DRUG CALCULATIONS

MAKING IT EASY

CLASS OUTLINE1) review roman numerals2) review apothecary measurements3) review conversions4) review 3 steps to dosage

calculations5) practice, practice, practice

Plugging in to MemoryRoman Numerals

APOTHECARY MEASURES What are we talking about?

CONVERSIONS - WITHIN SYSTEMS

- BETWEEN DIFFERENT SYSTEMS

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)

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)

STEPS TO CONVERSION

WITHIN SYSTEMS1) Write down what you know in a ratio

or fraction format:

Example: 1 Gram 1000 milligrams

2) Write down what you desire in a ratio or fraction format to complete the proportion:

Example: 3 Grams x milligrams

Remember:

The numerator and denominator must be the same unit of measurement

The unknown value is referred to as “x”

The completed proportion:

1 Gram 3 Grams 1000 mg : : x milligrams

Cross multiply

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 1 1 X = 3000

BETWEEN SYSTEMS

1) Write down what you know in a fraction format:

15 grains 1 gram

2) Complete the proportion by writing down what you desire:

15 grains 30 grains 1 gram : : X grams

HINT: Keep the units of measurements in the correct spaces!

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 = 2 ANS: 2 Grams

VOILA!!

3 STEPS TO DOSAGE CALCULATION:1) Convert to units of same system and

similar unit2) STOP AND THINK3) Desired over amount on hand times

quantity

EX: desired amount on hand x quantity

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?

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).

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.

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.

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.

PRACTICE, PRACTICE, PRACTICEAnd HOLLER if you need help!