First, if he vomited after Cerenia was given 30 minutes ago, he likely has absorbed some of this. Therefore, we'd not want to give any more. And I would also note that we would need to give it some more time before we can assume it was or wasn't helping with his nausea.
With that in mind and in regards ***** ***** question, the key here to whether we have him rushed in is whether he is vomiting profusely and whether we can get that settled for him. If he keeps vomiting in the next 30 minutes or so (us giving the Cerenia an hour to make a difference), then we'd opt to have him seen. (As well, if we thought he had eaten something toxic, was weak or collapsed). In the meantime though, we can try to soothe that stomach.
To start, we will need to rest that stomach for a few hours. We want to withhold food and offer water in sips or as ice cubes. If he settles down, we could potentially give him an antacid on top of the Cerenia. Common OTC pet safe options that can be used with this are Pepcid (More Info/Dose @http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid) or Zantac (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/ranitidine-hcl-zantac). 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. And I would note that if you give this and he cannot keep it down either, then we'd use that as a red flag that we need to bypass his mouth with injectable anti-vomiting medication from his vet.
If he does settle with stomach rest and the above, then we can put him on small meals (a spoonful with 30 minute breaks to start) of 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). There are also OTC vet diets that can be used (ie Hill’s I/D or Royal Canin’s sensitivity) too. The aim of these diets is that they will be better tolerated/absorbed by the compromised gut. Therefore, it should get more nutrients in and result in less GI upset. As long as improvement is being seen, I usually advise continuing this until the signs are settled, and then weaning him slowly back to his normal diet.
Since dehydration is a risk here, 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).
Finally, since he hasn't had bloody stools and once we settle the vomiting, you can consider trying a pet safe anti-diarrheal. As I am sure you appreciate, these would not be a cure for infectious issues; but it can still be of benefit. It will reduce diarrhea load, allow the body to absorb more water/nutrients, and soothe the upset gut. In regards ***** ***** options, the one we most commonly use is Kaolin/Kaopectate (More Info/Dose @ http://www.petplace.com/article/drug-library/library/over-the-counter/kaolin-and-pectin-kapectolin-k-p)). This is available OTC at most pharmacies. Otherwise, Propectalin, Canikur, Fast Balance, and Protexin Pro-Fiber (all OTC at vets, pet stores, and even Amazon) would be another option. All will slow diarrhea and those last ones have the added bonus of providing support to the delicate good GI bacteria. So, these can be used as a short-term means of soothing his upset GI.
Overall, there are a wide range of agents could trigger this GI upset we are seeing and the new treats are suspect. That said, we need to tread with care if he keeps vomiting. So, I would rest his stomach just now and monitor. Any more vomiting, we can have him seen. Otherwise, we can use the above. Of course, if he cannot keep that or water down at any point, 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 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.
All the best,
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