24/48 hour bug or take back to vet?

Hi, hoping for some advice. Yesterday lunchtime we caught our cat licking the bowl/residue of some leek & potato soup. I know leeks are toxic to cats. Later that evening he was vomiting so we took him to the vets, where he vomited some more. All his vital signs were checked and he was given an anti sickness (I think?) injection and given the all clear to come home. He didn't/hasn't vomited since. I checked on him during the night and lunchtime today and he's just remained in a loaf position in his bed very unresponsive and lethargic. We've left him plenty of water and he might have attempted to drink as there were some wet marks on the plastic sheet near his bed. Just so worried about him and don't know whether to take him back to the vet or whether this is just something that will pass over a 24/48 period?

Hello - not being active 24/7, I suspect that the moment for this question has gone and would remind readers always to call their vets' phoneline if they need emergency advice 'out of hours' - the details of someone who can help you should be on the answerphone message, even if the vets are closed.  However, in general, if an animal is very unresponsive and lethargic - more so that since they were last seen by a vet, or if the situation is continuing for longer than expected  - then it definitely constitutes a reason to seek in-person emergency help.  I don't know too much about your loved one, but hope that things went as well as they could have for him.   The emergency vet would usually consult the Veterinary Poisons Informations Service or similar, in order to assess whether specific toxin-related treatment was needed.  They would also offer to examine your cat, in order to establish whether fluids or other emergency treatments were necessary.