Patient-controlled medication delivery system

A medication delivery system comprising:

• an infusion pump including,
• a flexible fluid reservoir for storing a treatment fluid, said fluid reservoir having a treatment fluid inlet port and an inlet valve with an open position and a closed position,
• a rigid dosage chamber having a fluid outlet for the treatment fluid,
• a displacement piston slidably displacable within said dosage chamber,
• a flowpath providing fluid communication between said fluid reservoir and said dosage chamber, and
• an elastic member connected to said displacement piston, said elastic member transitionable from a more stressed position to a less stressed position to charge said dosage chamber with said treatment fluid from said fluid reservoir while said inlet valve remains in said closed position blocking said treatment fluid inlet port and transitionable from said less stressed position to said more stressed position to discharge said treatment fluid from said dosage chamber via said fluid outlet, wherein said elastic member displaces said displacement piston in a first direction away from said fluid outlet to expand said dosage chamber when said elastic member transitions from said more stressed position to said less stressed position, and wherein said displacement piston is displaced in a second direction toward said fluid outlet to contract said dosage chamber when said elastic member transitions from said less stressed position to said more stressed position;
• and
• a medicine catheter having first and second ends and a flow cross-section, wherein said medicine catheter is in fluid communication with said fluid outlet of said dosage chamber, and wherein said first end of said medicine catheter is positionable in a treatment site of a patient to deliver the treatment fluid to the treatment site.