Overview
This lecture explains how to calculate the quantity of an active ingredient needed in a compounded medication using percentage strength and total volume.
Steps to Calculate Ingredient Quantity
- Identify the percentage strength and total volume required for the compounded medication.
- Convert the percentage strength to a decimal by dividing by 100.
- Multiply the total volume (in milliliters) by the decimal strength to find the amount of ingredient in grams.
- Convert grams to milligrams by multiplying by 1,000, if needed.
Example Problems
- Example 1: 0.25% strength in 500 mL
- 0.25% = 0.0025
- 500 mL × 0.0025 = 1.25 g
- 1.25 g × 1,000 = 1,250 mg
- Example 2: 1% strength in 200 mL
- 1% = 0.01
- 200 mL × 0.01 = 2 g
- 2 g × 1,000 = 2,000 mg
- Practice Problem: 0.5% strength in 100 mL
- 0.5% = 0.005
- 100 mL × 0.005 = 0.5 g
- 0.5 g × 1,000 = 500 mg
Key Terms & Definitions
- Compounded preparation — a medication mixed according to a specific prescription.
- Percentage strength (%) — the concentration of an ingredient, expressed as parts per hundred.
- Decimal strength — percentage strength divided by 100, used for calculations.
- Milligram (mg) — a unit of mass; 1 gram = 1,000 milligrams.
Action Items / Next Steps
- Practice solving similar ingredient quantity problems.
- Prepare for the next lesson on calculating day supply.