1.
2.
3.
4.
Calculate one decimal place beyond the desired place.
Standardized conversions must be used to calculate answers.
Rounding Rules related to volumes:
•
Milliliter - when preparing oral liquids or injectable medicines (IM, IV
Push, SQ)
 less than 1 milliliter round to the hundredth
 greater than 1 milliliter round to the tenth
•
Milliliter - when administering IV infusions & tube feeding including IV
& tube feeding pumps round to the whole number
Rounding Rules if calculating for ounce, kilogram, microgram, milligram, gram,
units and milliequivalents:
•
Ounces: do not round
•
Kilograms: round to the tenth
•
Micrograms: round to the whole number
•
Milligrams, grams, units, milliequivalents:
 Less than 1, round to the thousandth
 1-10, round to the tenth
 Greater than 10, round to the whole number
•
Intravenous & tube feeding solution must be administered using a whole
number.
 Round drops per minute using the standard rounding rules.
Safe Dose Range
1. A child with otitis media is prescribed Amoxicillin 150 mg by mouth TID. The safe
dose range is 20-40 mg/kg/day in 3 divided doses. The child weighs 34 pounds.
Calculate the safe dose range (SDR).
Convert pounds to Kg; 2.2 lbs: 1 Kg:: 34 lbs: X
2.2 X = 34
X = 15.4545 kg= 15.5
Calculate Safe Dose Range: 20 mg X 15.5 = 310 mg
40 mg X 15.5= 620 mg
SDR is 310-620 per day in 3 divided doses or 103-207 mg per dose
Is the prescribed dose safe? YES Dose prescribed is 150 mg; SDR is 309-618 mg
divided by 3 or 103-207 mg per dose. Prescribed dose of 150 is less than the
maximum safe dose of 207 and therefore safe.
2. Rocephin (Ceftriaxone sodium) 600 mg IV q 12 hrs is prescribed for a child with
meningitis. The safe dose range is up to 100 mg/kg/day in 2 divided doses.
Calculate the safe dose for a child who weighs 31 pounds.
Convert pounds to Kg; 2.2 lbs.: 1 Kg:: 31 lbs: X
2.2 X = 31
X = 14.1 kg
Calculate Safe Dose Range: 100 mg X 14.1 = 1410 mg
SDR is 1410 mg per day in 2 divided doses or 705 mg per dose
Is the prescribed dose within the Safe Dose Range? YES Prescribed dose is 600 mg;
maximum safe dose is 1409 mg divided by 2 or 705 mg per dose. 600 mg is less than
705 mg and therefore prescribed dose is safe.
3. Morphine Sulfate 5 mg IV is prescribed for a child who weighs 12 pounds. The safe
dose range is 0.1-0.2 mg/kg q 4 hrs.
Calculate the safe dose in mg for this child.
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 12 lbs : X
2.2 X = 12
X = 5.5 kg
Calculate Safe Dose Range: 0.1 mg X 5.5 = 0.55 mg
0.2 mg X 5.5= 1.1 mg
SDR is 0.55-1.1 mg per dose every 4-hours.
Is this order appropriate? NO Dose prescribed is 5 mg; SDR is 0.55-1.1 mg per dose.
The 5 mg dose is well above the maximum safe limit of 1.1 mg so the prescribed dose
is not safe or appropriate.
4. A child who weighs 55 pounds is prescribed an anticonvulsant medication. The safe
dose range is 5mg to 10 mg/kg /dose of body weight. The dose prescribed is 75 mg.
Calculate the safe dose range for this child.
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 55 lbs : X
2.2 X = 55
X = 25 kg
Calculate Safe Dose Range: 5 mg X 25 = 125 mg
10 mg X 25= 250 mg
SDR is 125-250 mg per dose.
Is this order appropriate? NO Dose prescribed is 75 mg; SDR is 125-250 mg per dose.
