A fluid dispenser for use in controllably dispensing fluid medicaments, such as antibiotics, oncolytics, hormones, steroids, blood clotting agents, analgesics, bio-pharmaceuticals and like medicinal agents from a reservoir that has been filled from pre-filled containers. The fluid dispenser includes a housing to which fill-vials can be connected for filling the dispenser reservoir with the fluid, and a stored energy source provided in the form of a substantially constant-force spring that provides the force necessary to continuously and uniformly expel fluid from the device reservoir. The fluid dispenser also includes a fluid flow control assembly that precisely controls the flow of the medicament solution to the patient.