Is this a side effect of Capstar(but a good one?)?

I gave my cats Capstar by grinding it up and putting it in tuna. They both are acting fine, except one threw up the tuna about 2 hours after(not sure if it went in her system all the way). But my other cat usually is very wild, being rude, getting into things. Now, every time you pet her, she will purr like crazy, lay up against you, she is sleeping more, and acting more normal. She still plays, I don't think she is depressed, she just is more cuddly and nice. Is this some side effect? lol My cat isn't usually this nice, she goes through mean phases often but since I gave the pill to her last night she has been nice. She even let me comb her for like a minute without scratching me(she likes to bite combs and scratch arms if you try). lol