Download pharmacy math jeopardy! - Alaska Pharmacists Association

1/17/2015
Pharmacy Feud: Calculations review for Pharmacy Technicians
by Lara Nichols, PharmD, MPH
Alaska Native Medical Center, Transitions of Care Pharmacist
Objectives
• 1. Review the conversion between American
standard measurement to metric measurements
for weight, volume and temperature
• 2. Review dosage calculations for both retail and
hospital medications
• 3. Review IV flow rates calculations (ml/hr and
gtt/min
Learning assessment: Pretest
1. How many ounces are in 120ml of
amoxicillin?
2. What is the acceptable temperature in
Celsius that your refrigerator should register
in the pharmacy?
3. If a patient weighs 100kg and his dose is
6mg/kg/day. How much total drug will he
get per day?
Conversions - Weight
1 kilogram = 1000 grams
1 kg = 1000 g
Kilogram: largest measure of weight used in
pharmacy. Used for patient weights.
CATEGORIES
•
•
•
•
•
Conversions --- weight and volume
Temperature --- Fahrenheit and Celsius
Concentration --- mg/ml, percent and ratio
Dosage Calculations --- retail and hospital
IV Calculations --- flow rates (ml/hr and
gtt/min)
Conversions - Weight
1 gram = 1000 milligrams
1 g = 1000 mg
Gram: Used to measure bulk quantities of
drugs, e.g. bulk powders in the compounding
area. A few drugs are dosed in grams.
1
1/17/2015
Conversions - Weight
1 milligram = 1000 micrograms
1 mg = 1000 mcg
Conversions - Weight
Factors of 1000
1 kg = 1000 g = 1,000,000 mg = 1,000,000,000 mcg
(thousand)
(million)
(billion)
Milligram: Used to measure most drug doses.
Microgram: Used for doses of very potent
drugs, e.g. levothyroxine, digoxin.
Conversions - Weight
Conversions - Weight
Practice questions:
1. How many mg in a 1 g sucralfate tablet?
1 grain
1 gr
= 65 milligrams (apx)
= 65 mg (apx)
2. A premature baby weighs 2.5 kg. How many
grams does the baby weigh?
Grains are still used to measure doses for a few
of the oldest drugs, e.g. aspirin and
phenobarbital.
3. How many mcg of haloperidol in a 2 mg
tablet?
Conversions - Weight
Conversions - Weight
1 ounce = 30 grams (apx)
1 oz = 30 g (apx)
1 kilogram = 2.2 pounds
1 kg
= 2.2 lb
Ounces are used to measure ointments and
creams, e.g. a 1 oz tube of nystatin ointment.
Patient weights are measured in kilograms. Your
weight in kilograms is roughly half that of your
weight in pounds. Example: 132 lb = 60 kg
2
1/17/2015
Conversions – Weight
Practice Questions:
1. A 32.4 mg tablet of phenobarbital contains apx.
how many grains of phenobarbital?
2. A 30 g tube of bacitracin ointment contains how
many ounces of ointment?
3.If a baby weighs 6.6 lb, how many kg does it
weigh?
Conversions - Volume
1 Ounce = 30 milliliters (apx)
1 oz = 30 ml
Ounces are used to measure bulk quantities of
liquids.
Conversions – Volume
1 liter = 1000 milliliters
1 L
= 1000 ml
A liter is approximately the same as a quart. A
milliliter is about 1/5 of a teaspoon. 5ml = 1 tsp
Milliliters are used in pharmacy to measure
liquids of all types.
Conversions - Volume
Practice Questions:
1. An IV bag that contains half a liter of IV fluid
contains how many ml?
2. An 8 oz bottle of shampoo contains how many
ml of shampoo?
Conversions - Review
1 kg = 1000 g
1 g = 1000 mg
1 mg = 1000 mcg
1 gr = 65 mg (apx)
1 kg = 2.2 lb
1 oz = 30 g or 30 ml (apx)
1 L = 1000 ml
Temperature
Freezing:
32 degrees Fahrenheit = 0 degrees Celsius
32 °F = 0 °C
Boiling:
212 °F = 100 °C
Body Temperature:
98.6 °F = 37 °C
3
1/17/2015
Temperature
Conversions between Celsius and Fahrenheit:
C = ( F – 32) x 5/9
Example: It’s 23 °F outside. What is that in °C?
