A medical device configured to restrict medicament dispersion within a cerebrospinal fluid flow of the patient. The medical device including an implantable catheter having a distal end configured to be positioned within a flow of the cerebrospinal fluid, a proximal end, a body defining a lumen extending lengthwise along the implantable catheter configured to enable a flow of medicament from the proximal end to an infusion port located in proximity to the distal end, and a contoured surface defined by an exterior of the body in proximity to the infusion port configured to inhibit dispersion of the medicament within the cerebrospinal fluid.