Fenben works with gall bladder which processes fat , taking Fenben with fats and or oils provides better absorption this way as with all bendazoles . I been on Fenben for 2 plus years , 1st year twice a month then once a month for 6 months , now I take every other month for prevention , I take moxi with prazi alternating the months with fenben . I had no ill effects from taking any parasitic medications , but the worms did and they all died.