Thank you for reaching out. 

Misoprostol is known to cause uterine bleeding. If you experienced an actual flow (enough to require a pad or tampon to contain the bleeding) you should consider yourself niddah. 

If the bleeding was lighter than that, it is subject to the leniencies of staining and your status depends on where the blood was found and possibly the size and color of the stains.

Please see our page on Stains (Ketamim) for a detailed discussion of the leniencies of stains and the distinction between a stain and a flow, and feel free to get back to us with any further questions. 

B'Hatzlacha!