I am new, where do I start?
You are not alone, there are lots of people just starting out on their own personal research journey and interested in adding Research Pens to their protocol
There are many resources available online like videos, podcast, and blogs that explain reconstituting research compounds, loading research pens and techniques.
These research pens are used for many different purposes and there is an assumption that researchers have a basic institutional knowledge of intended use, how to disassemble, load cartridges, reassemble these devices. As a result we do not provide instructions with the orders.
With that said, we are happy to assist and answer detail questions. Please send a request to Info@pen-depot.com
SHIPPING SPEED - ORDERS RECEIVED PRIOR TO 2P ET TYPICALLY SHIP SAME DAY, VOLUME PERMITTING.
ALL OTHER ORDERS SHIP NEXT BUSINESS DAY.
Loading Cartridges and Priming the Pen
Pro Tips on loading a CLASSIC Pen Cartridge and Priming the Pen.
Once the compound is reconstituted, pull all the solution into a 3 or 5mL syringe. Set the syringe aside on a sterile surface while you prepare cartridge in next step.
Remove the empty cartridge from the sterile wrapper and set aside on sterile surface. Wipe the top of the cartridge with an alcohol wipe.
The recommendation is to create a vent for the cartridge by using a 100U Insulin syringe - remove the plunger and all caps and insert the syringe into the top of the cartridge. That is the end with the silver ring. This creates a relief valve and prevents a buildup of air in the cartridge which will push the big grey stopper out of the bottom causing you to lose your entire mixture.
With the vent still in the cartridge, insert the larger syringe with the diluted compound next to the smaller vent syringe and push in the peptide liquid slowly. You will hear the air escaping from the smaller vent syringe.Once all liquid is safe in the cartridge, set it aside while you prepare your pen assembly.
Disassemble Pen by PULLING the pen apart – DO NOT unscrew as the cartridge will stay in the pen top.
Once the pen top is off, then unscrew the clear cartridge holder from pen body.
Push the black plunger all the way up inside of the pen body if it is sticking out at all. Be gentle and remember this is a corkscrew mechanism so allow it to turn under your finger, or it will bend and break.
Insert filled cartridge into glass/plastic cartridge holder and screw it back on to the pen body. Sometimes you must press hard to get threads to start particularly on the V2 models.
Screw on a pen tip needle and REMOVE ALL COVERS and guards so the needle is exposed. While holding the pen with needle facing up, gently thump on glass to get air to surface (bubbles up.) Now all the air should be close to the top.
Evacuate the air by turning the dial on the pen to about 5 and while keeping the pen pointed upwards, press the end of the pen (which is now at the bottom) which will engage the plunger and move the stopper up into the cartridge also pushing the excess air out of the needle. – repeat until air is removed from cartridge. If the first push seems a little stiff that is natural. You may have to push just a little harder to break the stopper lose from the bottom of the cartridge.
NOTE: the plunger will not activate or move without a cartridge in the holder. If you turn the dial on the units before inserting a cartridge the unit will appear to be defective. It requires resistance to actuate.
Pro Tips for Loading Pre-Purged Easy Load Cartridges
Our Pre-Purged Easy Load Cartridges are designed to simplify filling by eliminating the need for venting and significantly reducing the risk of stopper blowouts. Follow these pro tips to ensure smooth filling, proper seating, and reliable pen operation.
1. Start with an air-free syringe
Before transferring compound, make sure all air is removed from the syringe. Trapped air can create excess pressure and agitation and interfere with smooth stopper movement.
2. Insert the needle carefully
When inserting the syringe needle into the self-sealing top of the cartridge, avoid nicking or damaging the stopper. A clean, straight insertion helps maintain the seal and ensures proper movement.
3. Expect initial resistance — this is normal
You will need to apply steady, consistent pressure to unseat the stopper and get it moving. After one or two fills, you’ll quickly develop a feel for the correct pressure. if agitation becomes a concern, you can unseat the stopper with a little air making sure to draw the air back out of the cartridge once unseated which will return the stopper to the original position at the top. .
