Oxycodone provides pain relief at a price Education Images/UIG via Getty Images

A new opioid drug blocks pain in monkeys without any apparent addictive or dangerous side-effects.

Opioids like morphine, oxycodone and fentanyl are good at stopping pain but can also be addictive. In the US alone, more than 46 people die every day from overdoses involving prescription opioids.

Mei-Chuan Ko at Wake Forest University in the US and his colleagues found they could simultaneously block pain and prevent addiction using a drug that activates two types of opioid receptors in the brain.


The first receptor – the mu opioid receptor – is the classic pain-relieving receptor targeted by traditional opioids. The second – the nociceptin opioid receptor – blocks the brain’s addiction-forming response, while also providing additional pain relief.

The drug, named AT-121, was 100 times better at reducing pain in monkeys than morphine. Ko and his colleagues assessed this by measuring how long the animals were prepared to keep their tails in uncomfortably warm water at 50°C after taking varying doses of the two drugs.

Stopping addiction

The novel opioid also had no apparent addictive properties. The monkeys in the study readily self-administered oxycodone and cocaine but not AT-121. This is a promising finding because monkeys and humans are close evolutionary relations and have similar addiction mechanisms, says Ko.

Another advantage was that AT-121 didn’t cause breathing problems, even at high doses. Existing opioids are dangerous when taken in excess because they can interfere with people’s ability to breathe.

At the moment, the drug must be administered by injection, but Ko’s team is working on developing a pill form.

The researchers hope to begin a clinical trial of AT-121 in 18 months’ time. If successful, it could become available to consumers in the next 6 years.

Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aar3483