IV Compounding Calculations

Sterile compounding is a crucial process in the pharmaceutical industry that involves preparing medication in a sterile environment. This process requires a high level of accuracy and precision, especially when it comes to sterile compounding math calculations.

In this article, we will discuss the various math calculations involved in sterile compounding, which are covered in Module 1 of the updated self-paced sterile compounding course and the IV certification course.

The main objective of Module 1 is to equip learners with the necessary knowledge and skills to perform math calculations involved in sterile compounding.

CLICK THIS LINK FOR MATH EXAMPLES OF SOME OF THE TOPICS DISCUSSED BELOW

Commonly Conversions & Abbreviations
Conversions and abbreviations are commonly used in sterile compounding. Some of the conversions include:

- 1 kilogram (kg) = 1000 grams (g)
- 1 liter (L) = 1000 milliliters (mL)
- 1 milligram (mg) = 1000 micrograms (mcg)

Abbreviations commonly used include
- QD - once daily
- BID - twice daily
- TID - three times daily
- QID - four times daily
- PRN - as needed
- IV - intravenous
- SQ - subcutaneous
- IT - intrathecal

Dimensional Analysis
Dimensional analysis is a mathematical technique used to convert one unit of measurement to another. This technique involves multiplying the given value by a conversion factor that cancels out the original unit and introduces the desired unit. For example, to convert 2 grams (g) to milligrams (mg), we multiply 2g by 1000mg/1g, which gives us 2000mg.

Ratios and Proportions
Ratios and proportions are used to compare two or more quantities. A ratio is the comparison of two values, while a proportion is an equation that states that two ratios are equal. For example, if we have a 1:3 ratio of medication to diluent, we can use a proportion to calculate the amount of medication needed for a given volume of diluent. See examples on this page for some of the topics discussed below.

Percent Strength
Percent strength is the percentage of the active ingredient in a solution. To calculate percent strength, we divide the amount of active ingredient by the total volume of the solution and multiply by 100. For example, if we have a solution containing 5g of active ingredient in 100mL of solution, the percent strength is 5%.

Liquid Dilutions
Liquid dilutions involve adding a diluent to a solution to reduce the concentration of the active ingredient. To calculate the amount of diluent needed, we use a proportion. For example, if we have a solution containing 10% active ingredient and we want to dilute it to 2%, we need to add 4 parts diluent for every 1 part of the original solution.

Solid Dilutions
Solid dilutions involve adding a diluent to a solid substance to reduce the concentration of the active ingredient. To calculate the amount of diluent needed, we use a proportion. For example, if we have a solid substance containing 50% active ingredient and we want to dilute it to 20%, we need to add 2 parts diluent for every 3 parts of the original substance.

Aliquots
An aliquot is a measured portion of a solution. To calculate the volume of an aliquot, we use a proportion. For example, if we have a solution containing 10% active ingredient and we need a 2% aliquot, we need to measure 1 part of the original solution and dilute it with 4 parts of diluent.

Alligation Calculations
Alligation calculations involve mixing two or more solutions to obtain a desired strength. This technique involves using a proportion to calculate the amount of each solution needed.

Powder Volume & Reconstitution
Powder volume and reconstitution involve calculating the amount of diluent needed to reconstitute a powder. To calculate the amount of diluent needed, we use the following formula Powder volume = Final volume - Diluent volume.

mEq & Osmolarity Calculations
mEq and osmolarity calculations are used to determine the amount of electrolytes and solutes in a solution. mEq is a measure of the chemical activity of a solute, while osmolarity is a measure of the concentration of solutes in a solution. To calculate mEq, we use the formula: mEq = (mg x valence)/MW. To calculate osmolarity, we use the formula: osmolarity/L = Wt. of substance/MW X number of particles x 1000.

Percent Strength & mEq Calculations
Percent strength and mEq calculations are used to determine the concentration of a solution. To calculate percent strength, we divide the amount of active ingredient by the total volume of the solution and multiply by 100. To calculate mEq, we use the formula: mEq = (mg x valence)/MW.

Individual Dosing Based On Weight
Individual dosing based on weight involves calculating the appropriate dose of medication for a patient based on their weight. To calculate the dose, we use a formula that takes into account the patient's weight and the desired concentration of the medication.

IV Drip & Flow Rates
IV drip and flow rates involve calculating the rate at which medication should be administered to a patient. This calculation takes into account the patient's weight, the desired concentration of the medication, and the rate at which the medication should be administered.

Tonicity Definition & Calculations
Tonicity is the measure of the osmotic pressure of a solution compared to the osmotic pressure of body fluids.

Body Surface Area
Body surface area is the measure of the total surface area of a person's body. This calculation is used to determine the appropriate dose of medication for a patient. To calculate body surface area, we use the commonly used DuBois and DuBois formula, which takes into account the patient's height and weight and is more accurate.

Math Quiz
To test your knowledge of sterile compounding math calculations, here are a few sample questions:

1. What is the percent strength of a solution containing 10g of active ingredient in 100mL of solution?
2. How many milligrams (mg) are in 2 grams (g)?
3. What is the rate of an IV drip that delivers 50mg of medication per minute to a patient who weighs 70kg?
4. How many milliliters (mL) of diluent are needed to dilute 10mL of a 20% solution to a 5% solution?
5. What is the body surface area of a patient who is 6 feet tall and weighs 150 pounds?

Sterile compounding math calculations are critical to ensuring accurate and safe medication preparation. Module 1 covers in more detail, the various math calculations involved in sterile compounding, including dimensional analysis, ratios, proportions, percent strength, liquid and solid dilutions, aliquots, alligation calculations, powder volume and reconstitution, mEq and osmolarity calculations, individual dosing based on weight, IV drip and flow rates, tonicity, and body surface area.

Understanding and applying these calculations is essential for anyone working in sterile compounding.