GEOFF BENNETT: Now the latest in our continuing coverage of how opioid addiction and overdose deaths have devastated the U.S.

Concerns are growing about overdoses that are linked with an animal tranquilizer mixed with opioids, and it's a problem increasing across the country.

Ali Rogin has more.

ALI ROGIN: Geoff, this week, the Biden administration declared the combination of that sedative, xylazine, and the opioid fentanyl a -- quote -- "emerging threat."

It's the first time any drug has been given that designation.

Veterinarians have been legally using xylazine, often referred to as tranq, for 50 years, but it made its way into U.S. street drugs sometime in the early 2000s.

And in the past two years, its use has spiked nationwide.

Joining me now is Dr. Raagini Jawa.

She's an assistant professor and clinician investigator at the University of Pittsburgh.

Dr. Jawa, thank you so much for joining us.

You regularly treat people who have been using xylazine.

What are some of the symptoms that you commonly see?

DR. RAAGINI JAWA, University of Pittsburgh: So I'm an infectious disease and addiction medicine provider, and I take care of patients in the Pittsburgh area, not only at our local needle exchange or syringe service program, but also in our addiction treatment clinic and in the hospital.

And a lot of my patients coming in for the last year have been exhibiting increasing symptoms of wounds and more complicated overdoses.

And they have just been telling me: "You know, Doc, something doesn't feel right.

And I'm having new symptoms that I haven't had when I was just using fentanyl or heroin alone."

ALI ROGIN: And how does xylazine differ from fentanyl?

And what's happening a lot now is the two are being combined.

So what happens when that takes place?

DR. RAAGINI JAWA: Yes, so there's -- we're learning a lot right now from our patients, because what we know from the original studies on xylazine that were done only on animals is, it has a myriad of effects.

And the most important effect is that it is a -- not an opioid, and it is a sedative.

What that means is, it can - - it's used in procedures for veterinarians.

But when it's mixed in with fentanyl, patients, human patients are exhibiting many symptoms.

One thing that they're saying is, this prolonged periods of sedation, that if they are using the drug, they're just out for several hours and they don't even realize it.

The second thing they're realizing is, they have chronic exposure to xylazine mixed in with whatever substance they're using are wounds.

And these wounds tend to happen all over their extremities, so on their arms or their legs.

And they can be quite painful.

And so those are some of the few symptoms that my patients are experiencing.

ALI ROGIN: So, these are two different drugs, but Narcan, naloxone, can still help, right?

DR. RAAGINI JAWA: Absolutely.

And it's really important, when we're thinking about public health messaging around xylazine, that the first step, if you're worried about someone who's overdosing, even if it's associated with xylazine, is to administer naloxone first, call for help, and then monitor patients.

Usually, we say wait two to three minutes before administering the second dose, and then watch for breathing, oxygen level, and provide supportive care.

ALI ROGIN: What do you think of the Biden administration's announcement this week that xylazine and fentanyl together are going to be treated as an emerging threat?

DR. RAAGINI JAWA: So, I'm really glad that the ONDCP released this statement.

And as an addiction medicine physician and someone who works with harm reduction organizations, we have been doing a lot of this work on the side for a while now.

And communities of researchers and harm reduction organizations have been banding together to meet our patients' needs.

And so hopefully we can leverage some of the federal attention and funding and bring all of these people in the community who've been doing some good work together.

And I think, hopefully, we can use this attention to bring them to the table as we're thinking about national strategies on how to deal with this problem.

The second thing I hope is that I hope the funding helps with research, and some of the funding goes to harm reduction organizations, like syringe service programs, so that we can have access to low-barrier drug checking, because, when you have a toxic, unregulated drug supply, my patients don't know what they're using.

They think they're buying heroin or fentanyl, but it might be something totally different.

And they're having these really devastating harms of being exposed to adulterants like xylazine.

ALI ROGIN: Right.

There's really a lot to do about this very yet unknown substance.

Dr. Raagini Jawa, thank you so much for your time.

DR. RAAGINI JAWA: Thank you.