A drug delivery device (10) includes a pressurized reservoir (12) incommunication with a flow path to an outlet (14). The flow path includes twonormally-closed valves (16, 18) and a flow restriction (18). A pressuremeasurementarrangement (22) measures a differential fluid pressure between two points(24, 26)along the flow path which span at least part of the flow restriction (18), oneof thepoints being between the valves (16, 18). A controller (28) selectively opensthevalves (16, 18) to deliver a defined quantity of the liquid medicament to theoutlet(14).
