Drowsy from allergy shot??

on firday i took marley to the vet and he was diagnosed with autoimmune disease. he was given an injection of antibiotic and b12 and an allergy injection. from what i can make out of the vets writing the allergy shot is called depomedril.
on the way home from the vet, marley vomited twice before we got home. (he has done this once before while riding in the car...but only vomited once) i called the vet and they attributed it to nerves and the car ride. he hasn't gotten sick since buy he has been acting a little strange. he seems more tired than usual, he will follow me around and just sit there looking sad. he always follows me but he usually doesn't look so pathetic. he has been sleeping more than normal, he plays but not as much. he is eating fine he just seems off, like drowsy or dopey. he is 8months and im not sure, as he is my first cat, when kittens start to act more like an adult cat. maybe this is part of it becuase i have noticed the past few weeks he seems to have mellowed about a bit.
i guess the main thing i am trying to figure out is if this is normal behavior with so much medicine or if there may be an underlying condition, but he was acting perfectly fine before i took him to the vet on friday. thanks for any advice and for putting up with me as i figure out how to properly care for my kitty!!

The shot is called Depo Medrol.
Cats can get tired from it.
Coco used to get that shot but she has to many bladder problems from it.
It should work well for your cat.
It worked good for Coco.
She never got very tired from it.
She did from the antibiotic shot though.

I don't know anything about that Depo but if it is an antihistamine it may make kitty sleepy, most anithistamines do cause drowsiness.

And it's not a "allergy shot", exactly. It's a steriod (glucocorticoid), methylprednisolone. This is an anti-inflammatory. As I've previously mentioned, allergic reactions do have an inflammatory factor - as does autoimmune damage.

I've had a cat get Depo Medrol along with antibiotic to help reduce swelling on a infection spay incision. It knocked her out, too.

Since the shot was given Friday, I'd call the vet just in case.

Depo Medrol has been used in my kitties on several occasions. They're often tired for awhile afterwards.