A medicament delivery device for administering a medicament to a user includes a medicament reservoir and an entrance port and an exit port each disposed adjacent the reservoir. A gas chamber disposed adjacent the entrance port. The device includes a pressurizing mechanism operable to pressurize said gas chamber to at least a prescribed pressure. A first frangible membrane extends across the entrance port and separates the reservoir from the gas chamber. A second frangible membrane extends across the exit port. When the pressurizing mechanism is attached, at least one of the first and second membranes is responsive to the prescribed pressure in the gas chamber to burst to allow gas to flow through the entrance port and the reservoir and to carry the medicament through the exit port.