Which of the following muscle relaxant has the maximum duration of action –

On this, there is controversy in different books :- According to Goodman & Gilman, Pancuronium is the longest acting. According to Lee Pipecuronium is the longest acting. Some books have given Doxacurium as longest acting (KDT, Ajay Yadav) You are lucky as you have got only one amongst these three. For this question doxacurium is the answer for sure.