A drug or device which is, in accordance with the practice of the trade, to be processed, labeled, or repacked in substantial quantities at an establishment other than the establishment where it was originally processed or packed, is exempted from the affirmative labeling and packaging requirements of this chapter, while it is in transit in intrastate commerce from the one establishment to the other, if such transit is made in good faith for such completion purposes only; but it is otherwise subject to all the applicable provisions of this chapter.