Pexion for dogs: Is rapid breathing during sleep a side effect?

You are correct that both of these medications are used to treat epilepsy in dogs. From the label of Pexion: "The pharmacological response to imepitoin (Pexion) may vary and efficacy may not be complete. Imepitoin is contraindicated in patients hypersensitive to it, with severely impaired hepatic function or severe renal or cardiovascular disorders." However, I could not find information that hyperactivity was a side effect of this medication. It could be that Jasmine is feeling uninhibited on this medication and thus does not know how to control her hyperactivity. A common side effect of Epiphen (phenobarbital) is sedation, but this effect commonly wears of with continued used. I could not find information on the same effect when using Pexion. Not knowing your dog's complete medical history and particular reasons for choosing anti-epileptic medications, I cannot make specific recommendations for her. I would recommend discussing these effects with your veterinarian. You may consider a consultation with a board certified veterinary behaviorist, or medications used for anxiety instead of seizures. Common supplements used for anxiety include Zylkene and Comfort Zone Adaptil Collars or Diffuser.

A single dose appropriate for her weight is unlikely to cause any severe effects as long as she has no additional health concerns. Monitor closely for any altered behaviour or other symptoms but these would be unlikely

I think many veterinarians would continue with both medications if the seizures were refractory to the first medication, but other times the goal is to try to transition from one anticonvulsant to another for various reasons. I would recommend asking the specialist or your veterinarian (whoever will be managing Jig’s seizures) what the long term plan is.

Pexion starts to work within a few hours and reaches steady state within three days. So that means you will see full effect pretty soon. Keep in mind that Pexion has been introduced to the market and indicated only for idiopathic epilepsy so for other kind of causes efficacy can be variable. Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

Prednisone can cause panting, but it shouldn't change the character of their breathing. (The panting should be the same sound/speed as his normal pant is). If it doesn't seem like he's just panting, get him in to see your vet. If he has other symptoms as well (coughing, labored breathing, vomiting, lethargy, etc) please seek emergency care. Thank you for asking Petco Pet Education Center, formerly Petcoach!

These drugs are both depressants and can be exaggerated when giving together. This can cause extreme sleepiness and low blood pressure in high doses. Difficulty breathing is not expected, but is very concerning, because this can be a life-threatening problem. Considering this, I recommend having a vet evaluate Ceasar as soon as possible. I also recommend not giving the chlorpromazine again without consulting your veterinarian. I hope that helps and Ceasar gets better soon.

Please do not discontinue Kasey's medication without consulting with your vet, as if he is on the phenobarbital to manage seizures or neurological issues, taking him off it may lead to a neurological issue. Try to get a video of the heavy breathing and contact your vet. This medication can lead to some lethargy initially, and that may be what your'e noticing. Show your vet the video, have them take a look at Kasey, and they can help you determine if anything needs to be changed regarding the phenobarbital.