alprostadil storage time

[ready2go]

hello guys . so i ordered a bottle of alprostadil and seller said there is enough for 12 doses depending on the amount used . but i read on line that once mixed it must be discarded after 24 hours [the portion in needle used the] and the whole bottle must be mixed.
so possibly 2 doses in 24 hours and the rest gets thrown out . the order cost over $40 if this is the case ,this is the first time and last time ill be using this method.