Methadone Tablets
Action and use
Opioid receptor agonist; analgesic.
Definition
Methadone Tablets contain Methadone Hydrochloride.
Content of methadone hydrochloride, C21H27NO,HCl
92.5 to 107.5% of the stated amount.
Identification
Assay
Weigh and powder 20 tablets. To a quantity of the powder containing 50 mg of Methadone Hydrochloride add 60 mL of water and 5 mL of glacial acetic acid, heat on a water bath for 5 minutes, mix with the aid of ultrasound for 10 minutes and dilute to 100 mL with water. Filter through a glass fibre paper, discarding the first 10 mL of filtrate, and dilute 20 mL to 100 mL with water. To 10 mL of the resulting solution add 10 mL of phosphate buffer pH 4.9 and 5 mL of a 0.4% w/v solution of picric acid. Extract with three 15 mL quantities of chloroform and dilute the combined chloroform extracts to 50 mL with chloroform. To 10 mL add sufficient chloroform to produce 20 mL and measure the absorbance of the resulting solution, Appendix II B, at the maximum at 350 nm using in the reference cell a solution prepared in the same manner but using a 5% v/v solution of glacial acetic acid and beginning at the words ‘Filter through a glass fibre paper…’. Calculate the content of C21H27NO,HCl taking 448 as the value of A (1%, 1 cm) at the maximum at 350 nm.