1. SOLUTIONS & SOLUBILITY Nina Sharma, PharmD Candidate 2016

2. Question 1: Unit Conversion The therapeutic range (plasma concentration associated with effect of a drug) is between 10 and 100 ng/mL. The patient’s plasma concentration is 200 uM. Is this patient over-dosed or under-dosed? (MW= 285 g/mol) mol/L 1 mol umol 200 umol 1 L X M = Molarity = 285 g 1 mol X ng 1 g X= ng 1 L ng 1 L X mL = 57,000 ng/mL Over-dosed 10 6 10 9 57,000,000 1000

3. Question 2: Powders The following questions are based on the Rx below: Salicylic Acid 5% Menthol 0.25% Talc. Additive: 80 g (add talc until total weight = 80 g) a. How many grams of salicylic acid should be used? b. How many grams of menthol should be used? % powder = X g / 100 g g X 5% = 5 100 80 g =4 g salicylic acid 0.25% = g 0.25 100 X 80 g =0.2 g menthol

4. Question 3: Solutions The following questions are based on the Rx below: Ephedrine Sulfate (ES) Solution 2.5%, 75 mL a. How many milligrams of ephedrine sulfate should be used? b. What is the molarity of the solution? (MW ES = 429 g/mol) % solution = X g / 100 mL 2.5% = g mL 2.5 100 X mg g 1000 1 X 75 mL = 1.875 g= 1,875 mg 2.5% = g mL 2.5 100 X mol g 1 429 X mL L 1000 1 = 0.058 mol/L

5. c. What is the mole % of the solution? (MW H20 = 18 g/mol) 2.5% = Question 3: Solutions Cont. mole % = [(mole solute) / (mole solute + mole solvent)] x 100% g mL 2.5 100 X 75 mL = 1.875 g mol g X 1 429 = 0.0043 mol ES 75 mL H20 X g H20 mL H20 1111 X mol g 1 18 = 4.167 mol H20 mole % = [(0.0043 mol ES) / (0.0043 mol ES+ 4.167 mol H20)] x 100% = 0.104%

6. d. What is the molality? Question 3: Solutions Cont. mol ES g H20 0.0043 75 = mol ES g H20 X 1000 X = 0.058 mol ES molality = mole solute/ 1000 g solvent molality = 0.058 mol ES/ 1000 g H20

7. The following questions are based on the Rx below: Clotrimazole 0.25%, 1 oz Question 4: Creams a. Express the prescription in metric units b. How much of the drug, in grams and grains, will be present in the product dispensed? 1 oz X mL oz 29.57 1 =29.57 mL 2.5% = g mL 2.5 100 X 29.57 mL = 0.074 g X mg g 1000 1 X grains mg 65 1 =1.14 grains

8. You are to compare a new peptide drug Peptidsone (Pep) and Prednisolone sodium phosphate (PSP). Prednisolone sodium phosphate is given as a 35 mg injection. Assuming that the ADME of these drugs is very similar, what is the dose equivalent of Peptidsone? (MW PSP = 484.39 g/mol, MW Pep = 1500 g/mol) Question 5: Dose Equivalence 35 mg PSP g PSP mg PSP X 1 1000 X mol PSP g PSP 1 484.39 X mol Pep mol PSP 1 = 0.00007 mol Pep X g Pep mol Pep 1500 1 mg g X 1000 1 =108.45 mg Pep

9. Questions? Email: npsharma@uw.edu