Pharmacy Technician Certification Exam Prep: Comprehensive Guide, Exams of Pharmacology

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Pharmacy Technician Certification

Review and Practice Exam

Lacher, Barbara;

Preface ..................................................................................................... iv

• CHAPTER 1 Preparing for the Exam and Taking the Test................................. Acknowledgments v
• CHAPTER 2 Pharmacy Calculations Review ..................................................
• CHAPTER 3 Pharmacology Review
• CHAPTER 4 Sterile and Nonsterile Compounding
• CHAPTER 5 Medication Safety................................................................
• CHAPTER 6 Pharmacy Law and Quality Assurance.....................................
  • and Drug Usage CHAPTER 7 Medication Dosage Forms, Routes of Administration,
• CHAPTER 8 Processing Medication Orders and Prescriptions
• CHAPTER 9 Pharmacy Inventory Management
• CHAPTER 10 Billing/Reimbursement and Information Systems
• APPENDIX A Practice Exam 1 + Answers
• APPENDIX B Practice Exam 2 + Answers....................................................
• INDEX

Pharmacy Technician Certification Review and Practice Exam

MULTIPLE-CHOICE QUESTIONS

A multiple-choice question usually begins with an incomplete sentence or question, known as a stem. The stem is followed by a series of choices for completing the sentence or answering the question, known as responses. The responses are usually lettered a , b , c , and d. Typically, there are four, sometimes five, responses to choose from. You complete the sentence or answer the question by choosing the correct or best response. For example, a typical multiple-choice question will look like this: (Stem) The capital of Illinois is: (Responses) a. Springfield b. Chicago c. Rockford d. St. Louis Generally, the directions are to pick the one best response. However, the directions vary, so read the directions and the stem carefully. You may be instructed to pick the incorrect option or to pick more than one option. There are also questions that present the stem as a complete statement. Key words to note in the stem are the subject of the question and any qualifiers or adjectives that further define the best answer.

PREPARATION FOR

OBJECTIVE EXAMS

You may be fresh out of the classroom with recent expe- rience in preparing for and taking objective exams, or you might not have taken an exam in quite some time. Whatever the case, it’s always useful to review good study skills. This section reviews some basic study and test preparation techniques. The first step is to go to the Pharmacy Technician Certification Board ─ PTCB.org ─ and complete all the necessary steps in registering to take the exam. Next, check all the pre-requisite requirements. Once you have registered to take the exam and completed the prepara-

You do not want to be late for the exam because you got lost. Estimate how long it will take you to get to the test center. You may even want to do a test drive. Find out where parking is available, or make a trial run on public transportation.

Be sure you understand the scope of the exam. In other words, how long is it and what material will it cover? What materials, if any, can you bring with you?

EXAM PREPARATION BASICS

Time Management

Every busy person needs a schedule. But planning your study schedule, you first need a thorough under- standing of how you study. Answer these basic ques- tions about yourself:  When is the best time of day for me to study?  How do I best learn? If you are unsure of the answers to these ques- tions, you may want to monitor yourself for a week. Develop a time chart and follow your activities. Are there any times of the day when you are more produc- tive than others? Think about how you learn, too. What tasks help you learn? Do you learn best by doing or by reading? Some people find reading aloud to be a helpful memorization technique. This kind of self-knowledge will guide you in developing your study schedule. Even though family and work responsibilities may take most of your time, try to use your most productive time of the day for your studies.

Work Habits

Get Organized

Design a workplace to be productive. Find a place that allows you to work efficiently with a minimum number of distractions. Also ensure that you have enough space to spread your work out, if required. Organize your workspace so that you have quick and easy access to everything you need.

Make a “To Do” List

tion, make sure you look at the What to Bring section. Double check the date, time, and place of the exam. Mark your calendar and be sure to find the location in advance.

