LESSON TWO Calculating Medication Dosages, Reading Labels ...oll9.nscc.ca/RNPDCFileStore/RNPDC/Asset/49600/MA_Lesson_2_Cal.4… · LESSON TWO Calculating Medication Dosages, Reading

Medication Administration: Lesson 2

January 2016 © RN Professional Development Centre & Nova Scotia DHW, Halifax, NS 1

LESSON TWO

Calculating Medication Dosages, Reading Labels and Documentation

Introduction The first step in medication administration is interpreting the prescribed order and determining how much medication will be given to the client. In this lesson, you will apply basic mathematical skills in order to perform the calculations required for administering medications. The use of decimals, simple fractions, formulas and the metric system units of measure will be briefly reviewed. Interpreting drug labels and how to apply this information to the calculation of medications will be described. There are numerous documentation skills required in medication administration, including transcribing orders, documenting medication administration and client’s response to medications. The lesson will review these skills as well as acceptable abbreviations used in the Canadian health care setting.

Learning Outcomes 1. Recognize and utilize terminology, metric measures, and abbreviations within the context of

medication administration.

2. Demonstrate appropriate use of the metric system and perform accurate dosage calculations required for safe medication administration. 3. Interpret orders and demonstrate appropriate transcription and documentation in simulated

situations. 4. Recognize differences in names of medications, and be able to

differentiate/choose appropriate medications by understanding written labels.

Required Readings

See required list



Math Review

Competent basic math skills are essential to the role of the Registered Nurse. It is important that you understand decimals and percentages, and how to add, subtract, multiply and divide. Although calculators are available in clinical settings, you still must know how to do these skills in order to ensure that your calculations are correct.

Please Read:

Lesson Two: Required Reading 1

Metric Conversions

In Canada the metric system is the unit of measurement that is commonly used, and often the nurse is required to convert from one unit of measurement to a different one. This will likely occur if the unit that the physician has ordered is different from the one that you have available. For example, the physician has order the medication in grams, and the concentration that you have is in milligrams.

REMEMBER THIS RULE: To convert a larger unit of measure to a smaller one, move the

decimal three places to the right. “downright” E.g. 0.95 g = 950 mg (grams are larger, mg are smaller)

…AND THIS RULE: To convert a smaller unit of measure to a larger one, move the

decimal three places to the left. “upleft” E.g. 200 ml = 0.2 L ( ml are smaller than L) E.g. 20mg = .020 = 0.02g (remember to put a zero before the decimal) Please Read:

Lesson Two: Required Reading 2



Dosage Calculations

The nurse is often required to calculate how much of medication is to be given to the patient, based on the prescription. While many health care organizations are using unit-doses that are pre-packaged by the pharmacist in the correctly calculated dose there will always be instances in which you will be required to calculate your own medication doses. Examples of these times include during the night shift, narcotics, in an emergency situation or for specific medications. Here are some examples of when you will be required to calculate the dose of a medication:

The medication order is for 10 mg, and the medication is in a liquid form, how many milliliters will you give?

The medication order is for 200 mcg, and the medication is in a tablet form, how many tablets will you give?

The medication order is for 1 g, and the medication is in an intravenous form, how much medication will you put in the mini bag? How fast will you infuse this medication?

In Canada the measurement system used is the metric system. Medication orders are generally written as the weight of a medication, which is either in micrograms, milligrams or grams. The concentration refers to how much medication is what amount of medication, for example how many milligrams of medication are in 1 milliliter of oral solution? 5 milliliters of injectable solution? One tablet? The concentration is always written on the medication label, and is essential to know when calculating how much medication will be given to the client.

Case Study Example Mrs. Brown is an 85-year old patient with a severe urinary tract infection. She is confused, lethargic and presently unable to take oral medication. The physician has ordered the following course of IV antibiotics:

Ciprofloxacin 200 mg IV q 12 hour You have a vial of Ciprofloxacin that contains 10mg per ml, how much Ciprofloxacin would you need?



There are two mathematical formulas that can help you to solve this problem; it is your choice which method you choose to use. It is recommended that you use the formula that you are most familiar with; both are discussed in your required readings. For the purposes of this review we will concentrate on the second method, the fraction or cross multiplication method.

So let’s review this again, we are to administer Ciprofloxacin 200 mg IV, and we have a vial that contains Ciprofloxacin 10 mg/ml. That means that for every milliliter of solution, there are 10 milligrams of Ciprofloxacin. This is known as the “standard equivalent”. In the other formula, it is known as the “dose on hand”. Let’s enter the measurements that we currently have into the formula.

