Proliposomal ropivacaine may offer valuable new option for pain relief

A new "proliposomal" preparation of the local anesthetic drug ropivacaine may provide a valuable new option for pain relief in some clinical situations, with key advantages over other types of slow-release local anesthetics, suggest a pair of reports in Anesthesia & Analgesia.

Ropivacaine

Proliposomal ropivacaine can deliver long-lasting pain relief with a single injection, with easier preparation and storage than current slow-release local anesthetic products, according to initial studies in animals and human volunteers. The new formulation was developed and tested by Dr. Yehuda Ginosaur of Hadassah Hebrew University Medical Center, Jerusalem, and colleagues.

New Product Doesn't Become 'Liposomal' Until It's Injected

Liposomal preparations are used as a way of delivering controlled-release of drugs or other products (for example, cosmetics). Liposomes are nano-sized "bubbles" that release their contents as they dissolve. Liposomal local anesthetics are currently available, but have some important limitations. They are complicated and expensive to manufacture and have a short shelf-life—less than one or two months, even with refrigeration.

To address these shortcomings, Dr. Ginosaur and colleagues developed the new "proliposomal" ropivacaine oil. Comparatively easy to prepare, proliposomal ropivacaine oil can be stored at room temperature for up to two years. Liposomes appear, and begin releasing their ropivacaine contents, only when the oil comes into contact with aqueous (water-containing) solutions—including blood plasma.

The researchers initially tested proliposomal ropivacaine in pigs, showing that it gradually released ropivacaine into the animals' circulation. Ropivacaine levels persisted, along with effective control of pain behaviors, for up to four days after application to a surgical wound.

Dr. Ginosaur and colleagues then proceeded to studies in human volunteers, who were injected with proliposomal or plain ropivacaine at separate locations in the lower back. While the amount injected was the same, the ropivacaine concentration of the proliposomal formulations was eight times higher: four percent versus 0.5 percent.

Proliposomal ropivacaine may offer valuable new option for pain relief: A new 'proliposomal' preparation of the local anesthetic drug ropivacaine may provide a valuable new option for pain relief in some clinical situations, with key advantages over other types of slow-release local anesthetics, suggest a pair of reports in Anesthesia & Analgesia.