1. A patient newly started on darunavir/ritonavir is also taking simvastatin for hyperlipidemia. Two weeks later he develops diffuse muscle pain and dark urine, and creatine kinase is markedly elevated. Integrating the pharmacology of the booster with that of the statin, which sequence best explains this event?
A) Ritonavir induced CYP3A4 (cytochrome P450 3A4), lowering simvastatin levels and paradoxically causing myopathy through statin withdrawal
B) Darunavir displaced simvastatin from albumin, and the freed drug was rapidly cleared, so subtherapeutic statin caused the muscle injury
C) Ritonavir potently inhibited CYP3A4, the enzyme that clears simvastatin, so simvastatin plasma concentrations rose dramatically and produced myopathy progressing to rhabdomyolysis
D) Simvastatin inhibited darunavir metabolism, raising the protease inhibitor to toxic levels that directly lysed muscle
E) The combination caused immune-mediated necrotizing myopathy unrelated to drug concentrations
ANSWER: C
Rationale:
The booster ritonavir is a potent inhibitor of CYP3A4, and simvastatin is heavily dependent on CYP3A4 for elimination. When the two are combined, simvastatin clearance falls and its plasma concentration rises dramatically—on the order of tens-fold—producing dose-dependent myopathy that can progress to rhabdomyolysis with elevated creatine kinase and myoglobinuria. Option C correctly chains booster inhibition to statin accumulation to muscle injury, which is why simvastatin is contraindicated with boosted PIs.
Option A: Option A inverts the mechanism: ritonavir inhibits rather than induces CYP3A4, and statin withdrawal does not cause rhabdomyolysis. Option B is wrong because the injury results from accumulation, not from protein-binding displacement and accelerated clearance.
Option D: Option D reverses the direction of the interaction; the booster raises the statin, not the reverse, and the toxicity is statin-mediated muscle injury. Option E invokes a concentration-independent autoimmune process inconsistent with this acute dose-related presentation.
2. A patient on dolutegravir with previously suppressed virus now has a low-level rebound and a subtherapeutic dolutegravir trough, yet pharmacy refill records and pill counts indicate excellent adherence. On further history she recently began an over-the-counter calcium plus iron supplement taken with her morning medications. Integrating INSTI pharmacology with this history, what is the most likely explanation?
A) Polyvalent cations in the supplement chelated dolutegravir in the gut when taken together, reducing its absorption and lowering trough concentrations despite genuine adherence
B) The supplement induced CYP3A4 (cytochrome P450 3A4), accelerating dolutegravir metabolism
C) Calcium and iron competitively displaced dolutegravir from plasma proteins, increasing its renal clearance
D) The supplement raised gastric pH, ionizing dolutegravir so it could not cross the gut wall
E) Iron supplementation directly mutated the integrase gene, producing resistance
ANSWER: A
Rationale:
This question integrates two module concepts: INSTIs chelate polyvalent cations, and apparent non-adherence can actually be a chelation interaction in a genuinely adherent patient. Calcium and iron taken simultaneously with dolutegravir bind it in the gut, reducing absorption and producing subtherapeutic troughs and possible low-level rebound even with perfect adherence; separation in time (or taking with food for certain agents) prevents this. Option A is correct. Option B is wrong because the cation interaction is gut chelation, not CYP3A4 induction, and dolutegravir is not primarily cleared that way.
Option C: Option C misattributes the effect to protein-binding displacement and increased renal clearance rather than reduced absorption. Option D invokes a pH-ionization mechanism that does not describe the cation chelation interaction. Option E is biologically incorrect; supplements do not mutate viral genes, and the trough is low because of reduced absorption, not resistance.
3. A patient on a cobicistat-boosted single-tablet regimen has a serum creatinine that rose 0.15 mg/dL in the first month and has remained stable since, with no proteinuria, normal electrolytes, and undetectable viral load. A covering clinician proposes switching the entire regimen out of concern for nephrotoxicity. Integrating the booster's pharmacology with sound management, what is the best course of action?
