In one form, the therapeutic agent delivery apparatus is used for infusing a therapeutic agent into a body lumen and includes a lumenal body defining a plurality of infusion ports for infusing the therapeutic agent into the body lumen, and a sensing element distal of the infusion ports and adapted to sense the amount of infused therapeutic agent or any compound derived from the therapeutic agent in the body lumen. In another form, the apparatus includes a lumenal body defining a plurality of infusion ports for infusing the therapeutic agent into the body lumen, and a filtration element distal of the infusion ports and adapted to deliver a reaction agent adapted to react with the therapeutic agent in the body lumen. A sensing element may be provided distal of the filtration element for sensing the amount of infused therapeutic agent or compounds derived therefrom in the body lumen.