Abstract: The present invention provides drug delivery compositions in both concentrated and diluted forms for use as vehicles in the administration of various active agents. The drug delivery compositions are primarily designed for use with lipophilic, amphipathic, and sparingly water soluble active agents, preferably drugs. The drug delivery compositions are to be administered to an animal to effect uptake of the active agent. The primary mode of administration is by intravenous, intra-arterial, intrathecal, intraperitoneal, intraocular, intra-articular, intramuscular or subcutaneous injection. The concentrated drug delivery compositions are formulated with a phospholipid component, a component selected from propylene glycol or certain polyethylene glycol compounds, a high HLB surfactant, and the drug component, with water and/or an oil component optional. The concentrated drug delivery compositions can be diluted with an aqueous fluid to form an oil-in-water microemulsion composition.