Alvimopan dihydrate (ADL 8-2698 dihydrate) is a potent, selective, orally active and reversible μ-opioid receptor antagonist, with an IC50 of 1.7 nM. Alvimopan dihydrate has selectivity for μ-opioid receptor (Ki=0.47 nM) over κ- and δ-opioid receptors (Kis=100, 12 nM, respectively) . Alvimopan dihydrate can be used for the research of postoperative ileus[1][2][3].