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Training · Controlled Substances

Small Draws Magnify Syringe Tolerance

A 0.5 mL measurement in a 5 mL syringe carries an ISO-based tolerance of ±0.08 mL. Across a multidose vial, small differences between the syringe reading and the amount removed can make the controlled-drug log harder to reconcile.

  • Partial-Volume Tolerance
  • Before-and-After Weighing
  • Current Dispense Records
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What Partial-Volume Measurement Looks Like

  • ±0.08 mL ISO-based tolerance for a 0.5 mL draw volume from a 5 mL syringe
  • 1.4%–18.6% Mean error range observed across small-volume measurements in a published syringe study
  • <20% Share of labeled syringe capacity associated with a greater likelihood of error above 5% in that study

Why Small Draws Are Harder to Reconcile

A syringe can be appropriate for preparing and administering medication while still being an incomplete tool for inventory accounting. Below half of nominal capacity, the ISO tolerance calculation includes a component based on the syringe's full capacity. That component becomes a larger percentage of a small draw.

  • Syringe size matters — a small measurement occupies more of a smaller syringe, which generally makes it easier to read and reduces relative tolerance.
  • Technique matters — plunger position and graduation spacing can affect a small-volume measurement, while needle gauge and length affect hub loss.
  • The syringe and vial answer different questions — the syringe shows the prepared volume; inventory reconciliation asks how much left the container.
  • Hub loss affects the inventory record — medication left behind in the needle hub came out of the vial even if it was not delivered to the patient.
  • Small differences accumulate — across repeated draws from a multidose vial, the written balance can move away from the physical balance.

A difference does not, by itself, mean someone prepared the dose incorrectly. It means the practice needs a separate, defensible way to measure inventory movement. Clinical dosing should continue to follow the veterinarian's order, the medication instructions, and the practice's procedures.

CSI-360 Workflow

Measure the Change in the Container

  1. Sign In and Select the Patient

    An approved user signs in with an RFID card, fob, or wristband and a PIN, then selects the patient read in from the connected PIMS.

  2. Scan and Weigh the Container

    The RFID label identifies the tracked item, and the scale captures its starting weight before medication is removed.

  3. Dispense and Weigh Again

    Staff prepare the dose according to clinic procedure, then return the container to the scale. CSI-360 compares the weights and uses the drug's stored density to calculate the volume removed.

  4. Save the Transaction

    The system saves the user, patient, item, measured amount, notes, and time in the same transaction record.

CSI-360 touch-screen kiosk, RFID reader, and digital scale
At the Cabinet

How CSI-360 Records a Measured Dispense

CSI-360 separates dose administration from inventory measurement. Staff still choose the syringe and follow the technique required by the veterinarian and clinic procedure; the system tracks how much inventory left the container.

  • Container-based measurement — the inventory record comes from the before-and-after weight, not only the syringe marking.
  • Hub loss is reflected in inventory — medication removed from the vial is part of the measured change, including liquid left behind in the needle hub.
  • One current transaction — the measured amount stays with the user, patient, item, notes, and time.
  • Clinic procedures still apply — dose verification, waste documentation, physical inventory, and required DEA records remain the practice's responsibility.
View CSI-360
Side by Side

Syringe Reading vs. Container Weighing

Measurement Syringe Reading Current product: CSI-360 Weighing
Primary Input Plunger position at a syringe marking Change in container weight
Small Draws Relative error can increase as less of the syringe capacity is used Inventory measurement does not rely on the syringe graduation
Hub Loss Not included in the delivered volume Reflected in the amount removed from the container
Record Entry Entered by staff Saved with the transaction
Reconciliation Compared with physical inventory later Measured dispense updates the running record
More from UID

More for Your Practice

Pair controlled-substance inventory with ISO readers for routine patient identification.

Common Questions

  • Does a difference mean someone prepared the dose incorrectly?

    Not by itself. Syringe tolerance, syringe size, technique, and hub loss can all contribute to a difference between the syringe reading and the amount removed from the vial. Document and investigate the variance according to your clinic's controlled-substance procedure.

  • Which measurements are most difficult?

    Measurements that use a small share of the syringe's labeled capacity. A published small-volume study found a greater likelihood of error above 5% when less than 20% of capacity was measured and recommended choosing a syringe as close as possible to the intended volume. Clinical decisions should still follow the veterinarian's order and clinic procedure.

  • What is hub loss?

    It is the small amount of medication left behind in the needle hub after administration. Before-and-after vial weighing reflects that medication in the amount removed from inventory, while the clinic documents administration and waste according to its procedures.

  • Should we stop using syringes?

    No. Syringes remain appropriate for preparing and administering medication when used according to the product instructions and clinic procedure. The separate issue is whether the syringe reading alone is enough for controlled-substance inventory reconciliation.

  • Does CSI-360 replace dose verification or DEA records?

    No. CSI-360 measures inventory movement and saves the cabinet-side transaction. The practice remains responsible for the medication order, dose verification, witnessed waste, physical inventories, receiving records, and any required DEA reports.

  • How does CSI-360 measure the amount removed?

    Staff scan and weigh the container before use, then weigh it again afterward. For liquids, CSI-360 uses the drug's stored density to convert the weight difference to volume and saves the result with the transaction. See the CSI-360 Product Page for the full workflow.

References

  1. Syringe design requirements and test methods: ISO 7886-1:2017.
  2. Small-volume measurement study: Jordan et al., "Development of Guidelines for Accurate Measurement of Small Volume Parenteral Products Using Syringes," Hospital Pharmacy 56(3), 2021.

Make Each Dispense Easier to Reconcile

CSI-360 measures the change in the container and saves the cabinet-side transaction as it happens. Tell us how your practice stores controlled substances, and we'll walk through the fit.

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