Levodopa stability in solution: time course, environmental effects, and practical recommendations for clinical use.

We defined the temporal stability characteristics of levodopa/carbidopa (LD/CD) solution, and determined the effects of temperature, ascorbate, and light on LD stability over 7 days. At room temperature and without ascorbate, LD levels significantly declined by 48 h. Ascorbate prolonged stability to 72 h. Refrigeration and freezing prevented a significant decline in LD levels for the full 7 days. Light or darkness had no effect on stability. LD/CD solution, if made daily, requires no special handling and longer stability is maintained with ascorbate, refrigeration, or freezing.