What a pen actually is
Inside the housing sits a sealed cartridge of reconstituted solution. The dial at the back advances a plunger by a fixed distance per increment, and that distance corresponds to a fixed volume. Nothing about the mechanism knows or cares what is in the cartridge: it moves liquid, and that is all it does.
That is also the pen’s advantage over a vial-and-syringe setup. The measuring step, the part where most handling errors happen, has been done at manufacture. Concentration is fixed, the increments are fixed, and drawing up by eye is taken out of the process entirely.
The trade-off is flexibility. A vial can be reconstituted to whatever concentration a protocol needs; a pen cannot be changed after filling. Which one suits a given piece of research depends on whether that flexibility is worth the extra handling steps.
A search for how to use a peptide pen usually bundles two questions together: how the device behaves, and what the figures printed on its cartridge mean. This page answers the first and hands the second to the calculator. It does not describe administration to anyone, because everything here is supplied under the research use only classification.
Four habits that protect the contents
The pen is robust. The peptide inside it is not.
Increments, not amounts
A pen dial counts increments of volume. What one increment represents in terms of the compound depends entirely on the concentration in the cartridge, which is why the same dial position on two different pens can mean two very different quantities.
The cartridge label carries the total content and the fill volume. Those two numbers, together with the per-increment volume in the pen’s documentation, are what turn a dial position into an actual figure. Our product pages state all three for every pen we supply.
If a protocol was written for vial-and-syringe volumes, translate it once, on paper, before touching the dial. The arithmetic is simple; doing it from memory at the fridge is how it goes wrong.
One further number belongs alongside the label figures. The cartridge states what it holds; the batch certificate states what analysis found, and the two ought to agree before any calculation rests on either. Where a vial is reconstituted instead, the diluent joins that record too, which is what the bacteriostatic water page is about.
- Freeze a filled penIce crystals damage dissolved peptide. If it froze, treat the cartridge as compromised.
- Leave it warm for convenienceRoom temperature is a countdown, not a storage condition, once the cartridge is in use.
- Swap needles between pensCross-contamination between cartridges is invisible and permanent.
- Trust a discoloured or cloudy cartridgeReconstituted peptide solutions should be clear. Change is information, and the sensible response is to set that cartridge aside.
Keep reading
Three pages that follow on directly.
About pens
The handling questions we are asked most.