1. Calculations Week 4 Jessica johnson, pharm. D.

2. Topics covered -Reconstitution of dry powders, or powder volume (section 11 in math book) -Reconstituted means that we are adding water, or another diluent, to a powder to make a liquid suspension or solution.

3. Reconstitution Liquid antibiotics, such as Amoxicillin suspension IV medications When reconstituting: it is recommended to add 1/3 of the diluent, shake vigorously, and then add the rest of the diluent. Why do you think this is? Why do you think that medications come in a powder form that needs to be reconstituted, instead of just coming in a liquid form?

4. Terminology Diluent = the liquid we add to the powder to dissolve it Powder volume = the volume occupied by the space of the powder (measured in mL) Final volume = the final amount of liquid medication after reconstitution occurs

5. Equation To determine powder volume, the amount of diluent, or the final volume we use the following equation: Final volume – Diluent = powder volume This can be rearranged depending on what you are solving for: Diluent + powder volume = Final volume Final volume – powder volume = Diluent

6. Practice using the equation We have a bottle of Amoxicillin suspensing. The final volume is 75 mL, and we have added 57 mL of sterile water. What is the powder volume? Final volume – diluent = powder volume 75 mL – 57 mL = 18 mL The powder volume is 18 mL

7. Practice Let’s do some practice from the book together

8. In some cases, the problems might not be that easy… In some cases, we will need to determine the concentration of the suspension, OR the final volume. Remember that the concentration is the same thing as the strength. It is the number that comes after the drug name. For example: Amoxicillin 400 mg/5 mL The concentration, or strength of this medication is: 400 mg/5 mL

9. Practice

10. You have a suspension for Pen VK 250 mg/10 mL. The powder volume is 10 mL, and the diluent added is 90 mL. What is the total amount of drug in grams in this suspension?

11. Solution

12. Practice What is the powder volume of this drug, if we are preparing it for IM use? If a patient needs to receive 500 mg, how many mL should be used? What drug class do you think this drug belongs to?

13. Homework Pg. 99 – 100 (all)