Keep a running list of all projects and assignments that are due. This will help ensure that you don’t forget about

CH 1 PREPARING FOR THE EXAM AND TAKING THE TEST

any major obligations. An article on time management recommends creating three lists^1 :

1. Daily to-do list —all of the tasks that need to be completed that day, such as homework due tomorrow.
2. Projects to-do list —all of the projects you have and when they are due. This list should be used to create the daily to-do list and should be reviewed several times a week.
3. Long-term to-do list —the projects that you would like to or need to work on sometime in the future, but for which there are not currently any assigned deadlines. This list should be reviewed about once a week to see if you can move any of these projects to the projects to-do list. Spending as little as 1 hour a week working on these long-term projects can lead to meaningful progress over time.

Prioritize

Often times, you will have many things you are working on simultaneously. Take time each day to prioritize what needs to be done first and work on items in that order. It is tempting to start on the easier things or the ones you are most interested in first. However, if it is at the expense of missing an important deadline, it will make your future stressful. Be mindful of deadlines and work first on things that have the earliest due dates.

Eliminate Distractors

Create an area with few distractions so you can concen- trate. Toward that end, the following is suggested:

 Attach a “do not disturb” sign if you are working in a room with a door. This lets others know not to bother you and will help to minimize unwanted interruptions.

 Stay in the zone. When people are talking around you, avoid getting pulled into the discussion, espe- cially if it is not relevant to your work.

 Stay focused on the task at hand.

 Consider using earplugs or headphones if you have to work in shared areas. This helps to minimize the chance that you will be distracted by a nearby conversation.

Avoid Procrastination

Nearly everyone has procrastinated at some point in time. However, most will testify that it caused more harm than good in the long run. Putting off an unpleasant task is human nature, but those who muster the self-discipline to see the task through will ultimately be successful in the end.

Allocate More Time than You Think You’ll Need

A general rule of thumb is that any task will almost always take more time to finish than you think it will. Think in small increments of time. Do not postpone studying because you do not have all afternoon to devote to your studies. Plan and organize small learning tasks that can occur in short blocks of time. It is easier to learn when you break your studies into smaller increments. For example, each of these is an increment: review your notes, generate questions from your notes, and make a question chart (more on that later) or key word list, and define key words. Don’t postpone your studies while you wait for that perfect free day. That free day may not come.

Question Charts One study technique that has been useful in organizing and learning information is a question chart. Question charts help you make connections between informa- tion that is new to you and what you already know—an important step in the learning process. For example, if your topic is medication administration, Table 1-1 gives an example of how to set up your chart.

Make question charts to cover all the main concepts in this review guide. Complete the charts as you read, revising and adding questions as you go, and then use them as study guides.

Computerized Testing

CH 1 PREPARING FOR THE EXAM AND TAKING THE TEST

through it by the end of the first hour. Remember to

Computerized testing poses a unique set of problems. People vary in their comfort level when dealing with computer programs. If you are not accustomed to working on a computer, it would be wise to complete a practice exam in that format prior to the actual test, if possible. The Pharmacy Technician Certification Board (PTCB) also offers a free practice exam and sells prac- tice exams on its web page ( www.ptcb.org ). There are also a number of free apps for your phone to help you prepare. Other programs with computerized standard- ized tests are available commercially.

Computerized tests often employ many of the same types of questions and question formats as paper tests, and you should use most of the same strategies (e.g., reading both the questions and the answers carefully). The PTCB exam allows you to skip items and mark items you want to go back to. It also allows you to go back and change your answer. There is only one correct answer per question and no penalty for guessing. It is important for you to try to pace yourself accordingly. Try to make your best answer in the time available and move on to the next question. An erasable board will be provided to serve as your scratch paper. You should not bring any electronic devices into the testing center, including calculators. You are permitted to use the on-screen calculator or handheld devices provided by the testing center. You will be required to lock all your personal items in a locker during the exam.

Test-Taking Strategies

Some basic strategies are helpful to most people taking objective tests. First, make sure you know how to navi- gate through the pages of the exam. The PTCB has a tutorial for this that can be accessed from their website. You are allowed to mark questions to review later; the exam will prompt you to go back to these questions.

