Patent ID: 7357944

Claim:
A method of producing prolonged analgesia, comprising administering to a subject in need of such treatment a liposomal composition comprising an analgesic drug, wherein said composition is characterized by: (a) the liposomes are GMV liposomes and have a size of at least 1000 nm; (b) the GMV liposomes contain multiple, non-concentric vesicles having a diameter less than 1000 nm; and (c) the liposomes have a drug to lipid ratio of at least 0.5% mole ratio; (d) wherein the liposomes are prepared by: (i) vortexing a lipid film with an aqueous ammonium sulfate medium containing said analgesic drug to be encapsulated, thus forming a first suspension; (ii) homogenizing the first suspension to form a second suspension of small unilamellar vesicles (SUV); (iii) repeatedly freeze-thawing said second suspension in liquid nitrogen followed by washing with water; and (e) incubating said analgesic drug with GMV liposomes formed in step (iii).