Acute toxicity and LD50/fatal dosages are fine when you're worried about acute overdoses or unintentional ingestions. Those are not the measures we are concern

Acute toxicity and LD50/fatal dosages are fine when you're worried about acute overdoses or unintentional ingestions. Those are not the measures we are concerned with when we're talking about uncommon or rare effects (which, like the Vioxx deaths, had an incidence of one in /thousands/ at standard dosages), or effects that manifest with /chronic/ usage (e.g., over years of use, as is common with anti-depressant therapy). What you're discussing is apples to oranges.