NAPLEX Practice Questions

The Relative Risk Reduction (RRR) quantifies the percentage by which the risk of an outcome is reduced in the intervention group compared to the control group.

1. Calculate the event rate (risk) in each group:

Risk in Rivaroxaban group (intervention): 17 / 1513 ≈ 0.0112 (1.12%)

Risk in Enoxaparin group (control): 57 / 1473 ≈ 0.0387 (3.87%)

2. Calculate the Relative Risk (RR):

RR = (Risk in intervention group) / (Risk in control group) = 0.0112 / 0.0387 ≈ 0.29

3. Calculate the Relative Risk Reduction (RRR):

RRR = 1 - RR = 1 - 0.29 = 0.71

As a percentage, RRR is 71%.

A. 39%: This is an incorrect calculation, potentially resulting from misapplication of the risk values in the formula.

C. 29%: This value represents the Relative Risk (RR), which is the ratio of the risks, not the reduction in risk.

D. 14%: This is an incorrect calculation and does not correspond to a standard biostatistical measure in this context.

E. 42%: This is an incorrect calculation, possibly confusing RRR with another statistical measure like absolute risk reduction.

1. Guyatt

G.

Rennie

D.

Meade

M. O.

& Cook

D. J. (2015). Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice (3rd ed.). McGraw-Hill Education. Chapter 13

"Therapy (Harm)

" section on "Measures of Association

" discusses the calculation of Relative Risk and Relative Risk Reduction.

2. Barratt

A.

Wyer

P. C.

Hatala

R.

McGinn

T.

et al. (2004). Tips for Learners of Evidence-Based Medicine: 1. Relative risk and odds ratios. Canadian Medical Association Journal

171(4)

353–358. https://doi.org/10.1503/cmaj.1021196. (This article defines RRR as 1 - RR on page 354).

3. University of California

San Francisco. (n.d.). Interpreting Proportions and Risk. UCSF School of Medicine

Training in Clinical Research Program Courseware. Retrieved from https://ticr.ucsf.edu/courses/briefcourses/docs/Proportions.pdf (This document provides the formula for RRR = 1 - RR on page 4).

Acute kidney injury (AKI) is categorized into prerenal, intrinsic, and postrenal causes. Postrenal AKI occurs due to an obstruction in the urinary tract downstream from the kidney, which impedes urine flow. This obstruction causes an increase in pressure within the urinary collecting system, leading to kidney damage. Benign prostatic hyperplasia (BPH) is a common cause of bladder outlet obstruction, where the enlarged prostate gland compresses the urethra. This blockage prevents urine from leaving the bladder, resulting in a classic example of postrenal AKI.

B. Heart failure causes prerenal AKI by reducing cardiac output and subsequent blood flow (perfusion) to the kidneys.

C. Dehydration is a cause of prerenal AKI, as volume depletion leads to decreased renal perfusion.

D. Renal vein thrombosis causes intrinsic AKI by inducing venous congestion and ischemic damage directly within the kidney tissue.

1. Saseen

J. J.

& MacLaughlin

E. J. (2020). Acute Kidney Injury. In J. T. DiPiro

G. C. Yee

L. M. Posey

S. T. Haines

T. D. Nolin

& V. Ellingrod (Eds.)

Pharmacotherapy: A Pathophysiologic Approach (11th ed.). McGraw-Hill. Chapter 42

Table 42-2 "Common Causes of Acute Kidney Injury

" classifies benign prostatic hyperplasia under "Postrenal AKI" and heart failure/dehydration under "Prerenal AKI."

2. Lameire

N.

Van Biesen

W.

& Vanholder

R. (2005). Acute renal failure. The Lancet

365(9457)

417–430. https://doi.org/10.1016/S0140-6736(05)17831-3. In Table 1

"Etiology of acute renal failure

" prostatic hypertrophy is listed as a cause of postrenal failure.

3. Levey

A. S.

& James

M. T. (2017). Acute Kidney Injury. Annals of Internal Medicine

167(9)

ITC66–ITC80. https://doi.org/10.7326/AITC201711070. The section "Etiology and Pathophysiology" states that postrenal AKI is caused by acute obstruction of the urinary tract

with prostatic disease being a common cause.

