# Calculation of Mixtures from Stock Medications

• Interpret labels for the weight/volume of solute in solvent

• Dilute stock medications to the required strength using strengths expressed as percentages, fractions, and ratios

• Calculate the weight/volume of active ingredient in a substance

• Using alligation, calculate the weight/volume of stock medications needed to prepare a desired compound

## Interpreting Solution Labels and Calculating Solutions In Percentages

With percentage preparations, the easiest method for calculation is the ratio and proportion method. If a review of the ratio and proportion method is necessary, see Chapter 2.

### Reducing and Enlarging Ordered Preparations

When a volume of a known solution requires reducing or enlarging to meet a physician’s order, the original strength of the preparation may be used for the calculation of the new volume or weight of the preparation. For example, using the above calculations in Example 13-4, if the physician desires 100 mL, the answer can be figured using ratio and proportion.