The primary objective for the nonclinical uses is to achieve having a stable solution for administration, vehicles are generally more the focus than the other types of excipients. The Appendix provides a modified version of S. C. Gad et al., the most comprehensive summary of common nonclinical vehicles and excipients and their tolerated levels by route, species, and duration of use. Vehicles are a subset of excipients. They are distinguished by being liquids, and their primary purpose is to dissolve or “carry” the active drug substance and solid-phase excipients. Aqueous vehicles are generally preferred, but the utilization of oily vehicles for lipid-soluble materials is acceptable. Food oils such as corn oil can be used, but mineral oils should never be used. There are several definitions for an excipient. In some cases, the definition can be simple, yet in other cases the definition is more encompassing and complex.