The second step is to use your time wisely. Set your- self a schedule. Using your time wisely is dependent on reviewing the test carefully. Be aware of how many and what types of questions you must answer. You should have an idea at what time it will be when you are halfway done with the exam. For example, if you have 2 hours for a test, you should be at least halfway

leave extra time for particularly tough questions and for review. Work as rapidly as possible with a reason- able assurance of accuracy. The PTCB allows 2 hours to complete 90 multiple-choice questions.

The third strategy is to read carefully. This includes both the directions and the questions. Sections of the exam may vary, so take time to read the directions care- fully at the beginning of each new section, and keep those directions in mind while answering the questions. Making careless mistakes because you misunderstood the directions is not an effective test-taking strategy! For example, the directions may read, “select the incor- rect response,” or “mark the two best answers.”

Part of reading carefully involves reading the ques- tions as they are, not as you would like them to be. In other words, don’t look for answers you have memo- rized. Answer the question. Many people find it helpful to mark the key words in the stem so they do not forget them or misinterpret them. Also look for and mark the question words. This will help you answer the question as written. Some common question words are what , how , when , and define.

A fourth strategy is to leave your assumptions at home. You should not anticipate or assume trick ques- tions. For example, you may know the correct answer is d, but you feel you have already answered too many questions with d. Take the question at face value and mark the answer you think is correct. Also, do not assume that methods or procedures you use at work are necessarily the correct ones. “Because that’s the way we do it around here” may not be based on fact or best practice.

Going through the test at least two or even three times is another strategy for successful test taking. Go through the test completely the first time and answer all the “easy” questions that you are sure of. While you are doing the first run-through, mark the questions you need to come back to by marking the square in the top left of the page that says “review later.” By answering all the easy questions first, you can be assured that you have answered the questions you know. This strategy also builds confidence. In the stem of one question, you may also find an answer to another question.

Pharmacy Technician Certification Review and Practice Exam

On the second run through, answer the questions that you are unsure of by considering all the alterna- tives and eliminating the options you know are inap- propriate or incorrect. Relate the remaining options to the stem and balance them against each other. Use the information obtained from other questions to help you.

On the third run through, look at the remaining questions. If it is in your best interest to guess, do so. Always guess if your chances of gaining points are greater than your chances of losing points. Use the following strategies for intelligent guessing:  The most general option is often the correct one because it allows for exceptions. If three of the four options are specific in nature and one is more general, choose the more general option.  The correct choice is most often a middle value. If the options range in value (e.g., from high to low or from big to small), then eliminate the extreme values and choose from the middle values.  The longest option is often the correct one. If three options are much shorter than the fourth, then choose the longest answer.  When two options have opposite meanings, then the correct answer is usually one of them.  Look for grammatical agreement between the stem and the answers. For example, if the stem uses a singular verb tense, then the answer should also be singular. Eliminate the answers that don’t produce grammatically correct sentences. Most multiple- choice questions are designed as sentence comple- tions.  Do not leave questions blank; they will be marked wrong.

TROUBLE AREAS IN

OBJECTIVE EXAMS

A couple of areas are problematic for most people taking objective exams. The first problem area deals with specific determiners. There are positive- and negative-specific determiners. Positive-specific determiners include all , every , everybody , everyone , always , all the time , invari- ably , will certainly , will definitely , will absolutely , and the best. Negative-specific determiners include none , not one ,

nobody , no one , never , at no time , will certainly not , will definitely not , will absolutely not , the worst , and impos- sible. When specific determiners like these are included in an option, that option is usually incorrect. These words make statements absolute, and there are few absolutes in the world.

However, some specific determiners are associ- ated with correct statements. Look for more general terms such as often , perhaps , seldom , generally , may , and usually. Life more often reflects statements that use these kinds of words, rather than the absolute terms presented in the previous paragraph. When you are reading the question, circle the specific determiner so you keep careful track of them. Don’t ignore them when answering the question.