C = ( F – 32) x 5/9
C = (23 – 32) x 5/9
C = -9 x 5/9 = -9 x 5 = -5 °C
9
Temperature
Celsius
Fahrenheit
Freezer
Refrigerator
-20 to -10°
2 to 8°
-4 to 14°
36 to 46°
Controlled
Room
Temperature
20 to 25°
68 to 77°
Temperature
It’s 30 °C outside. What is that in Fahrenheit?
C = ( F – 32) x 5/9
30 = (F - 32) x 5/9
9 x 30 = (F – 32) x 5 x 9
5
9 5
270 = (F – 32)
5
54 = F - 32
F = 54 + 32 = 86 °F
Concentration – mg/ml
• Concentration = amount of drug per unit
volume
• Mg/ml is the most common way that
concentration is expressed
• 20mg/ml solution --- each milliliter contains
20mg of drug
These are acceptable temperature
ranges as defined by the USP.
Concentration - Ratio
•
•
•
•
•
•
•
Concentration can also be expressed as a ratio
The ratio is defined as grams per ml
1:1000 = 1 g / 1000 ml
1:100 = 1 g / 100 ml
1:10 = 1 g / 10 ml
1:200,000 = 1 g / 200,000 ml
Epinephrine is one of the few drugs still
expressed in ratio concentrations.
Concentration – Ratio
• Converting ratio concentrations to mg/ml
• 1:1000 = 1 g / 1000 ml = 1000 mg/1000 ml =
1 mg/ml
• 1:100 = 10 mg/ml
• 1:10 = 100 mg/ml
• Shortcut: Multiply numerator (top number)
by 1000 and divide to get mg/ml
4
1/17/2015
Concentration - Percent
• Concentrations can also be expressed as
percents, or parts per 100.
• Percent concentration is defined as g / 100ml.
• 1 % = 1g/100ml = 1000mg/100ml = 10mg/ml
• 10%=10g/100ml=10000mg/100ml=100mg/ml
• Shortcut: To convert a % concn. to mg/ml,
multiply by 10.
•
•
•
•
Concentration
Percent (g/100ml)
Ratio (g/ml)
Mg/ml
0.01%
1:10000
0.1 mg/ml
0.1%
1:1000
1 mg/ml
1%
1:100
10 mg/ml
10%
1:10
100 mg/ml
50%
1:2
500 mg/ml
Concentration
Dosage Calculations
Most drugs are expressed as mg/ml
Some drugs use other measures of “weight”
Heparin and insulin are measured in units/ml
Electrolytes are often measured in mEq/ml
(e.g sodium bicarbonate) or mmoles/ml (e. g.
potassium phosphate)
• Set what you have or already know EQUAL TO
what you want or need.
•
HAVE = WANT
• Make sure units on both sides are the same. If
not, convert.
• Use cross multiplication to solve the equation.
Dosage Calculations
Dosage Calculations
Example # 1 : Retail pharmacy
Example # 2: Hospital pharmacy
You have a bottle of diphenydramine oral solution that is labeled “12.5
mg / 5ml”.
The Rx reads “Take 50 mg bid po for 5 d”. (take 50mg twice daily by
mouth for 5 days)
What is the patient’s dose in ml? How many ml total are needed to fill
the Rx?
HAVE
= WANT
12.5 mg = 50 mg
5 ml
x ml
Units on both sides match. Cross multiply.
12.5 (x) = 5 (50)
12.5 (x) = 250
x = 20 ml is the patient’s dose.
To fill the Rx: 20 ml x 2 doses/day x 5 days = 200 ml
You have a vial of calcium gluconate labeled “10%”. Your IV label says
to prepare an IV with 2 g calcium gluconate in 100ml NS. How much
calcium gluconate do you need to draw up?
HAVE = WANT
10 % = 2 g
x
Change 10 % to mg/ml. Change 2 g to mg.
