Review Tolerable Levels of Nonclinical Vehicles and Formulations Used in Studies by Multiple Routes in Multiple Species With Notes on Methods to Improve Utility Shayne Cox Gad 1 , Charles B. Spainhour 2 , Catherine Shoemake 3 , Danielle R. Stackhouse Pallman 2 , Alain Stricker-Krongrad 3 , Philip A. Downing 4 , Richard E. Seals 4 , Leslie Anne Eagle 1 , Kara Polhamus 5 , and Jennifer Daly 5 Abstract Formulation of nonclinical evaluations is a challenge, with the fundamental need to achieve multiples of the clinical exposure complicated by differences in species and routes of administration-specific tolerances, depending on concentrations, volumes, dosing regimen, duration of each administration, and study duration. Current practice to approach these differences is based on individual experience and scattered literature with no comprehensive data source (the most notable exception being our 2006 publication on this same subject). Lack of formulation tolerance data results in excessive animal use, unplanned delays in the evaluation and development of drugs, and vehicle-dependent results. A consulting firm, a chemical company, and 4 contract research organizations conducted a rigorous data mining operation of vehicle data from studies dating from 1991 to 2015, enhancing the data from this author’s 2006 publication (3 of the six 2015 contributors were also 2006 contributors). Additional data were found in the published literature. The results identified 108 single-component vehicles (and 305 combination for- mulations) used in more than 1,040 studies across multiple species (dog, primate, rat, mouse, rabbit, guinea pig, minipig, pig, chick embryo, and cat) by multiple routes for a wide range of study durations. The tabulated data include maximum tolerated use levels by species, route, duration of study, dose-limiting toxicity where reported, review of the available literature on each vehicle, guidance on syringe selection, volume and pH limits by route with basic guidance on nonclinical formulation development, and guidance on factors to be considered in nonclinical route selection. Keywords animals, nonclinical studies, routes, safety, species, vehicles, formulation, excipients Introduction From the point of initiation of development of a new drug or other test material, continuing on until the therapeutic enters serious clinical trials, perhaps the weakest link in investigations of both pharmacodynamic and toxicodynamic evaluations are formulations. In evaluating the nonclinical safety of potential new drugs, it is required that the material of interest be formu- lated in a manner that allows adequate administration of the test substance, with little or no effects on test animals attributable to the vehicles used in the delivery of the actual test material. The formulation must be chemically and physically suitable for the intended route of administration, optimize the stability of the active ingredient, and preferably (in most cases) maximize the systemic bioavailability of the drug. Because historically the process of vehicle selection has been mostly one of custom or personal choice, a range of vehicles have been most commonly used in formulation. Regrettably, information as to their suit- ability, utility, and the volume of nonclinical use limitations and species-specific considerations are not generally reflected in the literature or taught in any formal manner. Although recent years have seen the appearance of training courses on preformulation and articles on the development of early formulations (ie, Li and 1 Gad Consulting Services, Raleigh, NC, USA 2 Calvert Laboratories, Scott Township, PA, USA 3 Sinclair Laboratories, Columbia, MO, USA 4 BASi Laboratories, Mount Vernon, IN, USA 5 MPI Laboratories, Mattawan, MI, USA Corresponding Author: Shayne Cox Gad, Gad Consulting Services, 4008 Barrett Drive Suite 201, Raleigh, NC 27609, USA. Email: scgad@ix.netcom.com International Journal of Toxicology 2016, Vol. 35(2) 95-178 ª The Author(s) 2016 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1091581815622442 ijt.sagepub.com