A locking mechanism for maintaining a position of a catheter on a beaded connector tube of an implantable device. A first lock member has a plurality of slots formed along its outer surface. A second lock member is dimensioned such that at least a slotted portion of the first member is receivable in an axial passageway of the second member. The second member has a plurality of tabs extending into the axial passageway wherein a tab is receivable in a respective slot to form a locking connection between the lock members. The lock members are aligned upon formation of the locking connection wherein the connector tube and catheter are receivable along the respective axial passageways, and the beaded connector tube portion is disposed on an opposite side of the tabs from the implantable device.