e18256 Background: The importance of monitoring Adverse Drug Reactions (ADRs) is undeniable, because it may limit the therapy and lead to stop a cancer treatment. Early identification and appropriate clinical management, prior to after chemotherapy, may mitigate or reverse undesirable effects. Effective Pharmacovigilance occurs through active participation and assertive communication among health professionals. In this context, the present work is aimed at quantifying Pharmaceutical Interventions after ADR and its impact on therapy. Methods: The data collection was done by analysis of the Nursing Evolutions on the ADR presented during infusion. After identifying them, the Clinical Pharmacist investigates and suggests interventions in a pre-chemotherapy scheme to the Oncologist, if pertinent. Work performed between April 2016 and January 2017, at a private Oncology Clinic in Rio de Janeiro, Brazil. Results: During the period, 60 pharmaceutical interventions were performed on prescriptions of patients who presented adverse drug reactions. Of these, 40 patients (67%) did not present the same reaction again and 20 patients (33%) presented it again, despite the change in pre-chemotherapy. The most common reactions were hypersensitivity (47%) and abdominal colic (43%). The most commonly prescribed drugs were hydrocortisone (22%), diphenhydramine (25%) and atropine (40%). Conclusions: These findings reaffirm pharmacovigilance as an important multidisciplinary instrument to promote the safe use of drugs, the efficacy of cancer treatment and the improve of quality of life in cancer patients. This importance is strengthened in the oncology clinic, in which patients are more likely to present possible ADR due to the frequent use of multidrug therapy.