Cartridge

Cartridges are sealed plastic containers that hold insulin for refillable insulin pens. Most contain 3ml (300U normally) of insulin. Cartridges are made to fit only certain types of pens; if you have a Novo Nordisk pen, neither Eli Lilly nor Aventis insulin cartridges will fit it. Analog, r-DNA/GE/GM, and some CP Pharma bovine and porcine insulins are available in cartridge form. In Europe, 3 ml cartridges are more commonly sold than vials.

A closer look at a PenFill cartridge; this is Novo Nordisk's Novolin 70/30 insulin.

Plastic cartridges (at least according to Novo Nordisk) are actually made of glass, and coated with plastic, to avoid interaction between the insulin and the plasticizer chemicals. So essentially they are small vials. Like a vial, you can extract insulin from them using a syringe for its greater dosage precision, though you need to remember two special rules:

• Inject an approximately equal volume of air before drawing insulin, to equalize pressure
• Don't replace a cartridge in a pen after using a syringe on it.

Prefilled disposable Insulin pens such as the Novo Nordisk Flexpen are essentially cartridges too, and may also be used with syringes as above. Again, don't use them as pens after using with a syringe.

Lente insulins and PZI insulins of any origin are not available in any types of cartridges because the insulins can't be properly resuspended for use in them.

Further Reading

• Pictorial showing cartridges used with syringes for fine doses of insulin