How do I calculate the dose when a 100‑unit vial of Botox (onabotulinumtoxinA) is reconstituted with 2.5 mL saline and drawn up with a 0.3 mL syringe?

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Botox Reconstitution Dose Calculation

A 100-unit vial reconstituted to a final volume of 2.5 mL yields a concentration of 40 units/mL.

Concentration Calculation

Concentration = 100 units ÷ 2.5 mL = 40 units/mL.

Dose Drawn From a Given Syringe Volume

Dose = (40 units/mL) × (0.3 mL) = 12 units.

Unit Per Syringe Volume Conversion

0.1 mL = 4 units.
0.3 mL = 12 units.

Final Dose

The 0.3 mL drawn from the reconstituted 100-unit vial contains 12 units of onabotulinumtoxinA.