A) Switch immediately to an unboosted regimen because any creatinine rise on cobicistat signals true renal injury
B) Add a loop diuretic to force creatinine clearance and protect the kidney
C) Stop all antiretroviral therapy until renal function fully normalizes
D) Recognize the rise as the expected cobicistat artifact from inhibition of creatinine tubular secretion via the multidrug and toxin extrusion protein 1 (MATE1) transporter, with preserved true glomerular filtration, and continue the effective regimen while monitoring
E) Order a renal biopsy to characterize the cobicistat-induced glomerular lesion
ANSWER: D
Rationale:
This integrates the cobicistat creatinine artifact with the clinical judgment not to disrupt an effective regimen. Cobicistat inhibits MATE1, blocking tubular secretion of creatinine and producing a small, early, stable rise in serum creatinine while true glomerular filtration is preserved; the absence of proteinuria, stable course, and virologic suppression all fit the artifact.
Option D: Option D correctly continues effective therapy with monitoring.
Option A: Option A misreads the artifact as true injury and discards a working regimen.
Option B: Option B is inappropriate because a loop diuretic neither treats nor clarifies this artifact and risks volume depletion.
Option C: Option C needlessly interrupts suppressive therapy, risking rebound and resistance.
Option E: Option E pursues an invasive biopsy for a benign, well-characterized pharmacologic artifact.
4. A treatment team is selecting a regimen for a patient with a history of erratic adherence and concern about future resistance. They are weighing a boosted darunavir-based regimen against other options. Integrating darunavir's resistance pharmacology with this clinical concern, which statement best captures the rationale for considering boosted darunavir here?
A) Darunavir should be avoided in poorly adherent patients because a single missed dose immediately selects high-level resistance
B) Darunavir's exceptionally high genetic barrier—requiring simultaneous accumulation of multiple major protease mutations for failure—makes it relatively forgiving of imperfect adherence with respect to selecting resistance, which is the basis for considering it when adherence is a concern, accepting its interaction and metabolic tradeoffs
C) Darunavir requires no booster, eliminating drug interactions, which is why it suits poorly adherent patients
D) Darunavir is preferred here because it has no metabolic or lipid effects of any kind
E) Darunavir is chosen because it acts on integrase and therefore shares the resistance barrier of dolutegravir
ANSWER: B
Rationale:
This integrates darunavir's high genetic barrier with a real-world adherence decision. Because clinically meaningful darunavir failure requires the simultaneous accumulation of several major protease mutations—each with a fitness cost—the drug is relatively forgiving with respect to selecting resistance, which is why a boosted darunavir regimen is sometimes favored when adherence is uncertain, accepting its CYP3A4 interaction burden and metabolic tradeoffs. Option B is correct.
Option A: Option A inverts the property: a single missed dose does not immediately produce high-level resistance, which is precisely the point. Option C is factually wrong because darunavir is boosted (with ritonavir or cobicistat) and therefore carries interactions.
Option D: Option D overstates its safety; PIs as a class have metabolic and lipid effects, though darunavir's are comparatively modest. Option E misclassifies darunavir as an integrase inhibitor; it is a protease inhibitor.
5. Two patients require rifampin for tuberculosis. Patient 1 is on a ritonavir-boosted protease inhibitor; Patient 2 is on dolutegravir. Integrating how rifampin's enzyme induction interacts with each regimen, which statement correctly describes the appropriate management for both?
A) Rifampin can be continued unchanged in both patients because neither regimen is affected by induction
B) Both regimens must be permanently abandoned because rifampin destroys all antiretroviral activity irreversibly
C) For Patient 1, double the protease inhibitor dose; for Patient 2, no change is needed because dolutegravir is not induced
D) For both patients, add a second booster to overcome induction and continue rifampin
E) For Patient 1, rifampin is contraindicated because potent CYP3A4 (cytochrome P450 3A4) induction collapses boosted protease inhibitor exposure and undermines boosting; for Patient 2, dolutegravir can be continued with rifampin by doubling the dose to 50 mg twice daily to offset induction of its clearance pathways
ANSWER: E
Rationale:
The same inducer leads to opposite management because the two regimens depend on different pharmacology. Rifampin potently induces CYP3A4; in a boosted PI regimen this collapses PI exposure and defeats the boosting strategy, so rifampin is contraindicated. Dolutegravir is cleared by UGT1A1 (uridine diphosphate glucuronosyltransferase 1A1) and CYP3A4, and rifampin induction can be offset by doubling dolutegravir to 50 mg twice daily, which restores adequate exposure. Option E integrates both correctly. Option A is wrong because both regimens are affected by induction.
Option B: Option B overstates the effect as permanent and universal. Option C errs on Patient 1 (the boosted PI cannot simply be dose-doubled around rifampin and is contraindicated) and on Patient 2 (dolutegravir does require dose adjustment).
