First, right off the bat let me say that you need to avoid Dexamethasone like the plaque here since its not indicated and could make her situation much worse. The Penicillin can be used daily but you need to calculate the dose based on her weight and the IU per millilitre strength of preparation she has had. Generally speaking, we use 1500IU per pound of BJ's weight daily. Now with appetite loss in the cat, we do have some worries. Common causes we need to consider include dental/oral pain (ie bad teeth, oral trauma, etc) bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, or ingestion of harmful items (ie toxins, plants, non-edible items). Furthermore, at her age there would also be worry of systemic organ issues (ie kidney or liver disease, cancer, etc). And just to note, if she isn't eating she won't have much stool to pass.
With this all in mind, we can try some home supportive care to try to settle her stomach. To start, to counter nausea, can consider treating her with a OTC pet safe antacid. [ie Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Tagamet (More Info/Dose Here @ http://www.petplace.com/article/drug-library/library/over-the-counter/cimetidine-hcl-tagamet)]. Whichever you choose, we’d give this 20 minutes before food to allow absorption. Of course, do double check with your vet if she has a known health issues or is on any medications you haven't mentioned.
Afterwards, you can consider starting her on an easily digestible diet like h boiled chicken, boiled white fish, scrambled eggs, or meat baby food (as long as its garlic/onion free). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. Or if she cannot be tempted, then we can offer or syringe feed watered down canned food, Hill's A/D, Royal Canin Recovery, or Clinicare Canine/Feline Liquid Diet. All of these are critical care diets that are calorically dense, so a little goes a long way nutrition-wise and we need to head off fatty liver syndrome making this worse.
Since dehydration is a risk here, we need to keep an eye on her hydration. To check that she isn't dehydrated, there are a few things you can test. Further to checking for gum moisture, do make sure she doesn’t have sunken eyes and that she doesn’t have a "skin tent" when you lift the skin. To see how to check these parameters for dehydration, you can find a good video HERE (http://www.ehow.com/video_12232503_dog-dehydrated.html). If you are seeing any signs of dehydration already, then that would be our cue to have her seen before this becomes an additional issue for her (especially as it is often dehydration that makes them feel unwell).
Finally, I wanted to note that if funds are a concern, there is help. First, if you have a VCA or Banfield veterinary hospital near you, then you might consider taking advantage of their free first consult offers. You can find vouchers for this via VCA: (http://www.vcahospitals.com/main/offer) & Banfield : (http://www.banfield.com/landing-pages/coupon). Otherwise, you could consider checking out the Humane Society's database (http://www.humanesociety.org/animals/resources/tips/trouble_affording_pet.html). They have a lot of branches nationwide, along with ties to other assistance organizations that can keep down costs and surely will be willing to help.
Overall, her signs do raise a few concerns here. Therefore, we’d want to start supportive care to settle her stomach. If she doesn’t respond to the above within 12-24 hours; then we'd want to get a local vet involved using one of the above options to give her the best chance of surviving this.
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