First, do be careful if he is growling when you examine him. This could be a hint of him being sore, so we do need to tread with care. As well, Cephalexin is fine for bladder issues or skin ones; but its not ideal here as it can cause nausea/vomiting/diarrhea. So, we'd not want to give any more. Especially since his refusal to drink is very suspicious of nausea. Some dogs will refrain from eating and drinking when sick to their stomach to avoid the risk of vomiting. In regards ***** ***** triggers for this, we’d be most concerned about potential bacterial or viral gastroenteritis, pancreatitis, parasites/protozoa infections, general dietary indiscretions, and ingestion of harmful items (ie toxins, plants, non-edible items).
With this all in mind, we can try some home supportive care to try to settle his stomach. To start, if you can safely medicate him, you can try him with an OTC pet safe antacid like Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid), Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac), or 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 offering food to allow absorption. Of course, do double check with your vet if he has a known health issues or is on any medications you haven't mentioned.
Once that has had time to absorb and he is steadier on his stomach, you can consider starting him on a light/easily digestible diet. Examples you can use are cooked white rice with boiled chicken, boiled white fish, cottage cheese, or scrambled eggs (made with water and not milk). The aim of these diets is that they will be better tolerated/absorbed by the compromised gut and reduce upset. As well, rice and protein sources all do have high water contents which will indirectly help get fluids in.
Since dehydration is a risk in this situation, we need to keep an eye on his hydration. To check this and ensure he’s not becoming dehydrated, there are a few things you can test. Further to checking for gum moisture, you will want to make sure his eyes are not looking sunken and that he 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 him seen before this becomes an additional issue for him (especially as it is often dehydration that makes them feel unwell).
Though since he hasn’t been vomiting, we can consider syringing fluids (water or electrolytes) as needed. When doing so, we‘d aim to give 48ml per kilogram of his weight daily. Though if he is being grumpy, this may not be a practical option.
Overall, his refusal to drink is a sign we often see with nausea. Therefore, in his case, we’d want to start supportive care to settle his stomach. If he cannot keep that or water down, appears dehydrated already, or doesn’t respond to the above within 12-24 hours; then we'd want to get his vet involved. They can assess his hydration, rule out fever, make sure there is nothing in his stomach that shouldn't be there, discomfort, or any sinister viruses present. Depending on their findings, his vet can treat him with injectable anti-vomiting medication +/- antibiotics to settle his stomach, and get him back feeling like himself.
Please take care,
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