4. Slow down once the stopper starts moving
As soon as the stopper begins to travel, reduce your injection speed. Transfer the compound slowly and smoothly to prevent agitation—just as you would with a traditional cartridge fill.
5. Monitor stopper position during full fills
If transferring a full 3 mL volume, keep a close eye on the 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 may affect pen operation.
If this occurs, 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 your cartridge as sterile as possible, do not fully remove it from the sterile pouch prior to filling.
Instead:
Gently 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 then remove the cartridge from the pouch only after filling is complete
This approach minimizes environmental exposure while keeping the loading process controlled and consistent.
Venting Options
Pen-Depot Research Pens ONLY use 3ml - 11ML Long Stopper cartridges.
The maximum compound capacity is exactly 3mL Please consider this in your research protocol.
When transferring compounds to the cartridges for use, it is necessary to vent the cartridge to prevent the rubber stopper from blowing out the bottom of the cartridge.
Here are some techniques to keep your compounds safe.
Our 2 Recommended Options are below
These are the preferred and most controlled way to transfer compound into a cartridge while maintaining a closed, sterile environment.
“Vent Air Displacement Method”
Prepare 3 to 5mL syringe with your compound:
Prepare a vent:
Use a 1 mL standard insulin syringe as an air vent.
Unwrap the syringe, remove all caps and needle guards, and pull the plunger completely out.
You’ll be left with an empty syringe barrel, which will act as a vent allowing air to escape during transfer.
Create the vent path:
Insert the open syringe barrel into the self-sealing top of the cartridge.
This will serve as the air outlet while filling.
Begin compound transfer:
Insert a 3 mL syringe containing your compound directly next to the vent and inject slowly.
As the compound enters the cartridge, the displaced air will escape smoothly through the vent barrel, preventing back-pressure or stopper movement.
Result:
This process maintains a closed system, minimizes pressure buildup, and protects the sterile interior of the cartridge — making it a safe and controlled transfer method for research and compounding use.
"The Pump Displacement Method"
Prepare a 3 to 5mL syringe with your compound:
Remove all air from the transfer syringe before beginning.
Connect to the cartridge: Insert the syringe containing your compound into the self-sealing end of the cartridge.
Create vacuum transfer: Gently pull the syringe plunger upward to draw a small amount of air from the cartridge. Then release the plunger — the compound will begin to self-transfer into the cartridge.
Repeat the process: With the syringe still attached, pull the plunger up again to draw in another small amount of cartridge air, then release it. Each cycle will continue to move the compound slowly into the cartridge while displacing air back into the syringe. Continue until complete: Repeat this gentle pull-and-release motion until all air is removed from the cartridge and all compound has transferred. Fine-tune if necessary: If the flow slows or stalls, use short, slow plunger pumps — transferring only a small amount at a time and fully releasing the plunger between pumps to allow air to backflow into the syringe.
⚠️ Caution:
Do not pump too quickly or with excessive pressure.
Rapid or forceful plunger movement can cause the cartridge stopper to dislodge or blow out of the bottom of the cartridge.
What is the difference between V1, V2 and V3 model.
V1 models have a solid pen which allows you to completely close off the pen creating a sealed environment for storage. They come in different styles which include 60 unit standard size and 80 Unit slimline models.
V2 model have the “Injecthru” feature with a hole and retractable ring on the pen cap end. This allows for sight free needle administration. For those researchers with needle apprehension, this unique feature will hide the needle during administration. They only come in 60 unit standard versions.
V3 model - well really this is a V0 old model. It is a version of the V2 model just in slimline form. Caution should be taken if buying this model as if the intent is to use the inject thru functionality it will not work with all pen tips due to the hole design.
Pen-Depot does not sell this model as it creates lots of confusion.
