Dose is probably really low if you just used dried milk thistle and you need to refining and purify it to take via an IV. Same goes with acetylcysteine for Tylenol a overdose, you need to get it via an IV and you can’t just take the over the counter supplement.
Also, every household that has Tylenol should have, and co-administer, N-acetyl-cysteine (NAC) because it's hepatoprotective. The stinky sulfurous supplement that the FDA partially banned.
The question is, why not the plant itself? (Dried and powdered in a readily available pill)