As you can see from above, we know the concentration of the vial that is in stock and we know how many miligrams the physician has ordered. What we don’t know is how many milliliters we need to take from the vial of Ciprofloxacin, and so we will refer to this number as “x”. How do we solve for x? This is simple, basic multiplication of fractions.

Solving for Proportion Dose desired ______________ X ml = x Dose on hand

Cross Multiplication Standard Ordered Equivalent Dose ________ = _________ # ml X ml

Cross Multiplication 10 mg 200 mg ______ = ______ 1 ml x ml



So, based on our calculations, 200 mg of Ciprofloxcin is equal to 20 mls of the IV vial that we have on hand (concentration of 10 mg/ml). To prevent medication errors it is important that after we complete a dosage calculation we ask ourselves, “Does this seem right?” In this situation, it does seem logical that if there is only 10 mg of Ciprofloxacin in 1 ml, then we will need a large amount of milliliters to have 200 milligrams. This “common sense” check is extremely important when calculating dosages, if it doesn’t seem right, it probably isn’t.

Let’s practice again, the physician now wants to treat Mrs. Brown’s Vitamin B12 deficiency anemia and he orders:

Vitamin B12 IM 100 mcg X 1 dose You have an ampule of Vitamin B12 that contains 500 mcg/2 ml. How much medication do you need? How do we solve this problem?

What we know = 500 mcg per 2 ml (standard equivalent) What do we need to know = how many mls is needed for a dose of 100 mcg?

(ordered dose)

Cross Multiplication 10 mg 200 mg ______ = ______ We must cross multiply the fractions, as seen

below: 1 ml x ml

10 mg 200 mg ______ ______ = 10 mg X (x)ml = 200 mg X 1 ml 1 ml x ml

10 mg X (x)ml = 200 mg X 1 ml 10x = 200 10x = 200 10 10 X = 20



So we’ve calculated that we need 0.4 mls of vitamin B12 to obtain 100 mcg, does that make sense? Well if the vial contains 500 mcg in 2 mls, then we can easily determine that 1 ml contains 250 mcg. So it does make sense that 100 mcg would be less than one half of a ml of solution! Remember, the prescriber should always prescribe the medication in terms of the amount of the “weight” of the medication, which is how many milligrams or grams are required for this client, in order to achieve a therapeutic effect. It is your role to determine how much of the form of the medication is required to be given in order to achieve this dose. This is referred to as dosage calculation. You may also be required to do some metric conversions if the order is different from the available medication. For example, the physician orders the medication in grams, and the available medication is in milligrams. Examples: Acetaminophen 650 mg = 2 acetaminophen tabs that each have a concentration of 325 mg = 20 ml of oral solution that has a concentration of 160 mg/5ml = 1 rectal suppository that has a concentration of 650 mg. Morphine 5 mg = 0.5 ml of oral solution that has a concentration of 10 mg/ml = 1 rectal suppository that has a concentration of 5 mg = 1 ml of injectable solution that has a concentration of 5 mg/ml

Cross Multiplication 500 mcg 100 mcg ______ = ______ We must cross multiply the fractions, as seen

below: 2 ml x ml

500 mcg 100 mcg ______ ______ = 500 mcg X x ml = 100 mcg X 2 ml 2 ml x ml

500 mcg X x ml = 100 mcg X 2 ml 500x = 200 500x = 200 500 500 X = 0.4



Please Read:

Lesson Two: Required Reading 3 and 4

Once you complete your required readings practice your math skills with the following learning activity. These questions will help you to prepare for your quiz!



Activity 1 Review

1. Indicate the abbreviations for the three basic units of measure of the metric system that

nurses most often use.

a) Weight: ____________

b) Length_____________

c) Volume ____________

2. What prefixes used in metric measurement describe the following?

One thousand times _______________

One hundredth part of _____________

One thousandth part of _____________

One millionth part of _______________

3. Why is it important to place a zero in front of a decimal number (e.g. 0.60 ml) ? _____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

_____________________________________________________________________________

4. What is the name for the following metric abbreviations?

g __________ kg _______ mg ______ mcg ______ ml ______ 5. Complete the following:

1 kg = _______ g 1 g = ________ mg 1 mg = _______ mcg



6. Convert the following by moving the decimal: 0.05 kg = __________ g (larger to smaller) 457 L = ______ ml (larger to smaller) 128 mcg = _____ mg (smaller to larger) 5,600 ml = ______ L (smaller to larger) 7. Change the following fractions to decimals. Carry division three decimal places as necessary.

