Ch 20: Systems of Measurement Three Systems Avoirdupois (household system) Metric Apothecary (rarely used) © 2013-2015

Metric System Conversion Factors: Micro – one millionth Milli – one thousandth Centi – one hundredth Deci – one tenth Kilo – one thousand © 2013-2015

Metric System Metrics are expressed in the form of decimals 1000mcg = 1mg 1000mg = 1g 1000g = 1kg 1000ml = 1L Metrics are expressed in the form of decimals ie.) 300ml = 0.3L © 2013-2015

Avoirdupois System Conversion Factors: 3 tsp = 1 tbsp 2 tbsp = 1 oz 16 oz = 1 pt 2 pt = 1 qt 4 qt = 1 G 16oz = 1 lb © 2013-2015

Conversion Factors Between Systems 1 tsp = 5 ml 1 tbsp = 15 ml 1 oz = 30 ml (29.57ml) 1 pt = 480 ml (473ml) 1 G = 3840 ml (3784ml) 1 g = 15.4 gr 1 gr = 60 mg (64.8mg) 1 kg = 2.2 lb 1 lb = 454 g 1 oz = 30 g (28.35g) Why are there 2 values listed for some conversions? The values listed in the parentheses are the exact values for the conversion. The other is an approximation. It is acceptable to use the approximation when calculating amounts to be dispensed, but always use the exact values when performing compounding calculations. YOU SHOULD KNOW BOTH! © 2013-2015

Class 4 Slides Pharmacy Math Continues……. Ch 21: Conversions Pharmacy Math Continues……. © 2013-2015 copyright 2013-2015 Mark Greenwald - all rights reserved

Remember Always set up your units first Be sure the unwanted units cancel and you are left with the appropriate answer Then plug in your values and calculate the answer © 2013-2015

Conversions X X 2.3 oz = ? ml 2.3 oz 30ml x = 69 ml 1 oz Arrange the units so they will cancel and solve Value x Conversion Factor = Answer 2.3 oz 30ml X x = 69 ml 1 oz X The units of ounces cancel, and you are left with milliliters © 2013-2015

Conversions X X X X 1.3 kg = ? grams 1.3 kg 2.2 lb 454g x x = 1,298g Value x Conversion Factor x Conversion Factor = Answer 1.3 kg 2.2 lb 454g X X x x = 1,298g 1 kg 1 lb X X © 2013-2015

Try This One 2 kg = ? ounces © 2013-2015

Conversions 2 kg = ? ounces 2 kg 2.2 lb 454g 1 oz 1 kg 1 lb 30g X X X x x x = 67oz 1 kg 1 lb 30g X X X © 2013-2015

One More for the Road 60 oz = ? Liters © 2013-2015

One More for the Road 60 oz = ? liters X X X X 60oz 30ml 1 L x x = 1.8 L 1 oz 1000ml X X © 2013-2015

CH 22: Methods of Measurement Whenever we measure something, we have an inherent ‘Margin of Error” produced No measurement can be 100% accurate What we strive to do is minimize this potential for error © 2013-2015

How Can We Minimize the Margin of Error? Use the appropriate type of measuring equipment Use the appropriate size of equipment Let’s discuss correct Methods of Measurement…. © 2013-2015

Measurement of Solids Small Samples Large Samples The pharmacy torsion balance Large Samples The pharmacy scale © 2013-2015

The Torsion Balance Very accurate Measures Small Amounts of Material 6 mg to 120 g Used with pharmacy weight set © 2013-2015

Use of the Torsion Balance Clean pans Use weighing papers to avoid sample contact with the pan Level the balance (zero the balance) Place sample in center of left pan Weights in center of right pan © 2013-2015

The Pharmacy Scale For larger samples May be electronic or mechanical Always be sure to level the scale before use © 2013-2015

Measurement of Liquids Small Volumes - Syringe or pipettes Larger Volumes - Graduated Cylinder Use at Home - Measuring spoon - Oral syringe - Medicine cup © 2013-2015

