MONDAY, April 8, 2024 (HealthDay news) -- A new vaccine might be able to block the toxic effects of the animal tranquilizer xylazine, which is being added to illicit drugs and increasing overdose risk.

The vaccine trains the immune system to attack the drug, and has been effective in animal trials, researchers said.

“We demonstrated that a vaccine can reverse the symptoms of a xylazine overdose in rodents,” senior researcher Kim Janda, a professor of chemistry at Scripps Research in La Jolla, Calif., said in a news release reporting their findings.

A rapid increase in lethal drug ODs attributed to illicit fentanyl laced with xylazine prompted the White House Office of National Drug Control Policy to declare this combination an emerging threat to the United States, researchers noted.

Xylazine can heighten the effects of opioids, including the drugs’ ability to slow or even stop breathing, researchers said. Unfortunately naloxone, the standard opioid OD reversal drug, is not effective against xylazine.

Xylazine also has been found in other street drugs, such as heroin and cocaine, researchers said.

Xylazine is thought to work by reducing blood flow to the brain. The drug also causes skin lesions and wounds that won’t heal, sometimes leading to limb amputations.

Researchers sought to create a targeted vaccine that would initiate an immune response to xylazine, protecting the body against the drug’s effects.

The team tested three vaccine formulations in which a xylazine molecule was paired with different protein types, in hopes of prompting an immune response that would create anti-xylazine antibodies.

One of the three vaccines significantly increased movement in mice given xylazine after 10 minutes, while two of the three led to an improvement in breathing.

Researchers also examined how these vaccines might keep xylazine from crossing the blood-brain barrier.

When injected, xylazine immediately crosses the barrier to bind with receptors in the brain.

Antibodies typically can’t cross the blood-brain barrier, but two of the three vaccines showed a strong ability to stop xylazine from reaching brain receptors.

A provisional patent has been filed on the research. The team next plans to try and create an antibody that will reverse the effects of both fentanyl and xylazine.

“A monoclonal antibody treatment could be given in tandem with the vaccine to provide both immediate and long-term protection from both opioid substance use disorders as well as opioid-xylazine overdoses,” Janda said. “This strategy could make a significant impact on the opioid epidemic.”

The new study was published recently in the journal Chemical Communications.

More information

The U.S. Centers for Disease Control and Prevention has more on xylazine.

SOURCE: Scripps Research, news release, April 3, 2024