Thank you for your patience. Salem's vomiting today is certainly a concern, and you will have to continue to keep rehydrating him as you have been. There are a number of possible causes for his vomiting, and it could potentially be that his antibiotics were holding a potential issue at bay here, or even that the 7 day course of antibiotics have killed off some of Salem's good bacteria in his gastrointestinal tract. We also certainly have to consider whether there is something else going on here that is completely unrelated to the issue he received antibiotics for to begin with, or the antibiotics themselves.
If Salem continues to vomit throughout the night, then he will very quickly become dehydrated. With hold his regular food until the morning now, but do continue to encourage him to drink. If he can't even keep the water down that you are giving him in a dropper, then dehydration becomes a very real issue, and as such IV fluids administered by your local ER vet would be the best bet here.
For now, please keep an eye your boy's mucus membranes, capillary refill time and respiratory rate tonight as follows (do be careful that your boy doesn't try to bite you):
Mucus membranes - flip his lip and look at the color of his gums. They should maintain a nice salmon pink color. Get him to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on his gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.
Respiratory Rate - if he is continuously panting or open mouth breathing at all tonight, this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
For now, you may also want to try him with a little pepcid. The typical dose for this type of situation is 0.25mg per pound of body weight once daily. You can read more about the use of Pepcid in cats online here: http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid
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