"The D form of phenylalanine blocks enkephalinase, a pain-amplifying enzyme in the nervous system, while the L form increases the production of mood-elevating brain chemicals like norepinephrine and dopamine. Experts recommend taking up to 1,500 mg of DLPA daily in two or three divided doses between meals."
The article says that it also works like an antidepressant, gives you energy, and acts as an appetite suppresent.
One can feel effects between one week and one month of taking it.
I just bought some at iherb.com, Twinlab DLPA 500 mg, $10 for 60 capsules, and have been taking it for 3 days. I'm also doing other stuff to help with the pain (mine comes from herniated disk), including getting epidural shots and exercising. I thought it would be worth trying this supplement also.