100 mg = 2000 mg
ml
x
100 (x) = 2000 (1)
x = 20 ml
5
1/17/2015
Dosage Calculations
Example # 3: Dosing by weight
A baby weighs 8.8 lb. The baby has an order for furosemide 20mg/kg/day, to
be given every 6 hours.
What is the baby’s daily dose? How much will it get every 6 hrs?
HAVE = WANT
20 mg = x__
kg
8.8 lb
Units are not the same. Convert lb to kg. ( 1 kg = 2.2 lb)
20 mg = x
kg
4 kg
20 (4) = x (1)
x = 80mg daily
Every 6 hours = 4 times daily
80mg/4 = 20 mg every 6 hours
IV Calculations
• Finding the flow rate
• Use FLOW RATE = VOLUME / TIME
• Example: an IV is 500ml and is given over 2
hours. What is the flow rate in ml / min?
• flow rate = volume / time
• Flow rate = 500 ml / 2 hours
• Convert hours to min (1 hour = 60 min)
• Flow rate = 500 ml / 120 min
• Flow rate = 4.2 ml / min
IV Calculations
Example # 2: An IV is running at 10ml/min. Total volume is 1000 ml.
How long will it run in hours?
FLOW RATE = VOL/TIME
10 ml = 1000 ml
1 min
x min
Units are the same.
10 (x) = 1000 (1)
x = 100 min. Convert min to hours (1 hour = 60 min)
HAVE
= WANT
1 hour =
x__
60 min
100 min
1 (100) = x (60)
100 / 60 = x = 1.67 hours
IV Calculations
• FLOW RATE = VOLUME / TIME
• Examples of IV flow rates: 60 ml / hr
1 ml / min
The flow rate tells how rapidly the IV is being
administered.
IV Calculations
Finding the duration of an IV (how long will it run?)
Use FLOW RATE = VOLUME / TIME
Example #1: A Protonix drip is running at 25 ml/hr. It is a 250ml
IV bag. How long will it run?
FLOW RATE = VOLUME / TIME
25 ml = 250 ml
1 hr
x hr
Units are the same.
25 (x) = 250 (1)
x = 10 hours
IV Calculations
IV sets are calibrated in gtt/ml (drops/ml).
Typical sets are 10, 15, 20 or 60 gtt/ml.
Pharmacy uses a flow rate of ml/hr or ml/min
But nurses use flow rates of gtt/min.
Steps:
1. using FLOW RATE = VOLUME / TIME, find the flow rate
for the IV in ml / min
2. Multiply flow rate (ml / min) by the set calibration ( gtt
/ ml). Answer will be flow rate for IV in gtt / min.
ml x gtt = gtt
min
ml
min
6
1/17/2015
IV Calculations
IV Calculations
Example: A nurse has an IV of 150ml that needs
to be infused in 1 hour using a set that is
calibrated at 15 gtt/ml. What should she set the
drip rate at (in gtt/min)?
FLOW RATE = VOL / TIME
150ml / 1 hour = 150 ml / 60 min = 2.5 ml / min
2.5 ml x 15 gtt = 37.5 gtt / min
min
ml
Another example: Nurse has an IV of 150ml of
NS to administer over 3 hours. She is using a set
calibrated at 60 gtt/ml. What flow rate in
gtt/min should the nurse use?
Flow rate = volume / time
150 ml / 180 min = 0.83 ml / min
0.833 ml
min
x 60 gtt = 50 gtt/min
ml
Questions?
Category: Weight and Volume
Conversion
Conversion
• 1. How many mcg in a mg?
• 2. How many mg in 2 g?
• 3. How many ml in an ounce?
• 4. How many ounces in 120 ml?
• 5. How many lb in a kg?
• 6. How many ml in a liter?
7
1/17/2015
Conversion
Category: Temperature
• 1. Which is larger: a mg or a mcg?
• 2. If patient weighs 50 kg: is it a baby or an adult?
• 3. How many mg are in half a gram?
• 4. If an adult weighs 50kg, are they fat or thin?
• 5. How many grams in a 2 oz tube of cream?
