Injectable liposomal formulations of opiorphin as a new therapeutic strategy in pain management

Opiorphin is an endogenous peptide with a strong analgesic effect, superior to that of morphine and without the several side effects of morphine and morphine-like drugs. Conventional and PEGylated liposomes were developed, aimed at protecting the drug from rapid metabolization and improving its therapeutic efficacy. In vivo rat experiments proved that PEGylated liposomes were more effective than conventional liposomes, significantly enhancing intensity and duration of the pain-killing effect. Opiorphin-PEGylated liposomes showed a more intense and prolonged pain-killing effect than morphine at the same dosage. Therefore, this new formulation could represent a noticeable improvement in pain management therapy, as a valid morphine alternative.