Medication Calculation

D = Desired Dose
Q = Quantity of Solution
H = Strength on Hand
X = Unknown quantity of Drug
Sample:
  • Physician orders 500 mg of ibuprofen (desired Dose) for a patient and you have 250 mg (Quantity on Hand) tablets (Quantity of solution) on hand.
  • Solution: D ÷ H x Q = X 500mg ÷ 250 mg x 1 tablet = 2 tablets Answer: 2 tablets.
Sample:
  • Physician orders 1500 mg of liquid ibuprofen for a patient. Quantity of Ibuprofen is 500 mg in 1 cc, how much will you administer?
  • Solution: 1500 mg ÷ 500 mg x 1cc = 3 cc Answer: 3 cc
Dosage and Conversions
Sample:
  • MD orders 300 mg of Ibuprophen to be taken by a 6 kg infant every 4 hours. Label shows 75 – 150 mg/kg per day. Is the physician’s order within normal range?
  • Solution: 6 x 75 = 450 mg (minimum dosage per day); 150 X6 = 900 (maximum dosage per day) 24 ÷ 4 = 6 dosages : 300 x 6 = 1800
  • Answer: Dosage is not within range
IV Calculations
[amount of fluid to be infused] x [drop factor] ÷ minutes to infuse = gtts/min
Sample:
  • Dr. A. orders your patient to receive 125 ml of D5W an hour for the next 8 hours. The nursing unit uses tubing with a drop factor of 10. What is the drip rate per minute?
  • Solution: Convert 1 hour to 60 minutes: 1250 x 10 gtts ÷ 60 minutes = 20.83 or 21 gtts/min
  • Answer: 21 gtts/min
Sample:
  • Dr. B. orders a liter of D5W to run this 8-hour shift. The drop factor is 15. What is the drip rate per minute?
  • Solution: 1 liter = 1000 cc of solution, next convert 8 hours to minutes (8 X 60 minutes) = 480 minutes 1000 cc x 15 gtts ÷ 480 minutes = 31.25 or 31 gtts/min
  • Answer: 31 gtts/min
Sample:
  • Your patient weighs 200 lb and the order is to infuse 250 mg dobutamine in 500 ml NS at 10 mcg/kg/min. How many milligrams of dobutamine will infuse per hour?
  • Solution: 200÷2.2= 90.90kg: 60 minutes = 1 hour: 10 mcg x 90.90kg x 60 min=5454.54 mcg/hour ÷ 1000 = 54.54mg/hr or 54.5mg/hr
  • Answer:54.5mg/hr
The “7 Rights” of Medication Administration
  1. Right Patient
  2. Right Drug
  3. Right Dose
  4. Right Route
  5. Right Time
  6. Right Documentation
  7. Right to Refuse
Conversion Table
  • 1 kilogram (kg) = 1000 grams (g)
  • 1 gram (g) = 1000 milligrams (mg)
    • Convert Grams to Milligrams by Multiplying grams by 1,000
    • Convert Milligrams to grams by dividing milligrams by 1,000
  • 1 milligram (mg) = 1000 micrograms (mcg)
  • Grains (gr.) 15 = 1 Gram (g) or 1000 milligrams (mg)
    • To convert g. to gr multiply by 15
    • To convert gr to g divide by 15.
  • 1 Grain (gr.) = 60 Milligrams (mg)
    • To convert gr. to mg multiply gr. by 60
    • To convert mg to gr. divide mg. by 60
  • 1ml = 1 cc
  • 1 ounce = 30 ml
  • 1 tablespoon (T or tbsp) = 15 ml
  • 1 teaspoon (t or tsp) = 5 ml
  • 2.2 lb = 1 kg
  • To convert pounds to kg divide pounds by 2.2
  • To convert kg to pounds multiply by 2.2

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