Cat lethargic, drooling, vomiting after Cerenia. Side effects or ER?

I am guessing the injection given was Cerenia. Side effects are uncommon with the use of this medication, but the most commonly noted side effects were: drooling, drowsiness, diarrhea, and appetite loss. I would be worried and I think he needs to get back to the vet. Were any x-rays or blood testing done? If not, that needs to be done to figure out what is going on. This sounds like it could be something more serious going on. If it was just a simple upset stomach he should be feeling MUCH better after that injection and not sleeping for 10 hours. I would be worried.

The injection is called Cerenia, if this didn't help then you must take him back to the vet for a blood test and xray/ulrasound, he might be suffering from either a foreign body in the GI tract or severe gastrointestinal infection.

Cats can sleep a lot when they are not feeling well. I'd keep an eye on Batman for now. If he's still this lethargic in the morning, isn't eating or drinking, or is vomiting, take him back into the vet right away. Best of luck.

These are not side effects of the medications, these are symptoms related directly to the medical condition that caused the vomiting in the first place. if by tomorrow you see no improvement you will need to take her back to the vet.

Poor SoCo sounds extremely ill, and the symptoms you are describing are a medical emergency. As a senior cat, he could have many things wrong with him including dental problems, diabetes, kidney failure, hyperthyroidism, liver failure, or cancer among others. He needs veterinary care now to diagnose what is causing all his symptoms so he can be treated. Please take him into an ER vet clinic; if there isn't one in your area, there will be a vet on call for emergencies. The information to reach that vet is found on a clinic's answering machine or website.

It is not uncommon to have one more vomiting episode after cerenia while it is still building in her system. The constant licking may be a sign of nausea. There is no way to know how serious anything is without those test, but it is a good a sign she drank a little. I would take her food and water away for now and let her stomach rest and empty the water she just drank. After 4 hours I would try a small amount of water and a little food to see if the nausea has passed and how she handles it. If she continues to vomit, then you may want to ask about Care credit or further options to get the test done. If she is not getting any worse those medicines will last for 24 hours so it is reasonable to see how she feels by tomorrow

Poor Moe! From what you're describing here, I'm afraid he sounds quite sick. Vomiting, not eating, and acting lethargic are always very concerning symptoms, especially since he's been sick for 2-3 days now and seems to be getting worse. Unfortunately, these are very vague symptoms that could be caused by almost any kind of illness, so it's hard to say what might be wrong without being able to examine him and run some tests. I do think that this sounds like a serious, potentially life-threatening problem that shouldn't wait until tomorrow, so I would recommend taking him to an emergency clinic today to be seen. If you're not sure where to go, try calling your regular vet's office - their voicemail message should have contact information for your nearest ER or an on-call doctor for emergencies.