How to fill a cartridge with transfer and vent needles
A 3 mL glass cartridge is sealed at both ends: a rubber plunger at the bottom and a crimped cap with a rubber septum at the top. To fill it you push liquid in through the septum with a syringe. The air that was inside has to go somewhere, and if it has no way out the pressure pushes the plunger out of the bottom of the cartridge. That is what the vent needle prevents. This guide covers the equipment and the handling. For how much to add when you reconstitute, the reconstitution calculator in the ShotLog app does the math.
How to fill a cartridge
- Sanitize the rubber septum at the top of the cartridge with an alcohol pad, then push the air vent needle through the septum.
- Push the syringe needle through the same septum at the top, next to the vent, and transfer up to 3 mL of solution into the cartridge. Transfer solution slowly, allowing the air to escape the cartridge through the air vent. Remove syringe, but leave the air vent.
- Leaving the air vent inserted, purge remaining air from cartridge by pushing the cartridge plunger up until little to no air bubbles remain. Remove air vent. Cartridge is now ready for pen use.
What you need to fill a cartridge
- 3 mL luer lock syringe with a 23G 1 inch needle: the transfer syringe. It holds a full cartridge's worth, the luer lock keeps the needle on, and the 1 inch length reaches through the septum with room to spare.
- Vent needle, 31G 13 mm luer lock: goes through the septum first and stays in while you fill, so displaced air escapes through it instead of building pressure. Sterile, individually wrapped, single use.
- ReconStation: a 3D printed stand that holds the cartridge upright with slots for the transfer and vent needles and a purge press for the last step. It ships with one 3 mL luer lock needle, one air lock needle and one cartridge.
- 3 mL glass cartridge, fresh from its sterilization pouch.
- An alcohol pad for the septum.
Why the vent goes in first
Push liquid into a sealed cartridge with no vent and the air inside is compressed until something gives. Usually it is the plunger, which shoots out of the bottom along with everything you just put in; sometimes it is the glass. With a vent needle through the septum, the air leaves as fast as the liquid arrives and the plunger stays put. Fill slowly so the vent keeps up. When the fill is done, pull the transfer syringe first and the vent second, so the last of the air leaves through the vent.
Purging the last air
With the vent still in, push the plunger up from the bottom until the bubble at the top is gone. On the ReconStation, that is the purge press in the centre: set the cartridge on it and press down. The ReconStation Cartridge Holder has the same purge station built into its base. Then remove the vent. The septum reseals after each puncture during normal use.
Can I use a pen needle or a smaller syringe to fill?
A pen needle has no syringe fitting, so it cannot transfer anything; it is only for the pen. A 0.5 mL U-100 syringe will push liquid through the septum, but it takes six fills to move what the 3 mL syringe moves in one, and its fixed needle is short and fine, so it is slow. The 3 mL luer lock syringe is the tool made for the job.
After filling
The cartridge is ready for the pen. Go to the cartridge loading guide, then prime the pen and clear the air. A filled cartridge is single use: once it is empty, discard it and start with a fresh one. Questions go to [email protected].
Watch the cartridge filling video on the how-to videos page.
Products in this guide
Related guides
For research use only. Not for human or animal therapeutic, clinical, or diagnostic use. Not FDA-approved.
