In general, you can't include in your medical expenses the cost of a prescribed drug brought in (or ordered shipped) from another country. You can only include the cost of a drug that was imported legally. For example, you can include the cost of a prescribed drug the Food and Drug Administration announces can be legally imported by individuals.
You can include the cost of a prescribed drug you purchase and consume in another country if the drug is legal in both the other country and the United States.