Then show answer as a percentage.

2/5 = = % 18/30 = = %

8/64 = = % 1/5 = = %

6 ½ = = % 1 ¼ = = %

8. Basic math review. Show all calculations.

a) 1978 + 445 =

b) 2.01 + 0.04 =

c) 732 – 255 =

d) 1.023 + 0.98 =

e) 10.35 – 1.87 =

f) 396 x 287 =

g) 23.12 x 0.78 =

h) 2125 25=



9. Complete the following decimal/fraction conversions. Take to the lowest denominator or to two decimal places.

Decimal Fraction

a) 0.38 = _________

b) ____ = 5/8

c) 2.015 = _________

d) = 4 2/3

10. Complete the chart using the following symbols <, >, =

a) 2/3 _ __ 5/8

b) 7/8 90%

c) 0.87 70/100

d) 4/5 0.8

11. Solve the following problems. (If necessary record to 2 decimal places)

a) What is 0.45% of 75?

b) There are 18 instructors for 240 students. What is the ratio of instructor to students? Give the lowest ration possible.

12. Complete the following conversions between systems.

a) 2.7 L = ____ ml

b) 0.3 mg = mcg

c) 0.35 L = mls

d) 5.6 g = mg

e) 35 cm = mm

f) 140 lbs= kg

g) 60 in. = cm



13. Solve for x in the following problems

1. 156 = x 13 21 2. x = 365 2.64 15

14. Determine the value of x in the following situations. a) 50mg per 3 ml = 600mg per x ml x = _____ b) 1.5mg per 1 tab = 4.5mg per x tab x = _____ c) 125mg per 5 ml = 85mg per x ml x = _____ d) 375mg per 5 ml = x mg per 6ml x = _____



Reading Labels

It is of paramount importance that the Registered Nurse be familiar with reading medication labels. The following reviews the various components of the medication label, as seen below.

Trade Name

The trade name is also referred to as the brand name or proprietary name; it is the manufacturer's name for the drug. Notice that the brand name is very prominent on the label and is capitalized. It is important to remember that different manufacturers may market a drug under different trade names. The trade name is followed by an®, which is the registration symbol. Some medications may have the abbreviation™ after the trade name, which stands for trademark. In the example above the trade name is Dilaudid.

Generic Name

This is a name given by the manufacturer that first develops the medication. Medications have only one generic name. Prescribers are ordering medications more often by the generic name, so nurses need to know the generic name as well as the trade name. Pharmacists in many institutions are dispensing medications by generic name to decrease costs. Sometimes only the generic name may appear on a medication label or package. This is common for drugs that have been used for many years and are well known and do not require marketing under a different trade name. Demerol is the trade or brand name; however, it is often seen with the generic name only (meperidine). The figure below shows Demerol labels with various strengths. Note that only meperidine is indicated on the label. As stated previously, by law, the generic name must be identified on all drug labels.



(Gray Morris, Deborah C.. Calculate with Confidence, 4th Edition. Mosby)

Dosage Strength and Total Volume

It is important to recognize the difference between the dosage strength and the total volume to avoid confusion and errors. On the lamivudine label, shown below, 240 ml is the total volume, and the dosage strength is 10 mg/ml.

(Gray Morris, Deborah C. Calculate with Confidence, 4th Edition. Mosby)

Total Volume- how

much solution is in the vial

Dosage

strength-a ratio of

amount of

drug per amount of

solution; the concentration

of the medication



In the above example, the concentration of the lamivudine oral soluation is 10 mg/ml. There are 10 mg of medication in every mililiter of solution. The total amount of solution in a full bottle is 240 mls, which means that there is a total of 2400 mgs of medication in the full bottle. As we have already discussed, you need to know the dosage strength, or concentration of the medication, in order to calculate the required dose.

Drug Forms

Labels may also indicate abbreviations or words that describe the form of the drug. Examples include CR (controlled release), LA (long acting), DS (double strength), SR (sustained release), and XL (long acting)


Expiration Date

Remember to always read the expiration date. After the expiration date, the drug may lose its potency or cause adverse or different effects. Never give an expired medication.

(Gray Morris, Deborah C. Calculate with Confidence, 4th Edition. Mosby)



Instructions Some medications will also contain instructions for mixing, including what type and how much solution to reconstitute with the powdered medication. Sometimes these instructions will be on the label, or included in a product instruction sheet.


Now that we have reviewed dosage calculations and reading labels, let put it all together into some practical review questions. These questions will help you to prepare for your quiz!