75 mg is below the maximum safe dose of 250mg therefore the prescribed dose is
safe. However you also must consider the fact that 75 mgs is below the lowest
therapeutic dose of 125 mg. Therefore, although the prescribed dose is safe it will
likely not be effective and is not an appropriate dose.
5. A 17-year-old is prescribed an intravenous medication for encephalitis. The safe dose
range is 12 mg to 16 mg/ kg of body weight to. The child weighs 85 kg. The
prescribed dose is 1200mg.
Calculate the safe dose range for this child.
Calculate Safe Dose Range: 12 mg x 85 = 1020 mg
16 mg x 85= 1360 mg
SDR is 1020-1360 mg per dose.
Is this order appropriate? Dose prescribed is 1200 mg; SDR is 1020-1360 mg per
dose. 1200mg is below the maximum safe dose of 1360 mg and above the minimum
therapeutic dose of 1020 therefore the prescribed dose is safe and appropriate.
Dose to be Administered
1. A child is to receive 0.5 mg/kg of a medication intravenous push for observed seizure
activity. The child weighs 61.6 pounds.
Calculate the dose to be administered in mg.
Convert pounds to Kg; 2.2 lbs: 1 Kg:: 61.6 lbs: X
2.2 X = 61.6
X = 28 kg
Calculate dose to be administered:
0.5 mg: 1 kg: X mg: 28 kg
14 = 1 X
Administer 14 mg
2. An adolescent is prescribed a medication to treat adverse medication effects. The
usual dose is 1.5 mg/kg. The adolescent weighs 105.6 pounds.
Calculate the dose to be administered
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 105.6 lbs : X
2.2 X = 105.6
X = 48 kg
1.5 mg: 1 kg:: X mg : 48 kg
72 = 1 X
Administer 72 mg
3. A 6-year-old is prescribed a decongestant at 4 mg/kg/ dose. The child weighs 52.8
pounds.
Calculate the dose to be administered.
Convert pounds to Kg;
2.2 lbs : 1 Kg :: 52.8 lbs : X
2.2 X = 52.8
X = 24 kg
Calculate dose to be administered: 4 mg: 1 kg:: X mg : 24 kg
96 = 1 X
Administer 96 mg
4. An expectorant of 12 mg/kg/dose is prescribed for a young child. The child weighs
39.6 pounds.
Calculate dose to be administered:
Convert pounds to Kg; 2.2 lbs: 1 Kg :: 39.6 lbs : X
2.2 X = 39.6
X = 18 kg
12 mg: 1 kg:: X mg : 18 kg
216 = 1 X
Administer 216 mg
5. A newborn is to receive 0.0625 mg/kg/dose of a medication by injection for
coagulation. The baby weighs 8.8 pounds.
Calculate the dose to be administered
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 8.8 lbs : X
2.2 X = 8.8
X = 4 kg
Calculate dose to be administered: 0.0625 mg: 1 kg:: X mg : 4 kg
0.25= 1 X
Administer 0.25 mg
Volume to be Administered
1. Phenytoin (Dilantin) suspension 55 mg PO BID is prescribed for a child with a
seizure disorder. Available is Dilantin 125 mg/5 ml suspension.
Calculate the volume to be administered in ml.
125 mg : 5 ml :: 55 mg : X
125 X = 275
X = 2.2 ml
Administer 2.2 ml
2. Acetaminophen (Tylenol) 60 mg is prescribed PO for a 5-month-old infant.
In the supply closet you have 325 mg tablets, 80 mg chewable tablets,
120 mg/5 ml elixir and 80 mg/.8 mL drops.
Which form would be the best choice for this child?
The child is 5-months-old and therefore unable to take either the chewable tablets or
the regular tablets. The oral suspension or the drops could either one be administered.
Since infants generally do not like taking medication, the drug form with the smallest
volume would be better tolerated. Most nurses would choose the drops.
How much will you give?
