The first dose of Misoprostol should be taken approximately 24 hours after Mifepristone. If you take Misoprostol later than this, it is not usually a problem. In most cases, Misoprostol will still be effective if taken later than 24 hours after Mifepristone.
Research has shown that Misoprostol works with the same efficacy whether it is taken at 12 hours, 24 hours, 48 hours, or as much as 72 hours after Mifepristone. If you forget to take Misoprostol, you should take it as soon as you remember.