1. DRUG CALCULATIONS
MAKING IT EASY 

2. CLASS OUTLINE 1) review roman numerals
2) review apothecary measurements
3) review conversions
4) review 3 steps to dosage calculations
5) practice, practice, practice 

3. Plugging in to Memory
Roman Numerals

4. APOTHECARY MEASURES
What are we talking about?

5. CONVERSIONS
- WITHIN SYSTEMS
- BETWEEN DIFFERENT SYSTEMS

6. WITHIN SYSTEMS MEMORIZE: 1 gram (g or G) = 1000 milligrams (mg)
1 liter (l or L) = 1000 milliliters (ml or mL)
3 teaspoons (t) = 1 tablespoon (T)
1 cubic centimeter (cc) = 1 milliliter (ml)

7. BETWEEN SYSTEMS MEMORIZE: 1 gram (G, GM, gm) = 15 grains (gr)
60 milligrams (mg) = 1 grain (gr)
1 tablespoon (T) = 15 ml
1 kilogram (kg) = 2.2 pounds (lb)
1 ounce (oz) = 30 ml or 30 cc
1 cc = 15 drops (gtt) or 15 minims (mx)
1 inch (in) = 2.5 centimeters (cm)

8. STEPS TO CONVERSION

9. WITHIN SYSTEMS
1) Write down what you know in a ratio or fraction format:
Example: 1 Gram
1000 milligrams

10. 2) Write down what you desire in a ratio or fraction format to complete the proportion:
Example: 3 Grams
x milligrams

11. Remember:
The numerator and denominator must be the same unit of measurement
The unknown value is referred to as “x”

12. The completed proportion:
1 Gram Grams
1000 mg : : x milligrams
Cross multiply

13. 1 GM x X mg(s) = 3 GM x 1000 mg
Drop the terms used for units of measurement: 1 X = 3(1000)
Solve for X: divide both sides of the equation by the number preceding X:
X = 3000
X = 3000

14. BETWEEN SYSTEMS 1) Write down what you know in a fraction format:
15 grains
1 gram

15. 2) Complete the proportion by writing down what you desire:
15 grains grains
1 gram : : X grams
HINT: Keep the units of measurements in the correct spaces!

16. Drop the units of measurement
Cross multiply
15 x X = 30 x 1
15X = 30
Solve for X: Divide each side by the number in front of X : X = ANS: 2 Grams

17. VOILA!!

18. 3 STEPS TO DOSAGE CALCULATION:
1) Convert to units of same system and similar unit
2) STOP AND THINK
3) Desired over amount on hand times quantity
EX: desired
amount on hand x quantity

19. SAMPLE PROBLEMS 1) Convert: 300 mg to grams
2) Convert: 120 mg to grains
3) Convert: 30 gr to grams
4) A child who weighs 55 pounds weighs ____
kilograms?

20. 5) A patient is restricted to four 8-ounce glasses of water per day
5) A patient is restricted to four 8-ounce glasses of water per day. The nurse knows that the patient’s fluid intake is restricted to ____ mls per day.
6) The nurse administered aspirin gr v. She knew this was equivalent to _____milligrams(s).

21. 7) Potassium chloride tablets are available in 300 mg doses
7) Potassium chloride tablets are available in 300 mg doses. The physician prescribed gr v. Give ____ tablet(s).
8) The physician prescribed Capoten, 1.5 grams daily in three equal doses, for hypertension. The nurse would give _____ 1000 mg tablet(s) three times a day.

22. 9) Lasix 30 mg, IM, is prescribed as a diuretic
9) Lasix 30 mg, IM, is prescribed as a diuretic. Lasix was available as 40 mg/mL. The nurse would give ______mL.
10) Scopolamine 0.3 mg was ordered subcutaneously as a preanesthetic medication. The medication was available in ampules containing grains 1/200 per mL. The nurse would give _____mL.

23. 11) The physician prescribed 25 mg of Librium, IM
11) The physician prescribed 25 mg of Librium, IM. Add 2 mL of diluent to yield 100 mg/2ML. The nurse should give _____ mL.
12) The physician prescribed 5 mg of Garamycin for a child. The medication is available as 20 mgs/mL. To give 5 mg, you would give ____ mL.

24. PRACTICE, PRACTICE, PRACTICE
And HOLLER if you need help!