Loading and venting guide
Step-by-step guides for loading Classic cartridges and Pre-Purged Easy Load cartridges, our two recommended venting methods, and how to prime your pen before first use.
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1. Loading Classic cartridges
Classic cartridges require venting during fill to prevent the rubber stopper from being pushed out the bottom by built-up air pressure.
1. Prepare the compound
Once your compound is reconstituted, pull all of the solution into a 5 mL syringe. Set the syringe aside on a sterile surface while you prepare the cartridge.
2. Prepare the cartridge
Remove the empty cartridge from its sterile wrapper. Wipe the top of the cartridge (the end with the silver ring) with an alcohol wipe.
3. Create a vent
Insert a 100U insulin syringe — with the plunger and all caps removed — into the top of the cartridge (the silver ring end). This creates a relief valve and prevents air buildup, which would push the grey stopper out the bottom and cause you to lose your mixture.
4. Transfer the compound
With the vent still in the cartridge, insert the larger syringe with the diluted compound directly next to the vent and push in the compound slowly. You'll hear the air escaping through the vent.
5. Prepare the pen
Once all liquid is in the cartridge, set it aside. Then:
- Pull the pen apart — do NOT unscrew, or the cartridge holder will stay inside the pen cap.
- Once the cap is off, unscrew the clear cartridge holder from the pen body.
- Push the black plunger all the way up inside the pen body if it's sticking out (gently — it's a corkscrew mechanism).
6. Install the cartridge
Insert the filled cartridge into the cartridge holder and screw it back onto the pen body. V2 threads may require firm pressure to start.
7. Prime the pen
See section 4 below.
2. Loading Pre-Purged Easy Load cartridges
Our Pre-Purged Easy Load Cartridges simplify filling by eliminating the need for venting and significantly reducing the risk of stopper blowouts.
NO VENT IS NEEDED FOR THIS MODEL.
1. Start with an air-free syringe
Remove all air from the transfer syringe before beginning. Trapped air creates excess pressure and agitation and interferes with smooth stopper movement.
2. Insert the needle carefully
Insert the syringe needle into the self-sealing top of the cartridge. Avoid nicking or damaging the stopper — a clean, straight insertion maintains the seal.
3. Expect initial resistance — this is normal
Apply steady, consistent pressure to unseat the stopper and get it moving. After one or two fills you'll develop a feel for the right pressure.
If agitation becomes a concern, you can unseat the stopper with a small amount of air — but draw that air back out of the cartridge once the stopper is unseated, which returns the stopper to its original position at the top.
4. Slow down once the stopper starts moving
Once the stopper begins to travel, reduce your injection speed. Transfer the compound slowly and smoothly to prevent agitation.
5. Monitor stopper position during full fills
If transferring a full 3 mL volume, keep a close eye on stopper position relative to the bottom edge of the glass.
Do not push the stopper past the bottom edge of the cartridge. Over-travel can compromise proper attachment to the pen body and affect pen operation. If this happens, keep the syringe inserted and gently push the stopper back until it is even with the bottom of the glass barrel before continuing or removing the syringe.
6. Maintain sterility during loading
To keep the cartridge as sterile as possible, do not fully remove it from the sterile pouch before filling. Instead:
- Push the cartridge forward inside the pouch so the self-sealing end is exposed through the paper side.
- Insert the syringe and complete the transfer.
- Remove the cartridge from the pouch only after filling is complete.
3. Venting methods (Classic cartridges only)
Pen-Depot Research Injection Pens use only 3 mL / 11 mm long-stopper cartridges. Maximum compound capacity is exactly 3 mL.
When transferring compounds into Classic cartridges, venting is necessary to prevent the rubber stopper from blowing out the bottom of the cartridge. We recommend either of these two closed-system methods.
Method 1: Vent Air Displacement (recommended)
This is the preferred method — controlled, closed-system, and protects sterile interior.
1. Prepare your compound syringe
A 3 to 5 mL syringe loaded with your compound.
2. Prepare the vent
- Use a 1 mL standard insulin syringe as an air vent.
- Unwrap it, remove all caps and needle guards.
- Pull the plunger completely out — you're left with an empty syringe barrel that acts as a vent.
3. Insert the vent
- Insert the open syringe barrel into the self-sealing top of the cartridge.
- This serves as the air outlet during filling.
4. Transfer the compound
- Insert your compound syringe directly next to the vent.
- Inject slowly.
- Displaced air escapes through the vent barrel, preventing back-pressure or stopper movement.
Result: A closed system that minimizes pressure buildup and protects the sterile interior of the cartridge.
Method 2: Pump Displacement
1. Prepare a 5 mL syringe
Load with your compound. Remove all air from the transfer syringe before beginning.
2. Connect to the cartridge
Insert the syringe into the self-sealing end of the cartridge.
3. Create vacuum transfer
Gently pull the syringe plunger upward to draw air from the cartridge. Then release the plunger — the compound will begin to self-transfer.
4. Repeat the cycle
With the syringe still attached, pull the plunger up again to draw remaining air, then release. Each cycle moves compound into the cartridge while air flows back into the syringe.
5. Fine-tune as needed
If flow slows or stalls, use short, slow plunger pumps. Transfer small amounts at a time and fully release between pumps to allow air backflow.
Caution: Do not pump too quickly or with excessive pressure. Rapid plunger movement can dislodge or blow out the cartridge stopper.
4. Priming your pen
Once the cartridge is loaded and the pen is reassembled, prime the pen before first use.
- Screw on a pen tip needle and remove all covers and guards so the needle is exposed.
- Hold the pen with the needle facing up and gently thump the glass to bring air bubbles to the top.
- Turn the dial on the pen to about 5 units.
- Keep the pen pointed upward and press the end of the pen (now at the bottom). This engages the plunger, moves the stopper up into the cartridge, and pushes excess air out through the needle.
- Repeat until air is removed from the cartridge.
The first push may feel a little stiff — that's normal. You may need to push slightly harder to break the stopper loose from the bottom of the cartridge.
Questions? info@pen-depot.com · +1-267-737-8433