decem There is no constant dosage for Milk thistle, Milk thistle comes in several concentrations and the main active substance is Silymarin(silybin, silydianin and silychristin), some brands have 80% others 60% and so on, you can find it written on the supplement "milk thistle extract standardized to whatever% silymarin"
the recommended dosage for Silyamrin varies from 200-800mg/day divided into 3 doses throw the day
e.g if you got milk thistle with 60% concentration, and you wanna take 600mg silymarin then you're going to take 1000mg of Milk thistle
no1stunna Vitamins, Amino Acids and other supplements that protect the liver can be taken same time of consuming oral Steroid but regard herbs, I don't think it's gonna be a good idea, we still don't know if this herbs are going to interact with oral AS or not, just take herbs in between doses