Reconstitution & Powder Volume Practice
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Reconstituting a powdered drug adds diluent to reach a target concentration, but the dry powder itself occupies space (the powder or displacement volume), so the final volume is greater than the diluent added.
Formulapowder (displacement) volume = final reconstituted volume − volume of diluent added
Worked example
A 1 g vial reconstituted to 100 mg/mL needs a final volume of 10 mL. If the label says to add 9.5 mL diluent, the powder volume = 10 − 9.5 = 0.5 mL.
💡 Add the displacement volume to the diluent when finding concentration — ignoring it overestimates the strength.