I found this recipe in a book called "A Woman's Book of Choices: Abortion, Menstrual Extraction, RU-486" by Rebecca Chalker and Carol Downer.
The books says to take 6-10 grams of ascorbic acid a day for 5-10 days. It says specifically ascorbic acid. Don't use vitamin C with bioflaviniods in it, because they work to prevent miscarriage. Read the label and check the ingredients, write down what to look for if you think you won't remember when you get to the store. Tons of vitamin c products are available, look for the cheap generic brands, they are usually the ones that have pure ascorbic acid. Don't use anything that has Rose-hips in it, they contain bio-flaveniods which help to prevent miscarriage. this is not recommended though.