Many nursing students believe that their studies are going great until they come to pharmacology. It is difficult trying to learn and understand all of those drugs and their side effects. However, dosage calculations really put fear into many students.

So the next few blogs will be looking at this topic. Few of us are mathematical wizards, but using dimensional analysis to solve your dosage problems make the process easy. If you want to calculate a dosage, or the rate of a drip, this method is very useful.

Let us first examine the steps of dimensional analysis by working on a simple problem

The MD prescribed 50 mgs of a medication. It is stocked in a concentration of 100mg/ml. What dose should you give in milliliters

1. GIVEN -identify the given quantity -50 mg

2. WANTED -Identify the wanted or unknown quantity - x ml

3. CONVERSION- Write down the equivalents that are needed to convert between systems -100mg =1ml

4. THE PROBLEM - set up the fractions so that the units that you need to cancel are both in the numerator and denominator. This helps to isolate the unit you are looking for -
50 mg x 1ml

1 x 100 mg

5. UNWANTED UNITS -cancel unwanted units - cancel out mgs (words only not the numbers)
50 x 1ml

1 x 100

6. MULTIPLY, MULTIPLY, AND DIVIDE - multiply the numerators - multiply the denominators and divide =
50

100

50 = 0.50 ml of the solution

100

Not bad - Happy Nursing/NCLEX

Dr. Harriette

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