Prefilled single-dose syringe

DETAILED DESCRIPTION We claim: 1.
Prefilled single-dose syringe, comprising: an ampoule open at at least one of its ends and provided with a narrowed-diameter portion neighboring said open end; a stoppering device fitted into said ampoule to stopper said narrowed-diameter portion, which stoppering device is movable axially between a first storage position and a second injection position, and featuring an internal conduit communicating with said ampoule when said stoppering device is moved into its second position; a capsule attached to said stoppering device and fitted onto the shank of said open end of said ampoule, said capsule provided with a tip adapted for carrying a needle and having an axial channel, which axial channel is intended to communicate with said internal conduit of said movable stoppering device when it is moved into its second position; and at least one membrane microfilter fixed permanently within the syringe between the lower end of said movable stoppering device and the bottom of the capsule so that the fluid to be injected is in contact with said microfilter only when said stoppering device is in said injection position.
2.
Syringe as in claim 1, distinguished by the fact that the membrane microfilter features pores with a maximum diameter of between 0.
2 and 5 micrometers.
3.
Syringe as in claim 1, distinguished by the fact that the membrane microfilter is made of a substance selected from the following groups: polyamides, acrylic copolymers coated with nonwoven polyamide, cellulose esters, polytetrafluorethylene, polypropylenes.
4.
Prefilled single-dose syringe featuring a barrel open at at least one of its ends and provided with a narrowed-diameter portion neighboring said open end; a stoppering device fitted into said barrel to stopper said narrowed-diameter portion, said stoppering device being movable axially between a first storage position and a second injection position, said stoppering device having an internal tube; a nozzle attached to said stoppering device and fitted onto the shank of said open end of said barrel and provided with a ferrule equipped with an axial channel, said axial channel intended for communication with said internal tube of said movable stoppering device when said stoppering device is moved into its second injection position; and at least one membrane microfilter pressed between the lower end of said stoppering device and the bottom of said nozzle