11798465 Drug Calculations

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.

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

Example Doctor's order:Give deltasone 7.5 mg PO now.Available : deltasone 2.5 mg tablet.

Answer

AVAILABLE

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

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

Example Doctor's order:Give 500 cc D5RL to be infused in 6

hrs. You should regulate the I.V at:

Answer

noituloS

X cc 005 X srh 651

m 06

0057

063

m/pord 12

51

( x (

( 06 X (

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 (

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

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

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

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?

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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

: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

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

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)

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

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

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

Example Order:

Administer 1000 cc at 50 gtt/min.

Answer

exit

Example Order:

Administer 1000 cc at 50 gtt/min.

5 hrs

exit

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

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

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

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

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

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

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

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

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?


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

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

ml 60 90 min

=

X ml 60 min

x 90 = 3600

x = (ml/hr) 40

exit

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

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

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

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

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?


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.

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

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

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

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

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

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

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

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

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11798465 Drug Calculations