The second problem area deals with negative terms. It is more difficult to interpret statements that contain negatives than it is to interpret statements without negatives. Here’s an example of a double-negative state- ment: “Donald works well with patients. Therefore it is not untrue to say that he may be a good pharmacy technician.” Cross out the not and the un- and reread the statement. It means the same thing but is easier to understand. Negatives include words such as no , not , none , and never , and prefixes such as il -, un -, and im -. Negative prefixes are particularly difficult because they are easily overlooked when reading a statement. Under- line negatives in the question so you do not overlook them when answering the question.

Another common trouble area in objective tests is “all or none of the above” questions. One way to confirm the choice of “all of the above” is to find two correct answers among the options. For example, if you are confident that two of the four options are correct, then choosing “all of the above” is a pretty safe bet. Similarly, if you find one that is definitely incorrect, the “all of the above” must be ruled out.

The last type of question that is usually problem- atic for test takers is the best choice option. The options presented may not contain the correct answer, but possibilities from which you choose the best option. Another way of thinking of it is to consider the correct option as the least problematic. Select your answer by a process of elimination.

Pharmacy Technician Certification Review and Practice Exam

however, test anxiety is so severe that it prevents them from performing at their best. If you experience severe anxiety, you may benefit from personal counseling.

CONCLUSION

Now that the exam is over, you deserve a reward. Be kind to yourself. However, do spend a few minutes to review what worked for you and what didn’t. Think about your preparation. Did you allow yourself enough time? Did you understand what was important to study and learn and what were minor details? How about the test itself? Did you glance over the test, run through it several times, and save time for review and checking your answers? One of the most important lessons in life is to learn from your experiences, so evaluate your performance and learn how you can make it better. You may register and take this examination again if you need to. Most likely, there will be other exams in your life.

This chapter presented an overview of objective tests, basic study skills, and test-taking strategies. It also presented some simple techniques for relaxation to refresh you. But remember, no matter how effective the strategies, there is no substitute for thorough prep- aration. Begin your preparation early, be organized, use small increments of time, break your studying down into small tasks, and relax.

References

1. Schommer JC. Time management techniques for phar- macists. Available at: www.InetCE.com. Accessed November 1, 2018.
2. Hill KT. Interfering effects of test anxiety on test per- formance: a growing educational problem and solutions to it. Ill Sch Res Dev. 1983;20:8–19.

CHAPTER

PHARMACY

CALCULATIONS

REVIEW

Learning Outcomes

After completing this chapter, you will be able to

■ Explain why it is important to follow a standardized approach when using math in pharmacy.

■ Convert between fractions, decimals, and percentages.

■ Convert between different systems of measurement.

■ Perform and check key pharmacy calculations, including the calcula- tions needed to interpret prescrip- tions and those involving patient- specific information.

This chapter reviews the fundamentals of calcula- tions and how those calculations are applied in phar- macy. For additional review and practice problems, see Chapter 12, Pharmacy Calculations, in Manual for ffhar- macy Technicians , 5th Edition.

KINDS OF NUMBERS

Arabic numbers is the system of notation that is preferred in pharmacy practice. This is the system we are most familiar with, consisting of the numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. From these numbers, fractions and decimal numbers are written.

Roman numerals consist of a numbering system using letters to represent numbers. Roman numerals are used to designate numbers and are often used in prescription writing to designate quantities to be dis- pensed or the number of a unit of medication the patient is to take. Roman numerals are used in prescrip- tion writing because they are more difficult to alter in the case of controlled substances. The following rules apply to the Roman numbering system:  When a Roman numeral of equal or lesser value is placed after one of equal or greater value, the value of the numerals is added.  A numeral cannot be repeated more than three times.

Converting Mixed Numbers to

Decimal Numbers

The process of converting mixed numbers to decimal numbers involves the following two steps:

1. Write the mixed number as a fraction.

Method: Multiply the whole number and the denominator of the fraction. Add the product (result) to the numerator of the fraction, keeping the same denominator.

Example: 2 3/4 = [(2 × 4) + 3]/ = 2 times 4 plus 3 over 4 = 11/

2. Divide the numerator by the denominator.

Example: 11/4 = 11 divided by 4 = 2. An alternate method involves the following three steps:

1. Separate the whole number and the fraction.

Example: 2 3/4 = 2 and 3/

2. Convert the fraction to its decimal counterpart.

Example: 3/4 = 3 divided by 4 = 0.