80 mg: 0.8 ml :: 60 mg : X
80 X = 48
X = 0.6 ml of the drops
Or
120 mg : 5 ml :: 60 mg : X
120 X = 300
X = 2.5 ml of elixir
Administer 0.6 ml of the drops (best answer) or 2.5 ml of elixir
3. Furosemide (Lasix) 8 mg PO BID is prescribed for an infant in congestive heart
failure.
Available is a multidose bottle containing Furosemide 40 mg/5 mL.
Calculate the correct volume in ml.
40 mg: 5 ml :: 8 mg : X
40 X = 40
X = 1 ml
Administer 1 ml
4. Nystatin solution 200,000 u QID is prescribed for an infant with oral candidiasis.
Available is Nystatin solution 100,000 u/mL.
Calculate the correct volume in ml.
100,000 u : 1 ml :: 200,000 u : X
100,000 X = 200,000
X = 2 ml
Administer 2 ml
5. A child is prescribed Ampicillin 125 mg IV q 6 hrs. Available is Ampicillin 1 gram
in powdered form. Directions read; mix in 4 ml of sterile water, yielding 250 mg/ml.
Calculate the correct amount to be administered at each dose.
250 mg: 1 ml :: 125 mg : X
250 X = 125
X = 0.5 ml
Administer 0.5 ml
Maximum safe concentrations
1. The order is for Nafcillin 225 mg IV q 12 hrs. After reconstituting the powdered
form, you have 250 mg/1 ml. The drug is to be added to a syringe for intermittent
infusion via syringe pump. Directions are to dilute to maximum concentration of
20 mg/ml.
How much solution will be placed in the syringe?
20 mg : 1 ml :: 225 mg : X ml
20 X = 225
X = 11.3 ml
Add 11.3 ml of solution to the syringe
2. A child with meningitis is prescribed an antibiotic to be given intravenously. The
dose is 125 mg and the maximum concentration is 5 mg/ml.
Prior to adding the medication, how much IV solution should be added to the
syringe?
5 mg : 1 ml :: 125 mg : X ml
5 X = 125
X = 25 ml
Add 25 ml of solution to the syringe
3. Ceftazidine 900 mg is prescribed to be given IV. This drug can be administered
safely at a maximum concentration of 50 mg/ml.
What is the least amount of fluid in which you could administer the dose?
50 mg : 1 ml :: 900 mg : X ml
50 X = 900
X = 18 ml
Add 18 ml of solution to the syringe
4. Vancomycin HCl is prescribed to be given intravenously. The dose is 40 mg and
the maximum safe concentration is 1 mg/ml.
Prior to adding the medication, how much IV solution should be added to the
syringe?
1 mg : 1 ml :: 40 mg : X ml
1 X = 40
X = 40
Add 40 ml of solution to the syringe
5. Amphotericin B is prescribed to be given intravenously to a child with sepsis. The
dose is 12 mg and the maximum safe concentration is 0.5 mg/ml.
What is the least amount of fluid in which you could administer the dose?
0.5 mg : 1 ml :: 12 mg : X ml
0.5 X = 12
X = 24 ml
Add 24 ml of solution to the syringe
Infusion Rates
1. The nurse is preparing to administer Nafcillin 225 mg intravenously. Including
the medication, the bag contains 12 ml of solution. The drug can be safely
administered over 30 minutes.
At what rate per hour should the IV pump be set to administer this medication?
12 ml X
0.5 hr
60
60
=
24 ml/hr
2. A child with meningitis is prescribed an antibiotic to be given intravenously. The
dose is 125 mg. Including the medication; the minibag contains 25 ml of solution.
The drug can be safely administered over 30 minutes.
At what rate per hour should the IV pump be set to administer this
medication?
25 ml X
0.5 hr
60
60
=
50 ml/hr
3. Ceftazidine 900 mg is prescribed to be given IV. , including the medication; the
mini-bag contains 18 ml of solution. The drug can be safely administered over 15
minutes.
