Is my cat on his way out?

I brought my elderly cat (a 17 year old Manx) to the vet yesterday, spent $500, and so far no real results. They gave him an anti-biotic and a pro-biotic, and want me to get a urine sample from him, which I'll do.

My cat is not in pain, but is extremely lethargic, can no longer jump on a footstool, which he used to sleep on the sofa. He is eating almost nothing, but a few pieces of kibble out of my hand, and treats and 2 small shrimp. (I cut up the shrimp and throw the pieces a few feet just to make him move a little, which he does.) He does drink water normally, though. He appears to be nearly deaf and for awhile his sense of smell has been on the decline. He rarely defecates, but the last time he did (a few days ago) he pooped about 4x his normal amount, something he had never done before. The doctor says he is not constipated. He was in much better shape about a month ago.

The doctor said he has a loud heart murmur, something he did not have at his last checkup about 7 months ago. (In fact, then, the doctor commented on how healthy his heart was.) The doctor also said he has surprisingly good teeth for such an old cat.

Do you have any thoughts on what could be wrong with the cat or how I might address his lack of appetite and severe lethargy? If he's simply on his way out, how long do you think it might be and is there a chance that he'll die peacefully in his sleep?

Thanks.

Was a proper geriatric bloodwork panel done? - to check for the common conditions that affect geriatric kitties: to check for diabetes, kidney disease, thyroid issues, liver issues, etc? Bloodwork would also show whether there might be an infection going on somewhere (would show elevated white blood cell count)

If he has a loud murmur, it's possible his lethargy is related to heart issues?

Did Vet say kitty was dehydrated at all? if not really eating, even though he's drinking good you say, he still could be a little dehydrated?

What's his normal diet - dry food? or canned or both?

Does kitty go outside at all?

Have you tried canned food? Fancy Feast (canned) is one that most cats love, even ill ones that have poor appetite. Why don't you buy a few different flavors of it (they're the small cans). Warming up canned food a little in the microwave is a good idea for it makes it 'smellier' and therefore more enticing to a cat. Just put some on a plate, add a little water, then nuke it for 15 seconds........make sure to test it to ensure it's not "hot".....you just want it warm...mix it up good so that the little bit of water you add is mixed in...the extra fluids will be good for kitty.

You could also try some of those Whiskas Pouches of food, or Meow Mix Deli.....foods that have a "gravy" in them........cats often like the gravy.

Re: kitty's pooping.........the time that kitty did go, was it hard? like rabbit turds (constipated) or normal formed stools?

Can you get some chicken and boil or broil it and see if kitty will eat this?

Does kitty ever seem "short of breath"?....breathing a little faster just from walking or maybe going up or down the stairs?

If kitty is so lethargic, you should consider ensuring that litterbox is in a convenient place.............so kitty doesn't have to walk so far (or maybe up or down stairs) to access it............I know when I rescued a very old siamese kitty, she ended up developing heart problems (heart failure, actually) and she just didn't have the energy to walk very far without having to lie down....so toward the end I ensure her litterbox was very closeby.

Did Vet check thyroid function? Overactive thyroid is very common older cats....and initially you'll see an increase in appetite despite weight loss but as the disease progresses and goes untreated, a lack of appetite can result.......and the heart can be affected.

Could be over active thyroid (hyperthyroidism). Our present cat and our previous cat both have/had hyperthyroidism.

Fairly easy to check for, and is treatable. Please ask your vet about checking for hyperthyroidism.