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Alligation in Pharmaceutical Calculations

  • Alligation in Pharmaceutical Calculations is a method used in pharmacy for mixing solutions or components of different concentrations to achieve a desired concentration.

  • It’s useful in compounding and preparing pharmaceutical mixtures.

Alligation Medial:

  • This method calculates the average strength of a mixture based on the quantities and concentrations of the individual solutions.

Formula:


  • Where:

    • C1,C2,… = concentrations of the solutions.

    • Q1,Q2,… = quantities of the solutions.

Alligation Alternate:

  • This method is used to mix two solutions of known concentrations to achieve a desired concentration.

Steps:

  1. Place the stronger and weaker concentrations on opposite sides of a grid.

  2. Write the desired concentration in the middle.

  3. Subtract the desired concentration from both the stronger and weaker concentrations (ignoring negative signs) to determine the parts of each solution.

Example:

  • To make 500 mL of a 10% solution using 15% and 5% solutions:

    • 15 – 10 = 5 and 10 – 5 = 5

  • This means equal parts of the two solutions should be mixed.


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