At what rate per hour should the IV pump be set to administer this medication?
18 ml X
0.25 hr
60
60
=
72 ml/hr
4. Vancomycin HCl 40 mg is prescribed to be given intravenously. Including the
medication; the mini-bag contains 40 ml of solution. The drug can be safely
administered over 1 hour.
At what rate per hour should the IV pump be set to administer this medication?
40 ml
1 hr
X
60
60
=
40 ml/hr
5. Amphotericin B 12 mg is prescribed to be given intravenously to a child with
sepsis. Including the medication; the mini-bag contains 24 ml of solution. The
drug can be safely administered over 1.5 hours.
At what rate per hour should the IV pump be set to administer this medication?
24 ml X
1.5 hr
60
60
=
16 ml/hr
Putting it all Together
1. A child with a Urinary tract Infection is prescribed Cefuroxine 250 mg
intravenously q 6 hrs. The vial contains 750 mg in 2 ml. The child weighs 11
pounds. The safe dose range is 50-100 mg/kg/dose.
Is the dose prescribed within the safe dose range?
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 11 lbs : X
2.2 X = 11
X = 5 kg
Calculate Safe Dose Range: 50 mg X 5 = 250 mg
100 mg X 5= 500 mg
SDR is 250-500 mg per dose
Dose prescribed is 250 mg; SDR is 250-500 mg per dose. YES Prescribed dose is
within safe dose range.
How much will you draw up?
Calculate the volume to be administered; 750 mg : 2 ml :: 250 mg : X
750 X = 500
X = .67 ml
Draw up and administer .67 ml
The drug is to be added to a syringe for infusion. Directions say maximum
concentration of 10 mg/ml over 30-60 minutes.
How much fluid will be placed in the syringe?
Calculate the concentration: 10 mg : 1 ml :: 250 mg : X ml
10 X = 250
X = 25 ml placed in syringe
At how many ml/hour will you run the IV?
25 ml X
0.5 hr
60
=
60
50 ml/hr
or
25 ml X
1 hr
60
=
60
25ml/hr
Add 25 ml of solution to the syringe pump and set the pump at either 25 or 50 ml
per hour.
1. A child with pneumonia has Nafcillin 225 mg prescribed to be administered
intravenously every 12 hrs. After reconstituting the powdered form, you have 250
mg/1 ml. The child weighs 9.9 pounds and the safe dose range is 50-75
mg/kg/day.
Is the dose prescribed within the safe dose range?
Convert pounds to Kg; 2.2 lbs : 1 Kg :: 9.9 lbs : X
2.2 X = 9.9
X = 4.5 kg
Calculate Safe Dose Range: 50 mg X 4.5 = 225 mg
75 mg X 4.5= 337.5 mg
SDR is 225-337 mg per day
Dose prescribed is 225 mg every 12 hours or 450 per day;
SDR is 225-337.5 mg per day. Prescribed dose is 225mg every 12 hours or
550mg per day well above the maximum safe daily dose therefore the
prescribed dose is not safe.
How much will you draw up? The correct answer would be none as the
prescribed dose is above the SDR. Under certain circumstances doses may be
given that are outside the normal range. The math that follows would be used
under those circumstances.
Calculate the volume to be administered; 250 mg : 1 ml :: 225 mg : X
250 X = 225
X = 0.9 ml
Administer 0.9 ml
The drug is to be added to a syringe for intermittent infusion. Directions are to
dilute to maximum concentration of 15 mg/ml and infuse over 30-60 minutes.
How much solution will be placed in the syringe?
Calculate the concentration: 15 mg : 1 ml :: 225 mg : X ml
15 X = 225
X = 15 ml
add 15 ml of solution to the buretrol
At how many ml per hour will you infuse the drug?
15 ml
.5 hr
X
60
60
=
30 ml/hr
or
Set IV pump at either 15 or 30 ml per hour.
15 ml X
1 hr
60
60
=
15ml/hr