Option D: Option D is incorrect because adding a second booster does not overcome rifampin's potent induction and is not the recommended approach.
6. A heavily treatment-experienced patient with multi-drug-resistant HIV needs an active agent, and the team considers an entry inhibitor. A tropism assay reveals dual/mixed-tropic virus (both CCR5 [C-C chemokine receptor type 5]- and CXCR4 [C-X-C chemokine receptor type 4]-using populations). Integrating maraviroc's pharmacology with this result, what is the correct conclusion?
A) Maraviroc is the best choice because dual/mixed tropism guarantees it will be active
B) Maraviroc should be started at double the usual dose to cover both co-receptors
C) Maraviroc is not appropriate because it has no activity against CXCR4-using virus, and any detectable X4 or dual/mixed population predicts virologic failure; an agent active regardless of tropism—such as the capsid inhibitor lenacapavir or the post-attachment inhibitor ibalizumab—should be considered instead
D) Maraviroc will work because tropism does not affect CCR5 antagonist activity
E) Maraviroc should be combined with enfuvirtide specifically to convert the virus back to R5 tropism
ANSWER: C
Rationale:
This integrates maraviroc's mechanism with entry-class selection in salvage therapy. Maraviroc blocks only the CCR5 co-receptor and has no activity against CXCR4-using virus; when a dual/mixed-tropic population is present, any X4-using virus predicts failure, so maraviroc is inappropriate and a tropism-independent agent (for example, lenacapavir or ibalizumab) should be selected. Option C is correct. Option A is wrong because dual/mixed tropism predicts maraviroc failure, not success.
Option B: Option B is incorrect because dose escalation does not give maraviroc activity against X4 virus. Option D contradicts the defining limitation of CCR5 antagonists.
Option E: Option E is incorrect; combining drugs does not shift the virus back to exclusive R5 tropism, and that is not how enfuvirtide works.
7. Atazanavir inhibits the enzyme uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1), and raltegravir is eliminated by UGT1A1-mediated glucuronidation. Integrating these two facts, what is the predicted consequence of co-administering atazanavir with raltegravir?
A) Atazanavir inhibition of UGT1A1 reduces raltegravir glucuronidation, raising raltegravir plasma concentrations
B) Atazanavir induces UGT1A1, lowering raltegravir concentrations to subtherapeutic levels
C) The two drugs do not interact because they are eliminated by completely separate pathways
E) Co-administration converts raltegravir into an irreversible UGT1A1 inhibitor, eliminating all glucuronidation
ANSWER: A
Rationale:
This integrates a shared metabolic pathway across two drug classes. Raltegravir depends on UGT1A1 glucuronidation for elimination, and atazanavir is a UGT1A1 inhibitor; inhibiting that pathway slows raltegravir clearance and raises its plasma concentration. Option A correctly predicts this interaction.
Option B: Option B inverts the effect by claiming induction; atazanavir inhibits, not induces, UGT1A1. Option C is wrong because the drugs converge on the same UGT1A1 pathway and therefore do interact.
Option D: Option D misstates the mechanism and direction; the interaction is metabolic at UGT1A1, not absorption-based, and atazanavir's hyperbilirubinemia stems from its own UGT1A1 inhibition. Option E is biologically incorrect; raltegravir does not transform into an irreversible enzyme inhibitor.
8. A clinician is counseling a treatment-naive woman of African ancestry about an integrase strand transfer inhibitor (INSTI)-based regimen and asks how the choice of tenofovir prodrug might influence weight. Integrating the INSTI weight-gain signal with the backbone choice and demographic modifiers, which statement is most accurate?
A) INSTIs reliably produce weight loss, and the effect is largest in this patient group
B) INSTI-based regimens are associated with weight gain that tends to be greater when combined with tenofovir alafenamide (TAF) than with tenofovir disoproxil fumarate (TDF), and the gain appears larger in women and in persons of African ancestry, so this should be discussed when selecting the backbone
C) Weight change on INSTIs is identical regardless of the tenofovir prodrug and is unaffected by sex or ancestry
D) Only protease inhibitors, not INSTIs, are associated with weight gain, so the backbone is irrelevant
E) The weight effect is entirely an artifact of fluid retention and reverses within one week
ANSWER: B
Rationale:
This integrates three module facts: INSTI-associated weight gain, its greater magnitude with TAF than TDF, and apparently larger effects in women and persons of African ancestry. Together these justify discussing backbone choice and expectations with this patient.
