Hello. alli does not affect vitamin B6 - it is a water soluble vitamin. You can take a B6 supplement, but you should be taking a mulitvitamin which provides 100% of the RDA of B6. The vitamins alli may block some of the absorption of are the fat-soluble ones - A,D, E and K.
Hope this helps!
Maria Marzella Sulli, Pharm.D.