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Drugs and Dosage


Calculation of Weight Based IV DripsDrugs can be administered to clients in continuous IV drips.

The medication bag/syringe is labeled with the concentration of medication in the solution (i.e. units/ml,mcg/ml, meq/ml).
The medication order will be used to determine the setup of the problem. Ratio and proportions can be set up to solve these problems, and depending upon the complexity of the order several steps may be needed.

The following examples will show you the basis for solving these problems.

A. When the order is written as mg/hr.

ExampleOrder: Fentanyl 5 mg/hr.
The bag is labeled 250 mg in 500 ml of solution.
How fast will the IV need to be infused to give the correct dose?

1. The IV rate will be as an hourly rate, so no conversion needs to be made for time.
If the order was written with a different time, you would need to calculate the mg/hr. (use ratio and proportion)

2. Put the problem in ratio and proportion.
5 mg = 250 mg 5 (500) = 250 x 2500 x = 10 ml/hrx ml 500 ml 250 IV rate

B. The order may be written as unit of measurement/ Kg of weight/ hour.

Example Order: Heparin 100 units/Kg/hr.
The label on the solution reads 10,000 units/50 ml.The patient weighs 70 Kg.

How fast should the solution run to give the correctdosage?
1. First you need the total dosage/hr.Dose (units/hr) x weight in Kg equals the hourly dose.
If the weight isin lbs, that must be converted to Kg first.100 units x 70 Kg = 7,000 units/hr2.

Now put the dose in ratio and proportion with the concentration.7,000 units = 10,000 units

10,000x = 50 (7,000) x= 350,000 x= 35 ml/hrx ml 50 ml 10,000 rate

C. When the order is written as unit of measurement/ Kg of wt/minute.
Example Order: Dopamine 20 mcg/Kg/minute.
The bag is labeled Dopamine 100 mg/50 ml.The patient weighs 88 lbs.

How fast will the IV run to give the dose?

1. First because the weight is in lbs, you must convert lbs. to Kg.(88 lbs = 40 Kg)
2. Find the hourly dose. Because it is written in mcg/K/min you must multiplyby 60 minutes to get the hourly dose.

20mcg x 40 Kg x 60 minutes = 48,000 mcg/hr3.

Note that the concentration is in mg/ml not mcg, so you must convert too btain like units of measure.
100 mg = 1mg x=100,000 mcg/mlx mcg 1000 mcg

4. Lastly set the problem up in ratio and proportion.

100,000 mcg = 48,000 mcg/hr 100,000x = 2,400,000 x = 24 ml / hr IV rate50 ml x ml

Practice Exam #7
1. Order: Morphine 5 mg/hr. The syringe is labeled 100 mg/ 100 ml. How fast will theIV run to deliver the correct dosage? ____________ _______
2. Order: Heparin 50 units/Kg/hr. The solution is labeled 1000 units/ ml. The patient weighs 10 Kg. What is the correct rate? __________
3. Order: Dobutamine 10 mcg/Kg/min. The bag is labeled 1 mg/ ml. The patientweighs 23 Kg. What is the correct rate? ____________ ________
4. Order: Pitocin 5 miliunits/minute. The bag is labeled 10 units/liter. What is the correct rate?_______ _________ ___
5. Order: Ritodrine 0.05 mg/min. The bag is labeled 0.15 gm/500 ml. The patientweighs 198 lbs. What is the correct rate in ml/hrs?_____ _____

1. 5 mg = 100 mgx ml 100 ml100x = 500 mlx = 500 = 5 ml/hr. rate100
2. a. 50 units x 10 Kg x 60 min = 30,000 units/hrb. 30,000 units = 1000 unitsx ml 1 ml1000x = 30,000 (1)x = 30,000 = 30 ml/hr IV rate1000
3. a. 10 mcg x 23 kg x 60 min = 13,800 mcg/hrb. 13,800 mcg = 1 mgx ml 1 ml

NOTE: You must have like units of 1mg = 1000 mcgc. 13,800 mcg = 1000 mcgx ml 1 ml1000x = 13,800 (1)x = 13,800 = 13.8 ml/round to 14 ml/hr1000

from: nclex-rn


Jayson James said...

Such a nice post. appreciable and helpful for all. I am working with ink dosing unit