The patient has a confirmed methicillin-sensitive Staphylococcus aureus (MSSA) infection. The first-line treatment for serious MSSA infections is an anti-staphylococcal penicillin (e.g., oxacillin) or a first-generation cephalosporin (e.g., cefazolin). Given the patient's non-severe penicillin allergy (rash) and documented prior tolerance of a cephalosporin, the risk of cross-reactivity is extremely low. Cefazolin is the most appropriate choice as it provides targeted, narrow-spectrum bactericidal therapy, adhering to principles of antimicrobial stewardship by de-escalating from broad-spectrum vancomycin.

A. Oxacillin: This is an anti-staphylococcal penicillin and would be a first-line choice, but it is inappropriate due to the patient's documented penicillin allergy.

B. Doxycycline: This agent is generally bacteriostatic and not preferred for treating severe, deep-seated bactericidal infections like pyomyositis when more effective options are available.

C. Ceftaroline: This is a fifth-generation cephalosporin with MRSA activity. Its use for a confirmed MSSA infection is unnecessarily broad-spectrum and poor antimicrobial stewardship.

D. Daptomycin: This agent is also unnecessarily broad for MSSA. It is typically reserved for MRSA or cases of severe, anaphylactic beta-lactam allergies.

1. Liu

C.

Bayer

A.

Cosgrove

S. E.

et al. (2011). Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clinical Infectious Diseases

52(3)

e18–e55. Section: "What is the preferred therapy for invasive MSSA infections?"

Recommendation 1. The guideline states

"For patients with invasive MSSA infections

a β-lactam antibiotic is the agent of choice... Cefazolin is an alternative for patients with a history of a mild

non-IgE-mediated reaction to penicillin." https://doi.org/10.1093/cid/ciq146

2. DiPiro

J. T.

Yee

G. C.

Posey

L. M.

Haines

S. T.

Nolin

T. D.

& Ellingrod

V. (2020). Pharmacotherapy: A Pathophysiologic Approach (11th ed.). McGraw-Hill Education. Chapter 93

"Bone and Joint Infections." This chapter identifies nafcillin

oxacillin

or cefazolin as the drugs of choice for MSSA osteomyelitis

a similar deep-seated infection.

3. Picard

M.

Robitaille

G.

Karam

F.

et al. (2019). Cross-reactivity to cephalosporins and carbapenems in penicillin-allergic patients: two systematic reviews and meta-analyses. The Journal of Allergy and Clinical Immunology: In Practice

7(8)

2722–2738.e5. This meta-analysis supports the low risk (<1%) of cross-reactivity between penicillins and first-generation cephalosporins in patients with non-severe penicillin allergies. https://doi.org/10.1016/j.jaip.2019.05.038

Specific gravity is the ratio of the density of a substance to the density of a reference substance, which for liquids is typically water (density ≈ 1 g/mL). Therefore, the density of the serum protein is numerically equal to its specific gravity, i.e., 1.27 g/mL. The weight (mass) of a substance can be calculated by multiplying its volume by its density.

Weight = Volume × Density

Weight = 1000 mL × 1.27 g/mL

Weight = 1270 g

B. 127mg: This represents a significant miscalculation in both magnitude and units; it would be the weight of approximately 0.1 mL.

C. 12.7mg: This is incorrect in both magnitude and units, representing a calculation error of several orders of magnitude.

D. 12.7gm: This is a decimal placement error; it would be the correct weight for a volume of 10 mL, not 1000 mL.

E. 1.27gm: This is also a decimal placement error; it would be the correct weight for a volume of 1 mL.

1. Ansel

H. C.

& Stoklosa

M. J. (2016). Pharmaceutical Calculations (15th ed.). Wolters Kluwer. In Chapter 5

"Density

Specific Gravity

and Specific Volume

" the text explains that the weight of a substance can be found by multiplying its volume by its specific gravity (p. 63

Example Calculation).

2. United States Pharmacopeia and National Formulary (USP 43-NF 38). (2020). General Chapter Specific Gravity. This chapter defines specific gravity and its relationship to density

confirming that for a substance with a specific gravity of X

its density is X g/mL when referenced to water.

