The active ingredient acetaminophen (in Germany available as paracetamol) is a very widely distributed free accessible pharmaceutical and also very cheap. In England e.g. it is even available in drugstores on the bargain counter. Nevertheless, acetaminophen is a serious chemical substance which, in case of a severe overdose or already existing liver diseases, lead to life-threatening complications, e.g. organ failure with death.

Using an organ-on-a-chip model, a German-Israeli research team had determined that the toxic metabolite N-acetyl-p-benzoquinonimine (NAPQI) of acetaminophen have a much faster a damaging effect on the mitochondria in much lower dose as previously assumed (1). In addition, an inflammatory reaction is initiated which damages the liver.

Source:
http://viewpoints.iu.edu/science-at-work/

(1) http://www.invitrojobs.com/index.php/en/news/news-archive/item/1778-organ-on-a-chip-new-mechanism-of-paracetamol-discovered