A medicament delivery device for administering a medicament to a user includes a medicament reservoir and an entrance port and an exit port and a gas chamber disposed adjacent the entrance port. The device includes a pressurizing mechanism to pressurize the gas chamber. The device also contains frangible membranes and may include a piercing member. In use, the frangible membranes in the device are responsive to pressure in the gas chamber and are either pierced or burst to allow gas to flow through the entrance port and the reservoir and to carry the medicament through the exit port.