• 6. A 64.8 mg tablet is how many grains?
Temperature
• 1. Water freezes at ? °C
• 2. Water boils at ? °C
? °F
? °F
Temperature
1. - 4 °F is how many degrees C?
2. A properly working refrigerator should register between what range in °C?
3. A properly working refrigerator should register between what range in °F?
• 3. Body temperature is ? °C ? °F
4. If the A/C is broken and the pharmacy is at 90 °F, is it too hot to store drugs safely?
• 4. Give the formula to convert between °C and °F.
5. If the heat is broken and the pharmacy is at 55 °F, is it too cold to store room
temperature drugs?
• 5. 50 °C is how many °F?
6. The freezer is registering -5 °C. Is it working properly?
• 6. Which is lower, 0 °C or 0 °F?
Category: Concentration
Concentration
1. D5 is what percentage strength of dextrose? How many mg/ml
is this?
2. 20% is how many mg/ml?
3. A 5 % tube of ointment has how many mg of drug in each mg
of ointment?
4. 1:100 is the same as how many mg/ml? What percent?
5. What is 10% written as a ratio concentration?
6. What is 0.1% written as a ratio concentration?
8
1/17/2015
Concentration
Category: Dosage Calculations
1. A vial label says “40 mEq in 20ml”. How many mEq in 1 ml?
2. 900mg/6ml is equivalent to how many mg/ml? What percent
concentration?
3. A solution that is 5% strength has how many mg/ml?
4.Which is more concentrated: 1:100 or 1:1000?
5. Which is more concentrated: 1:1000 or 1mg/ml?
6. Normal saline is what percentage strength of sodium chloride? How
many mg/ml is this?
Dosage Calculations
1. You have a 2 mg/ml solution of Drug X. Patient needs 4 mg. How many ml
is this?
Dosage Calculations
1. A prescription states “Take 1 cap q 6hr”. How many caps for a 10 day supply?
2. A prescription states “Take 3 ml po ac for 10 days”. How many ml to dispense?
2. Now the patient needs a 5 mg dose. How many ml?
3. Now the patient needs a 1 mg dose. How many ml?
3. A patient weighs 100 kg. Their dose is 3mg/kg/day. How many mg will they get in a
day?
4. If this drug is to be given 3 times a day, how many mg will be in each dose?
4. An IV needs 100 mg of Drug X added to it. How many ml to add?
5. A prescription states “Take 2 tabs bid”. How many tablets for a 30 day
supply?
5. A baby weighs 4.4 lb. It needs Drug Z dosed at 15mg/kg/day. How much drug will
baby receive daily?
6. If Drug Z is to be given q 4 hr, how many mg in one dose?
6. A prescription states “Take 3 tabs qhs”. How many tablets for a 90 day
supply?
Category: IV Calculations
IV Calculations
1. Give the basic formula used in all IV calculations.
2. What is the flow rate in ml/hr for an IV of 600 ml to be given over 10
hours?
3. What is the flow rate in ml/min for this IV?
4. How long will it take for a 1000ml IV running at 200ml/hr to run
out?
5. How long will it take for a 100 ml IV running at 2 ml/min to run out?
6. The doctor told the nurse to infuse 500ml of D5 at 50ml/hr. The bag
has been hanging for 2 hours and has run out. Is there a problem?
9
1/17/2015
IV Calculations
1. Pharmacy IV labels typically have flow rates in ?
2. If a nurse is manually setting the flow rate, she will typically use a
flow rate in ?
3. If an IV is to run at 1 ml/min and the nurse has a set calibrated at
10gtt/ml, she should set the flow rate at ?
4. A flow rate of 90 ml/hr is how many ml/min?
5. If an IV is to run at 90 ml/hr with a set calibrated at 30 gtt/ml, what
will be the flow rate in gtt/min?
Learning assessment: Posttest
1. How many ounces are in 120ml of
amoxicillin?
2. What is the acceptable temperature in
Celsius that your refrigerator should register
in the pharmacy?
3. If a patient weighs 100kg and his dose is
6mg/kg/day. How much total drug will he
get per day?
10