Download Medication Calculation Guidelines(1).

MEDICATION CALCULATION GUIDELINES
Think critically to avoid drug calculation errors. Do not rely only on your ability to do
MATH.
Basic Guidelines for Rounding
Don’t round unless you have to Carry at least two decimal places (hundredths)
throughout the entire problem
When you have to round, only
The smaller the number the more decimal places
round at end of the problem and should be carried...hundredths place is a general
not while working the problem
guideline
Round capsules and drops to
Parts of capsules and drops cannot be administered
Whole Numbers
Round injectable medications
Use a 1 cc syringe (Tuberculin syringe) which is
less than 1 mL to Hundredths
calibrated in hundredths
(two decimal places)
Round injectable medications
Use a 3cc or larger syringe which is calibrated in
more than 1 mL to Tenths (one tenths
decimal place)
Guidelines for Rounding Critical Care Meds
Critical care medications are usually
If pump can be set to administer meds to the
administered via pump or controller
hundredths' place, carry the problem to the
thousandths and round to the hundredths
The smaller the number the more
This is especially true for pediatric patients
important it becomes to not round too
soon
Guidelines for Expressing Dosages with a Decimal
Do not use trailing zeros after a decimal
If intending to give 1 mg of a medication
point for doses expressed in whole
and dose is expressed as 1.0 mg, the dose
numbers
may be misinterpreted as 10 mg
Use zero before a decimal point when the
If intending to give 0.5 mg of a medication
dose is less that a whole number
and the dose is expressed as .5 mg, the dose
may be misinterpreted as 5 mg
Remember: Lead Don’t Follow
MEDICATION CALCULATION GUIDELINES
Critical Care IV
Dosages of certain IV medications must be titrated to administer a specific dosage per
unit of time, for example, mg per minute, mcg per minute, or units per hour.
Dimensional analysis (factoring) can be used to calculate flow rate, or when the flow rate
is known, to assess the dosage being administered per unit of time.
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Setting up the formula
On the left side of the equation, place what it is you are solving for (what you are
being asked to calculate).
On the right side of the equation, place the available information from the
problem in the form of a fraction (ratio). The numerator must be the same as the
unit being calculated (what you are solving for).
Enter the additional factors from the problem. Set up the numerator for each
subsequent fraction so that it matches the unit in the previous denominator.
Cancel out the like units on the right side of the equation. The remaining unit
should match the unit on the left side of the equation (you have set up the problem
correctly).
Solve the equation by:
a. Multiplying the numerators
b. Multiplying the denominators
c. Divide the numerator by the denominator in the resulting fraction
Example:
Order: Heparin 25,000 units in 250 mL D5W to infuse at 500 units per hour on an
infusion pump.
mL
hr
=
250 mL
X 500 units
25,000 units
1 Hr
= 5 mL/Hr
MEDICATION CALCULATION GUIDELINES
1. To calculate the dosage being administered:
Example:
The patient is receiving Isuprel at 30 mL/hr. Solution is available in 2 mg Isuprel in
250 mL D5W.
Calculate how many mcg/ min the patient is receiving.
Mcg =
min
1000 mcg X 2 mg
X
1 mg
250 mL
30 mL
1 hr
X
1 hr
60 min
= 4 mcg/min
Example:
Order: Drug XYZ 100mg mixed in 250 mL of fluid with drop factor of 60 gtt/mL and
infusing at 10 gtts/min. What is the mcg/min being administered?
Mcg =
min
1000 mcg X 100 mg X
1 mg
250 mL
1 mL
60 gtt
10 gtt
1 min
= 66.67 mcg/min
2. The dosage may be titrated according to the patient's weight each day.
Example:
Drug A premixed – 50,000 units/600 mL
Order: 70 units/kg/h
Patient weighs 269 lbs
How many mL/h are required to get the required units?
mL
hr
=
600 mL X
50,000 units
70 units X
Kg/hr
S:/Forms/AS/Medication Calculation Guidelines
Revised: October 1, 2008
1 kg X
2.2 lb
269 lb
= 102.7 mL/hr