Multi-compartment pre-filled mixing syringes with bypass

1. A multi-compartment medical device for segregated storage and on demand mixing of at least two components and expression of a resulting mixture from the device, comprising:

a) a tubular barrel extending along an axis and having a front end and a rear end spaced axially behind the front end wherein the front end has an opening to express the mixture and a removable cap on said opening;

b) a gasket sealing the rear end of the tubular barrel and having an aperture;

c) a plunger located between the gasket and front end that is axially slidable within the tubular barrel that subdivides the tubular barrel into a front compartment between the plunger and the opening and a rear compartment between the plunger and the gasket;

d) a stem attached to the plunger and projecting axially rearward out of the rear end through the gasket, said stem sealing the aperture and axially slidable through the gasket aperture while maintaining the seal, with the dimensions of the aperture closely corresponding to dimensions of the stem; and

e) at least one bypass in the barrel that is positioned between the front end and the rear end of the tubular barrel so as to enable fluid movement of the components between the front compartment and rear compartment; wherein the plunger and the rear compartment are located axially behind the front compartment,

wherein said front compartment is partially filled with a first component and said rear compartment is at least partially filled with a second component, and wherein at least one of the components is a fluid,

wherein the first component is a lyophilized protein, the second component is a fluid for reconstitution, substantially all the first component is positioned substantially in close proximity to the front end; the plunger separates the first component and the second component and is positioned in close proximity to the front end; the bypass is positioned in the rear compartment between the gasket and the plunger; and the length of the bypass is less than the length of the rear compartment,

wherein a vacuum is generated in the front compartment and pressure is generated in the rear compartment upon pulling the plunger towards the rear end, with the device oriented horizontally or horizontally ±30° and with the bypass facing downwards, said vacuum being from about 0.9 atmosphere to about 0.1 atmosphere; wherein the second component flows through the bypass and contacts the first component; and wherein the length of the bypass is from about 20% to about 80% of the length of the rear compartment.

2. A method of separately storing and mixing of at least two components and then expressing a resulting mixture from a medical device according to claim 1 comprising: (a) Moving the plunger using the stem within the barrel towards the back end with the device oriented horizontally or horizontally ±30° and with the bypass facing downwards, thus forming vacuum in the front compartment; (b) Allowing the second component to move through the bypass into the front compartment and to mix with the first component; (c) Optionally moving the plunger within the barrel towards the front end and then towards the back end or vice versa; (d) Optionally repeating step (c) until the components are mixed; (e) Turning the medical device with the front end downwards with the device perpendicular to the ground ±45° (f) Repeating step (c) until the mixture moves into the front compartment; (g) Removing the cap from the opening on the front end of tubular barrel; (h) Expressing the mixture through the opening by pushing the plunger towards the front end.