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

Posted in: Fundamental of Nursing,Pharmacology