Transcript Introduction to Medication Calculation

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Introduction to Medication
Calculation
Student Success Immersion Program
University of Maryland, School of Nursing
Presentation created by Amanda Pfaff, RN, BSN
Objectives
 Introduce different forms of medication administration
 Reading a drug label
 Required conversion factors
 Types of medication calculation
 Rounding rules
 Dimensional Analysis
Why is it important?
 Medication administration is one of the chief
responsibilities of a nurse
 Nurses are often the “last line of defense”
 Solid knowledge base helps prevent errors
Do Not Panic!
 This is an introduction
 You are not expected to know
this material at this time
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Different Types of Medication
 Oral Medications
 Supplied in a variety of forms
 Tablets are the most common
 If patient has difficulty swallowing some tablets can be
broken, crushed, or capsules can be opened
 Enteric coated and sustained/extended release should
NEVER be crush
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Oral Medications cont.
 Oral medications may also come in liquid form
 Elixirs and oral suspension
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Parenteral Medications
 Parenteral: Outside the GI tract
 Given when they can’t be given orally or when a rapid
onset is desired
 Absorbed directly in the bloodstream
Parenteral Routes
 Subcutaneous Injection: Beneath the skin, in fat
 Intramuscular Injection (IM): in the muscle
 Intradermal Injection: within the skin
 Intravenously (IV): within the vein
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Parenteral Forms
 Supplied as a liquid or as a powder that needs to be
reconstituted
 Ampules: single dose containers, need to be broken, made
of glass
 Vials: Glass or plastic container that is sealed with rubber
stopper
 Vials often contain more than 1 dose of the medication
Reconstitution
 Some drugs are unstable in
liquid form and must be in
powder form until they are
ready for use
 Reconstituted: Dissolved
with sterile diluents
 Common Diluents: sterile
water, sterile normal saline
(NS), and 5% dextrose
solution (D5W)
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Parenteral Forms
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IV Administration
 Gravity infusion
 Infusion pumps
 IV push (IVP)
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 IV Piggybacks (secondary infusions)- medications infused
in addition to regular IV fluids, smaller amount
IV Administration
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IV Administration
IV drip
(via gravity or infusion pump)
Why do you need to round to a whole number?
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IV Administration
IV Push
Why don’t you need to round to a whole number?
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Reading a Drug Label
7
1.
2.
3.
4.
Brand name
Generic name
Dose
Manufacturer
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5. Expiration
6. Safety warnings
7. Form
Measurements
 Metric System is system of choice
 All answers expressed as decimals NOT fractions
 More accurate and simplistic
Measurement Conversions
 1000 ml = 1 L
 5 ml = 1 tsp
 15 ml = 1 Tbsp
 3 tsp = 1 Tbsp
• 1000 mcg = 1 mg
• 1000 mg = 1 g
• 2.2 lb = 1 kg
 30 ml = 1 oz
 240 ml = 1 cup
 8 oz = 1 cup
At the time of your test it is
expected that you will have
these conversions memorized.
Common Metric Measures –
Practice
Convert the following:
1 g = ____ mg
0.015 g = ____mg
750 mg = _____ g
0.5 L = ____ mL
0.0004 g = _____ mg
1.2 g = _____ mg
0.008 g = ____ mg
Common Metric Measures –
Practice Answers
Convert the following:
1 g = 1000 mg
0.015 g = 15mg
750 mg = 0.75g
0.5 L = 500 mL
0.0004 gm = 0.4 mg
1.2 g = 1200 mg
0.008 g = 8 mg
Common Metric Measures –
Practice
1. Convert 1.5 oz. into an equal volume of tablespoons (Tbsp.).
2. A patient weighs 154 lbs. What is this patient’s weight in
kilograms?
3. The doctor instructed Bob to take 1 tablespoons of cough
syrup every 12 hours. Bob only has teaspoons available to
measure with. How many teaspoons should he take for each
dose?
4. There are 2 bottles of milk of magnesia on the shelf at the
pharmacy. One contains 10 oz. and the other has 300 mL.
Which has the larger volume?
Common Metric Measures –
Practice- Answers
1.
2.
3.
4.
3 Tbsp.
70 kg
3 tsp.
They are equal.
Units
 Some medications are measured in units
 Common medications in units are: Heparin, Insulin,
Epogen, Penicillin
 Only insulin is measured and given in insulin syringes
 Most other medications can be given in syringes marked in
milliliters
 Important to understand difference between units and
other units of measure
Unit Syringes
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Pediatric Dosages
 Children differ from adults because of their weight, height,
metabolism of drugs, and immature body systems
 Medications are calculated using the child or infant’s weight
 Weight is always in kilograms
 You will not be expected to do pediatric dosing in your first
semester
Daily Dose Ranges
 Many drugs have “do not exceed” or “maximum doses” given in
a range
 The nurse and/or pharmacist must calculate the high and low
end of the range to determine accuracy
 Any dose outside the therapeutic range is unsafe whether it is
to high or to low.