3. Add the whole number to the decimal fraction.

Example: 2 plus 0.75 = 2.

Converting Decimal Numbers to

Mixed Numbers or Fractions

The process of converting decimal numbers to mixed numbers involves the following two steps:

1. Write the decimal number over 1, dividing it by 1. (Remember that dividing any number by 1 does not change the number.)

Example: 3.5 = 3.5/

2. Move the decimal point in both the numerator and denominator an equal number of places to the right. The number of places the decimal point needs to be moved is determined by the number of digits fol- lowing the decimal point in the numerator.

CH 2 PHARMACY CALCULATIONS REVIEW

Example: Because there is only one digit fol- lowing the decimal point in 3.5, move the decimal point one place to the right in both the numerator and the denominator: 3.5/1 = 35/10. The number will remain the same as long as the same steps are taken with the numerator and the denominator. Remember that the decimal point of a whole number always follows the last digit.

3. Simplify the fraction.

Example: 35/10 = 7/2 = 3 1/ Medication errors can occur when decimals are used incorrectly or misinterpreted. Sloppy handwriting, stray pen marks, and poor quality faxed copies can lead to misinterpretation. Decimal point errors can lead to medication underdoses or overdoses.

Hundreds, tens, ones, tenths, hundredths, thousandths FIGURE 2–1. Numbers to the left of the decimal point represent whole numbers, and numbers to the right of the decimal point represent quantities less than 1.

Rules Governing Use of Decimals

1. Decimals should only be used when absolutely necessary. For example, five milligrams should be written as 5 mg, not 5.0 mg; the decimal point and trailing zero are not necessary. Use of a trailing zero in this example could be misinterpreted as 50 mg.
2. Only zeros serving as place holders should be included after the decimal. For example, if you wish to write seven and five hundredths, it should be written as 7.05 with no zeros following the last significant digit (in this case, the 5).
3. A decimal point should not appear without a number before it. If you wish to write one-half mil- ligram, it should be written as 0.5 mg, not .5 mg. This is referred to as proper use of a leading zero. Failure to use a leading zero in this example could lead someone to mistakenly read the number as 5 mg rather than 0.5 mg.

Pharmacy Technician Certification Review and Practice Exam

Percentages ffercentage (%) means “by the hundred” or “in a hundred.” Percents are just fractions, but fractions with a set denominator. The denominator is always one hundred (100). Example: “50%” means “50 in a hundred” or “50/100” or “1/2”

Converting Percentages to Fractions To convert a percentage to a fraction, one would write the number preceding the percent sign over 100 and simplify the resulting fraction. Example: 25% = 25/100 = 1/

Converting Fractions to Percentages

Percentage means “by the hundred” or “in a hundred.” Percents are fractions with a denominator of 100. To convert a fraction to a percentage, one must take the following steps to convert the fraction to one in which the denominator is a hundred. This is easiest when the fraction is in the form of a decimal.

1. Write the fraction in its decimal form.

Example: 3/4 = 3 divided by 4 = 0.

2. Write the decimal over 1.

Example: 0.75/

3. To obtain 100 as the denominator, move the decimal point two places to the right. To avoid changing the value, move the decimal point two places to the right in the numerator as well.

Example: 0.75/1 = 75/

4. Because we already know that “out of a hundred” or “divided by a hundred” is the same as percent, we can write 75/100 as 75%. Concentration Expressed as a

 ffercent volume-in-volume (v/v) is the milliliters of drug in 100 mL of the product. These concentration percentages will be discussed in detail a little later in this chapter.

Ratio and Proportion

A ratio shows the relationship between two items. For example, when calculating a dose, a ratio can be used to show the number of milligrams in the dose required per one kilogram of patient weight, which is written as mg/kg and read as “milligrams per kilogram.” Two ratios with the same units can be combined to create a proportion , or a statement of equality between two ratios.

