Drug-drug interactions are a key consideration when determining which NK-1 antagonist to use in patients receiving highly emetogenic chemotherapy. We discuss the issues for (fos)aprepitant, netupitant, & rolapitant. A nice aprepitant review (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5595939/) and the case for an aprepitant-vincristine interaction (https://doi.org/10.1177/1078155219870840).