Importance

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Abstract

An automatic injection device includes a drug-filled vessel having a flexible membrane over a first opening thereof and a puncturable seal in a wall thereof, a hollow needle attached at a first end to the flexible membrane and having a sharp end positioned proximate the puncturable seal housing. A pressure source such as a combustible propellant provides a compressed gas above the flexible membrane to force the membrane into the drug-filled vessel, forcing the hollow needle through the puncturable seal and the drug contained in the vessel through the hollow needle. After the drug has been substantially evacuated from the vessel, the membrane is allowed to return to its pre-expanded state thus retracting the hollow needle into the vessel. Preferably, the flexible membrane is an elastomeric material having a plurality of concentrically configured corrugations to allow expansion of the membrane into the vessel. The inner surface of the vessel may have a dome-like shape such that expansion of the membrane into the vessel substantially matches the dome-like shape and thus forces substantially the entire amount of the drug from the vessel.

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First Claim