Insulin syringe unit conversion: difference between revisions
Diff·revision 39 → 40·22:40, 28 Jul 2025
Difference between revision 39 and revision 40 of Insulin syringe unit conversion. 8 lines changed; the page grew by 1,006 bytes.
| Revision 39 — 19:56, 16 Jul 2025 ColdChainCleo (talk) convert prose to table for comparability 5,079 bytes ±0 | Revision 40 — 22:40, 28 Jul 2025 ForestPlotFinn (talk) expand §Sources of error 6,085 bytes +1,006 | ||
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| 54 | Two observations follow. A tenfold error in assumed concentration produces a tenfold error in delivered mass with no change in the syringe reading and nothing visibly wrong. And at high concentrations a single graduation carries a large mass, so the resolution of the syringe becomes the limiting factor on dose precision: at 20 mg/mL, one unit is 200 µg, and half a graduation cannot be read reliably.{{r|iso7886b}} | 54 | Two observations follow. A tenfold error in assumed concentration produces a tenfold error in delivered mass with no change in the syringe reading and nothing visibly wrong. And at high concentrations a single graduation carries a large mass, so the resolution of the syringe becomes the limiting factor on dose precision: at 20 mg/mL, one unit is 200 µg, and half a graduation cannot be read reliably.{{r|iso7886b}} |
| 55 | 55 | ||
| + | 56 | == Sources of error == | |
| + | 57 | ; Scale confusion : Transferring a unit figure between U-100 and U-40 scales, as above. | |
| + | 58 | ; Unit-as-mass : Treating "units" as a quantity of drug. This is correct only for insulin, for which the international unit is defined by biological activity and for which the syringe scale was designed.{{r|who}} | |
| + | 59 | ; Graduation reading : Estimating between graduations. ISO 7886 permits a volume tolerance of a few percent of nominal capacity, which at the bottom of a 1 mL barrel is a substantial fraction of the reading.{{r|iso7886b}} | |
| + | 60 | ; Air and dead space : A bubble displaces solution; [[Syringe dead space|dead space]] retains it. Neither changes the barrel reading. | |
| + | 61 | ; Rounding : A computed 12.4 units cannot be drawn on a barrel graduated in whole units. Rounding to 12 is a 3% dose reduction, which matters more at low doses than high ones. | |
| + | 62 | ||
| 56 | == References == | 63 | == References == |
| 57 | {{reflist}} | 64 | {{reflist}} |
| ⋮ | ⋮ | ||
| 59 | <ref name="iso7886b">ISO 7886-1, ''Sterile hypodermic syringes for single use — Part 1: Syringes for manual use''. International Organization for Standardization.</ref> | 66 | <ref name="iso7886b">ISO 7886-1, ''Sterile hypodermic syringes for single use — Part 1: Syringes for manual use''. International Organization for Standardization.</ref> |
| 60 | <ref name="fdavet">US Food and Drug Administration, Center for Veterinary Medicine — guidance on U-40 insulin products and syringe compatibility.</ref> | 67 | <ref name="fdavet">US Food and Drug Administration, Center for Veterinary Medicine — guidance on U-40 insulin products and syringe compatibility.</ref> |
| + | 68 | <ref name="who">World Health Organization Expert Committee on Biological Standardization — definition of the international unit for insulin.</ref> | |
| 61 | 69 | ||
| 62 | == See also == | 70 | == See also == |