Final answer:
The most important factor when reconstituting a medication is tonicity. The drug should be formulated in an isotonic solution to prevent red blood cells from bursting.
Step-by-step explanation:
When reconstituting a medication, one of the most important factors to consider is tonicity. Tonicity refers to the concentration of solutes in a solution compared to the concentration of solutes in the cells. In order to prevent red blood cells from undergoing hemolysis (bursting), the drug needs to be formulated in an isotonic solution with the blood.