I tried it after doing as much research as I can online. There's a few warnings about it 1.) blood pressure will go up (Could endanger you and the baby) and there's been a case where the baby had serious complications.
Well I got some. From one site the dosage was 500g every half an hour till labour sets in. I tried it. They usually come in 40g pills so that's a lot of pills to swallow and it made me feel like a pill guzzler.
Contractions did seem to come on, especially while doing other things that were pro-labour, especially walking. After awhile it all settled down again.
So, my conclusion, is yes and no, it'll probably start up contractions, but if you're body/baby is not ready you're just putting yourself into false labour that goes nowhere.
Good luck though!