Biological actions of drug solvents

Many biologic agents are weakly soluble in water. Therefore, they should be dissolved in organic lipophilic solvents (vehicles). A drug vehicle is a substance of no therapeutic value that is used to convey an active biological agent to the site of its action. Ideally, it should be biocompatible, 100% reliable, with no biological effect per se. However, presently used vehicles have pleiotropic effects, which are often unknown to researchers, and often cause misleading conclusions. In this review we summarize data on biological effects of the three most commonly used lipophilic drug vehicles dimethylsulfoxide (DMSO), propylene glycol (PG) and ethanol. Besides in experimental models, the data, where available, are shown on effects of solvents in therapeutic use in humans. In conclusion, some recommendations are given on the use of drug solvents in experiments.