This is from the designersupps web site=
A Word About Liver Protectants
A lot of people have been using liver protectant supplements such as Silymarin and NAC to help protect their liver from damage when using methylated compounds. However, I feel that this is a bad idea. When you use compounds that increase gluthione levels in the liver, it will increase the breakdown of oral drugs, making them less effective. Although increasing liver enzymes is good for your liver, it is bad for any drugs you want to take and allow them to pass through your liver unabated. A better idea would be to use liver protectant supplements before and after a cycle to help your liver rebuild its enzymes after they have been damaged by methylated compounds.
I have no idea if using liver protectants on a cycle will inhibit gains in any significant degree, but it could. Keep that in mind when planning your cycle.