It is necessary that the medicine be in their original bottles and proper script. This is to ensure that fake medicine is not given to unsuspecting patients. It is also meant to avoid evasion of taxes.
"Bringing Medications or Filling Prescriptions Abroad
A traveler going abroad with a preexisting medical problem should carry a letter from the attending physician, describing the medical condition and any prescription medications, including the generic names of prescribed drugs. Any medications being carried overseas should be left in their original containers and be clearly labeled. Travelers should check with the foreign embassy of the country they are visiting to make sure any required medications are not considered to be illegal narcotics. (A listing of foreign embassies and consulates in the U.S. is available on the Department of State?s website at http://www.state.gov/s/cpr/rls/dpl/32122.htm. Foreign embassy and consulate contact information can also be found on the Country Specific Information for each country.)"