Proper Aseptic Technique to Prevent Coring of Sterile Vials

What is Coring?

Coring is when a small piece of a vial’s rubber stopper breaks off and contaminates the contents of a sterile vial. It can typically be noticed floating on top of or inside the medication or stuck to the inside wall of the vial. This small foreign body can then be aspirated into a syringe and injected into a patient. Because of its small size, personnel is not on the lookout for this, or if visualization is blocked by a label, a matching background, or a colored vial, the coring may go unnoticed.3

Although coring is most likely a low-frequency event, other reports of coring, as well as patent applications for needles that prevent coring, suggest that coring continues to occur and is a problem that has not been completely solved.3

Following the recommended techniques and using the proper size equipment when puncturing a vial, can reduce the risk for coring.


Before You Puncture the Vial

Medications should be drawn up in a designated clean medication preparation area that is not adjacent to potential sources of contamination, including sinks or other water sources. Water can splash or spread as droplets more than a meter from a sink. In addition, any item that could have come in contact with blood or body fluids, such as soiled equipment used in a procedure, should not be in the medication preparation area.

Examples of contaminated items that should not be placed in or near the medication preparation area include used equipment such as:

  • syringes
  • needles
  • IV tubing
  • blood collection tubes
  • needle holders (e.g., Vacutainer® holder)

The medication preparation area should be cleaned and disinfected on a regular basis, and any time there is evidence of soiling. In addition, there should be ready access to necessary supplies (such as alcohol-based hand rub, needles and syringes in their sterile packaging, and alcohol wipes) in the medication preparation area to ensure that staff can adhere to aseptic technique.1

From an infection control perspective, the safest practice is to prepare an injection as close as possible to the time of administration to the patient. This is to prevent compromised sterility (i.e., microbial contamination or proliferation) or compromised physical and chemical stability (e.g., loss of potency, adsorption to the container) of the medication when it is transferred outside of its original container and stored for a period of time before administration.

If there is a need for “pre-drawn syringes,” one option is to purchase conventionally manufactured pre-filled syringes, which undergo quality assurance, including sterility and stability, testing by the manufacturer.1

Knowing the parts of a syringe and needle is crucial, not only for proper injection techniques but also to keep an aseptic field before injecting a medication. Notice the bevel of the needle. This part of the needle is key to prevent coring when entering a rubber stopper.


parts of a syringe


Proper Puncture of Vial

Proper hand hygiene should be performed before handling medications, and the rubber septum should be disinfected with 70% isopropyl alcohol prior to piercing it and allow the alcohol to dry.

To prevent coring, the needle should be inserted at a 45–60° angle with the opening of the needle tip facing up (i.e., away from the stopper), sometimes referred to as “bevel up”. A small amount of pressure is applied, and the angle is gradually increased as the needle enters the vial. The needle should be at a 90° angle just as the needle bevel passes through the stopper.3



proper angle of needle to prevent coring



Smaller gauge needles may reduce the risk of coring but may make the cored piece more difficult to see should coring occur. Using blunt fill needles may also reduce the risk of coring (and needle stick injuries).3

To prevent vacuum formation, inject air into the vial equal to the volume to be withdrawn. When reconstituting a powdered drug, withdraw a volume of air equal to the amount of the diluent to be added. This will prevent positive pressure from developing inside the vial.2

Inspect the medication-filled syringe and the vial from which the medication was drawn for any signs of coring, small flecks, or pieces of the rubber stopper.



Single-Dose Vials:

  • Are not designed for entry on multiple occasions.
  • Must be used within 1-hour or discarded.


  • Must be discarded after opening and not stored for any period of time.

Multi-Dose Vials:

  • Contain one or more antimicrobial preservatives and are designed for entry on multiple occasions.
  • Discard within 28 days of initial entry, unless otherwise specified by the manufacturer. 4


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  4. Trissel Revisions to USP Chapter Examining Sterile Compounding Practices. Presented as an Exhibitor Theater at the 42nd ASHP Midyear Clinical Meeting December 3, 2007.
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