 Example: Vancomycin is unsafe to the kidneys if too high but
ineffective against infection if too low.
Rounding Basics
 Round up to the next highest number if the digit to the
right of the decimal is ≥ 5
 The number stays the same if the digit to the right of the
decimal is < 5
Rounding Rules
 Round all IV drip rates to a whole number
(by gravity or infusion pump)
• Round all other answers to the nearest tenth
(includes IV push)
 *If the question involves Kg, round Kg’s 1st, then
continue problem with rounded weight. Round other
calculations at the end of the problem.
Rounding examples
 2.667 = 2.7 (rounded up)
 2.444 = 2.4 (stays the same)
 3.579 = 3.6 (rounded up)
 1.2214 = 1.2 (stays the same)
Rounding to the whole number
 Same rules apply
 Examples:
 1.5666 = 2 (rounded up)
 2.4566 = 2 (stays the same)
 3.0999 = 3 (stays the same)
 4.9010 = 5 (rounded up)
Dimensional Analysis
 A format for setting up problems
 Advantage: Only need one equation to set up ANY
problem
 Similar to Algebra!
Dimensional Analysis
• Place what you are solving for to the left of the equal sign
• To the right of the equal sign set up your equation
• First numerator is information you have about what
you are solving for
• First denominator is information you have that relates
to the first numerator
• Unit of measure for second numerator is the unit of
measure for the first denominator
Example of Dimensional Analysis
The NP orders Augmentin 500mg PO daily. The drug arrives
from pharmacy in 250mg tablets. How many tablets will you
administer?
Solving for tablets.
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 =
1 𝑡𝑎𝑏𝑙𝑒𝑡 500 𝑚𝑔
x
250 𝑚𝑔
1
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 =
1 𝑡𝑎𝑏𝑙𝑒𝑡 500 𝑚𝑔
x
250 𝑚𝑔
1
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠= 2 tablets
Example of Dimensional Analysis
The physician orders quinidine 0.6 g PO q 4 hr. Quinidine is
supplied in 200 mg tablets.
 (A) How many tablets will you give for one dose?
 (B) How many tablets will you give in 24 hours?
Part B
Part A
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 =
1 𝑡𝑎𝑏𝑙𝑒𝑡 1000 𝑚𝑔 0.6 𝑔
x
x
200 𝑚𝑔
1𝑔
1
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 =
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 =
1 𝑡𝑎𝑏𝑙𝑒𝑡 1000 𝑚𝑔 0.6 𝑔
x
x
200 𝑚𝑔
1𝑔
1
You will give 18 tablets in 24 hrs
𝑋 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 = 3
Give 3 tablets for one dose
3 𝑡𝑎𝑏𝑙𝑒𝑡𝑠 24 ℎ𝑟
x
4 ℎ𝑟
1
Infusion Pump Rates
Always mL/hr
50 𝑚𝐿 60 𝑚𝑖𝑛
x
30 𝑚𝑖𝑛 1 ℎ𝑜𝑢𝑟
50 𝑚𝐿 60 𝑚𝑖𝑛
x
30 𝑚𝑖𝑛 1 ℎ𝑜𝑢𝑟
3000 𝑚𝐿 100 𝑚𝐿
=
30 ℎ𝑜𝑢𝑟 ℎ𝑜𝑢𝑟
Calculating Gravity Drip Rates
Always gtt/min
100 𝑚𝐿
1 ℎ𝑟
20 𝑔𝑡𝑡
x
x
1 ℎ𝑟
60 𝑚𝑖𝑛 1𝑚𝐿
100 𝑚𝐿
1 ℎ𝑟
20 𝑔𝑡𝑡
x
x
1 ℎ𝑟
60 𝑚𝑖𝑛 1𝑚𝐿
2000 𝑔𝑡𝑡 33.3 𝑔𝑡𝑡 33 𝑔𝑡𝑡
=
=
60 min
𝑚𝑖𝑛
𝑚𝑖𝑛
Advice for Medication Calculation
 Make sure you are answering what the question is ASKING
 Evaluate your own learning style and do what works best for you
 Choose a method which you can do consistently and accurately
• When asked if a dose is safe, remember that going under AND
going over a dose range is UNSAFE!
• You have to round IV drips to the whole number, you can’t
calibrate ½ of a drop! 
 Remember: CONVERT, CALCULATE, AND MOST
IMPORTANTLY…..CRITICALLY THINK (Does your answer make
sense?)
Practice Makes Perfect
 Medication calculation is a skill
 Don’t get frustrated
 Math with a purpose (Patient safety!)
Questions?
Lets practice!