Why I’m Not Prescribing the “New” Noise Phobia Medication Sileo


A little over a year ago, a frantic gentleman zoomed into my clinic’s parking lot with a dog. As he crossed the threshold of the hospital, the dog took her last breath and expired.

The man was despondent, but he wasn’t the dog’s owner. He had hit the dog on Interstate 280 at, as he put it, “freeway speed.” He had stopped, and at great personal risk he had picked the dog off of the highway and loaded her into his now bloodied car. He spent about half an hour in the hospital collecting himself, and then he went on his way still visibly shaken.

The dog had no collar (it probably had been knocked off when she was hit). She did, however, have a microchip. I called the owner with the bad news. He was incredulous; his dog, he said, was in the yard. He went to look for her, and then came to the clinic when he realized she was gone. He identified the remains.


Dumbstruck, he wondered aloud how and why the dog had gotten out of the yard and wound up on an interstate.

I couldn’t say how the dog got out, but I knew exactly why. The date was July 4, 2015. The dog certainly had been scared by fireworks and had decided to run.

She was the first of three that night. The second dog also was dead on arrival after being hit by a truck. The third jumped through a plate glass window, but the owner caught him before he got hit. He required surgery for a fractured tibia.

I have long held the belief that whenever someone touches a match to a fireworks fuse, they are potentially killing a dog. Dogs hate fireworks.

So, it came as little surprise when my mother contacted me recently to ask for advice about her dog and the then-upcoming Independence Day weekend. She said that her vet had recommended a product called Sileo. What did I think of it?

My thought was that I had never heard of it, so I did what anyone would do: I fired up Dr. Google. But had she asked me a week later, I certainly would have known. The manufacturer of Sileo engaged in a marketing blitz leading up to July 4.

Sileo is a new product, and it is the first product that is FDA-approved for the treatment of noise phobia in dogs. However, it is not a new drug at all. Rather, it is a new formulation of a drug that has been around for quite some time — dexmedetomidine.

I have a tremendous amount of experience with dexmedetomidine. In veterinary medicine, it is sold as Dexdomitor, which is used as a sedative. It also has pain-killing properties.

I like to use dexmedetomidine because, when used properly, it is very safe. In fact, the product, sold as Precedex (which I imagine is just a bottle of Dexdomitor with a different label and a much different price tag), is being touted as the sedative to use for human patients too sick for other very safe sedatives such as propofol.

Sleeping dog by Shutterstock.
Sleeping dog by Shutterstock.

The astute among you will notice that I just called propofol safe. You may remember propofol from several years ago, when Michael Jackson died from propofol complications. How could it be safe?

Propofol and dexmedetomidine are, in my experience, safe until they’re not. What makes propofol safe is that it is very short lasting. If a patient stops breathing (a not uncommon side effect), a breathing tube can be placed and the patient can be manually ventilated for a few minutes until the drug wears off.

Dexmedetomidine has a low rate of complications. Crucially, it has a reversal agent that can be administered intravenously if necessary to block its effects and reverse complications.

However, when an animal suffers complications from dexmedetomidine, the situation can get really hairy. I estimate that I have used dexmedetomidine approximately 1,000 times. Of those patients, I have nearly lost two who received the stuff, and one of them received only a microdose. Fortunately in both cases, we were able to intubate, ventilate, and reverse the medication before it claimed the patient. Both animals were back to normal within a few minutes — but the stress of those few minutes probably took a year off of my life.

So the take-home point in my opinion about dexmedetomidine is that it is extremely safe when used in a hospital setting under professional supervision. What about Sileo?

It’s administered at home, under owner supervision. What happens if there are complications?

Of course, the hope is that there will not be complications. Sileo is administered transmucosally, which means that it is absorbed through the gums. Perhaps this limits absorption to the point that the risk vanishes. Or perhaps not. And let us not forget the potential for user error that could lead to overdoses.

Oh, and as Colombo would say, just one more thing. In my experience, dogs who receive Dexdomitor by injection become sensitized to noise. Noises seem to disrupt the sedative effects. Yet it’s approved for noise phobias.

Let’s be clear: I’m not against Sileo. Perhaps it will work great. However, until it’s proven, I’m not prescribing it for my patients. In my years as a veterinarian, I have seen many products released with great fanfare, only to be quietly withdrawn after they didn’t work out.  If Sileo stands the test of time, I will incorporate it into my practice.

Let’s hear from you, readers. Have you used Sileo? What was your experience?

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