In 1947 David Lester and Leon Greenberg found strong evidence that paracetamol was a major metabolite of acetanilide in human blood, and in a subsequent study they reported that large doses of paracetamol given to albino rats did not cause methemoglobinemia.
Godine 1947. biokemičari David Lester i Leon Greenberg su otkrili jake dokaze da je paracetamol bio osnovni metabolit acetanilida u krvi ljudi, a naknadne studije su pokazale kako velike doze paracetamola koje su se davale albino pacovima nisu uzrokovale methemoglobinemiju.