Sick cat worse after vet visit

Hi
Mina seems to have a food allergy so we are trying novel proteins. I'm ok with vet diets on average. BUT, somehow the vet office sold me a very old bag of food. I did not realize until too late, a week later. I thought she was being picky. Anyway, I took her to the vet yesterday, my regular one was not in.
This doctor is the owner of the place. She was so sorry and did a bunch of test on her tab.

Some things given are: fluids, sedation, cerenia, famotidine and mirtazapine.

Mina arte when I brought her home last night but during the night got worse. She stayed huddled in her carrier, did not eat or drink and did not use the litter box.

She is a very vocal cat but has not made a peep. So lovable but won't come out of carrier.

Could any of those meds caused this?

I am calling different vets this morning to get her in for second opinion. They won't be open for hours.

Mirtazapine 15mg
Famotidine Inj

What signs/symptoms was Mina showing with her food allergies?  

Did she have new symptoms with the out of date new food?  

Cats don't like change.  Did your vet tell you how to slowly incorporate the new food so she would accept it?  I honestly don't understand why vets give cats drugs to make them want to eat when they do not.  Find out the cause of their nausea FIRST, then treat that.  Don't give drugs.  I think that is a mistake to ignore such a serious symptom.  

It's hard to say which med would have caused her to react the way she has.  I would think the sedation and mirtazepine would be the cause of that.  I don't know anything about cerenia (except that it's an anti-emetic?)  

Poor Mina!! The stress of taking my cat to the vets alone used to be enough to keep him quiet for a couple of days and sounds like she's had a lot done there. Hope she's comes around soon xxxxx

Mina was eating Pro Plan grain free kibble and started vomiting every time she ate it. Before that Hills WD then she refused to eat it.

She also has trouble with her anal glands and I take her in every month to be expressed.

Mina will be five in September. I got her about a year ago and was told she only likes dry food.

Ok, because I can work on switching her over to wet. Before I can do that, I need her to eat period.

Oh and of course she gets constipated, hence trying to get her to eat wet food. Dr. says pumpkin but Mina won't touch it!

Unrelated she also has bouts of chin acne.

I love my girl, need to figure it all out.

Have an appointment with a different vet this morning. Hopefully he can help. I think the old dry food from vet was going bad and upset her tummy.

She has only been eating chicken based food as that is her fav.