Example: Ratio: Diphenhydramine 12.5 mg/5 mL means there are 12.5 mg of diphenhydramine in every 5 mL of cough syrup. If we wanted to determine how many mg of diphenhydramine were in 10 mL of cough syrup, we could set up a proportion.

5 g of dextrose in 100 mL of water (this solution is often abbreviated “D5W”). Therefore: 5 g of dextrose in 100 mL of a D5W solu- tion equals 50 g of dextrose in 1,000 mL of a D5W solution;

or

5 g/100 mL = 50 g/1,000 mL If three of the variables of a proportion are known, one can easily solve for the fourth variable. For example, if the standard dose of a medication is 4 mg per kg of patient weight, and the patient weighs 70 kg, we can set up a proportion to determine how many mg of the drug are needed for this patient:

Example: 4 mg (^)  x mg

Percentage  ffercent weight-in-weight (w/w) is the grams of a drug in 100 grams of the product.  ffercent weight-in-volume (w/v) is the grams of a drug in 100 milliliters (mL) of the product.

1 kg 70 kg “ x ” represents the unknown value (in this case, the number of mg of the drug) that you will find when you solve this problem.

Pharmacy Technician Certification Review and Practice Exam

1. Determine the known and unknown ratios.

Known: 1 mL/250 mg Unknown: X mL/500 mg

2. Write the proportion: X mL/500 mg = 1 mL/250 mg
3. Cross multiply: X mL × 250 mg = 1 mL × 500 mg
4. Divide: X mL = 1 mL × 500 mg/250 mg
5. Simplify: X mL = 2 mL Answer: Draw up 2 mL in the syringe to prepare a 500-mg dose of chloramphenicol.

UNITS OF MEASURE

Metric System The metric system is based on the decimal system, in which everything is measured in multiples or fractions of 10.

Standard Measures

The standard measure for length is the meter. The standard measure for weight is the gram. The standard measure for volume is the liter.

Prefixes The prefixes below are used to describe multiples or fractions of the standard measures for length, weight, and volume.

Latin Prefixes

Latin prefixes denote fractions.

micro- (mc): 1/1,000,000 = 0. milli- (m): 1/1,000 = 0. centi- (c): 1/100 = 0. deci- (d): 1/10 = 0.

Greek Prefixes

Greek prefixes denote multiples.

deca- (da): 10

hecto- (h): 100

kilo- (k): 1,

mega- (M): 1,000,

Prefixes with Standard Measures

Length

The standard measure is the meter (m). 1 kilometer (km) = 1,000 meters (m) 0.001 kilometer (km) = 1 meter (m) 1 millimeter (mm) = 0.001 meter (m) 1,000 millimeters (mm) = 1 meter (m) 1 centimeter (cm) = 0.01 meter (m) 100 centimeters (cm) = 1 meter (m)

Volume

The standard measure is the liter (L). 1 milliliter (mL) = 0.001 liter (L) 1,000 milliliters (mL) = 1 liter (L) 1 microliter (mcL) = 0.000001 liter (L) 1,000,000 microliters (mcL) = 1 liter (L) 1 deciliter (dL) = 0.1 liter (L) 10 deciliters (dL) = 1 liter (L)

Weight

The standard measure is the gram (g). 1 kilogram (kg) = 1,000 grams (g) 0.001 kilogram (kg) = 1 gram (g) 1 milligram (mg) = 0.001 gram (g) 1,000 milligrams (mg) = 1 gram (g) 1 microgram (mcg) = 0.000001 gram (g) 1,000,000 micrograms (mcg) = 1 gram (g) Oral solid medications are usually expressed in mg or g. Liquid medications are usually expressed in mL or L. When filling medication orders, it is critically impor- tant that the technician pays careful attention to the units to prevent medication errors and potential patient harm. If a dose or volume is not available commercially,

1 000 mg

How many milligrams are in a 1 ¼ -grain low-dose aspirin?

the correct amount must be compounded or measured. Doing so may require converting between units of the metric system.

