Dosage Calculation Course Review

DOSAGE CALCULATION System Of Measurement

RATIO & PROPORTION REQ’D : : GIVEN

Metric System

Weight: 1 Kg = 1000g

WEIGHT : : WEIGHT

1g = 1000mg

VOLUME

VOLUME

1mg = 1000mcg Volume:

Note: for easy solving make sure the 2 numerator

1L = 1000ml

are the same units, convert unit if necessary

1L = 10dl

Hint: Read question carefully for requested

1ml= 1cc Length :

Example:

1m = 100cm

If the drug label 12.5mg in e very 5ml. How

1m = 1000mm

many milligram would be needed for a RX of 75ml.

Apothecary to Metric

Weight:

REQ’D : : GIVEN

1 lb = 454g

 __X__ : : 12.5MG (CROSS MULTIPLY)

1 oz = 30g

75MG

5ML

1gr = 65mg 1kg = 2.2lb

X (5ML) = (12.5MG)(75ML)

1g = 15gr Volume:

 _X (5ML) = (12.5MG) (75ML)

1 floz = 30ml

(5ML)

(5ML)

1 pt = 480ml 1 gal = 3840ml

X = 12.5MG (75)

X = 937.5 MG

5

5

Household to Metric

Volume:

X = 187.5 MG

1 tsp = 5ml 1 tbsp = 15 ml

DOSE/BODY WEIGHT/ DAILY REGIMEN

1 ml = 20 gtt

(MG/KG/DAY)

1 cup = 240ml

Step 1: convert weight into kg Step 2: multiply pt weight in kg by the

CONVERSION Given W/ UNIT X EQUIVALENT VALUE FROM THE SOM SOM VALUE (UNIT OF THE GIVEN)

Example: 0.5kg = _____g SOM “1kg = 1000g”

0.5kg X 1000g =500g 1kg

recommended dose Step 3: find daily regimen (QID or q6h; TID or q8h; BID or q12h). Divide step 2 by daily regimen Example: Recommended pediatrics dose for amoxicillin is 0.25mg/kg QID. What is the best dose for a 12 year old child who weights 95lbs? Dose  0.25mg/kg Body Weight 95lbs Daily Regimen   QID

Step 1: 95lbs X __1kg__ = 43.18kg

INFUSION RATE

2.2 lb Step 1: Step 2: 0.25mg X 43.18kg = 10.8mg

Flow rate (gtt/min)

ans should be: ml_

Drop Factor (gtt/ml)

min

Kg Step 2: volume (ml) Step 3: 10.8mg = 2.7mg

ml/min

4 Step 3: minutes or hours

Flow Rate(AKA infusion rate) Flow Rate formula (gtt/min)

Note: DF is the IV set delivery given by the

Volume (ml) X Drop Factor (gtt/ml)

manufacturer

Time (min) OR Flow Rate (ml/hr)

Example: RX NSS 500ml

Volume (ml)

The IV administration set delivers 20gtt/ml and

Time (hour)

the flow rate set is at 40gtt/min. What is the infusion

Note: If drop factor not given use 60gtt/ml

time in hours?

Example:

Step1: 40 gtt/min = _2ml_

Flow Rate Formula (gtt/min)

20 gtt/ml

min

What will be the rate in gtt/min, if the pt receives 1L over an 8hr period of time and the drop factor is 15 gtt/ml?

Step2: _500ml_ = 250 min 2ml/min

Vol (ml)

X DF gtt/ml

Time (min)

Step 3: 250min X _1hr_ = 4.17hrs 60min

1L

X 15 gtt/ml

8 hour

(1L som: 1L=1,000ml) conversion ans: 1000ml (8h som: 1h= 60min)

1000ml_ X 480min

15gtt__

Conversion ans: 480min

ml

15000gtt = 31.25 gtt/min 480min Example: Flow Rate (ml/hr) RX antibacterial 300ml over 2.5hr. What is the infusion rate in ml/hr? Volume(ml) Time (hr) 300ml___ = 120ml/hr 2.5hr