ISSN: 1091-5818 print / 1092-874X online DOI: 10.1080 ...

1 International Journal of Toxicology,25:499 521, 2006 Copyrightc American College of ToxicologyISSN: 1091-5818 print / 1092-874X onlineDOI: Vehicle Use in Studies by Multiple Routesin Multiple SpeciesShayne C. Gad and Crystal D. CassidyGad Consulting Services, Cary, North Carolina, USAN icolas AubertCIT Safety and Health Research Laboratories, Evreux Cedex, FranceBart SpainhourCalvert Laboratories, Olyphant, Pennsylvania, USAH eide RobbeMPI Research, Mattawan, Michigan, USAThe laboratory toxicologist is frequently faced with the chal-lenge of selecting appropriate vehicles or developing utilitarian for-mulations for use in in vivo nonclinical safety assessment there are many vehicles available that may meet physicaland chemical requirements for chemical or pharmaceutical formu-lation.

2 There are wide differences in species and route of adminis-tration specific to tolerances to these vehicles. In current practice,these differences are largely approached on a basis of individualexperience as there is only scattered literature on individual vehi-cles and no comprehensive treatment or information source. Thisapproach leads to excessive animal use and unplanned delays intesting and development. To address this need, a consulting firmand three contract research organizations conducted a rigorousdata mining operation of control (vehicle) data from studies datingfrom 1991 to present.

3 The results identified 65 single componentvehicles used in 368 studies across multiple species (dog, primate,rat, mouse, rabbit, guinea pig, minipig, chick embryo, and cat) bymultiple routes. Reported here are the results of this effort, includ-ing maximum tolerated use levels by species, route, and duration ofstudy, with accompanying dose limiting toxicity. Also included arebasic chemical information and a review of available literature oneach vehicle, as well as guidance on volume limits and pH by routeand some basic guidance on nonclinical formulation , Nonclinical Studies, Routes, Safety, Species,VehiclesFormulation, even at the rudimentary level employed for ini-tial studies used to evaluate the safety of new drug candidates, isReceived 9 May 2006; accepted 24 July correspondence to Shayne C.

4 Gad, Gad ConsultingServices, 102 Woodtrail Lane, Cary, NC 27518, USA. E-mail: the weakest link in both pharmacology and toxicologyfor drugs and industrial and agricultural the preclinical safety assessment of potential new drugs,it is required that the material of interest must be suitably for-mulated in a manner that allows adequate administration of thetest substance, with little or no effects in test animals that is at-tributable to the vehicles used in producing such a formulation must be suitable for the intended route of ad-ministration, maintain the stability of the active ingredient, andpreferably maximize the systemic bioavailability of the , the vehicle(s)

5 Or formulation is specified by thesponsor of a study, but more frequently is the informed choiceof the laboratory conducting specified safety the process of vehicle selection has been mostly oneof custom or personal choice, there are many vehicles whichhave seen use in preclinical formulation. However, results as totheir suitability, utility, and limitations on their use are not gen-erally reflected in the literature or taught in any formal such information is not attainable in any readily avail-able place. This paper is intended to at least begin to fill this Preclinical Formulation PrinciplesDosing formulations for preclinical studies should be selectedwith consideration of a number of desirable characteristics assummarized in Table 1 (Gad 1994; Gad and Chengelis 1997).

6 Animal use and care guidance provides limits to volumes thatmay most commonly be administered by each of the commonroutes. These limits are presented in Table 2 (Gad 1994; Gadand Chengelis 1997).Toprovide information to all those who in the future mustselect suitable vehicles for formulation for nonclinical dosing ofanimals, a data mining operation was C. GAD ET 1 Desirable characteristics of a dosing formulation and itspreparationPreparation of the formulation should not involve heating of thetest material to a point anywhere near altering its chemical orphysical characteristics, or so as to harm test animals receivingthe the material is a solid and is to be assessed for dermal effects,its shape and particle size should be preserved.

7 If intendedfor use in man, topical studies should be conducted with theclosest possible formulation to that to be used on test materials (mixtures) should be formulatedso that the administered form accurately represents the orig-inal mixture ( , components should not be selectively sus-pended or taken into solution).Formulation should preserve the chemical stability and identityof the test formulation should be such as to minimize total adminis-tered test volumes. Use just enough solvent or vehicle unlessthere is reason to dilute the active formulation should be as easy as possible to accuratelyadminister.

8 Highly viscous solutions or suspensions shouldbe pH of dosing formulations should be between 5 and 9, or bases should not be used to dilute or solubilize (forboth humane reasons and to avoid pH partitioning or stabilityissues in either the gut or the renal tubule) the test a parenteral route is to be employed, final solutions shouldbe as nearly isotonic as possible. Do not assume a solutionwill remain such upon injection into the blood stream. It isusually a good idea to verify that the drug stays in solutionupon injection by placing some drops into for use by parenteral routes should be as endotoxinfree as possible.

9 Particularly if the test material (or formu-lation component) is biologically derived or produced, theyshould be evaluated for acceptable endotoxin content beforeactual formulation preparation to preclude if use is to be more than a single injection, steps(such as filtration) should be taken to ensure suitable 1994; Gad and Chengelis separate organizations undertook a review of their filesto identify and collect data on control vehicles they had usedin studies over the previous 15 years (1991 to present). Each invivo study conducted during this period had its vehicle controlgroup evaluated. If the vehicle was other than water, the high-est no-observable-adverse-effect level (NOAEL) for the vehi-cle formulation used was determined and this was added to thedatabase.

10 Extracted in this manner by the participating organiza-tions (Calvert, CIT, Gad Consulting Services [GCS], and MPI)were the maximum nontoxic volume identified in these reviewedTABLE 2 General guidelines for maximum dose volumes by routeVolume shouldRoutenot exceedNotesOral20 ml/kgFasted animalsDermal2 ml/kgLimit in accuracy ofdosing/availablebody surfaceIntravenous1 ml/kgOver 5 ml/kgAt any one mlPer ml in rat; 1 mlin rabbitInhalation2 ml/nostril inmonkey or dogGad 1994; Gad and Chengelis by species, route, and duration. The nature of any doselimiting toxicity for a vehicle or vehicle combination was alsoidentified.