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.  Household system: lacks standardization; not accurate for measuring medicine  Metric system: developed in late 18th century to standardize measures and weights for European countries ◦ Units based on factors of 10 ◦ Prefixes denote increases or decreases in size of unit  Apothecary system: system of liquid units of measure used chiefly by pharmacists

5.  Uses household measures when an approximate dose is acceptable  Uses a system of weights and measures based on 1 pound containing 16 fluid ounces  Calibrated in units that most people are familiar with such as teaspoon and cup  The drop, tablespoon, and teaspoon are the only household measures still used in pharmacology ◦ Disinfectants: cups, quarts and gallon

7.  System of liquid measure used by pharmacists; also called the common system  Derived from the British apothecary system of measures  Units in the apothecary system: ◦ Volume: Minim = liquid volume of a drop of water from a standard medicine dropper  60 minims = 1 fluid dram  8 fluid dram = 1 ounce ◦ Weight: Grain = basic unit of weight measurement  1 grain of wheat = 60 mg.  480 grains = 1 oz = 1 oz, 12 oz = 1 lb

10.  A.k.a. the international system (SI)  Units are based on factors of 10  Base units are meter (length), liter (volume), and gram (weight)

11.  King – kilo (k)- = one thousand units = 1,000 (10 3 )  Henry – hecto- = one hundred units = 100 (10 2 )  Died – deka- = ten units = 10 (10)  L = vol.; Mightily = meter; G = gram = 1 unit = 1  Drinking – deci (d)- = one tenth of unit = 0.1 (10 -1 )  Chocolate – centi (c)- = one hundredth of unit = 0.01 (10 -2 )  Milk – mili (m)- = one thousanth of unit = 0.001 (10 -3 )  More – micro (µ or mc) - = one millionth of unit = 0.000001 (10 -6 )  Naughtily – nano (n) - = one billionth of unit = 0.000000001 (10 -9 ) kg to g = move decimal point 3 places to the right g to kg = move decimal point 3 place to the left l to ml = move decimal point 3 places to the right ml to l = move decimal point 3 places to the left Converting from larger to smaller units – multiply (MORE) Converting from smaller to larger units – divide (LESS)

13.  KNOW TABLE 2-3 pg. 33  Always validate answer. 66 lbs = __________ kg. 1 kg = 2.2 lb X = 66 lb X = (66 lb / 2.2 lb) * 1 kg = 30 kg

14.  In the Fahrenheit system, water freezes at 32 degrees; water boils at 212 degrees  In the Celsius system, water freezes at 0 degrees; water boils at 100 degrees  Comparison: ◦ 212 – 32 = 180 ◦ 100 – 0 = 100 ◦ 180 ÷ 100 = 1.8 C = (F – 32)/1.8 F = 1.8C + 32 98.6 F = ___________ Celsius Degree Celsius = (Degree Fahrenheit – 32)/1.8 Degree Celsius = (98.6 degree Fahrenheit – 32)/ 1.8 = 37 degree Celsius

15.  Must know correct amount of drug to administer to a patient  Must be in same system of measurement  Weight conversion factor: 2.2 lb = 1 kg  Remember that drugs can be measured in mcg, mg, g, gr, ml, l, units  Remember that drugs can be dispensed or administered in tablets, ml, l, capsules

16.  STEP 1: Convert weight into kg (IF DOSAGE mg/kg) ◦ 1 kg = 2.2 lbs ◦ X = 22 lbs ◦ X = (22 lbs/ 2.2lbs) * 1 kg = 10 kg  STEP 2: From dosage to dose ◦ Dosage: 2mg/kg ◦ Dose: 10kg * 2mg/kg = 20 mg

17.  STEP 3: From dose to amount administered ◦ 20 mg ◦ Tablets: 40 mg, 80 mg and 100 mg  ½ of the 40 mg tablet (assuming that tablet is scored!!)  ½ tablet – 40 mg ◦ Solution: 10 mg/ ml  (20 mg/ 10 mg) * 1 ml = 2 ml  2 ml of 10mg/ml drug solution  STEP 4: Total dose: BID for 7 days  Tablet: 7 tablets  Solution: 28 ml of the 10mg/ml solution

18. HOMEWORK 1 DOSAGE DUE TOMORROW

19.  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.