Reconstitution calculator (revision 18)
Old revision·17:27, 6 Dec 2024·CategoryBot
| Reconstitution calculator | |
|---|---|
A U-100 syringe scale is a volume scale: 42 units is 0.42 mL regardless of what the vial contains. | |
| Inputs | Vial mass (mg), diluent volume (mL), dose (mg or µg), syringe scale |
| Outputs | Concentration, dose volume, syringe units, doses per vial |
| Method | |
| Concentration | C = m / V |
| Dose volume | Vd = D / C |
| Syringe units | U = Vd × S, S = 100, 50 or 40 per mL |
| Assumption | Negligible volume displacement by the solid |
| Reference tool infobox · conventions | |
The reconstitution calculator relates the four quantities involved in dissolving a lyophilised peptide and drawing a dose from it: the mass of solid in the vial, the volume of diluent added, the intended dose, and the reading on the syringe barrel. All four are connected by one division, and almost every error reported in the literature and in community accounts is a confusion between two of them rather than a failure of the arithmetic itself.[1]
The calculation is a routine unit conversion: concentration is mass divided by volume, dose volume is dose divided by concentration, and a syringe unit is one hundredth of a millilitre on the U-100 scale. The tool below performs those operations and shows each intermediate result, because the intermediate is where a mistake becomes visible.
This page is a reference tool and not a clinical decision aid. It converts numbers a reader enters; it does not select a dose, and it has no knowledge of the vial, the label claim, or the person. See Project:Medical disclaimer.
The calculator
[edit]Enter the label mass of the vial, the volume of diluent, and the intended dose. The tool reports the resulting concentration, the volume that dose occupies, the reading on the selected syringe scale, and how many doses the vial contains.
Worked examples
[edit]The tool's defaults correspond to the first row below. Each row is a division; none of them requires a calculator, and reproducing one by hand is a useful check that the inputs were entered as intended.
| Vial | Diluent | Concentration | Dose | Dose volume | U-100 units |
|---|---|---|---|---|---|
| 5 mg | 2.0 mL | 2.5 mg/mL | 0.25 mg | 0.10 mL | 10 |
| 5 mg | 2.0 mL | 2.5 mg/mL | 0.50 mg | 0.20 mL | 20 |
| 5 mg | 1.0 mL | 5.0 mg/mL | 0.25 mg | 0.05 mL | 5 |
| 10 mg | 2.0 mL | 5.0 mg/mL | 2.5 mg | 0.50 mL | 50 |
| 10 mg | 1.0 mL | 10 mg/mL | 1.0 mg | 0.10 mL | 10 |
| 15 mg | 3.0 mL | 5.0 mg/mL | 7.5 mg | 1.50 mL | 150 |
| 2 mg | 2.0 mL | 1.0 mg/mL | 100 µg | 0.10 mL | 10 |
The last row illustrates the most common unit confusion: a dose expressed in micrograms against a concentration expressed in milligrams per millilitre. One thousand micrograms is one milligram, so 100 µg of a 1 mg/mL solution is 0.1 mL — ten units on a U-100 syringe, not one hundred.
References
- ^ United States Pharmacopeia, General Chapter <797>, "Pharmaceutical Compounding — Sterile Preparations". USP–NF, current revision.