Yes, there is medication. There is also Feliway and rescue remedy which may
help, sold at pet stores. How about some catnip? Does it calm him? What
about
tiring him out with vigorous play with a toy on a string? You can also try
behavioral modification to make him feel more loved, less insecure or
frightened. Maybe you should lock him in your bedroom when people are over
initially and visit him a lot to keep him happy. Sounds like he is a young
high
strung cat. They do mellow as they get older.

The question is how much older. Tiggy used to growl and hiss at anyone who
didn't live here. She started warming up to a few people (and all the people
she warmed up to were animal people) in the last year or so. As she's now
16, it took her 14 years to mellow.

She is a real pest because she would check out everyone who came in here but
heaven help them if they reached down to pet her. As soon as she entered a
room I'd warn people not to try to touch her. If they didn't make a move
toward her she would just sniff, mark them with her head and leave them
alone. She was never aggressive toward anyone if they just ignored her.
There were times I'd close her in the bedroom if there were small children
visiting. Sometimes they just can't leave the animals alone. If you have a
house full of people another room where it is quiet would probably be less
stressful.

You can try the Feliway like Mary said and see if it helps any. They have a
diffuser that plugs into an outlet and runs all the time that may calm him
down. I think they also have a spray that can be used in the carrier to make
a trip to the vet more tolerable.

You could try giving him a timeout in another room when he acts up with the
roommate.

If he will leave people alone as long as they leave him alone you should be
able to find a way for all to coexist.

W