Download - 11798465 Drug Calculations
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Drug Calculations
Continue Examples
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Converting factors
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Common Abbreviations
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Dosage Forms
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Solution Measurements
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Miscellaneous Usage in the
Hospital
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Abbreviations to Avoid
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gMicrograms should be written out, insist on
it!
__ ss or ss
Write out one-half or 1/2 clearly.
ODOrdered daily? Write out daily. QD, if legible,
should be acceptable.
n or N Nightly? QN? Write out nightly or use hs.
d or D Daily? Write out how many days.
BTOrdered at bedtime? Write out bedtime or
use the standard hs.
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Examples
Fishing for
answers?
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Example Doctor's order:0.25 mg of digoxin p.o. On hand: 0.5 mg tablets
Answer
1
0.25
= 1 X 0.250.5
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Example Doctor's order:0.25 mg of digoxin p.o. On hand: 0.5 mg tablets
0.5 tablet
1
0.25
= 1 X 0.250.5
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Example Doctor's order:Give deltasone 7.5 mg PO now.Available : deltasone 2.5 mg tablet.
Answer
AVAILABLE
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Example Doctor's order:Give deltasone 7.5 mg PO now.Available : deltasone 2.5 mg tablet.
3 tablet
AVAILABLE
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Example Doctor's order:Give ranitidine 40 mg PO ABT.Available is ranitidine 20 mg tabletHow many tablet you should give?
Answer
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Solution
40 X 120
4020
2 tablets
ABT
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Example Doctor's order:Give 7500 i.u of heparin injection S/C .Available:( heparin injection 5000
i.u/ml)How many ml you should give?
Answer
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Solution
7500 X 15000
75005000
1.5 ml
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Example Doctor's order:Give 500 cc D5RL to be infused in 6
hrs. You should regulate the I.V at:
Answer
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noituloS
X cc 005 X srh 651
m 06
0057
063
m/pord 12
51
( x (
( 06 X (
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Example Doctor's order:Give 1500 cc normal saline over 4 hrs. You should regulate the I.V at:
Answer
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noituloS
X cc 0051 X srh 451
m 06
00522
042
m/pord 49
51
( x (
( 06 X (
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Example Doctor's order:Give 1000 cc dextrose 5% I.V Q 8 hrs. You should regulate the I.V at:
Answer
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noituloS
X cc 0001 X srh 851
m 06
00051084
m/pord 13
51
tixe
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Example Doctor's order:Give 3 L of I.V fluid 5% D/0.45%
normal saline over 24 hrs.(the drop factor is 60 gtt/ml).
You should regulate the I.V at:
Answer
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noituloS
X cc 0003 X srh 4206
m 06
000081
0441
521m/pord
51
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Example Doctor's order:Give 3000 cc dextrose 5% I.V Q 6 hrs,
drop factor is 20 gtt/m)How many drops should you give per
minute?
Answer
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noituloS
X cc 0003 X srh 602
m 06
00006
063
66.661)761(
51
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Example Doctor's order:Give penicillin 600.000 u I.M statAvailable: (penicillin 800.000 u/2 cc)How many ml should you give?
Answer
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Example Doctor's order:Give penicillin 600.000 u I.M statAvailable: (penicillin 800.000 u/2 cc)How many ml should you give?
1.5 ml
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Example Doctor's order:Give G/S 2000 cc I.V Q 24 hrs,The rate will be how many drop per
minute?
Answer
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Example Doctor's order:Give G/S 2000 cc I.V Q 24 hrs,The rate will be how many drop per
minute?
21 drop/m
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Example The physician orders IV fluids to
hydrate a client.The order is written as "D5NS 4 Liters over 24 hours." Looking at the package indicates the drip factor of the tubing is 15 gtt/ml. What is the drip rate?
Answer [email protected]
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Example The physician orders IV fluids to
hydrate a client.The order is written as "D5NS 4 Liters over 24 hours." Looking at the package indicates the drip factor of the tubing is 15 gtt/ml. What is the drip rate?
42 gtt/m
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:Shortcut method when you know the ordered ml/hr
gtt/ml: divide the ml/hr by 4 15
gtt/ml (typically blood products): divide ml/hr by 6 10
gtt/ml: divide ml/hr by 3 20
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4 / 175 = 43.75
gtt/min
6 / 175 = 29.16
gtt/min
3 / 175 = 58.33
gtt/min
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ExampleThe client's K+ is 2.0 mEq/dl and the
physician orders a potassium bolus of 40 mEq of KCl in 200 ml of NS to
be delivered at a rate of 10 mEq/hr. What is the drip rate inmicrodrops ?
(.(Ideal, deliver on a pump
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This is a two-part problem. Calculate the concentration of the KCl in the NS using ratio and proportion
mEq 40
ml 200 = mEq 10
x ml
40x
= 2000
x = 50
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Now you can use the IV formula.
ml 50
60 min x gtt 601 cc
x 60 50 = 3000
60 / 3000 = 50Answer: 50 (microgtts/min)
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Calculating flow rate Flow rate refers to number of ml of
fluid to be infused over one hour (ml/hr).
