How to prevent vial coring

What is vial coring? And what are the risks?

Vial coring is when a small piece of a vial's rubber cap breaks off and gets into the vial itself and/or the fluid inside. This is generally caused by repeat insertion of needles through the vial cap.

There is not much clear evidence about the risks of vial coring but potential issues include the possibility of drawing up and injecting small pieces of rubber. This is not necessarily dangerous but probably best avoided.

Another issue is that the hole in the vial cap may be large enough that it stays permanently open and allows air, dust and other contaminants to enter the vial. It may also allow fluid to leak out if the vial is not kept upright.

Overall, while the risks associated with vial coring are not entirely clear, there are safeguards which are helpful and relatively easy to implement.

How to prevent coring

There are various steps which you can take to reduce the risk of vial coring:

  • After puncturing the cap of a new vial the first time you use it, it is generally advisable to choose a different insertion site each time you draw.

  • If your vial’s stopper does not have a mark designating the appropriate spot to pierce (i.e. a raised circle around the centre), then it is recommended to insert your drawing needle close to the crimped metal collar to avoid concentrating punctures in one area.

  • It can be helpful to use narrower gauge needles for drawing up medication, as these will disturb the seal the least

    • Depending on the carrier oil and viscosity of the HRT that you are using, it may be possible to use 25-30 gauge needles for drawing up.

  • Silicone caps may be less susceptible to coring than butyl rubber due to the material properties of silicone.

  • When inserting needles through the vial cap, you can use the 45°-90° puncture technique. This involves inserting the needle at a 45–60° angle with the opening of the needle tip facing up (i.e. away from the stopper). As the needle enters the vial, a small amount of pressure is applied as you slowly increase the needle to a 90° angle. The needle should be at a 90° angle just as the needle bevel passes through the stopper.

  • You can use 45–90° puncture technique both the first time you use the vial and for subsequent injections. You can also do this with both sharp and blunt needles.

  • Some people find that reinserting blunt drawing needles into an existing puncture can help reduce coring. Given the thickness (18g) of these needles and the potential for repeated strain on a puncture site, we do not tend to recommend this approach.

We provide money to buy all types of injecting supplies, including sharp and blunt needles, through our healthcare fund. You can contact us to make a request.

  • Check out the video below for a step-by-step tutorial on the above method.

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