3. University of Toledo

College of Pharmacy and Pharmaceutical Sciences. Pharmaceutics I (PHPR 2050) Course Packet. The section on "Pharmaceutical Calculations" covers the relationship between weight

volume

and specific gravity

defining the formula: Weight (g) = Volume (mL) × Specific Gravity (p. 12).

Incidence rate, also known as incidence, is a fundamental measure of disease frequency. It quantifies the number of new cases of a health outcome that develop in a population at risk during a specified period. The key components of this definition are the focus on new cases (distinguishing it from prevalence), the specific population at risk in the denominator (excluding those who already have the disease or are immune), and the defined time period over which these new cases are observed. This measure is crucial for understanding the risk of developing a disease and for studying disease etiology.

B. Prevalence rate measures the proportion of a population with a disease (both new and existing cases) at a specific point in time.

C. Mortality rate measures the frequency of death in a defined population during a specified interval.

D. Odds ratio is a measure of association that quantifies the odds of an outcome occurring in an exposed group compared to a non-exposed group.

E. Confidence Interval is a statistical range that estimates the precision of a point estimate, indicating where the true population parameter likely lies.

1. Centers for Disease Control and Prevention (CDC). (2012). Principles of Epidemiology in Public Health Practice

Third Edition. An Introduction to Applied Epidemiology and Biostatistics. Lesson 3: Measures of Risk

Section: Incidence Rate. Retrieved from https://www.cdc.gov/csels/dsepd/ss1978/lesson3/section2.html

2. Gordis

L. (2014). Epidemiology (5th ed.). Elsevier Saunders. Chapter 3: Measuring the Occurrence of Disease: I. Morbidity

pp. 40-43. (This is a standard textbook in epidemiology used in numerous university public health programs).

3. Boston University School of Public Health. (n.d.). Measures of Disease Frequency. PH717 Module 2. Retrieved from https://sphweb.bumc.bu.edu/otlt/mph-modules/ep/ep713diseasefrequency/ep713diseasefrequencyprint.html (This university courseware explicitly defines incidence as "the number of new cases of a disease that develop in a population at risk over a specified time period.")

Divalproex sodium carries a well-documented risk of hepatotoxicity and dose-related thrombocytopenia/other cytopenias. Therefore, authoritative sources direct clinicians to obtain liver function tests (LFTs) and a complete blood count (CBC, including platelets) at baseline and at periodic intervals during therapy. These tests allow early detection of liver injury and hematologic toxicity, the two most clinically significant adverse effects requiring intervention or drug discontinuation.

B. Serum ammonia – checked only if encephalopathy or unexplained lethargy occurs; not recommended for routine periodic monitoring.

D. Pulmonary function – valproate does not impair lungs; no guideline advises routine PFTs.

E. Serum creatinine – nephrotoxicity is not characteristic of valproate; routine renal monitoring not listed in labeling or AHFS.

1. Depakote (divalproex sodium) Prescribing Information

AbbVie Inc.

rev. Aug 2020: Section 5.1 (Hepatotoxicity) & Section 5.9 (Thrombocytopenia) – “Obtain baseline and periodic LFTs and CBC with platelet count.”

2. American Hospital Formulary Service (AHFS) Drug Information 2024

“Valproic Acid and Derivatives

” Monitoring Parameters subsection

pp 3420–3421 – recommends baseline/periodic liver function tests and CBC.

3. Patsalos PN et al. Therapeutic drug monitoring of antiepileptic drugs. Epilepsia. 2008;49(7):1242 (Table 2). DOI:10.1111/j.1528-1167.2008.01561.x – lists routine monitoring of LFTs and hematology for valproate.

Acarbose is classified as an alpha-glucosidase inhibitor. Its mechanism of action involves the competitive and reversible inhibition of pancreatic alpha-amylase and membrane-bound intestinal alpha-glucosidase hydrolase enzymes. These enzymes are essential for the digestion of complex carbohydrates, such as starch and sucrose, into absorbable monosaccharides like glucose. By inhibiting these enzymes, acarbose delays the breakdown and subsequent absorption of carbohydrates from the small intestine, which in turn blunts the postprandial increase in blood glucose levels.

B. Metformin primarily decreases hepatic glucose production and intestinal glucose absorption, while also improving peripheral insulin sensitivity. It does not inhibit carbohydrate breakdown.

