i researched them a lot before i bought any the first time, and i found out that you have to have approx 300mgs daily of the sylmarin the active ingredient in milk thistle for it to have any benefit on the liver , so hunted and hunted for a brand where one tablet contained the full 300mg of silymarin so that i didnt have to take more than 1 tablet of it daily, and finally found a brand from fortis health so have taken them ever since.
here is a link if you are interested into the recommended dosage for different purposes of milk thistle..
Milk Thistle Dosage
hope you find this helpful xx