A cannulated drug delivery sheath having an annular wall and having a channel located within and extending partially through the annular wall. The annular wall defines a first lateral recess and a second lateral recess that are configured to respectively seat first and second cassettes containing therapeutic agents. The first and second lateral recesses have at least one first inlet port and at least one second inlet port, respectively. Also within the annular wall of the sheath is a first and second manifold. The first manifold is in fluid communication with the channel at one end and in fluid communication with the at least one first inlet port at another end. Similarly, the second manifold is in fluid communication with the channel at one end and in fluid communication with the at least one second inlet port at another end.