Activity 2 Review

1. Use the label below to identify the information requested.


a) Trade name___________________________

b) Generic name___________________________

c) Form___________________________

d) Dosage strength (when reconstituted)___________________________

e) Total volume (when reconstituted)___________________________

f) Solution used for reconstitution___________________________

g) Amount of solution used for reconstitution ____________________

h) The physician orders a client to be given 300 mg of this medication. How much oral solution will you give the client (in milliliters)? ____________________

i) The physician orders a client to be given 500 mg of this medication. How much oral solution will you give the client (in milliliters)? ____________________




a) Trade name___________________________

b) Generic name___________________________

c) Form___________________________

d) Dosage strength ___________________________

e) Total volume ___________________________

f) The physician orders you to give 150 mg of this medication. How much oral solution will you give the client (in milliliters)? ___________________________

g) The physician orders you to give 300 mg of this medication. How much oral solution will you give the client (in milliliters)? ___________________________




a) Trade name___________________________

b) Generic name___________________________

c) Form___________________________


e) Total amount ___________________________




a) Trade name___________________________

b) Generic name___________________________

c) Form___________________________


e) Total amount ___________________________

f) The physician has ordered the client to receive 400 mg of this medication. How much oral solution will you administer? ___________________________

g) The physician has ordered the client to receive 1g of this medication. How much oral solution will you administer? ___________________________



Documentation

It is extremely important that you document that you have administered a medication in a timely, appropriate fashion. Never document that a medication has been given prior to actually giving it. Ensure that you use approved abbreviations that are acceptable in your health care organization (refer to the policy). But before you can administer a medication, it is important that the order be transcribed onto the Medication Administration Record (MAR). The MAR may be in the form of medication cards or even on a computer printout. Regardless, it is generally the role of the Registered Nurse to transcribe medication orders. Transcription to the MAR includes the following:

Order dates

Medication Dose Route of administration Frequency Stop date (if applicable) Initials (in appropriate place)

Most facilities require three checks on a transcribed order. The first check is done by the original transcriber. The second check is done by another nurse, and involves carefully reading both the original prescribed order as well as the transcribed order and ensuring it is correct. The third check is generally done every 24 hours, in which one nurse designated to the task (often on the night shift) reviews the chart and re-checks all orders that were written in that 24 hour period. This is to ensure that the transcribed orders were indeed done correctly, and that no orders were missed on the chart. Ideally, order transcription should occur shortly after the order has been written by the prescriber. At the same time pharmacy is notified of the new prescription. Make sure you follow these steps when transcribing an order:

Read the order carefully Concentrate on copying it correctly Check it again once you are finished Sign and date on the “Physician’s Order Sheet” next to the orders transcribed, if multiple

orders place a check mark next to each order transcribed and use a bracket to indicate the group of orders transcribed.

Other documentation standards:

Only use black ink, with the exception of red ink that may be used on the MAR to underline/circle specific documentation to draw attention to an issue

All dates are to be recorded as year/month/day All time is to be recorded in the 2400 clock format Signatures are to include a minimum of first initial and full surname with professional

designation (e.g., SN for student nurse, or RN).



Use standards times for medication administration as per your health care organizations’ policy

All medication administration blocks should begin with the first AM dose:

TIME

2016/01/03 2016/01/04 2016/01/05 2016/01/06

Acetaminophen 650 mg po QID

0600

KM

1200

1800 TC

2400

TC

When a medication is discontinued, draw a diagonal line through the transcription block

and write “discontinue”, the date and initial. Try not to obliterate the written order. Then draw a line through the remaining spaces on the MAR for the medication and write “Discontinue” on the line.



Conclusion

This lesson reviewed the role of the nurse in preparing to give a medication, such as calculating the dose and reading the medication label. It also discussed the importance of documentation, which involves documenting the mediation was administered and the client’s response to the medication. If you find that you are having major difficulties with the math component of this course you must contact faculty. It is expected that you be able to calculate dosages in the clinical setting in order to ensure that your clients receive safe, effective nursing care.



Answer Key Activity 1 Review

1. Indicate the abbreviations for the three basic units of measure of the metric system that nurses most often use.

d) Weight: mcg, mg, g

e) Length: mm, cm, m

f) Volume: ml, l, dl

2. What prefixes used in metric measurement describe the following?

One thousand times: Kilo

One hundredth part of: Cent

One thousandth part of: Mili

One millionth part of: Micro

3. Why is it important to place a zero in front of a decimal number (e.g. 0.60 ml) ?

This is important to help prevent medication errors, for example .5 mg may be

mistaken for 5 mg, which could lead to a serious medication error.