Each move of the decimal to the left or to the right represents an increase or decrease. As long as you know the order of prefixes, and the magnitude represented, you can easily convert from one unit to another.

Another way to convert between units would be to multiply the units by their corresponding conversion factor. A conversion factor is a fraction that represents the number of parts present in each unit. For example, 1 gram = 1000 milligrams. Therefore, this conversion g factor can be represented as (^) 1,000 mg. This conversion

factor can be used to convert milligrams into grams.

Example: Convert 65 milligrams (mg) to grams (g).

65 mg 

1 g  0.065 g

Note: The milligram units will cancel out, leaving grams in the final answer.

APOTHECARY SYSTEM

The apothecary system was originally developed in Greece for use by physicians and pharmacists. This system has historical significance for the profession of pharmacy, but the metric system is replacing it. The Joint Commission (TJC) recommends that healthcare providers avoid using apothecary units because they are largely unfamiliar and often confused with metric units. There has been a decrease in the use of the apoth- ecary system in hospitals, but apothecary units are still used in community pharmacy.

The most common apothecary measure appearing today is the grain. One grain may represent 65 milli- grams (a 5-grain aspirin tablet is equal to 325 mg) or one grain may represent 60 milligrams (a 1-grain thy- roid tablet is the same as 60 mg of thyroid).

CH 2 PHARMACY CALCULATIONS REVIEW

Avoirdupois System

The avoirdupois system is a French system of mass that includes ounces and pounds. In the United States, this is the system of mass commonly utilized, in which 1 pound equals 16 ounces. Assume this conversion when performing pharmacy calculations unless otherwise stated.

Household System

The household system is the most commonly used system of measuring liquids in outpatient settings. Prescribers frequently refer to teaspoons or tablespoons when writing prescriptions. The term drop is used commonly; however, cau- tion should be used when working with this measure, especially with potent medications. The volume of a drop depends not only on the nature of the liquid but also on the size, shape, and position of the dropper. To accurately measure small amounts of liquid, use a 1-mL syringe (with milliliter markings) instead of a dropper. Eye drops are an exception to this rule; they are pack- aged in a manner to deliver a correctly sized droplet.

Equivalencies between Systems

The systems that have been described lack a close relationship among their units. For this reason, the preferred system of measuring is the metric system. The tables of weights and measures below give the approxi- mate equivalencies used in practice ( Table 2-1 ).

Using the proportion method, you can convert from household to metric units.

Time Conversion

It is also important to know how to convert between the 12-hour and 24-hour clock because many institu- tions refer to medication administration by the 24-hour clock. The 24-hour clock, also known as military time, does not include am or pm to designate hours of the day. Instead, the hours represent the number of hours and minutes since midnight and range from 0–23. It is reported without a colon separating hours and minutes (example: 2130 = 9:30 pm).

Example: Convert 4:15 pm to the 24 hour clock. 12 + 4 = 16 hours in the 24 hour clock Note: 4 PM is 4 hours past 12 noon 4:15 pm = 1615 in the 24 hour clock

PATIENT-SPECIFIC

CALCULATIONS

As science progresses, we are learning more about medi- cations and how they work in the body. Researchers are also discovering how medications target specific sites and how their safety or efficacy may differ from one patient to the next. Some medications may be adminis- tered at a common dose across all patient types, while doses of other medications must be calculated based on factors specific to the individual patient to be safe and effective. Three examples of patient-specific calcula- tions that may influence drug dosing include:

1. Body surface area
2. Ideal body weight
3. Body mass index

Although some of the calculations may be confusing or cumbersome, such as body surface area, nomograms — graphical representation of the key variables in the calculation—are available to use and provide a quick and easy way to determine the result.

Determining Body Surface Area

The square meter surface area (body surface area) is a measurement that is used instead of kilograms to estimate the amount of medication a patient should receive. Body surface area (BSA) takes into account the

CH 2 PHARMACY CALCULATIONS REVIEW

patient’s weight and height. BSA is always expressed in meters squared (m^2 ) and is frequently used to dose chemotherapy agents. The following equation is used to determine BSA. When using the equation below, units of weight (W) should be kilograms (kg), and height (H) should be cen- timeters. For example, a man weighing 150 lbs (68.2 kg) and standing 5′ 10 ″ (177.8 cm) tall has a BSA of 1.8 m^2.

