Suitable amphipathic polymers include, but are not limited to, poloxamer P-188, polyetherester copolymers such as polyethylene glycol and polylbutylene terephthalate copolymers, polyethylene glycol and polypropylencoxide copolymers, polyethylene glycol and polypropylene glycol block copolymers.The amphipathic polymers also include a family of polyetheramines known as Jeffamine??.