20 free NAPLEX practice questions

Correct answer: B · 100 mL of the 50% injection

The final solution must contain 10 g of dextrose in every 100 mL, so 500 mL holds 50 g. The 50% injection supplies 50 g in every 100 mL, or 0.5 g per mL, so 50 g ÷ 0.5 g/mL = 100 mL. The same answer comes from C1V1 = C2V2: 50% × V1 = 10% × 500 mL, so V1 = 100 mL, and water brings the volume to 500 mL. Using 50 mL would give only 25 g, a 5% solution. Using 250 mL would give 125 g, a 25% solution. Using 400 mL swaps the two volumes and would give 200 g, a 40% solution.

Look for this next time: For a dilution, find the grams of solute the final product needs, then divide by the stock strength (C1V1 = C2V2).

Correct answer: D · 31 drops per minute

Eight hours is 480 minutes, so the solution must run at 1,000 mL ÷ 480 min, about 2.08 mL per minute. Each milliliter is 15 drops with this set, so 2.08 × 15 is about 31.25, which rounds to 31 drops per minute. The figure 125 is the hourly rate in milliliters (1,000 mL ÷ 8 h), not a drop rate. About 21 drops per minute is what a 10 drops/mL set would need, and about 42 drops per minute is what a 20 drops/mL set would need, so both use the wrong drop factor.

Look for this next time: Drops per minute = volume (mL) × drop factor (drops/mL) ÷ time (minutes).

Correct answer: A · 25 patients

The number needed to treat (NNT) is the reciprocal of the absolute risk reduction, the difference between the event rates in the two groups. Here the absolute risk reduction is 10% − 6% = 4%, or 0.04, so the NNT is 1 ÷ 0.04 = 25 patients treated for 3 years to prevent one stroke. The answer 4 treats the 4-percentage-point difference itself as the NNT. The answer 40 comes from the relative risk reduction (4 ÷ 10 = 40%), a different measure. The answer 17 is 1 ÷ 0.06, which uses only the treatment group's event rate.

Look for this next time: NNT = 1 ÷ absolute risk reduction; always state the time frame of the trial with it.

Correct answer: C · 12.5 mg/L

In first-order elimination the concentration falls by half during each half-life, whatever the starting value. Eighteen hours is three half-lives of 6 hours, so 100 mg/L becomes 50 mg/L after 6 hours, 25 mg/L after 12 hours, and 12.5 mg/L after 18 hours, or 100 × (1/2)³. The value 50 mg/L stops after one half-life, and 25 mg/L stops after two. The value 33.3 mg/L divides the starting concentration by the number of half-lives, three, instead of halving it once for each half-life.

Look for this next time: After n half-lives of first-order elimination, the concentration is the starting value × (1/2)ⁿ.

Correct answer: C · Assessing safety and dosage in a small group of people

FDA's overview of clinical research describes Phase 1 as a study of 20 to 100 healthy volunteers or people with the disease or condition, lasting several months, with safety and dosage as its purpose; FDA notes that about 70% of drugs move on to the next phase. Confirming efficacy while monitoring adverse reactions is FDA's description of Phase 3, which enrolls 300 to 3,000 volunteers who have the condition. Tracking safety once a drug is sold is not the job of a first-in-human study. Comparing prices is a pharmacoeconomic question, not the purpose of any phase FDA lists.

Look for this next time: Phase 1 studies a small group for safety and dosage; Phase 3 studies hundreds to thousands for efficacy and adverse reactions.

Correct answer: A · Explain that Schedule II refills are prohibited, so a new prescription is needed

Under 21 CFR 1306.12(a), the refilling of a prescription for a Schedule II controlled substance is prohibited, so the patient needs a new, valid prescription. A phone call from the prescriber's office does not turn a refill into something the regulation allows, and no 30-day window or five-refill allowance applies to Schedule II. The same section, in paragraph (b), lets a prescriber issue multiple Schedule II prescriptions that together cover up to a 90-day supply when stated conditions and state law allow it, but those are separate prescriptions written by the prescriber, not refills authorized at the pharmacy.

Look for this next time: Federal law prohibits refills of Schedule II prescriptions; each fill needs its own prescription (21 CFR 1306.12).

Correct answer: D · When FDA has approved it as interchangeable, subject to state law

FDA explains that an interchangeable biosimilar may be substituted for the reference product at a pharmacy without the intervention of the prescriber, and that, depending on state laws, a biosimilar that is not interchangeable typically has to be prescribed by name. Substitution therefore depends on the product's interchangeable status and on the state's pharmacy law. A shared core name does not establish interchangeability, and not every biosimilar carries that designation. A patient's earlier use of a biosimilar is not the condition FDA describes for substitution at the pharmacy.

