Maybe it's just psychosomatic, but I feel like European-made zolpidem (like Stilnox) has much stronger effects for me than US-made Ambien. It feels VERY different. Much more intense, and I get far more dissociated and confused.
I think Stilnox and Ambien are made by the same company (correct me if I'm wrong) but could their formulation be different?
I also agree about taking it on an empty stomach.