Destaining Methadone Syrup 4 mg/mL-contains artificial raspberry aroma

The methadone syrup that we have always prepared according to the same composition and in the same way of preparation, has since shortly after a few hours of dark pink, because of the addition of artificial raspberry aroma, to colourless. The color change probably indicates some instability, but we do not know where it can come from. The syrup is always kept in a brown bottle of 300 mL in a dry, dark place at room temperature. Changing the cooking method does not help, and the taste has remained the same according to the patients. The pH of the syrup is 5 to 6. The protocol used is as follows: -Methadonic hydrochloride weighing 1.2 g -Dissolve in low distilled water 20 mL -Add conserved sugar syrup 150 mL -Add Aroma of raspberry fantasy 2.25 g -Aanlengen with distilled water AD 300 mL