Researchers have developed a new type of opioid that targets pain in rats without causing unpleasant side effects. Their work was conducted in Berlin and published in the journal Science.

Opioids are highly addictive and kill 91 Americans every day, according to the Centers for Disease Control and Prevention. In addition to dependence, there are many other side effects that come along with opioids such as tolerance, constipation, nausea, sleepiness, confusion, depression, decreased sex drive, itching, sweating, and increased sensitivity to pain. The drugs are used to treat moderate-to-severe pain, and are typically prescribed to those who have surgery, experience serious injury, or have cancer.

Read: Do Opioids Make Chronic Pain Worse? New Study Looks At Morphine, Oxycodone, And Other Prescription Meds

The newly developed opioid, called NFEPP, works by targeting only the area experiencing pain, which eliminates side effects that harm other parts of the body, reports MedicalXpress.

The researchers note that when your body is in pain, inflammation occurs to aid with healing. Those inflamed body parts are also typically more acidic. There goal was to create an opioid that would only target the specific acidic, inflamed body parts.

NFEPP was tested on rats and found to work similar to fentanyl, which is an opioid that is 50 to 100 times more potent than morphine. The new drug relieved pain, but did not cause any side effects.

The study authors conclude more testing needs to be done on animals before there is a human trial. If the drug proves to be effective on humans, this will be a breakthrough in pain management.

Opioid addiction is a serious public health problem. Since 1999, the number of overdose deaths involving opioids has quadrupled, the CDC reports.

See also: How Did Opioid Drugs Get To Be So Deadly? A Brief History Of Its Transition From Trusted Painkiller To Epidemic

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