Background: According to the Third Consensus of Granada of the WHO an adverse event (AE) is an unfortunate situation/event that occurs during the pharmacological treatment of a disease and that may not necessarily be related to the use of one or more medications. An adverse reaction (AR) is an unfortunate situation/event that is directly related to the use of a medicine. A medication-related problem (MRP) is an unexpected result in the treatment with a certain medication, resulting in the appearance of adverse events/reactions. Objectives: Determine and analyze the incidence of adverse events, adverse reactions and medication-related problems in patients treated for rheumatoid arthritis. Methods: Of a large cohort of approximately 6,000 patients with rheumatoid arthritis (RA) in a specialized center, between 2018 and 2019 pharmaceutical chemist intervention was performed on those patients who reported AEs, ARs and MRPs during their treatment. These reports were made by the treating doctors, the pharmaceutical chemist and directly by the patients to the treating institution. Interaction between medications, adherence to them, patient lifestyles during pharmacotherapy, sociodemographic variables and support relative networks were monitored and investigated. The severity of the events and reactions was evaluated using the Dader method of therapeutic drug monitoring, Morisky Green test to measure adherence and the variables of the Naranjo algorithm in order to characterize them as AEs, ARs or MRPs and determine level of damage to the patient. The cases were analyzed in the pharmacovigilance committee of institution and their causality is defined giving solution to the cases and their follow-up according to relevance. Results: The analysis yielded a cohort of RA 296 patients (44 men-15%, 252 women-85%) who reported AEs, Ars and MRPs. 181 patients (61%) in management with conventional DMARDS and 115 patients (39%) in biological therapy were identified. The highest incidence occurs in ages between 70 and 79 years (36% of cases); more commonly in women (85% of cases); more commonly using convDMARDs (61% of cases), all this being statistically significant (p <0.05). The classification resulted in 66 (22%) AEs, 117 (40%) ARs and 35 (12%) MRPs. The reported causality was probable in 236 cases (79%), possible 46 cases (16%), unlikely: 14 cases (5%) according to the classification of the Naranjo algorithm. GENDER TYPE OF EVENT/REACTION Men 44 15% convDMARDs 178 BIOLOGICS 118 Women 252 85% Cardiovascular 5 Cardiovascular 23 p< 0.05 AGE Dermatological 37 Dermatological 55 p< 0.05 Betw 20 and 40 yo 74 25% Digestive 84 Digestive 9 p< 0.05 Betw 45 and 50 yo 68 23% Inflamatory 23 Inflamatory 16 Betw 51 and 70 yo 33 11% Non-adherence 15 Non-adherence 8 Betw 70 and 79 yo 107 36% Neurological 8 Neurological 0 p< 0.05 Betw 80 and 99 yo 14 5% Respiratory 6 Respiratory 7 TYPE OF THERAPY convDMARDs 181 61% Biologics 115 39% CAUSALITY Probable 236 79% Possible 46 16% Unlikely 14 5% Conclusion: The range of population where AEs, ARs and MRPs most occur are in people over 70 years old; are more common in women and in those who are in conventional DMARDs therapy. The most common AEs, Ars and MRPs with conventional therapy are digestive disorders and in case of biological therapy are dermatological reactions with a mainly probable causality. More studies are needed to clarify these results. References: [1]Third Consensus of Granada on Drug Related Problems (DRP) and Negative Outcomes associated with Medication (NOM). Ars Pharm 2007; 48 (1): 5-17 Acknowledgments: This project was carried out by the scientific direction and the pharmacy of Biomab - Center for Rheumatoid Arthritis Disclosure of Interests: Wilberto Rivero: None declared, Pedro Rodriguez: None declared, Michael Cabrera: None declared, Pedro Santos-Moreno Grant/research support from: I have received research grants from Abbvie, Biopas-UCB, Janssen, Novartis, Pfizer., Speakers bureau: I have been a speaker for Abbvie, Biopas-UCB, Janssen, Lilly, Novartis, Pfizer, Roche, Sanofi.