The past two weeks have seen an uptick in thunderstorms here in Adelaide. With them comes the inevitable: owners asking for help for their panicked dogs, and dogs being picked up on the streets after desperate escape attempts.
What can be done for these poor suffering creatures? I’ve talked about noise phobias before, but now we have a new tool in our fight against this major welfare issue.
Sileo: The New Noise Sensitivity Drug
Sileo (pronounced “SEE-layo” not “si-LAY-o”) is a syringe loaded with a gel containing dexmedetomidine, an alpha-2 agonist sedative. It’s the first time that a drug of this strength has been registered for dog owners to use.
Therefore, we have to be very careful, as you’ll see later. That’s also why dog owners can only get it prescribed after a checkup and a discussion with their vet.
Sileo is indicated for the alleviation of acute anxiety and fear associated with noise in dogs. Ironically, (but perhaps understandably given the difficulty) Sileo has not been evaluated during thunderstorms even though they are likely to be its main use. It has been trialled against fireworks, with the results you see above.
Sileo’s Safety In Dogs & People
The first thing you’ll notice once you get it is the extremely child resistant packaging. This should serve as a warning to keep it well away from children at all times and wear gloves when using. The good news it that is took me to actually read the instructions before I could open the box.
Vets already know too well that dexmedetomidine can cause low blood pressures, body temperatures and heart rates. We also see it being a little unpredictable from dog to dog. The same dose that ‘barely touches the sides’ in one dog can be dangerous to another.
For safety’s sake, please avoid using Sileo in any dog with significant sickness or pre-existing illness. This could include even temporary problems like the severe stress caused by the noise phobia itself if they become heat stressed or dehydrated. If it is used in very hot or cold conditions, you will also need to be careful that your dog’s body temperature stays in the correct range.
I would also be very careful combining it with other anxiety medications that cause sedation like trazodone or clonidine. Dogs with noise phobias often have a whole drugs cabinet and it would be very tempting to use more than one in times of stress.
Lastly, I would never use it in young puppies or in breeding females.
Having given all these dire warnings, the fact remains: there is a tremendous need for an effective drug for noise phobia in dogs. That’s why it’s often worth taking the risk.
When To Give Sileo
Like all anxiety medications, Sileo will work best if it is given before exposure to whatever causes the fear. Therefore, try to predict the stressful event (such as by watching the weather radar for approaching thunderstorms), and give it 30 to 60 minutes before. This is how long it takes to work.
If you aren’t able to predict, it’s still worth giving the drug as soon as you hear the noise or your dog starts showing signs of anxiety. It just may not work as well under these conditions.
After giving the correct dose, do not give any more, even if the results are insufficient. After 2 hours, you can give a second dose, and then every 2 hours up to a maximum of 5 doses, as long as your dog remains free of side-effects.
Sileo is not supposed to be swallowed, and will probably not work if it is. Instead, it is applied to the inside of the mouth between the upper teeth and the cheek. Therefore, absorption could be a problem in dogs with severe gum or dental disease. It could also be a problem if you feed your dog shortly afterwards. I would wait 30 minutes.
How To Give Sileo
Sileo comes in a metered dose syringe with a rotating ring to set the correct dose. The earlier model had a locking mechanism but it caused many overdosages in the USA due to the ring lock not engaging. Having used this update, it seems hard to accidentally overdose.
Please read the enclosed leaflet very closely as it contains detailed descriptions and pictures of how to use it properly.
In brief, you rotate the ring right down to the syringe barrel then back until the correct number of dots is exposed between the syringe barrel and the ring. It will then cause the plunger to stop at the correct place when you squeeze it into your dog’s mouth.
Sileo Dosage Chart
| Bodyweight of dog (kg) | Number of dots | Doses in syringe |
| 2.0 – 5.5 | 1 • | 12 |
| 5.6 – 12 | 2 •• | 6 |
| 12.1 – 20 | 3 ••• | 4 |
| 20.1 – 29 | 4 •••• | 3 |
| 29.1 – 39 | 5 ••••• | 2 |
| 39.1 – 50 | 6 •••••• | 2 |
| 50.1 – 62.5 | 7 ••••••• | 1 |
| 62.6 – 75.5 | 8 •••••••• | 1 |
| 75.6 – 89 | 9 ••••••••• | 1 |
If the dose is more than 6 dots, divide the dose between both sides of the mouth.
Sileo Side Effects
Alpha-2 agonists are known to cause vomiting in some dogs. Therefore, don’t be too concerned is there is a brief vomit as it starts to take effect. Any more than this and you will need to seek help.
Other side effects will generally be related to excessive drowsiness and sedation, including a low heart and breathing rate, and low temperature. Adverse effects should not last more than two hours but there will be some variation between dogs.
If your dog appears excessively sedated, or breathing too slowly, please seek immediate veterinary care. There is an antidote available which should almost immediately reverse the effects.
How Well Does Sileo Work?
The graph at the start shows the results of a European placebo-controlled double-blinded field study. 71 dogs with a history of fireworks phobia were treated at New Year’s Eve with a maximum of five doses at two hour intervals. For comparison, 73 dogs were treated with a placebo containing no drug.
You can see that 75% of the treated dogs had a good or excellent response, compared with 33% of placebo-treated dogs. There was a statistically significant difference (p<0.0001) between dexmedetomidine and control in favour of dexmedetomidine.
At the same time note that there were still plenty of dogs who responded very poorly. And it’s also worth noting that in this study, the treatment was able to be started in most cases before the onset of the noise.
So:
- Sileo won’t help every dog enough on its own
- Sileo may cause excessive side effects in some dogs
- Sileo will be expensive for larger dogs if it’s needed very often
For all these reasons, we need to not forget the other options.
Medications For Noise Sensitivity
Dogs with anxiety to noise are treated with both drugs and environmental manipulations. A quick list includes:
- being a calming and reassuring presence
- creating a ‘safe zone’ where your dog likes to hide
- getting a dog behaviourist consultation
- benzodiazepines like alprazolam and diazepam
- clonidine
- trazodone
- gabapentin
- dexmedetomidine
Visit this page for a longer discussion of these options. One thing I will take the time to specifically warn you about here, though, is Adaptil. You can read why on this page, but a simple summary is that it just doesn’t do enough. The placebo effect shown above should be sufficient warning to always be guided by science when you can.
And one last grumble. As an ancient-language fan, the name ‘Sileo” grates on me a bit. It’s Latin for “I am silent”, which speaks all too loudly to how we sometimes approach mental health in animals. That is, as problems for us, not them.
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By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.