C. Dapagliflozin is an SGLT2 inhibitor that works in the kidneys to block glucose reabsorption, thereby increasing urinary glucose excretion.

D. Pioglitazone is a thiazolidinedione that acts as a PPAR-γ agonist to increase insulin sensitivity in adipose tissue, skeletal muscle, and the liver.

E. Sitagliptin is a DPP-4 inhibitor that prevents the breakdown of incretin hormones, leading to increased insulin secretion and suppressed glucagon release.

1. Brunton

L. L.

Hilal-Dandan

R.

& Knollmann

B. C. (Eds.). (2018). Goodman & Gilman's The Pharmacological Basis of Therapeutics (13th ed.). McGraw-Hill Education. Chapter 47: Agents That Affect Blood Glucose

Section: "Alpha-Glucosidase Inhibitors."

2. University of Michigan Medical School. (n.d.). Pharmacology of Drugs for Diabetes Mellitus. Endocrine Pharmacology (Pharm 626) Course Materials. Section on "Alpha-glucosidase inhibitors."

3. Scheen

A. J. (2003). Clinical Pharmacology of Acarbose. Diabetes & Metabolism

29(4 Pt 2)

4S73-4S78. https://doi.org/10.1016/s1262-3636(03)72785-8 (See Abstract and Introduction section for mechanism).

The calculation requires a three-step process. First, convert the patient's weight from pounds (lb) to kilograms (kg) by dividing by the conversion factor of 2.2 lb/kg. Second, calculate the total hourly dose in units by multiplying the patient's weight in kg by the prescribed dose rate. Finally, determine the infusion rate in mL/hr by dividing the total hourly dose (units/hr) by the available concentration (units/mL).

1. Weight in kg: 125 lb / 2.2 lb/kg = 56.82 kg

2. Total dose: 56.82 kg 18 units/kg/hr = 1022.76 units/hr

3. Infusion rate: 1022.76 units/hr / 50 units/mL = 20.455 mL/hr, which rounds to 20.45 mL/hr.

A. 5.15 mls/hr: This result likely stems from a significant miscalculation, possibly involving incorrect conversion factors or misplaced decimals during the calculation steps.

B. 10.23 mls/hr: This is approximately half the correct rate, suggesting a mathematical error such as an unnecessary division by two.

C. 40.9 mls/hr: This is double the correct rate, indicating a potential multiplication error where division was required or an error in the initial weight conversion.

E. 18 mls/hr: This answer incorrectly uses the dose rate (18) as the final infusion rate, failing to account for the patient's weight and the drug concentration.

1. Stoklosa

M. J.

& Ansel

H. C. (2013). Pharmaceutical Calculations (14th ed.). Lippincott Williams & Wilkins. Chapter 11

"Isotonic and Buffer Solutions

" and Chapter 13

"Intravenous Admixtures and Flow Rates

" cover the principles of dilution

concentration

and rate calculations. The methodology for weight-based dosing is a fundamental concept discussed.

2. University of Kentucky College of Pharmacy. (n.d.). Dosage Calculations Review. This resource provides practice problems and foundational principles for pharmaceutical calculations

including weight-based dosing and IV infusion rates. The core steps of converting weight

calculating total dose

and determining the final rate are standard procedures taught. (Available via university pharmacy program websites).

3. University of Washington School of Pharmacy. (2018). Pharmaceutical Calculations Workbook. Section on "Calculations for Intravenous Admixtures

" pp. 45-52. This workbook details the step-by-step process for calculating infusion rates for weight-based medications like heparin

emphasizing the dimensional analysis used in the explanation.

A dichotomous variable, also known as a binary variable, is a type of categorical variable that can have only two possible, mutually exclusive outcomes. In this question, "Sex" (when defined as male/female), "Pain yes/ Pain no," and "alive / dead" all represent variables with exactly two categories. These are fundamental data types used in biostatistics and clinical trials to represent the presence or absence of a condition, a specific outcome, or a demographic characteristic. Variables with more than two ordered categories, such as cancer grade or NYHA class, are classified as ordinal variables, not dichotomous.

D. Grade of Breast Cancer: This is an ordinal variable because it has more than two categories (e.g., Grade 1, 2, 3) that follow a specific order of severity.

E. NYHA I-IV: This is an ordinal variable representing the New York Heart Association functional classification, which has four distinct, ordered levels of heart failure severity.

