Embodiments of the invention provide infusion systems for the intravenous or other delivery of drugs and other therapeutic agents to a patient including a human or mammal. The therapeutic agents may be dissolved in solution or comprise the solution itself. Embodiments of the systems can utilize a chemical reaction to predictably drive a flow of drug(s) through a catheter or other flow path and into the patient. More specifically, the reaction may include an acid-base reaction or any other reaction that produces a gaseous substance. The gas is produced and contained in an expandable drive balloon when the acid-base reactants are combined with a liquid. As the gas is produced, the drive balloon expands to exert pressure on a separately-contained drug reservoir which, in turn, pushes drug(s) from the reservoir into the flow path where the drug is ultimately delivered to the patient in a controlled and predetermined manner.