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Isotonicity Adjustment Calculator

Work out isotonicity adjustment instantly with clear inputs, formula shown and shareable results.

About Isotonicity Adjustment Calculator

Uses the sodium chloride equivalent method: the drug's tonicity contribution is subtracted from the 0.9 percent sodium chloride needed to make the volume isotonic.

Formula

E value method

Sodium chloride for isotonicity = 0.009 x volume (mL); drug contribution = drug mass x E value; sodium chloride to add = the difference

Worked example

With the default values below, Isotonicity Adjustment Calculator returns Sodium chloride to add of 0.2160. Change any input above and every figure here is recalculated in your browser.

Inputs used

Drug in the preparationaccepts 0.001–50 g
0.3 g
Sodium chloride equivalent (E value)accepts 0.01–1.5
0.18
Final volumeaccepts 0.5–1,000 mL
30 mL

Results

Sodium chloride to add
0.2160 g
Sodium chloride for isotonicity
0.2700 g
Tonicity contributed by the drug
0.0540 g NaCl equivalent
Status
Add the calculated sodium chloride to reach isotonicity

Step by step

  1. 1Values used
  2. 2E value method
  3. 3Sodium chloride to add= 0.2160 g
  4. 4Sodium chloride for isotonicity= 0.2700 g
  5. 5Tonicity contributed by the drug= 0.0540 g NaCl equivalent
  6. 6Status= Add the calculated sodium chloride to reach isotonicity

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

What is an E value?

The mass of sodium chloride osmotically equivalent to one gram of the drug.

Why does tonicity matter?

Hypotonic ophthalmic and parenteral solutions cause cell lysis and stinging; hypertonic ones cause pain and phlebitis.

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