As opioid-related deaths and addiction in the United States reach epidemic proportions, James Zadina has been attempting to engineer a new kind of neuropathy pain medication that would not have the devastating side effects often caused by commonly prescribed drugs such as Oxycontin. His pursuit is difficult because the very mechanisms that make those pills good at dulling pain are the ones that too often lead to crippling addiction and drug abuse. Like their close chemical cousin heroin, prescription opioids  can cause people to become physically dependent on them. Researchers have been trying for decades to “separate the addictive properties of opiates from the pain-reducing properties,” says David Thomas, an administrator at the National Institute on Drug Abuse.
Developing any kind of better painkiller is very hard largely because pain takes complex pathways in our bodies. The main way to kill pain is simply to reduce the signals that the body feeds to the brain. The article explains clearly how changes in the number or type of active cellular machines known as sodium channels can cause nerve pain when there are no threatening stimuli. Sodium channel blockers exist to block nerve pain but have limiting side effects particularly because it is difficult to target just a single channel.
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Source: MIT Technology Review, Adam Piore, August 11, 2016