Look for this next time: Only an FDA-approved interchangeable biosimilar can be substituted at the pharmacy without the prescriber, and state law still applies.

Correct answer: B · Give the patient the current Tdap VIS before this dose

CDC's instructions say that all health care providers in the United States who administer a covered vaccine must provide the VIS prior to administration of each dose, to the adult receiving it or to a child's parent or legal representative. Tdap is covered, because the list includes diphtheria, tetanus, and pertussis vaccines. The provider also records the VIS edition date and the date it was given in the patient's permanent medical record. Handing it over after the injection misses the timing, an earlier Tdap dose does not remove the requirement, and sending it to another clinician does not reach the person being vaccinated.

Look for this next time: Give the current VIS before every dose of a covered vaccine, and record its edition date and the date provided.

Correct answer: A · Mix the uncrushed tablets with coffee grounds or cat litter, seal it in a bag, and trash it

When take-back or mail-back is not readily available and the labeling gives no special instructions, FDA's steps are to remove the drugs from their original container, mix them with an unappealing substance such as dirt, cat litter, or used coffee grounds without crushing tablets or capsules, seal the mixture in a container such as a plastic bag, and put it in the household trash. FDA also says to scratch out personal information on the empty label. Crushing and rinsing down the sink is not among those steps, leaving tablets in a labeled bottle skips the mixing and the privacy step, and flushing is limited to medicines whose instructions call for it.

Look for this next time: Without take-back, FDA's trash method is: uncrushed drug plus an unappealing substance, sealed, in the trash, with the label scratched out.

Correct answer: D · Stop lisinopril and wait 36 hours before the first sacubitril/valsartan dose

The sacubitril/valsartan labeling contraindicates concomitant use with an ACE inhibitor and says not to administer it within 36 hours of switching from or to an ACE inhibitor. When switching from an ACE inhibitor, it calls for a washout period of 36 hours between the two drugs. Overlapping them for a week or keeping them together long term is the concomitant use the labeling contraindicates. Starting right after the last lisinopril dose skips the 36-hour washout. The same 36-hour rule applies in the other direction if a patient is switched back to an ACE inhibitor.

Look for this next time: Allow a 36-hour washout between an ACE inhibitor and sacubitril/valsartan in either direction; never give them together.

Correct answer: C · Call the prescriber: the pair is contraindicated, so pause simvastatin or change the antibiotic

The simvastatin labeling contraindicates concomitant use with strong CYP3A4 inhibitors and names select macrolide antibiotics, erythromycin and clarithromycin, among its examples. It adds that if treatment with a strong CYP3A4 inhibitor is unavoidable, simvastatin should be suspended during that course. The pharmacist therefore contacts the prescriber to suspend simvastatin for the course or to choose an antibiotic without this interaction. A short course is still concomitant use. Spacing the doses is not an option the labeling offers, and waiting for muscle symptoms after the course does not address a contraindicated combination.

Look for this next time: Simvastatin is contraindicated with strong CYP3A4 inhibitors such as clarithromycin; suspend it during an unavoidable course.

Correct answer: B · At least 4 hours after ingestion; earlier values can mislead

The Acetadote labeling says to obtain a plasma or serum acetaminophen concentration at least 4 hours after ingestion, because concentrations drawn earlier may be misleading: they may not represent the maximum concentration. When the time of an acute ingestion is known and the patient presents within 8 hours, the labeling uses the revised Rumack-Matthew nomogram with that concentration to decide whether to start treatment. A 2-hour value is the early level the labeling warns about, waiting 24 hours for enzymes delays the decision the nomogram is meant to support, and the nomogram plots a measured concentration against time, not the amount swallowed.

Look for this next time: For a single acute acetaminophen ingestion at a known time, draw the level for the nomogram at least 4 hours after ingestion.

Correct answer: A · Tendinitis and tendon rupture, which can occur on both sides

Levofloxacin carries a boxed warning for serious adverse reactions that include tendinitis and tendon rupture. Its warnings section says the risk of fluoroquinolone-associated tendinitis and tendon rupture is increased in patients over 60 years of age, in those taking corticosteroid drugs, and in patients with kidney, heart, or lung transplants, and that tendon rupture can occur bilaterally. She has two of those risk factors, so the pharmacist raises the risk with the prescriber and makes sure she knows the warning. Hearing loss, infusion flushing, and gum overgrowth are not the reactions the labeling links to age and corticosteroid use.

Look for this next time: Fluoroquinolone tendon rupture risk rises after age 60, with corticosteroids, and after kidney, heart, or lung transplant.

