Methadone hydrochloride is chemically described as 3-heptanone,6-(dimethylamino)-4,4-diphenyl-, hydrochloride. Methadone hydrochloride is a white, essentially odorless, bitter-tasting crystalline powder. It is very soluble in water, soluble in isopropanol and in chloroform, and practically insoluble in ether and in glycerine. Methadone hydrochloride has a melting point of 235°C, a pKa of 8.25 in water at 20°C, a solution (1 part per 100) pH between 4.5 and 6.5, a partition coefficient of 117 at pH 7.4 in octanol/water.
Methadone hydrochloride is a mu-agonist; a synthetic opioid analgesic with multiple actions quantitatively