1. Systems of Measurement in Veterinary Pharmacology Dr. Dipa Brahmbhatt VMD, MS, MPH

2.  ID and convert within and between metric, household and apothecary  Calculate drug dose: tablets/ solutions  Calculate solutions  Calculate dilutions  If time permits: fluid calculations (mostly in special topics: review)

3.  Refer to the practice problems in the back of chapter 2.  And…  CPTVT: Chapter 2  Dilutions and Solutions handout  Medical Mathematics and Dosage Calculations for Veterinary Professionals ◦ CHAPTER 6 ◦ CHAPTER 8 ◦ CHAPTER 10 ◦ Homework: Dose, Solution, Dilution ◦ What are my advisement times?

4.  Solutions are mixtures of substances not chemically combined with each other ◦ The dissolving substance of a solution is referred to as the solvent (liquid) ◦ The dissolved substance of a solution is referred to as the solute (solid or particles) ◦ Substances that form solutions are called miscible ◦ Substances that do not form solutions are called immiscible

5. concentration  The amount of solute dissolved in solvent is known as the concentration  Concentrations may be expressed as parts (per some amount), weight per volume (w/v), volume per volume (v/v), and weight per weight  Usually reported out as percents or percent solution  Remember that a percent is the parts per the total times 100.

6.  Parts: parts per million (ppm) means 1 mg of solute in a kg (or L) of solvent ◦ % conc. of 1:1000 epinephrine? ◦ % conc. = (1/1000)*100 = 0.1%  Liquid in liquid: the percent concentration is the volume per 100 volumes of the total mixture (1 ml/100 ml, 5 oz/ 100 oz)  Solids in solids: the percent concentration is the weight per 100 weights of total mixture (60 mg/100 mg, 4.5 g/ 100 g)

7.  Solids in liquid: the percent concentration is the weight in grams per 100 volume parts in milliliters (dextrose 5% = 5 g/100ml = 5000mg/100ml = 50mg/ml)

8.  How much NaCl needed to make 500mls of 0.9% solution ◦ X = (0.9g NaCl/ 100 ml) * 500 ml = 4.5 g (4.5 ml density is 1 mg/ml)  Prepare 1L of 4% formaldehyde fixative solution from 37% stock solution ◦ X = (4%/ 37%) * 1000 = 108 ml of stock solution ◦ 1000 ml – 108 mls of stock = 892 ml of solvent

9.  COMPLETE SOLUTIONS HANDOUT  HOMEWORK IS QUESTION 1-16 DUE TOMORROW

11.  Pure drugs are substances that are 100% pure  Stock solution is a relatively concentrated solution from which more dilute solutions are made  Ratio-proportion method: one method of determining the amount of pure drug needed to make a solution ◦ Amount of drug/amount of finished solution = % of finished solution/100% (based on a pure drug)  Remember that the amount of drug used to prepare a solution is added to the total volume of the solvent

12. Volume concentration method:  V s = volume of the beginning or stock solution  C s = concentration of the beginning or stock solution  V d = volume of the final solution  C d = concentration of the final solution V s x C s = V d x C d

13.  How much water must be added to 1L of 90% alcohol to change it to 40% ◦ V s x C s = V d x C d = 1,000mls x 90% = V d x 40% ◦ V d = 2250 mL ◦ 2250 mL – 1000 mL = 1250 mL

14.  How much 1:25 solution of NaCl is needed to make 3 L of 1:50 solution ◦ Convert to % ◦ (1/25)*100 = 4%; (1/50) * 100 = 2% ◦ V s x C s = V d x C d = V s x 4% = 3 L x 2% ◦ V s = 1.5 L

15.  Drug concentrations are sometimes listed in percents  Parts per total = parts (in g) per 100  The front of the vial specifies the concentration (for example, 2% lidocaine)  Use x g/100 ml to determine dose

16.  Drug concentrations are sometimes listed in percents  Parts per total = parts (in g) per 100  The front of the vial specifies the concentration (for example, 2% lidocaine)  Use X g/100 ml to determine dose ◦ Dosage: 3mg/ kg; weight: 15 lb dog; 2% lidocaine ◦ (15 lb/ 2.2 lb/kg) * 3mg/kg = 20.45 mg ◦ 20.45 mg / 20 mg/ml = 1.02 mL

17.  GO THROUGH DILUTIONS HANDOUT  HOMEWORK: pg. 58: 1-8 and pg. 62: 1-4. DUE TOMORROW

18.  Drug is in powder form because it is not stable when suspended in solution ◦ Cefazolin sodium, azithromycin, ampicillin  Such a drug must be reconstituted (liquid must be added to it: sterile water, saline, dextrose)  The label should state how much liquid to add  Powder may add to the total final volume of liquid being reconstituted  Label a reconstituted drug with the date prepared, the concentration, and your initials

21.  Romich, J.A. Pharmacology for Veterinary Technicians, 2 nd edition. 2010.  Bill, R.L. Clinical Pharmacology and Therapeutics for the Veterinary Technician, 3 rd edition. 2006.  Bill, R.L. Medical Mathematics and Dosage Calculations for Veterinary Professionals, 2 nd edition. 2009.