Correct answer: D · Into the outer front part of the thigh, through clothing if needed

The EpiPen labeling says to inject intramuscularly or subcutaneously into the anterolateral aspect of the thigh, through clothing if necessary, and not to inject intravenously or into the buttocks, digits, hands, or feet. It explains that an injection into the buttock may not provide effective treatment of anaphylaxis, and it tells caregivers of young children who may kick or move to hold the leg firmly during the injection. The labeling also says to seek immediate medical or hospital care along with using the device. A vein, the buttock, and the hand or finger are all sites the labeling rules out.

Look for this next time: Give an epinephrine auto-injector into the anterolateral thigh, through clothing if needed, then seek emergency care.

Correct answer: B · Do not use it until 2 weeks have passed since he stopped the MAOI

Pseudoephedrine Drug Facts say not to use the product if you are now taking a prescription monoamine oxidase inhibitor (MAOI) or for 2 weeks after stopping the MAOI drug, and to ask a doctor or pharmacist if you are not sure whether a prescription drug contains an MAOI. Five days after stopping phenelzine is still inside that 2-week window, so he should not use it now and can ask about other options. Having stopped the MAOI does not end the warning early, and neither a smaller amount nor bedtime use is an exception the label allows.

Look for this next time: Pseudoephedrine products: do not use with an MAOI or within 2 weeks after stopping one (Drug Facts).

Correct answer: C · MMR, even though she is not immune to rubella

CDC's guidelines say MMR vaccine is contraindicated during pregnancy, so her rubella protection has to wait until she is no longer pregnant. The same guidelines call for a dose of Tdap during each pregnancy, with an optimal window between 27 and 36 weeks of gestation, so 28 weeks fits. Women who are or will be pregnant during influenza season should receive inactivated influenza vaccine. Pregnancy is not a contraindication to hepatitis B vaccine, and CDC says pregnant women who have not been vaccinated should receive it, since vaccination is recommended for all adults aged 19 to 59.

Look for this next time: In pregnancy, MMR and varicella are contraindicated, while Tdap (each pregnancy) and inactivated influenza vaccine are recommended.

Correct answer: A · Keep vitamin K intake consistent, avoid drastic diet changes, and tell her care team

The warfarin labeling tells patients to eat a normal, balanced diet with a consistent intake of vitamin K and to avoid drastic changes in dietary habits, such as eating large amounts of leafy green vegetables. It also lists increased vitamin K intake among the factors that can decrease the INR response, so a sudden daily salad could lower her INR rather than raise it. Her care team needs to know about the change so monitoring can follow it. Saying greens have no effect contradicts the labeling, and skipping doses on salad days is not a strategy the labeling supports.

Look for this next time: On warfarin, keep vitamin K intake consistent; a sudden increase can lower the INR response.

Correct answer: D · Duplicate acetaminophen from two products, a liver injury risk

Both products contain acetaminophen, which is a therapeutic duplication. The boxed warning in hydrocodone/acetaminophen labeling says acetaminophen has been associated with acute liver failure, and that most cases of liver injury are associated with doses that exceed 4,000 milligrams per day and often involve more than one acetaminophen-containing product. The pharmacist explains the overlap and helps the patient avoid taking both. The over-the-counter product contains no opioid, so there is no opioid duplication. Nothing in the case suggests an opioid allergy or a grapefruit juice problem.

Look for this next time: Check every product a patient takes for acetaminophen; duplicate products are a common route to liver injury.

Correct answer: C · VAERS, the system that CDC and FDA run together for vaccines

VAERS, the Vaccine Adverse Event Reporting System, is a national early warning system for possible safety problems with US-licensed vaccines, run jointly by CDC and FDA. It accepts reports of adverse events after vaccination; anyone can report, and health care professionals are required to report certain events. FDA's MedWatch page sends vaccine reports to VAERS, because vaccines use a different reporting pathway. A state board complaint is not the federal vaccine safety system, and DEA reporting concerns controlled substances, not reactions to a vaccine.

Look for this next time: Report adverse events after vaccination to VAERS; MedWatch covers other human medical products.

Correct answer: B · Class I, used when serious adverse health consequences or death are reasonably probable

21 CFR 7.3(m) defines three recall classes. Class I is a situation in which there is a reasonable probability that use of, or exposure to, a violative product will cause serious adverse health consequences or death, which matches this notice. Class II covers products that may cause temporary or medically reversible adverse health consequences, or where the probability of serious consequences is remote. Class III covers products not likely to cause adverse health consequences. The regulation defines no Class IV. The pharmacy then follows the recall notice's instructions for the affected lot.

Look for this next time: Class I recall: reasonable probability of serious harm or death; Class II: temporary or reversible harm; Class III: harm unlikely.