A catheter extending from a distal end which, when in an operative position is inserted within a body of a patient, to a proximal end, the catheter comprising a charge holding cavity to which a therapeutic compound is to be supplied and a wall including inner and outer portions, an inner surface of the inner portion surrounding the charge holding cavity with an outer portion surrounding at least a portion of an outer surface of the inner portion, wherein the inner portion is formed so that a first diffusion rate of the therapeutic compound therethrough is different from a second diffusion rate through the outer portion.