)total # of milliliters )volumetotal # of hours = X ml/hr
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Example Order:
500 ml NS bolus over 3 hours
Answer
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Example Order:
500 ml NS bolus over 3 hours
167 ml/h
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Example The nurse makes rounds and notes
that the current IV bag contains approximately 450 ml. The IV flow rate is 150 ml/hr. How long will it be before the nurse must hang a new bag?
Answer exit
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Example The nurse makes rounds and notes
that the current IV bag contains approximately 450 ml. The IV flow rate is 150 ml/hr. How long will it be before the nurse must hang a new bag?
3 hrs exit
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Example Order:
Administer 1000 cc at 50 gtt/min.
Answer
exit
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Example Order:
Administer 1000 cc at 50 gtt/min.
5 hrs
exit
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Example John is to receive Cleocin 150 mg IV
q 8 hours.The nurse dilutes the medication to a total volume of 30 ml and plans to deliver it via an infusion pump over thirty minutes. What would be the flow rate?
Answer exit
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Example John is to receive Cleocin 150 mg IV
q 8 hours.The nurse dilutes the medication to a total volume of 30 ml and plans to deliver it via an infusion pump over thirty minutes. What would be the flow rate?
60exit
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Example For the client whose weight is 130 lbs
and has dopamine ordered at 8 mcg/kg/min, what rate should the infusion pump be set for a solution of 400 mg dopamine in 250 ml D5W?
Answer
exit
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Client's weight: 130 lbs Dosage: 8 mcg/kg/min Solution: 400 (mg) in 250 (ml)
Tip Convert wt to kg. 130 / 2.2 =
59.09 kg Find concentration of dopamine in
1 cc. mg 400 250 ml = x mg 1 ml250x = 400
x = 1.6
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3) Concentration is 1.6 mg /cc. Convert the mg to micrograms. 1.6 (mg) x 1000 (mcg per 1 mg) =
1600 mcg/cc.Now that you have gathered all the information, plug it into the
formula
unit"/kg/min) ") 8 X 59.09 )wt in kg)X 60 )min/hr) )1600 )"unit" / ml =
28363.32
1600
x = 17.72717.727 or 18 ( ml/hr) will dialed on the pump
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Example A client is receiving dopamine at 12
ml/hr. The solution hanging indicates "D5W 250 ml/200 mg dopamine". The client weighs 133 lbs. What is the dosage (mcg/kg/min) the client is receiving?
Answer exit
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Flow rate: 12 ml/hr Solution: 200 mg dopa / 250 cc D5W Client's weight: 133 lbs
Tip1) Convert wt to kg. 133 / 2.2 =
60.45 kg 2) Find concentration of dopamine
in 1 cc.
mg 200 250 ml =
x mg 1 ml
250x = 200
x = 0.8
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3) Concentration is 0.8 mg/ml. Convert mg to mcg. 0.8 (mg) X 1000 (mcg per 1 mg) =
800 mcg /ml.Now that you have gathered all the information, plug it into the
formula.
The dosage the client is receiving is 2.65 mcg/kg/min.
ml/hr) ) 12X 800 ("unit"/ml) (Time) 60 min/hr X( 60.45 (weight in kgs =
9600
3627
X = 2.65
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Example A client is receiving a heparin drip at
22 ml/hr via an infusion pump. The label on the liter bag of D5W indicates 40,000 U of heparin. How many units of heparin does the client receive per hour?
Answer [email protected]
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U 40,000 1000 ml = x U 22 ml 1000x = 880,000
x = 880
.The client is receiving 880 U of heparin per hour
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3) Concentration is 0.8 mg/ml. Convert mg to mcg. 0.8 (mg) X 1000 (mcg per 1 mg) =
800 mcg /ml.Now that you have gathered all the information, plug it into the formula.
The dosage the client is receiving is 2.65 mcg/kg/min.
ml/hr) ) 12X 800 ("unit"/ml) (Time) 60 min/hr X( 60.45 (weight in kgs =
9600
3627
X = 2.65
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Example The physician becomes concerned
about Johns renal function and orders the Vancomycin dose (60 mg) to be infused over 90 minutes instead of the usual 60 minutes. If the Vancomycin dosage is diluted into 60 ml of IV fluid, what will be the flow rate? (Given on an IV pump for control.)
Answer
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ml 60 90 min
=
X ml 60 min
x 90 = 3600
x = (ml/hr) 40
exit
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Example John's primary IV is running at 34 ml/hr while
NPO. When the nurse runs the Vancomycin (250 mg IV q 8 hr) in over 90 minutes [volume is 100 ml--(2 50 ml syringes)], the primary IV is stopped. The ampicillin (395 mg IV q 6 hr) is given concurrently in 10 ml of fluid over 30 minutes. He received 2 boluses of aminophylline (20 ml each over 20 minutes). The IV fluids were stopped while the aminophylline infused. Since microtubing was used for the medications, total flush is negligible (approximately 3 ml). What is Johns total intake for 24 hours?
