I need help identifying a softcore flick on CineMax or HBO.?

The basic story line was that these vampire like woman would end up devouring their mates. There are two scenes that particularly stick out. One included a sex scene in the back of a van and I remember the girl on top and the other, shortly after this scene, I believe, took place on a bed with the girl on bottom. I realize that is not much to go on, but...