Option B: Option B states the integrated picture correctly.
Option A: Option A inverts the direction (gain, not loss). Option C contradicts the observed TAF-versus-TDF difference and the demographic modifiers.
Option D: Option D incorrectly excludes INSTIs from the weight signal; the signal is in fact prominent with INSTI-based regimens. Option E mischaracterizes the gain as transient fluid retention, whereas the observed weight gain accrues over months and is not a one-week artifact.
9. A patient on long-acting injectable cabotegravir plus rilpivirine (CAB+RPV) will be relocating and cannot continue clinic-based injections. Integrating the pharmacokinetics of the depot formulations with resistance prevention, what is the correct plan?
A) Simply stop the injections; because the drugs clear within a day, no bridging therapy is required
B) Continue injections indefinitely at home with no oral therapy, since the long tail guarantees protection forever
C) Stop the injections and wait until both drugs are fully undetectable before considering any further antiretroviral therapy
D) Begin a fully suppressive oral antiretroviral regimen promptly—about when the next injection would have been due—because declining subtherapeutic depot concentrations create a prolonged functional monotherapy window (cabotegravir for months, rilpivirine for up to years) that can select resistance if left uncovered
E) Replace the injectables with single-agent oral rilpivirine, which is sufficient to prevent resistance during the tail
ANSWER: D
Rationale:
This integrates the prolonged depot pharmacokinetics with the resistance risk they create. After the last injection, cabotegravir and rilpivirine decline slowly—cabotegravir detectable for months, rilpivirine for up to years—so concentrations pass through a subtherapeutic range that constitutes functional monotherapy and can select resistance. The correct plan is to start a fully suppressive oral regimen promptly, around when the next injection would have been due. Option D is correct. Option A is wrong because the drugs do not clear within a day.
Option B: Option B ignores the eventual decline below therapeutic levels. Option C leaves the patient uncovered during the very window in which resistance is selected. Option E provides inadequate single-agent coverage, itself a setup for resistance.
10. A patient takes a medication that is primarily a CYP2D6 (cytochrome P450 2D6) substrate. The team must choose between a ritonavir-boosted and a cobicistat-boosted regimen and wants to minimize the impact on that co-medication. Integrating the isoform-selectivity difference between the two boosters, which prediction is correct?
A) Cobicistat will raise the CYP2D6 substrate more than ritonavir because cobicistat strongly inhibits CYP2D6
B) Neither booster affects the CYP2D6 substrate because boosters act only on CYP3A4 (cytochrome P450 3A4) and never on other isoforms
C) Both boosters inhibit CYP2D6 identically, so the choice makes no difference for this co-medication
D) Ritonavir will lower the CYP2D6 substrate by inducing CYP2D6, whereas cobicistat will raise it
E) Ritonavir, which inhibits CYP2D6 in addition to CYP3A4, is more likely to raise concentrations of the CYP2D6 substrate, whereas cobicistat—being comparatively more selective for CYP3A4—is expected to affect it less
ANSWER: E
Rationale:
This integrates the booster isoform-selectivity difference with interaction prediction for a specific co-medication. Ritonavir inhibits CYP2D6 (and CYP2C9 and others) in addition to CYP3A4, so it is more likely to raise a CYP2D6 substrate, whereas cobicistat is comparatively more selective for CYP3A4 and is expected to affect a pure CYP2D6 substrate less. Option E is correct.
Option A: Option A reverses the agents. Option B is wrong because ritonavir clearly inhibits isoforms beyond CYP3A4.
Option C: Option C ignores the very difference the question hinges on.
Option D: Option D incorrectly claims ritonavir induces CYP2D6; ritonavir inhibits it.
11. A heavily treatment-experienced patient has multi-drug-resistant HIV with documented resistance across the nucleoside, non-nucleoside, protease, and integrase classes, and the virus is dual/mixed-tropic. Integrating the mechanisms of the newer agents, which approach offers genuine activity in this setting?