Answer exit
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Vancomycin runs for 1.5 hrs x 3 doses .hrs IV is stopped 4.5 =
Primary or maintenance IV :fluids
hr) minus 4.5) 24 .hrs 19.5 =
Primary fluid is stopped while:aminophylline is infusing
min x 2 20 minutes 40 =
hr 30 minutes minus 19 40 minutes
hr 50 minutes )18.84 hrs) 18 =x 34 ml
ml 640.5 =
Vancomycin : cc x 3 100 =300.ml
Ampicillin: cc x 4 10 =40.ml
Aminophylline: cc x 2 20 =40.ml
Normal salineflush:
)approximate) = 3ml
3 + 40 + 40 + 300 + 640.5 = .ml / 24 hrs 1023.5
.John's daily intake, based on all therapeutic modalities, is 1023.5 ml
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Example Crystal has an IV infusing at KVO (10
ml/hr). She receives an antibiotic in 22.5 ml q 8 concurrently. One ml flush is given after each antibiotic. She is given 30 ml of formula q 3.
She had diaper weights of 17 ml, 33 ml, 55 ml, 45 ml, 52 ml, 50 ml, 15 ml, and 36 ml.
Calculate her I & O for the past 24 hours.
Answer
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Intake:
IV @ 10 ml/hr x 24 hr = 240 ml
Med of 22.5 ml x 3 )q8) = 67.5 ml
Flush of 1 ml x 3 = 3 ml
Formula of 30 ml x 8 )q 3) = 240 ml
.Crystal's intake is 550.5 ml for the past 24 hours
Output:
36 + 15 + 50 + 52 + 45 + 55 + 33 + 17 ml 303 =
.Crystal's output is 303 ml for the past 24 hours
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Example John also has an order for ampicillin
sodium 395 mg IV q 6 hr. The safe range for his type of infection in the literature is 100-200 mg /kg /day. Is this a safe dose?
Answer [email protected]
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Calculate the recommended range: Minimal: 100 mg x 20 kg = 2000 mg Maximal: 200 mg x 20 kg = 4000 mg
Recommended range is 2000 - 4000 mg. Actual dose is: 395 x 4 )q 6 hr) = 1580 mg / day Compare the two values. The actual dose is less than the recommended dose. Dose is safe, but not necessarily therapeutic.
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Example The physician stopped Johns
gentamicin and cleocin when the culture report came back. His new orders include Vancomycin 250 mg IV q 8. The literature indicates that the minimal dilution concentration for infusion should be 2.5 mg / ml if given through a peripheral intravenous line (PIV). How many ml of diluent will the nurse need to mix the Vancomycin to meet this safety requirement?
Answer
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Example The physician stopped Johns
gentamicin and cleocin when the culture report came back. His new orders include Vancomycin 250 mg IV q 8. The literature indicates that the minimal dilution concentration for infusion should be 2.5 mg / ml if given through a peripheral intravenous line (PIV). How many ml of diluent will the nurse need to mix the Vancomycin to meet this safety requirement?
100 ml
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Example A newborn has an order for 0.15
micrograms of Prostin VR (alprostadil) per hour to maintain patency of the ductus arteriosus. The pharmacy prepared a Prostin drip with 25 mcg alprostadil in 50 ml of D5W. What hourly rate is needed to deliver the dosage of medication as ordered?
Answer
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Example A newborn has an order for 0.15
micrograms of Prostin VR (alprostadil) per hour to maintain patency of the ductus arteriosus. The pharmacy prepared a Prostin drip with 25 mcg alprostadil in 50 ml of D5W. What hourly rate is needed to deliver the dosage of medication as ordered?
0.3 ml/hexit
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Example John is to be given an Aminophylline
bolus of 30 mg in 20 ml of fluid over 20 minutes. The primary IV is running at 40 ml/hr. The drip factor of the tubing (buretrol) is 60 gtts/cc or minidrip. What is the flow rate needed to deliver the Aminophylline bolus as ordered?
Answer exit
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Example John is to be given an Aminophylline
bolus of 30 mg in 20 ml of fluid over 20 minutes. The primary IV is running at 40 ml/hr. The drip factor of the tubing (buretrol) is 60 gtts/cc or minidrip. What is the flow rate needed to deliver the Aminophylline bolus as ordered?
60 ml/hexit
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Example John is a pediatric client in a hospital in
which the policy is to place all children on IV therapy on a buretrol and to only fill the buretrol no more than two-three hours worth of fluid. The nurse fills the buretrol to 90 ml at 10 a.m. If Johns IV is running at 34 ml per hour, how long will it be before the nurse will need to fill it again?
Answer exit
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90 ml 34 (ml/hr) = 2.65 hrs However,0.65 hrs = ? minutes
hr 1
60 min = hr 0.65
X min
1x = 39.00
X = 39
Answer = 39 minutes Add this to the 2 hours. 10 a.m. + 2 hr 39 minutes = 12:39
p.m.
At 12:39 p.m. the buretrol will need more fluid added so that air does not get
into the tubing. [email protected]