The new tablet is the regular 10 mg Ambien with a sandwich layer of slow release Ambien 2.5 mg. One of the criticisms of the regular Ambien is that it didn't last through the night. So, they give you the same 10 mg effect you're used to, and add on a trickle release of just a pinch more Ambien, to extend the peak plasma concentration a little longer (say, two hours longer), giving you a pill that is effective a couple of hours longer than before.

Lar