BSA values are frequently used to calculate doses of chemotherapeutic agents. There are several similar equations that are used, such as the Mosteller formula , which is:

BSA (m^2 ) =

Ideal Body Weight

Ideal body weight (IBW) is an estimate of how much a patient should weigh based on his or her height and gender. IBW is expressed as kg.

DOSAGE CALCULATIONS

Basic Principle

The technician should always look for what is being asked:  Number of doses  Total amount of drug  Size of a dose Given any two of the above, the technician can solve for the third. Number of doses, total amount of drug, and size of dose are related in the following way: Number of doses = Total amount of drug/Size of dose

This proportion can also be rearranged as follows: Total amount of drug = (number of doses) × (size of dose) or

[ height ( cm ) × weight ( kg )] 3,

Pharmacy Technician Certification Review and Practice Exam

Size of dose = Total amount of drug/Number of doses Dosage calculations can be based on weight, BSA, or age.

Calculating Dose Based on Weight Certain medications require patient-specific dosing. Depending on the medication, BSA or weight-based dosing may be employed. For example, pediatric dosing is frequently determined by the weight of the child. If diphenhydramine syrup is dosed 5 mg/kg per day, and the child weighs 43 lbs, how many mg should the child receive in one day?

1. Convert all necessary values to the appropriate units. 2.2 lb (^)  43 lb 1 kg x kg

x kg =

(^43) lb × 1 kg = 19.5 kg 2.2 lb

2. Set up a proportion with the available information, and solve for x. 5 mg 

x mg 1 kg 19.5 kg x mg = 5 mg × 19.5 = 97.5 mg Dose (in mg) = [dose per unit of weight (in mg/kg)] × [weight of patient (in kg)]

Dose/day (in mg/day) = [dose/kg per day (in mg/kg per day)] × [weight of patient (in kg)] To find the size of each dose— The technician should divide the total dose per day by the number of doses per day, as illustrated in the following formula: Size of Dose = Total amount of drug/Number of doses

Calculating Dose Based on BSA BSA is expressed as meters squared (m^2 ). To calculate the amount of a dose on the basis of BSA: The techni- cian should simply multiply the BSA in m^2 times the dose per m^2 as provided in the order or other labeling.

Day’s Supply Part of the dispensing process is to ensure that a patient receives a sufficient quantity of the medication to last for the desired duration. To determine the day’s supply , evaluate the dosing regimen to determine how much medication per dose, then how many times the dose is given each day, and then for how many days the medi- cation will be given.

Example:

Metoprolol 50 mg po twice daily for 30 days (25 mg tablets available)  The dose is 50 mg, which will require 2 of the 25-mg tablets. The dose is given twice daily, which will require 2 tablets × 2 = 4 tablets per day.  The medication regimen will last 30 days, so 4 tab- lets per day × 30 days = 120 tablets.

Calculating the quantity needed of an oral medication is fairly straightforward, but calculating topical prod- ucts may be a bit more challenging. For eye drops, the drops per mL may vary, depending on the viscosity of the drops.

Example:

Betaxolol ophthalmic solution 2 drops in each eye twice daily for 10 days (5-mL dropper bottle available; assume 1 mL = 20 drops for this ophthalmic solution, which is a common estimate for many ophthalmic solutions).

1. The patient will take 4 drops twice daily for a total of 8 drops per day.
2. The patient will use 8 drops per day for 10 days for a total of 80 drops.
3. Set up a proportion to determine mL needed per day.

8 drops per day = 20 drops

x mL per day = 1 mL

20 × x mL = 8 × 1 mL x = 0.4 mL per day The patient is taking the medication for 10 days so 0.4 mL × 10 days = 4 mL total volume needed to fill the prescription.