I've used it many times as a preventative herb... I really like it - it's a good natural killer.
Goldenseal is good too-I've used it often. Another natural killer.
Just space these things out, take one or the other 1 or 2 hours apart. Lemon juice in your water would be good.
I recommend you discuss what you want to do with your ND - You want things that will work together.