Let's Talk Pen Tips
Universal Fit Does Not Mean Universal Performance
All Pen-Depot research pens use standard insulin pen-tip needles.
These pen systems and needle designs were originally engineered for insulin — a very low-viscosity (thin) solution that flows easily through fine-gauge needles.
When pen systems are used with compounds that differ in viscosity or flow characteristics, additional mechanical considerations apply.
“Universal fit” refers only to how the needle attaches to the pen. It does not guarantee identical flow performance.
Internal geometry, wall thickness, bevel design, coating quality, and manufacturing tolerances vary between brands. These variables directly influence:
• Injection resistance
• Flow consistency
• Pressure equalization timing
• Post-injection drip behavior
When delivering compounds that are thicker than insulin, needle selection becomes a performance optimization decision.
Key Mechanical Variables
Gauge & Flow Capacity
Pen needles typically range from 29G–33G.
Lower gauge number = wider internal bore
Wider bore = reduced resistance and faster equalization
Higher gauge number = finer internal bore
Finer bore = increased resistance and slower flow
All standard gauges are mechanically compatible with the pen.
Flow rate is the difference and they may not be compatible with your compound.
While insulin flows easily through very fine gauges, higher-viscosity compounds may perform more consistently with a slightly wider internal diameter.
Needle-to-compound compatibility is a performance consideration — not a device limitation.
Thin-Wall Engineering
Thin-wall construction increases the internal diameter without changing the external gauge size.
This allows:
• Improved flow efficiency
• Reduced back-pressure
• Faster pressure equalization
• Minimal increase in insertion discomfort
For higher-viscosity solutions, thin-wall designs can significantly improve delivery smoothness.
Needle Length
Common lengths range from 4 mm to 12.7 mm.
Shorter needles prioritize comfort.
Longer needles may provide more consistent delivery through denser tissue and reduce superficial pooling as well as prevent blowback.
Bevel Design & Surface Coating
Precision-ground multi-bevel tips reduce insertion resistance.
Silicone coatings reduce friction, improve glide, and minimize drag during withdrawal.
Higher manufacturing quality results in:
• More consistent lumen diameter
• Smoother internal surfaces
• Reduced flow variation
• More predictable equalization timing
Why Needle Selection Matters
The pen generates controlled mechanical pressure.
The needle determines how that pressure translates into fluid flow.
When solutions differ from the low-viscosity fluids these systems were originally designed for, flow resistance increases. Proper needle selection helps restore balance between:
• Pressure
• Resistance
• Equalization timing
• Delivery smoothness
Selecting a well-manufactured, thin-wall, precision-ground needle improves consistency, reduces perceived resistance, and minimizes post-dose drip.
Practical Guidance
For optimized performance:
• Use high-quality, thin-wall pen needles
• Match gauge to solution viscosity
• Allow refrigerated solutions to warm naturally
• Remove and discard the needle after each use. Do not leave it attached to the pen while not in use.
• Hold 10–15 seconds after dose completion for pressure equalization
As a general rule selecting a 29/30 gauge with 5mm or longer length will provide the most research consistency.
Most of these can be found online at Amazon and other online diabetes stores.
Pen Tips. Here are some quick links to get you started.
Pro Tips
If using the “injecthru” V2 model please consider 5mm or longer pen tips.
Injection Resistance or Post-Dose Dripping
Injection Resistance or Post-Dose Dripping
Understanding Flow Dynamics in Precision Pen Systems
Occasional resistance during injection or a small drop at the needle tip after withdrawal is typically related to fluid dynamics and setup variables — not continued mechanical advancement of the device.
Once the dose dial returns to zero, the drive mechanism stops. Any fluid observed after withdrawal is generally the result of internal pressure equalization and flow resistance within the needle.
Understanding the interaction between solution properties, cartridge specifications, and needle selection ensures consistent performance.
