Actually ... I am NOT a fan of homeopathic medicines, but I just wanted to say that in general, this is not true. It is true with herbal medications, but not with homeopathic. That's because the way homeopathic medicines are made is by taking a tiny amount of something and diluting it many, many times.
In the end, basically, what you have is pure water

. There have been calculations of how much of the original substance remains, and although it depends on the particular homeopathic medicine, for many, there is statistically almost no chance that even a single molecule of the "active ingredient" remains in the "medication". I think there is one, occillicocium (sp?) that is quite popular. If you calculate it, if you created as much occillicoccium as there is matter in the universe, it would still be incredibly unlikely that a single molecule of the active ingredient would remain.
That is why homeopathic medicines won't interact with traditional medicines (since there is nothing in them). Don't want to rain on anyone's homeopathy parade... but if they work, they work via a placebo effect.

(don't want to go totally off topic here

) However, that being said, they are quite safe to take