Cat panting

I've had expedience of two of my cats panting
One is Tabby he panted for over 12 hrs after we gave him Capstar one night. Initially we didn't associate it with the Capstar tablet but then made that conclusion. He did it twice after being given this tablet. The first one it only lasted maybe 20 minutes on and off and we believed he just got hot in a sunny room. The second time he just kept panting. Because it was a hot summer we didn't realise it was the capstar but I know cats normally don't pant
So we stopped giving capstar gave Revolution but he panted for a short time after it. He has a brother who is allergic to all spot treatments we were told not to have any after vomiting after one and being off food. Tabby also once was sick after Advantage. It was more than 24 hrs later so we aren't sure if it was Advantage even his symptoms were weakness letheragy small fever and no eating or drinking. We took him to the vet same day and he spent 4 days there without them finding the cause but the fever gone and he resumed drinking and eating in over 48 hrs from when it started.. after the episode with capstar even though different symptoms I began to suspect the cause was the nicotinoid reaction as both drugs have this chemical in them
Well we don't know should we give Tabby any more Revolution as last time he had flea anemia as he had a lot. We now flea both cats manually as Snowy isn't allowed to have any treatment which doesn't get all thefleas and a few times resulted in injuries to us including deep punctures from bites because Snowy has flea allergy dermatitis and is sore and bites if we strike a sore point with the flea comb.
So my questions are can Revolution cause panting if anyone experienced it with their cat?
Also I have a stray at home he is getting used to our place he is tame I can carry him pat him but he doesn't allow fleaing so we give him Revolution however since he goes out he again has lots of fleas only 2 weeks after treatment
I noticed now it is warm the cat who is semi long hair tends to also pant. This seems to do with heat. My other two cats don't pant ever unless Tabby got those drug treatments and I never seen Snowy pant in my life. So my other question is can the semi long hair cat pant from hot weather? He has a fan where he is .

So the fur isn't too long above

Panting is not normal, especially after a flea treatment. They are most likely experiencing a 'flushing'  which adverse reactions will bring on, which feels like a wave of heat rising in the body. As for it being dangerous, definitely get hold of your vet to see if anyone else has reported it, it may be you are applying a wrong dose for that cat's weight. Research it on the internet too. Was there any way for the cat to reach it and lick it?  I applied it too low on the neck once and my cat panted like mad and had foam. I apply it now way up, almost between the ears and have never had this happen again. I also applied it to a cat and he itched for a month and most of his hair fell out, needless to say he doesn't get it that way anymore! You may find out it is a 'side effect' which means it can happen but is not real serious and not life threatening, like upset stomach when taking medications. An adverse reaction IS serious and may be life threatening like hives, or trouble breathing. I just researched Capstar on the internet and a side effect is excessive panting, most likely because it is oral.  I would definitely call a vet and ask if it is safe because they are having this side effect, or to switch to something else. It also said reinfestation of fleas can almost be immediate so a daily dose can be given. To me, that sounds kind of worthless! Check on it! All the luck and post us if you find something better!

We got all our cats apart from the one who comes and goes weighed so we know their weights and the one outside is heavier than my Tabby so everyone of them is over 4 kg for sure. We weighed the outside one too but it was not really accurate (I got on scales with and without cat). It is def a right dose. We have asked the vet they knew nothing about it apart from telling us Snowy is not supposed to have any flea treatment at all as he was vomiting non stop after Revolution. Initially he was ok then he was off food and then he got sick. It took a few months to develop his reaction. So we don't know what is causing the panting but I believe the medicine is. With Jack the stray I don't believe it is the medicine he only had one treatment two weeks ago and didn't pant after it but pants when the weather is hot. Tabby panted for about 9 hrs (not 12 as I stated above) but jacks panting comes and goes for days.

No it wasn't because he licked it either - the time they licked they just frothed and vomited because the taste is terrible and it's normal for a cat to do that the vet said

Capstar was only given because we had trouble with spot treatments and wanted to help the cat as much as we could. We gave capstar a few times a week. We also regularly use steam in our place like a Hoover Steamer that kills the fleas and eggs I believe too. We also did those spray flea and other insect bombs. So capstar was just something to help the cats get rid of fleas since we were scared giving them any spot treatments and in the past Revolution didn't work the well even though we used it regularly before the reaction developed.