The Graduated Cylinder Comes in various sizes (15ml – 500ml) Comes in glass or plastic Labeled in milliliters and ounces BEWARE OF THE MENISCUS! © 2013-2015

The Meniscus Phenomenon Occurs only with a glass graduate When the light passes through the glass walls of the graduate, a bending of the light occurs causing the surface of the liquid to appear curved. In order to accurately read the volume, you must read the level of the liquid from the lowest point of the curve Read at the bottom of the meniscus © 2013-2015

The Syringe Comes in various sizes (0.5ml-50ml) Comes with different types of needle attachments Available with needle attached or separate Available as an oral syringe with no needle (needles will not fit) Parenteral syringes are in sterile packaging © 2013-2015

Syringes May have different tips depending on their intended use Luer-Lok tip is a Becton-Dickinson design that locks the needle on the syringe with a twisting motion © 2013-2015

How to Read the Volume in a Syringe Always read the volume at the black ring closest to the tip of the syringe © 2013-2015

Ch 23: Pharmacy Math - Proportions Class 4 Slides Ch 23: Pharmacy Math - Proportions Proportions will be your most used pharmacy calculation Used when two expressions are directly related to one another For instance, if 1 kg of drug cost us $5, how much will 2 kg cost? both expressions contain cost per weight if they are set up as ratios, once the problem is solved, both ratios should be equal © 2013-2015 copyright 2013-2015 Mark Greenwald - all rights reserved

Proportions If a drug costs us $5 per kg, how much will 2kg cost us? What unit do we know BOTH values for? Kilograms – so that goes in the denominator © 2013-2015

Proportions Which expression do we know both values for? $5 per 1 kilogram So the expression on the left will be $5 / 1kg And the right expression is the unknown with kilograms in the denominator $5 / 1kg = x / 2 kg © 2013-2015

Proportions $5.00 x 10 = = $10 1kg 2kg 1kg Now we solve the equation: = = $10 1kg 2kg 1kg © 2013-2015

More Examples A formula calls for 42 capsules of 300mg of drug. How many milligrams would be required to make 24 capsules? © 2013-2015

More Examples 300mg x 7,200 = = 171.4 mg 42 caps 24 caps 42 A formula calls for 42 capsules of 300mg of drug. How many milligrams would be required to make 24 capsules? 300mg x 7,200 = = 171.4 mg 42 caps 24 caps 42 © 2013-2015

More Examples If 12 g of powder occupies 7ml of volume, how many milliliters will 150g occupy? © 2013-2015

More Examples 7ml x 1,050 = = 87.5 ml 12g 150g 12 If 12 g of powder occupies 7ml of volume, How many milliliters will 150g occupy? 7ml x 1,050 = = 87.5 ml 12g 150g 12 © 2013-2015

More Examples If a chemical costs $14.00 per kg, how many kilograms could $128.00 buy? © 2013-2015

More Examples 1kg x 128 = = 9.14 kg $14 $128 14 If a chemical costs $14.00 per kg, how many kilograms could $128.00 buy? 1kg x 128 = = 9.14 kg $14 $128 14 © 2013-2015

More Examples 500 Penicillin tablets cost $43.09. What would be the cost for 48 tablets? © 2013-2015

More Examples $43.09 x 2,068.32 = = $4.14 500tabs 48tabs 500 500 Penicillin tablets cost $43.09. What would be the cost for 48 tablets? $43.09 x 2,068.32 = = $4.14 500tabs 48tabs 500 © 2013-2015

One Last Example Five pieces of Bazooka bubble gum cost $0.58. How much would 39 pieces cost? © 2013-2015

One Last Example $0.58 x 2.62 = = $4.52 5 pcs 39 pcs 5 Five pieces of Bazooka bubble gum cost $0.58. How much would 39 pieces cost? $0.58 x 2.62 = = $4.52 5 pcs 39 pcs 5 © 2013-2015