Vented refill arrangement for implantable drug-delivery devices

An implantable device for administering a liquid, the device comprising:

• an outer shell defining an interior volume;
• within the interior volume, a pump assembly including a reservoir, a gas-driven forcing mechanism and a passage for conducting liquid from the reservoir to an ejection site outside the shell in response to pressure applied by the forcing mechanism;
• and
• a refill port assembly comprising:
• an orifice through a surface of the housing for receiving a refill needle;
• a first housing defining a first chamber having first and second open ends and fluidly coupled, via at least one bore through the first housing, to a ventable interior portion of the shell;
• a second housing defining a second chamber having an open end and fluidly coupled, via at least one bore through the second housing, to the drug reservoir;
• and
• first and second needle-penetrable septums,
• wherein the orifice, the first and second housings and the first and second septums are arranged in series with the first septum disposed between, and penetrably sealing, the orifice and the first open end of the first housing, and the second septum disposed between, and penetrably sealing, the second open end of the first housing and the open end of the second housing.