Syringe needle isolation device

A prefilled syringe assembly comprising:

• an elongate barrel having an open proximal end, a distal end, a chamber for retaining a quantity of fluid therebetween and a tip portion extending from said distal end having a passageway therethrough communicating with said chamber;
• a stopper slidably positioned in fluid-tight engagement inside said barrel;
• an elongate plunger rod for applying a distally-directed pressure on the quantity of fluid retained within said chamber, said plunger rod projecting proximally from said stopper and extending outwardly from said proximal end of said barrel;
• a housing extending outwardly from said tip portion of said barrel having a conduit therethrough in fluid communication with said passageway;
• a needle cannula having a proximal end, a distal end and a lumen therethrough, said proximal end of said needle connected to said housing so that said lumen is in fluid communication with said conduit;
• said housing including an internal valve assembly for allowing liquid under pressure in said chamber to flow distally through said conduit and said lumen while preventing unpressurized liquid in said chamber from flowing through said conduit and through said lumen;
• said internal valve assembly including a one-way valve having a proximal end surface disposed in fluid-tight contact with the tip portion of the barrel when the quantity of fluid in said chamber is not subjected to said distally-directed pressure and which is spaced away from the tip portion of the barrel when the fluid retained in the chamber is subjected to said distally directed pressure, said one-way valve thus configured to permit liquid flow through said passageway only in a distal direction away from said chamber and to preclude liquid flow through said passageway in a proximal direction;
• wherein a quantity of liquid held in said chamber will be isolated against inadvertent entry of liquid in a proximal direction through said lumen.