1. Solution Clarity & Complete Dissolution
If a reconstituted solution contains even microscopic undissolved particles, they can partially restrict the needle lumen and increase back-pressure.
Increased resistance during delivery may:
• Make the injection feel firm
• Extend equalization time
• Contribute to minor post-withdrawal dripping
Best practice:
• Gently swirl — never shake
• Confirm solution is fully clear before loading
• Do not use solutions containing visible particulate
2. Viscosity & Temperature
Viscosity describes a fluid’s resistance to flow.
Higher viscosity = greater flow resistance
Lower temperature = increased viscosity
Refrigerated solutions are naturally thicker and may require longer equalization time.
Allow solutions to reach room temperature prior to administration.
Do not heat.
3. Needle Gauge & Solution Compatibility
All standard pen-tip needle gauges are mechanically compatible with the Pen-Depot device.
However, performance is influenced by the interaction between the needle and the solution being delivered.
Flow characteristics depend on:
• Needle internal diameter
• Solution viscosity
• Reconstitution volume
• Temperature
Higher gauge number = smaller internal diameter
Smaller internal diameter = greater resistance
Greater resistance = longer pressure equalization time
For example:
33g = very fine internal diameter, slower flow
29–30g = slightly wider internal diameter, improved flow
All gauges function within the pen system. The difference is flow rate.
While every gauge is device-compatible, not every gauge is equally optimized for every solution type. Thicker or colder solutions may perform more consistently with a slightly wider internal diameter.
Needle-to-solution compatibility is a performance consideration — not a device limitation.
Selecting the appropriate gauge improves delivery smoothness, reduces resistance, and minimizes post-dose equalization drip.
4. Cartridge Compatibility & Alignment
Pen-Depot pens are engineered specifically for:
• 3 mL cartridges
• 11 mm long stopper geometry
• Defined glass wall tolerances
Using off-spec, prefilled, or non-standard cartridges may introduce:
• Plunger drag
• Uneven pressure
• Mechanical misalignment
• Increased resistance
Cartridge geometry and stopper length directly influence drive alignment and pressure distribution. Always verify cartridge specifications prior to use.
5. Air & Internal Pressure Stabilization (Priming)
Air pockets within the cartridge can compress and expand during delivery, affecting pressure stability.
Before each use:
• Dial a small increment
• Hold the pen upright with needle facing upward
• Gently tap to move air to the top
• Press until a small drop appears
This removes trapped air and stabilizes internal pressure for smooth, accurate delivery.
6. Equalization Timing
After the plunger stops advancing, internal pressure may still be normalizing.
Recommended hold time after dose completion:
Low viscosity: 8–10 seconds
Moderate viscosity: 10–12 seconds
Higher viscosity or fine gauge: 12–15 seconds
Maintain light forward pressure while withdrawing.
A small drop (one to two drops) after removal can be normal pressure equalization behavior, particularly when using finer gauge needles or higher-viscosity solutions.
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7. Needle Construction & Flow Efficiency
Not all pen-tip needles perform identically.
Variations in:
• Wall thickness
• Internal coating
• Bevel geometry
• Hub precision
Can significantly influence flow rate and resistance.
Thin-wall, silicone-coated, multi-bevel pen needles reduce resistance and improve equalization efficiency.
Always replace the needle after each use to maintain sharpness and prevent residue buildup.
What Is Considered Normal?
A minimal drop at the needle tip following withdrawal is typically a function of flow resistance and pressure equalization.
Performance Optimization Checklist
For consistent delivery:
• Confirm solution is fully dissolved and clear
• Allow refrigerated solutions to warm naturally for a few minutes
• Use cartridges meeting 3 mL / 11 mm stopper specifications
• Prime to remove trapped air
• Select needle gauge appropriate for solution viscosity
• Hold 10–15 seconds after dose completion
• Remove and discard pen tip needle after each use
Also make sure to read the section on "Let's Talk Pen Tip"