Long acting methadone formulations.
Studies conducted in this laboratory have indicated the feasibility of producing long-acting methadone tablets. In examining further, methadone hydrochloride suspensions were developed using spermaceti or eudragit retard-1 for particle coating. These procedures involved the addition of the active compound (methandone hydrochloride) to: a) melted spermaceti which was dried, and the dried mixture was pulverized and added to a methyl cellulose water solution; afterwards wild cherry syrup was added to the suspension, and b) Eudragit retard-1 crystals which were pulverized, dissolved in acetone/isopropanol (1:1) solvent system, dried, and to this product again the suspending agent methyl cellulose was added followed by wild cherry syrup to produce suspensions containing 10, 20, and 30 mg/ml methadone. These formulations were further used for in vivo studies, in male albino rats of Wistar strain. The pain threshold method was utilized in order to determine the duration of methadone. Over 75 h resistance to pain was recorded. Using the same technique, suspensions of methadone-naloxone combinations and the salts methadone-alpha-naphthalenesulfonate and methadone-o-benzoylbenzoate were prepared and examine similarly.