Peer review: blind reviewer and Annemeri Livinallli Objectives: To assess if the antiemetic prophylaxis prescribed to patients exposed to chemotherapy is following the Antiemesis guideline published by the National Comprehensive Cancer Network (NCCN) version 3.2018. Methods: A medication review was performed, considering antiemetic´s prescriptions of adult patients under treatment with moderate and high emetogenic potential antineoplastic agents, assisted on an outpatient basis in a tertiary public hospital, from May to September 2019. The information contained in the prescriptions was compared with the guideline recommendations in relation to the selection of the therapeutic class of the antiemetic, dose, route of administration, dosage regimen and duration of treatment, with the prophylaxis expected for the acute and delayed phases being evaluated. Results: Were included 87 patients, 38 and 49 of whom used chemotherapy drugs with high and moderate emetogenic potential, respectively. In the prescriptions containing highly emetogenic chemotherapeutic agents, the antiemetic therapy recommended for acute phase prophylaxis was incorrectly prescribed for 9 patients (23.7%), and the problem encountered was dexamethasone underdose (16.7%). In the delayed phase, problems were identified in the prescriptions of 35 patients (92.1%), including the prescription of inappropriate medication (57.4%), since the prescription contained ondansetron, not foreseen by the guideline at this stage, and the need for dexamethasone as an additional drug (18.5%). For 22 patients (44.9%) exposed to moderately emetogenic antineoplastic agents, the acute regimen was incorrectly prescribed, and the main problems identified were dexamethasone overdose (21.2%) and the need for dexamethasone as an additional drug (5.0%). Delayed antiemetic prophylaxis was incorrectly prescribed for 45 of them (91.8%), with ondansetron treatment duration longer than recommended (26.2%), need for dexamethasone or ondansetron as an additional medication (23.7%) and therapeutic duplicity (12.5%) the problems encountered. Conclusion: It is suggested the implementation of strategies aimed at increasing adherence to the guideline's recommendations by the prescribers, as well as access to medicines considered essential.