i am visiting my parents and they have kept my 8 years old cat. she was never too friendly and never liked to be petted but tonight she became very aggressive towards everybody with no apparent reason she had us all locked in one room and was following us and hissing at everybody in the house - we were all very scared - we have her locked in the kitchen now what should we do ?? can it be the hormones injection we gave her a week ago to stop her from getting pregnant ? she is now calling us to get her out of the kitchen but we are too affraid to get close - it is 12:45 am here so the vet will have to wait till tomorrow morning - help please ...

It could be a hormone injection......may I ask why you haven't had her spayed?? That could help alot. I do not tolerate my cats hissing at me and they will get a squirt of water and vinegar or water and lemon juice any time they do it. I have two little girls and three small dogs and my cats are taught that it is not accepted in the house.

You should try to find a 24 hour clinic/emergency animal hospital. Maybe the cat has an infection, or internal pain and is reacting. Or it definetly could be hormones.

i would go with the hormone theory. i know how hard it is for you to find vet care where you are but i really think you should have her spayed. if the vet can give her a shot to prevent pregnancies why can't her just spay her ?