An ambulatory drug infusion system includes a disposable ambulatory infusion pump and a flow regulator for regulating flow of the drug supplied from the disposable ambulatory infusion pump. The flow regulator includes a cylinder assembly of first, second and third cylinders arranged coaxially. The flow regulator includes a continuous spiral or helical liquid-flow channel formed between the first cylinder and the second cylinder fitted into the first cylinder. The regulator includes bypass through-holes in communication with the spiral or helical channel and formed in the second cylinder. The regulator further includes liquid-flow passages formed between the second cylinder and the third cylinder fitted into the second cylinder. The through-holes are in communication with the passages, respectively. One of the passages can be selected to choose a predetermined flow rate. The regulator further includes a diaphragm valve which can regulate fluid communication between the spiral liquid-flow channel and an outlet.