A) Re-use a boosted protease inhibitor at higher dose, since high-level PI resistance can be overcome by concentration alone
B) Add maraviroc, which will be active despite the dual/mixed tropism
C) Select agents whose targets lie outside the exhausted classes—such as lenacapavir (a capsid inhibitor), ibalizumab (a post-attachment CD4 [cluster of differentiation 4] domain-2 monoclonal antibody), or fostemsavir (a gp120 attachment inhibitor)—combined with any remaining active background drugs
D) Rely on long-acting cabotegravir plus rilpivirine, which is designed for multi-drug-resistant salvage
E) Withhold therapy until a completely new drug class is invented, since nothing currently active exists
ANSWER: C
Rationale:
This integrates the novel-mechanism agents with the logic of salvage therapy: when conventional classes are exhausted, activity comes from drugs that act at targets outside those classes. Lenacapavir (capsid inhibitor), ibalizumab (post-attachment CD4 domain-2 monoclonal antibody), and fostemsavir (gp120 attachment inhibitor) provide such activity and are used with any remaining active background agents. Option C is correct. Option A is wrong because high-level PI resistance is not overcome by dose escalation.
Option B: Option B is incorrect because maraviroc lacks activity against the CXCR4-using component of dual/mixed-tropic virus. Option D misapplies CAB+RPV, which is for virologically suppressed patients without resistance to its components, not multi-drug-resistant salvage. Option E is false because effective agents with novel mechanisms already exist for this exact scenario.
12. A patient who needs a protease inhibitor-based regimen has baseline dyslipidemia, and the team wants to minimize additional metabolic burden. Integrating the comparative metabolic profiles of the PIs with regimen construction, which choice is most consistent with that goal?
A) Choose darunavir-based therapy rather than lopinavir/ritonavir, because darunavir produces substantially less dyslipidemia than lopinavir/ritonavir, and avoid thymidine-analogue nucleosides that contribute to lipoatrophy
B) Choose lopinavir/ritonavir because it has the most favorable lipid profile of all protease inhibitors
C) Choose any protease inhibitor, since all PIs raise lipids identically and selection cannot reduce the metabolic burden
D) Add a thymidine analogue such as stavudine specifically to counteract PI-associated dyslipidemia
E) Avoid protease inhibitors entirely and use ritonavir alone as monotherapy to limit lipid effects
ANSWER: A
Rationale:
This integrates the comparative PI metabolic profiles with practical regimen building. Dyslipidemia is most pronounced with lopinavir/ritonavir and older PIs and substantially less with darunavir, and thymidine analogues such as stavudine and zidovudine contribute to lipoatrophy; choosing darunavir and avoiding thymidine analogues minimizes added metabolic burden. Option A is correct. Option B is wrong because lopinavir/ritonavir has one of the least favorable lipid profiles, not the most favorable.
Option C: Option C ignores the real differences among PIs that allow selection to reduce metabolic burden.
Option D: Option D is incorrect and harmful: thymidine analogues worsen, not counteract, metabolic and fat-distribution problems. Option E is unsound because ritonavir is a booster with no useful antiviral activity at booster doses and is never used as monotherapy.
13. A student asks why guidelines favor second-generation integrase strand transfer inhibitor (INSTI)-based regimens as first-line therapy over boosted protease inhibitor (PI) and non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens. Integrating resistance barrier, tolerability, and interaction profile, which explanation is most complete?
A) INSTIs are preferred only because they are cheaper, with no pharmacological advantage over PIs or NNRTIs
B) Second-generation INSTIs combine a very high resistance barrier (treatment-naive patients essentially do not select resistance at failure), rapid virologic suppression, good tolerability, and a relatively limited interaction profile—unlike NNRTIs, which have low resistance barriers, and boosted PIs, which require pharmacokinetic boosting with its attendant interaction burden
C) INSTIs are preferred because they require booster co-administration, simplifying interactions
D) NNRTIs are preferred over INSTIs for first-line therapy because they have the highest resistance barrier of all classes
E) Boosted PIs are preferred first-line because boosting eliminates all drug interactions and maximizes tolerability
ANSWER: B
Rationale:
This integrates several module themes into the first-line rationale. Second-generation INSTIs offer a very high resistance barrier (treatment-naive patients essentially do not select resistance at virologic failure), rapid suppression, good tolerability, and a comparatively limited interaction profile; by contrast, NNRTIs have low resistance barriers and boosted PIs carry the interaction burden of pharmacokinetic boosting. Option B assembles this correctly. Option A reduces the choice to cost and denies the pharmacological advantages. Option C is factually wrong because second-generation INSTIs do not require boosting, and boosting would add, not simplify, interactions.
Option D: Option D is incorrect because NNRTIs have low, not high, resistance barriers. Option E is wrong because boosting introduces rather than eliminates interactions and does not make PIs the preferred first-line class.
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