I'm taking EPO and have been since just before 35 weeks--and before that I was taking a more broad-based essential fatty acid supplement. I bought 500-mg EPO oil capsules and I take, generally, two during the day, at separate times, with meals. Then I insert one vaginally before I go to bed at night. I'm interested in what dosages others are taking as well, since it varies. It has been my experience with friends and doula clients that taking over 2,000 mg a day can lead to nausea and dizziness, but I don't know if that's common.
EPO is a prostaglandin precursor--it stimulates your body to make its own prostaglandins (which is the substance that thins and softens the cervix). Semen contains actual prostaglandins. Neither one of them is likely to send your body into labor unless it is already ready, but they will probably help you get some advance effacing done.
The body makes prostaglandins (series 1, 2, 3) naturally from reactions to what we ingest. So if we take evening primrose oil, which is an omega 6 acid containing gamma linoleic acid, a prostaglandin series 1 precursor, the body then has the essential component to release the prostaglandin on its own. Taking EPO allows the body to modulate the release of prostaglandins-- unlike an artificial induction preparation like prepidil or
cervidil or cytotec which is introduced to the body and is not naturally synthesized.
Edited to add: there is some debate over whether EPO is more effective orally or vaginally. So it covers the bases to take it both ways.