DRUG CALCULATIONS

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DRUG CALCULATIONS

• MAKING IT EASY
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CLASS OUTLINE

• 1) review roman numerals
• 2) review apothecary measurements
• 3) review conversions
• 4) review 3 steps to dosage calculations
• 5) practice, practice, practice
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Plugging in to Memory

• Roman Numerals

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APOTHECARY MEASURES

• What are we talking about?

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CONVERSIONS

• - WITHIN SYSTEMS
• - BETWEEN DIFFERENT SYSTEMS

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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)

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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)

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STEPS TO CONVERSION
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WITHIN SYSTEMS

• 1) Write down what you know in a ratio or
  fraction format
• Example 1 Gram
• 1000 milligrams

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

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• Remember
• The numerator and denominator must be the same
  unit of measurement
• The unknown value is referred to as x

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The completed proportion

• 1 Gram 3 Grams
• 1000 mg x milligrams
• Cross multiply

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• 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

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BETWEEN SYSTEMS

• 1) Write down what you know in a fraction
  format
• 15 grains
• 1 gram

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• 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!

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• 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

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VOILA!!
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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

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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?

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

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• 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.

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• 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.

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• 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.

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PRACTICE, PRACTICE, PRACTICE

• And HOLLER if you need help!