UQ researchers have discovered a way to turn tarantula venom into a painkiller. Credit:Alan Henderson Trials show one of these sodium pathways can be influenced by tarantula venom. The venom – one of 205 spider venoms tested - switches off the pathway and stops the brain registering pain. "It is like having an electric guitar, if you don't plug it in the amplifier, nothing much happens," Professor King said. "All of the things on the end of the nerves are still detecting pain, but the 'amplifier' is not there, which is this channel.

"So the brain never perceives any pain at all." The trick for researchers in recent years has been to refine the impact of the venom to influence only the sodium channel that registers pain. One of the other nine sodium channels controls the beating of the heart, while a third controls muscle spasms. "So if we choose the wrong way, we could stop the beating of the heart," Professor Glenn King said. "So if we develop a drug that blocks a sodium pathway that stops registering pain, but also stops the beating of the heart, we are going to kill the patient.

"They are going to die from heart failure. It will be a painless death, but they are still going to die." UQ's Institute of Molecular Research specialists have now been able to identify how to do this. Spider venom is the key, they discovered, because it contains very selective sodium channel inhibitors. "They certainly don't hit the one in the heart and they certainly don't hit the one in the muscles," he said. That has major pharmaceutical companies interested and is why Johnson and Johnson is now part of the new trials.

Tarantulas are important because they are big spiders, they are relatively easy to milk and they live up to 25 years. "So it is a spider you can keep in the lab for a long period of time and you can milk it and get reasonable amounts of venom," Professor King said. The tarantula venom has proven to be the best source of the molecule that switches off the very specific pain receptors, he said. "But they represent only a small fraction of the world population of spiders around the world and what we are trying to do now is look at other spiders." And how do you milk spider venom?

"You basically have to hold the spider down, or anaesthetise it, then get some forceps which have been electrified, and put some voltage across the fangs of the spider and force it to expel some venom," Professor King explained. "And if we get 10 micro-litres of venom, we get very excited." Professor King said researchers were not looking for a replacement for the aspirin. "They are plenty of options out there for that," he said. "We are looking for something for people that suffer long-term chronic pain, which represents – around the world – about 15 to 20 per cent of the population.

"For the elderly, the proportion is higher, up to 50 per cent to 65 per cent." Diabetic neuropathy, cancer treatments and osteoarthritis are the areas the tarantula drug researchers are targeting, Professor King said. He said the research strongly indicates it will be more effective than the current drugs on the market and less addictive. "We don't think there is going to be any side effects from these drugs at high doses," he said. "And the other important thing is we don't think people will build the 'tolerance' that you see with opioid drugs.

"In other words you have to keep upping the dose with time. "You should be able to use the same dose for the whole period when you are taking the drug." Very specific pain relief trials will continue on rats for two to three years and a commercial product could be used in five years, Professor King said.