Background: Appropriate antiemetic prescribing remains an unmet need in patients receiving emetogenic chemotherapy. Non-compliance with standard antiemetic guidelines is well reported, and a focus of the American Society of Clinical Oncology Choosing Wisely campaign. Using our medically integrated pharmacies, a community oncology practice sought to maximize compliance with national guidelines by minimizing the use of NK1 inhibitors for low and minimally emetogenic regimens and optimizing medications for highly emetogenic regimens per NCCN guidelines. Methods: A retrospective review of a medically integrated pharmacy antiemetic therapeutic interchange policy. Trained oncology pharmacists imbedded within 2 cancer centers evaluated all new chemotherapy orders to determine the level of emetogenicity per NCCN guidelines. Pharmacists then used a guideline compliant prespecified therapeutic interchange protocol to adjust the antiemetic medications. Patient education to enhance medication compliance was performed by the pharmacists, nurses, and in one on one treatment review sessions with an advance practice provider. Results: Of 271 low to minimally emetogenic regimens, 99% did not receive an NK1 inhibitor on the first cycle. Of 367 highly emetogenic regimens, 97% appropriately received guideline based therapy. Additionally, the use of olanzapine was non-existent in the practice prior to this protocol and increased to 55% of patients with highly emetogenic regimens. Conclusions: We demonstrated that a therapeutic interchange policy with a medically integrated pharmacist shows enhanced compliance with guideline based antiemetic medication usage. This system also allows rapid uptake of changes in supportive care guidelines such as rapid adoption of olanzapine. Efficacy results of this protocol will be reported separately.