Sterile Technique
Contamination does not announce itself. A vial that has been handled carelessly looks exactly like one that has not, and the consequences show up later or not at all. This covers the handling practices that keep a multi-dose vial usable across its life.
Why a multi-dose vial is the weak point
A sealed lyophilised vial is effectively sterile until something enters it. The moment a needle passes through the stopper, that changes, and it changes again with every subsequent puncture.
This is the entire reason bacteriostatic water exists. The 0.9 percent benzyl alcohol suppresses bacterial growth between withdrawals. It buys time; it does not sterilise, and it does not compensate for poor technique.
A pre-filled pen sidesteps most of this. The cartridge is a sealed system with a fresh needle per use and no repeated stopper punctures, which is why pens need no preservative. See pens compared with vials.
Before you start
- Clear the surface. A wiped, uncluttered work area with nothing that will be knocked into the field.
- Wash and dry hands. Gloves are optional for most handling but hands are not.
- Assemble everything first. Vial, diluent, syringes, swabs, sharps container. Reaching mid-procedure is when contamination happens.
- Check the vial. Intact seal, no cracks, contents as expected.
The stopper
Swab the rubber stopper with alcohol and let it dry. This second part is routinely skipped and it matters twice over: wet alcohol carried into the vial on the needle enters the solution, and alcohol only does its work during the contact time before it evaporates. Wiping and immediately puncturing gets you neither.
Swab before every puncture, not just the first. The stopper sits exposed between uses.
Needles
- A fresh needle for every puncture. Needles blunt on first pass through rubber, and a blunted needle cores the stopper, dropping fragments into the solution.
- Never re-sheath a used needle by holding the cap in your other hand.
- Do not touch the needle or lay it down between drawing and use.
- Sharps go in a sharps container, not household waste.
Coring is worth understanding because it is invisible. A blunt or badly angled needle punches out a small disc of rubber which falls into the vial. Entering at a slight angle with a sharp needle, bevel up, largely prevents it.
Drawing
Draw only what is needed. Returning unused solution to the vial reintroduces whatever the syringe has touched, and there is no benefit that offsets that risk.
Keep the vial upright and let the needle tip sit below the liquid surface. Drawing air alongside solution creates bubbles that make measurement unreliable.
Never decant into another container. Every transfer is another opportunity for contamination and another chance to lose track of concentration.
Between uses
Return the vial to refrigeration promptly. Store upright so the solution is not resting against the stopper, and keep it out of light. Mark the vial with the date of first puncture, because the 28 day bacteriostatic window starts then and no one remembers accurately a fortnight later.
More on degradation in storage and stability.
When to discard
Set a vial aside if any of these apply. None of them are recoverable.
- The solution is cloudy, or has strands, specks or visible particulate matter.
- Material will not dissolve after gentle swirling.
- Rubber fragments are visible, indicating the stopper has been cored.
- The vial has frozen, whether or not it looks normal now.
- The bacteriostatic window has passed.
- You are not certain of its handling history.
The last one is the hardest to act on and the most important. A vial whose history you cannot account for is not worth the doubt it introduces into everything downstream.