Scientists in the US have developed a painkilling technique that lasts up to seven days.
Writing in the journal PNAS, Harvard researcher Daniel Kohane and his colleagues describe how combining a nerve blocking agent called saxitoxin (STX) with a steroid called dexamethasone and packaging the mixture into tiny oily bubbles called liposomes can achieve powerful long term pain relief.
Working first with cells in a dish and then with rats which received injections of the liposomes into the sciatic nerve the team were able to show that the drug combination was non-toxic and the effect was reversible with time. Better still, unlike previous attempts to achieve long-term analgesia with the local anaesthetic bupivacaine which produced toxic damage to nerves and muscle cells, the STX, which is made by certain types of marine algae, had no apparent toxic effects.
From a clinical perspective it also produced very reproducible results, consistently blocking pain in the rats for 180 hours with just four hours leeway. This, say the researchers, suggests that the same trick could provide very prolonged nerve blocks with minimal toxicity in human patients.