Apothecary Conversion

Pro Calc Nursing 131

There are three systems of measurement being used in medication administration.

MetricApothecaryHousehold

This tutorial discusses converting units from the apothecary system of measurement to the metric system.

Apothecary/Metric Conversion


In the metric system liquid volumes are measured in milliliters or liters. Weight is measured in micrograms, milligrams, grams, or kilograms.

1 liter 1000 milliliter 1 kilogram

1,000,000 milligrams

1,000 grams

1,000,000,000 micrograms

In the apothecary system liquid volumes are measured in quarts, pints, ounces, drams, and minims. Weight is measured in grains.

1 quart 2 pints 32 ounces 256 drams 15,360 minims

1 ounce = 437.5 grains


Our Example Problem:Acetaminophen is available in mg. 10 gr of Acetaminophen must be prepared. How many

mg of Acetaminophen should be prepared?


Here are the 5 basic steps to change from one unit to another

Step 5 – Perform the math

Step 2 – Write down what you have

Step 1 - Identify that you need to convert

Step 3 – Write down your equivalent fraction

Step 4 – Reduce units


Our Example Problem:Acetaminophen is available in mg. 10 gr of

Acetaminophen must be prepared. How many mg of Acetaminophen should be prepared?

Step 1 Identify you need to convertThe question asks how of one type of unit should we prepare in another type of unit.

Step 2 Write down what you haveThe quantity we have – our known quantity - is 10 gr of Acetaminophen.Write this as a fraction with 1 on the bottom.

(Writing the amount as a fraction will help us when we multiply later.)

10 gr

1


Our Example Problem:Acetaminophen is available in mg. 10 gr of

Acetaminophen must be prepared. How many mg of Acetaminophen should be prepared?

Step 3 Relate the unitsAn equivalency chart will list how the units relate.


Conversions between Apothecary and Metric Units

32 fluid ounces 1 liter16 fluid ounces 500 milliliters8 fluid ounces 240 milliliters1 fluid ounce 30-32 milliliters1 fluid dram 5 milliliters15-16 minims 1 milliliter1 grain 60 mg


Step 3 Relate the unitsAn equivalency chart will list how the units relate.

We can write this fraction 2 ways:

We will write this equivalency as a fraction.

or

Because the fraction we wrote in step 2 has grains on the top, our next fraction must have grains on the bottom.

Our chart lists 1 grain = 60 mg.

1 grain

60 mg

60 mg

1 grain


Step 3 Relate the units

We now have:

x

To convert we will need to multiply our fractions.

10 grain

1

60 mg

1 grain


Step 4 Reduce the unitsCross off any matching pairs of unit labels. The label left should be what you want to find.

We now have:

In this example the only unit left is mg which is what we want to find.

We now have:

10 grain

1

60 mg

1 grainx


Step 5 Perform the math

10 grains is equivalent to 600 mg.

10 grain

1

60 mg

1 grainx

10 x 60 mg1 x 1

600 mg

1

= 600 mg


(reduce any fractions)

(include the units)

=

Our Example Problem:Acetaminophen is available in mg. 10 gr of Acetaminophen must be prepared. How

many mg of Acetaminophen should be prepared?

We should prepare 600 mg of Acetaminophen.


These are the steps we used.1. Determine the need to perform a metric conversion

(having one type of unit –apothecary- and want to know another type -metric)

2. Write down the starting term3. Find an equivalent fraction for the units.

Write the equivalent fraction down next to the starting term with the units you want to eliminate on the bottom

4. Reduce the units (Eliminate only the words that match in the top and bottom of your fractions.) When you are finished you should have only the terms you are looking for left.

5. Perform the math operations and reduce your answer. (In some calculations you may need to round as specified by your instructions.)


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Apothecary/Metric ConversionTutorial

Apothecary Conversion

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