Stability of methadone in four vehicles for oral administration

The stability of methadone in vehicles commonly used for oral administration was determined. Solutions of methadone were prepared in (1) orange-flavored Tang, (2) grape-flavored Kool-Aid, (3) apple juice, (4) grape-flavored Crystal Light, and (5) grape-flavored Crystal Light plus 0.1% sodium benzoate. For each of the first four preparations listed, two solutions were formulated at each methadone hydrochloride concentration of 0.2, 0.8, and 1.5 mg/mL; one set of three concentrations of each solution was stored in a refrigerator at 5 degrees C for up to 55 days, and the other set was stored unprotected from light at 20-25 degrees C for up to 17 days. Only three Crystal Light plus sodium benzoate solutions were prepared at the same methadone concentrations and stored at 20-25 degrees C for up to 29 days. Methadone concentrations were measured by high-performance liquid chromatography. Methadone was stable (loss of potency, less than 5%) for up to 17, 11, 9, and 8 days when stored at 20-25 degrees C in Kool-Aid, Tang, apple juice, and Crystal Light, respectively, and for up to 29 days when stored at 20-25 degrees C in Crystal Light plus sodium benzoate. Methadone was stable for up to 55, 49, 47, and 34 days when stored at 5 degrees C in Kool-Aid, Tang, apple juice, and Crystal Light, respectively. All the solutions that did not contain sodium benzoate and were stored at room temperature displayed unacceptable microbial growth after approximately two weeks. No significant loss of methadone potency occurred in any of the vehicles for oral administration during the study.