved statistically significant association with the development of a severe ADR. Whereas number of concomitant DMARD dropped from the model (HR: 1.23 [0.5-2.6]).

Conclusion: This study describes the incidence of severe ADR occurred in RA patients taking DMARD in real life conditions. The IR of severe ADR in our cohort was 1.8% patient-years, increasing to 3.6% in the population over 70 years old. Infection was the main cause of severe ADR followed by cancer. Caution might be taken regarding severe ADR in patients of female sex, those using biological DMARD, with higher ERS at the beginning of treatment or with certain comorbidities.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/severe-adverse-drug-reactions-due-to-disease-modifying-drugs-in-patients-with-incident-rheumatoid-arthritis/