Scientists have developed a new drug that could be a safer alternative to morphine for medical use. The researchers found that engineered variants of endomorphin, a naturally occurring chemical in the body, are as strong as morphine when it comes to killing pain.

On top of that, the medication doesn't produce any of the unwanted side effects that come with opium-based drugs – such as being extremely addictive. At this point, the findings only relate to tests in rats, but it's a promising start to what could be a powerful and less problematic painkiller.

Opioid pain medications are commonly used to treat severe and chronic pain, but in addition to their habit-forming qualities, patients also build up a tolerance to them over time. Hand in hand with their addictiveness, this can makes higher doses – and overdoses in drug abuse situations – dangerous. Overdoses can cause motor impairment and potentially fatal respiratory depression, resulting in thousands of deaths in the US every year.

In contrast, the researchers found that engineered endomorphin in rats produced similar pain relief without the problems stemming from opium-based drugs.

"These side effects were absent or reduced with the new drug," said pharmacologist and neuroscientist James Zadina from the Tulane University School of Medicine. "It's unprecedented for a peptide to deliver such powerful pain relief with so few side effects."

In their testing, the scientists found that their endomorphin variants produced equal or greater pain relief than morphine without causing substantially slower breathing in rats. When given a similarly potent dose of morphine to the animals, the animals experienced significant respiratory depression.

Motor coordination problems were also not evident in the rats given endomorphin, although significant impairment could be seen in animals on morphine. The engineered drug also produced far less tolerance than morphine.

To determine whether the new medication was addictive, the researchers ran several tests that they say are predictive of human drug abuse.

This included seeing whether the animals spent more time in a compartment where they received the substances. With morphine, the rats hung around, but with the endomorphin, they didn't.

In another experiment, the rats could press a bar to produce an infusion of the drug. The animals demonstrated effort to obtain morphine, but didn't press the bar to get the engineered drug.

The findings, published in Neuropharmacology, are an exciting development, given how problematic and destructive opium-based medications are, but it's early days for the researchers' neurochemical variants.

The team hopes to start human clinical trials within the next two years. If results in testing with people show similar effects to those observed in rats, we could really be onto something here.

Especially since new data came out recently showing that deaths from drug overdoses reached a new high in 2014 in the US, totalling some 47,055 people. As this is largely being driven by opiates – including prescription drugs – the sooner we can have less dangerous, non-addictive painkillers, the better.