So is it safe to insert acidophulous capsules into the vagina? and how effective is it?

Yes: It's a natural inhabitant of the vagina and gut and high levels can suppress candida or yeast.

Not known: I am not aware of any research result advising direct insertion of the capsulse directly into the vagina. I don't believe the bacteria themselves are of concern, but rather the packaging materials (the capsule/pellets). It actually makes more sense to replace the bacteria directly where it is needed, but we do not have such info at this time. Consult doc. Good luck.