Storage temperature effect on the stability of morphine and codeine in urine.

Urine samples collected from one laboratory volunteer and five alleged heroin addicts are prepared (without preservatives) in 5-mL aliquots in glass culture tubes and stored at room, refrigerator, and freezer temperatures. Total morphine, total codeine, free morphine, and free codeine in these samples are analyzed at 30-day intervals for an 11-month period. Total morphine and total codeine concentration decreases are observed for all specimens in all storage conditions. For samples stored in the refrigerator and freezer, similar concentration decrease patterns are observed for total morphine and total codeine, and the decreases range from approximately 10 to 40%. The concentrations of free morphine and free codeine show slight but steady increases. For samples stored at room temperature, large decreases of total morphine are observed for three out of 10 specimens, and total codeine and total morphine concentrations (in seven other specimens) show a decrease pattern similar to that observed for the freezer and refrigerator storage conditions. Three concentration change patterns are observed for free morphine: The type I pattern follows the same decrease pattern observed for freezer and refrigerator storage conditions; the type II pattern shows free morphine increases (after 30-90 days of storage) that remain relatively high for the entire 11-month period; and the type III pattern shows initial increases, followed by gradual decreases to levels that are comparable with the specimens' respective initial concentrations. Free codeine concentrations show slight and steady increases for the entire 11-month period in all specimens.