1. Sullivan

L. M. (2018). Essentials of Biostatistics in Public Health (3rd ed.). Jones & Bartlett Learning. In Chapter 1

"Introduction and Data Presentation

" dichotomous variables are defined as categorical variables with two possible responses. Examples provided are consistent with sex (male/female) and yes/no outcomes.

2. Boston University School of Public Health. (n.d.). Data Presentation. In BS704: Introduction to Biostatistics course materials. Retrieved from https://sphweb.bumc.bu.edu/otlt/mph-modules/bs/bs704summarizingdata/bs704summarizingdataprint.html. Section: "Types of Variables". This resource explicitly lists "Sex (male

female)" and "CVD (yes/no)" as examples of dichotomous variables.

3. Rana

R. K.

& Singhal

R. (2015). Chi-square test and its application in medical research. Journal of Practice of Cardiovascular Sciences

1(1)

69. https://doi.org/10.4103/2395-5414.157577. This article discusses variable types in the context of statistical tests

defining dichotomous variables as those with two categories

such as "male/female" or "smoker/non-smoker."

4. PennState Eberly College of Science. (n.d.). STAT 200: Elementary Statistics - Lesson 1.2: Categorical & Quantitative Variables. Retrieved from https://online.stat.psu.edu/stat200/lesson/1/1.2. This courseware defines a binary (dichotomous) variable as a categorical variable with only two possible outcomes

providing "gender (male

female)" as a primary example.

The patient's clinical presentation of a unilateral, throbbing headache associated with photophobia and nausea is characteristic of a migraine. The question asks for an abortive therapy, which is a medication taken to stop a migraine attack after it has started. Sumatriptan is a serotonin (5-HT1B/1D) receptor agonist (a "triptan") and is a first-line abortive treatment for moderate-to-severe migraine attacks. It works by causing vasoconstriction of cranial arteries and inhibiting the release of vasoactive neuropeptides. The other medications listed are used for migraine prophylaxis (prevention), not for treating an acute attack.

B. Gabapentin: This is an anticonvulsant medication sometimes used off-label for migraine prophylaxis, not for aborting an acute attack.

C. Amitriptyline: This is a tricyclic antidepressant that is established as an effective agent for migraine prophylaxis.

D. Propranolol: This beta-blocker is a first-line, evidence-based medication used for the prophylaxis of episodic migraines.

E. Diltiazem: This calcium channel blocker is not a standard first-line therapy for either abortive or prophylactic treatment of migraine.

1. Marmura

M. J.

Silberstein

S. D.

& Schwedt

T. J. (2015). The acute treatment of migraine in adults: the american headache society evidence assessment of migraine pharmacotherapies. Headache: The Journal of Head and Face Pain

55(1)

3–20. (In Table 2

"Triptans

" including sumatriptan

are listed with a Grade A recommendation as effective for acute migraine treatment). https://doi.org/10.1111/head.12499

2. Silberstein

S. D.

Holland

S.

Lipton

R. B.

& Dodick

D. W. (2012). Evidence-based guideline update: Pharmacologic treatment for episodic migraine prevention in adults: Report of the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. Neurology

78(17)

1337–1345. (In Table 2

propranolol and amitriptyline are listed as having Level A evidence for migraine prevention. Gabapentin is mentioned as having inadequate evidence to support its use). https://doi.org/10.1212/WNL.0b013e3182535d20

3. VanderPluym

J. H.

Halker Singh

R. B.

& Urtecho

M. (2021). Acute Treatments for Episodic Migraine in Adults: A Systematic Review and Meta-analysis. JAMA

325(23)

2357–2369. (This meta-analysis confirms that triptans are highly effective for acute migraine treatment

specifically for pain freedom at 2 hours). https://doi.org/10.1001/jama.2021.7939

4. University of California

San Francisco (UCSF) Headache Center. (n.d.). Medications for Migraine and Headache. UCSF Department of Neurology. (This educational resource clearly distinguishes between "Abortive Medications" like triptans and "Preventive Medications" like beta-blockers

antidepressants

and anti-seizure drugs). Retrieved from https://headache.ucsf.edu/medications-migraine-and-headache (Section: "Abortive Medications" and "Preventive Medications").