Safety and warnings
Important information about safe use of your Pen-Depot Research Injection Pen. Please read before purchase and before use.
On this page
Additional safety topics — storage, reconstitution, air bubble management, and more — will be added to this page as we expand our customer education materials.
1. Replacement cartridge holders — proper use
We sell replacement cartridge holders for use when the original holder on your Pen-Depot Research Injection Pen has cracked, broken, or worn out. Please read the following before purchasing or using a replacement holder.
For use on Pen-Depot Research Injection Pens only
Pen threads vary by manufacturer. We are unable to confirm whether our replacement cartridge holders will fit or function correctly on pens not purchased from Pen-Depot.
What replacement holders are for
Replacement cartridge holders are intended only to replace a holder on your existing Pen-Depot Research Injection Pen that is damaged or worn out. Once installed with a fresh cartridge, the pen is primed once and used until that cartridge is finished.
What replacement holders are NOT for
We've seen customers buy replacement holders to swap cartridges in and out of a single pen between doses — for example, rotating between two or three different compounds using the same pen. Please do not do this. Here's why:
- Re-priming wastes compound. Every time you remove and reinstall a cartridge, the pen must be re-primed. Over a week, the compound you waste often exceeds the cost of simply running a dedicated pen per compound.
- It risks misdosing. Re-priming and "un-priming" introduces real dosing error — you can end up under- or over-dosing without realizing it.
- It wears out the pen. The threading, plunger, and seals on injection pens are not engineered for repeated swaps. This kind of use causes premature failure and VOIDS the pen's warranty.
The safer, cheaper approach
If you're running more than one compound, use one pen per compound cartridge per cycle. It is safer, more accurate, and almost always less expensive once you factor in wasted compound and shortened pen life.
2. 3D printed spacers and aftermarket modifications
We strongly advise against the use of 3D printed spacers, extenders, or any aftermarket modifications designed to push the cartridge plunger past its engineered travel. These modifications create serious safety, dose accuracy, and equipment risks — and void the pen's warranty.
Why do manufacturers leave residual volume in cartridges?
The 0.03–0.05 mL of residual volume in a 3 mL cartridge is not a manufacturing oversight — it is an intentional design tolerance. The final fraction of fluid in any cartridge sits at the mechanical edge of the plunger's travel, where:
- Dose accuracy degrades. Once the plunger reaches its designed end-of-travel, additional mechanical force does not produce a linear, predictable fluid output. The displayed dose and the actual delivered dose can diverge — often without any visible indication.
- Fluid composition at the bottom of the cartridge may differ from the rest. Residual volume can include settled particulates or micro-bubbles that the cartridge geometry intentionally isolates from the deliverable portion.
- This margin aligns with recognized injection system standards, including ISO 7886 and ISO 11608, which govern dose accuracy and repeatable delivery.
Why are 3D printed spacers specifically a problem?
There are five distinct issues.
1. Dose inaccuracy and dosing error
The spacer changes how mechanical force is transferred through the plunger, producing inconsistent injection pressure and inconsistent delivered volume — even within the "extra" portion the spacer is attempting to recover. You can believe you are delivering the dialed dose and actually be delivering a partial or excessive one, with no visible indication that anything is wrong.
2. Mechanical damage to the pen
Spacers force the leadscrew, plunger drive, and dose-setting mechanism past their designed travel range. This commonly results in stripped threading, damaged dose mechanisms, and cracked cartridge holders. These failures are not always immediate or visible — a pen can be silently compromised before it fails on the next injection.
3. Cartridge stopper damage
Pushing the rubber stopper past its designed limit can deform it, compromise its seal, or in some cases push it past the cartridge neck entirely. Any of these can cause leakage, contamination, or uncontrolled fluid release.
4. Sterility risk
Consumer 3D printing materials (PLA, PETG, ABS) are not sterile and cannot be reliably sterilized at home. The layer-by-layer print surface is porous and is known to harbor bacteria. Introducing a non-sterile component into the sterile field of an injection device is a real contamination risk.
5. Material safety
Most consumer 3D printing filaments are not biocompatible. Even where the spacer does not directly contact the compound, it sits in close proximity to injection components and can shed particulates.
Warranty notice
Use of 3D printed spacers, extenders, or any aftermarket cartridge modification voids the pen warranty. Damage or failure caused by these modifications is not eligible for replacement or refund.
Questions? info@pen-depot.com · +1-267-737-8433