To decant the potion into the flask, one must have at least 6 doses of Serum 208 in their inventory, as well as one or more potion flasks. Using the flask on the potion will open a menu to decant them. The optimal inventory setup for decanting potions is 17 4-dose potions and 11 flasks.
Once a dose of the potion has been used on an Afflicted, no more doses can be added to it. After all six doses have been used up, the flask will shatter and disappear. Flasks can be combined together, but the empty flasks will be destroyed in the process.