Measurement and Dosage Calculations

Refer to your textbook Ch. 3

It is good to review your math skills and refresh your knowledge on fractions.  Check out pt 38-43 on adding, multiplying fractions.

 A fraction is way of expressing an amount that is part of a whole.

Add fractions and decimals Refer to your textbook pg 38-43

• To add fractions, the fractions must have the same denominators.
• The numerators (top numbers) are added and the denominator remains the same.

For example, 1/4 + 1/4 = 2/8 = 1/4.

• If the denominators do not match, the numbers must be written in a form in which the denominators are the same.
• If 1/2and 1/4 are to be added, both numbers must have the denominator of 4.
• To convert ½ to 4ths, multiply 1/2 by 1 in the form 2/2. 1/2 times 2/2 = 2/4. Then 1/4 and 2/4 may be added for a sum of 3/4.
• 1/2 x 2/2 = 2/4

• To add decimals, keep the decimal point in line and add. For example:

• Student should be able to determine, for example, that two gr. 1/4 tablets equal gr.1/2, or that two 0.5 g tablets equal 1.0 g.

(2) gr. 1/4 tablets = 2/4 or 1/2 gr. Tablet

Adding Fractions: Click Here 
Adding Decimals: Click Here  
Practice your fraction adding skills here: Click Here  
Practice your adding decimals skills here: Click Here

 Having a system of measurement has always been key in doctors prescribing drugs and also in the administration procress.  Refer to your textbook pg 43

Many drugs do have a dosage range.  Again, if you don’t know the dosage range check out your drug handbook or drug insert that the medication comes with.

The Apothecaries' System is the oldest measurement system on record. Refer to your textbook pg 43-44

Look at the chart to your right.  Learn these symbols and be able to recognize and understand.  The Roman numerals are used to indcate how many drams, grains, etc.

 Metric System  Refer to your textbook pg 44-46 and check out Table 3.2 on Lowercase Roman Numerals.

Prefixes are used to indicate multiples or divisions by ten.

• Deca-multiply by 10.
• Hect-multiply by 100
• Kilo--multiply by 1000.
• Deci--divide by 10.
• Centi--divide by 100.
• Milli....<Divide by 1000.
• Micro....<Divide by one million.

Household system Refer to your textbook pg 46

• This system is the most familiar to us because it is the units in which we used for cooking or around the house.  Teaspoon, tablespoon, ounce, cup, pint, quart, and gallon.

Converting between systems Refer to your textbook pg 48

• Important: any conversion must be performed by a licensed nurse or pharmacist-NOT a medication aide.
• Drug doses are usually converted at the pharmacy before they are filled and dispensed to administer/take.
• Just for your knowledge, even if the doctor writes the order in the Apothecary system, the pharmacy will likely dispense it in the metric system.
• 1 gram is equal to 1000 milligrams.

Calculating drug dosages Refer to your textbook pg 48-57

It is important as a Medication Aide to understand how to convert drug doses however, it is not the medication aide who does the conversion.  Have the nurse or physican to do this calculation.  The reason it is good for you to know so that in case there was an error made you may be able to recognize it.  Never feel bad for questioning a drug conversion rather consider it a double check system.  If you are administyering the medcation you should be aware of this. Calculating the dosage should only be performed by a pharmacist or nurse.

1 ounce = 30 ml (or cc) 
5 ml = 1 teaspoon 
1 liter = 1 quart 
1 kilogram = 2.2 Ibs 
15 m1 = 3 teaspoons = 1 tablespoon = Y. ounce 
15 minims = 1 ml= 1 cc 
1 dram (or fluidram) = 1 teaspoon

All medication aides need to have at least a basic understanding and concept of the relative size of units of measurement. For example, grams are larger than milligrams, or an ounce is larger than a dram.