Prozinc right? BCP PZI is different than Prozinc. Usually, Prozinc's peak is around +5 - +7 although every cat may react differently. The Prozinc cycle should look like a "smile" within a 12 hour cycle. You can read all about Prozinc on www.prozinc.us
This info is also in the stickies at the top of the prozinc forum - you should read them all (very useful information that will come in handy sooner or later)