4. What is the name for the following metric abbreviations?

g : gram kg : kilogram mg : milligram mcg : microgram ml : milliliter 5. Complete the following:

1 kg = 1000 g 1 g = 1000 mg 1 mg = 1000 mcg



6. Convert the following by moving the decimal: 0.05 kg = 50 g (larger to smaller) 457 L = 457, 000 ml (larger to smaller) 128 mcg = 0.128 mg (smaller to larger) 5,600 ml = 5.6 L (smaller to larger) 7. Change the following fractions to decimals. Carry division three decimal places as necessary.

Then show answer as a percentage.

2/5 = 0.4 = 40 % 18/30 = 0.6 = 60 %

8/64 = 0.125 = 12.5% 1/5 = 0.2 = 20 %

6 ½ = 6.5 = 650 % 1 ¼ = 1.25 = 125 %

8. Basic math review. Show all calculations.

i) 1978 + 445 = 2423

j) 2.01 + 0.04 = 2.05

k) 732 – 255 = 477

l) 1.023 + 0.98 = 2.003

m) 10.35 – 1.87 = 8.48

n) 396 x 287 = 113652

o) 23.12 x .78 =18.0336

p) 2125 25= 85



9. Complete the following decimal/fraction conversions. Take to the lowest denominator or to two decimal places.

Decimal Fraction

a) 0.38 = 38/100 = 19/50

b) 0.625 = 5/8

c) 2.015 = 2015/1000

d) 4.6667 = 4 2/3

10. Complete the chart using the following symbols <, >, =

e) 2/3 > 5/8

f) 7/8 < 90%

g) 0.87 > 70/100

h) 4/5 = 0.8

11. Solve the following problems. (If necessary record to 2 decimal places)

c) What is 0.45% of 75? 0.3375

d) There are 18 instructors for 240 students. What is the ratio of instructor to students? Give the lowest ration possible. 3/40

12. Complete the following conversions between systems.

h) 2.7 L = 2700 ml

i) 0.3 mg = 300 mcg

j) 0.35 L = 350 mls

k) 5.6 g = 5600 mg

l) 35 cm = 350 mm

m) 140 lbs= 63.636 kg

n) 60 in. = 150 cm



13. Solve for x in the following problems

1. 156 = x x = 252 13 21 2. x = 365 x = 64.24 2.64 15

14. Determine the value of x in the following situations.

a) 50mg per 3 ml = 600mg per x ml x = 36 ml b) 1.5mg per 1 tab = 4.5mg per x tab x = 3 tabs c) 125mg per 5 ml = 85mg per x ml x = 3.4 ml d) 375mg per 5 ml = x mg per 6ml x = 450 mg



Activity 2 Review



j) Trade name : Augmentin

k) Generic name : amoxicillin clavulanate

l) Form: oral suspension

m) Dosage strength (when reconstituted): 125 mg/ml

n) Total volume (when reconstituted): 100 ml

o) Solution used for reconstitution: water

p) Amount of solution used for reconstitution: 90 ml

q) The physician orders a client to be given 300 mg of this medication. How much oral solution will you give the client (in milliliters)? 12 ml

r) The physician orders a client to be given 500 mg of this medication. How much oral solution will you give the client (in milliliters)? 20 ml




h) Trade name: Epivir

i) Generic name: lamivudine

j) Form: oral solution

k) Dosage strength: 10 mg/ml

l) Total volume: 240 ml

m) The physician orders you to give 150 mg of this medication. How much oral solution will you give the client (in milliliters)? 15 ml

n) The physician orders you to give 300 mg of this medication. How much oral solution will you give the client (in milliliters)? 30 ml




f) Trade name: Calan SR

g) Generic name: verapamil hydrochloride

h) Form: sustained release caplets

i) Dosage strength: 240 mg

j) Total amount : 500 caplets




h) Trade name: Amoxil

i) Generic name: amoxicillin

j) Form: oral suspension

k) Dosage strength: 200 mg/5 ml

l) Total amount: 50 ml

m) The physician has ordered the client to receive 400 mg of this medication. How much oral solution will you administer? 10 ml

n) The physician has ordered the client to receive 1g of this medication. How much oral solution will you administer? 25 ml

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LESSON TWO Calculating Medication Dosages, Reading Labels ...oll9.nscc.ca/RNPDCFileStore/RNPDC/Asset/49600/MA_Lesson_2_Cal.4… · LESSON TWO Calculating Medication Dosages, Reading