random antiviral
A patient is hospitalized with influenza B.
Which antiviral should be avoided because it has no activity against influenza B?
A. Oseltamivir
B. Baloxavir
C. Amantadine
D. Peramivir
Answer: C
Why it's correct
Adamantanes (amantadine and rimantadine) only cover Influenza A.
Why the others are wrong
The remaining medications treat Influenza A and B.
A 27-year-old woman presents with dysuria and urinary frequency. Urinalysis is positive for nitrites and leukocyte esterase. She is otherwise healthy except for a documented history of Glucose-6-phosphate dehydrogenase deficiency.
Which antibiotic should be avoided?
A. Nitrofurantoin
B. Cephalexin
C. Fosfomycin
D. Amoxicillin-clavulanate
A. Nitrofurantoin
Why: Nitrofurantoin can cause hemolytic anemia in patients with G6PD deficiency.
A 42-year-old man is newly diagnosed with drug-susceptible pulmonary tuberculosis. He is started on isoniazid as part of his treatment regimen.
Which mechanism of action best describes isoniazid?
A. Inhibits bacterial RNA polymerase
B. Inhibits synthesis of mycolic acids in the mycobacterial cell wall
C. Inhibits arabinogalactan synthesis in the cell wall
D. Disrupts bacterial DNA gyrase
Answer: B. Inhibits synthesis of mycolic acids
Why it's correct
Isoniazid inhibits synthesis of mycolic acids, an essential component of the mycobacterial cell wall.
A 72-year-old man with hyperlipidemia takes simvastatin daily. He develops histoplasmosis and is prescribed itraconazole.
Which complication is he at highest risk for?
A. Tendon rupture
B. Rhabdomyolysis
C. Hypoglycemia
D. QT shortening
A 69-year-old woman with type 2 diabetes takes glipizide. She develops oral candidiasis and is prescribed fluconazole.
Which complication is most likely?
A. Hyperglycemia
B. Hypoglycemia
C. Hypertension
D. Hyperkalemia
Answer: B. Hypoglycemia
Why it's correct
Azoles can increase levels of oral hypoglycemic medications, leading to hypoglycemia.
patient develops CMV retinitis that is resistant to ganciclovir. The physician considers cidofovir.
Which pre-existing condition would make cidofovir particularly concerning?
A. Chronic kidney disease
B. Hyperlipidemia
C. Hypertension
D. Asthma
Answer: A
Why it's correct
Cidofovir is well known for nephrotoxicity and should be used cautiously in patients with kidney disease.
A 66-year-old man with atrial fibrillation takes Warfarin. He develops uncomplicated cystitis.
Which antibiotic requires the greatest caution because of a significant drug interaction?
A. Nitrofurantoin
B. TMP-SMX
C. Cefdinir
D. Fosfomycin
Answer: B. TMP-SMX
Why: TMP-SMX markedly increases INR and bleeding risk.
A patient is started on rifampin for pulmonary tuberculosis.
Which enzyme is directly inhibited by rifampin?
A. DNA gyrase
B. DNA polymerase
C. RNA polymerase
D. Topoisomerase IV
Answer: C. RNA polymerase
Why it's correct
Rifampin inhibits DNA-dependent RNA polymerase, preventing RNA synthesis.
A 75-year-old woman takes midazolam nightly for severe insomnia. She is diagnosed with esophageal candidiasis and started on ketoconazole.
Which adverse effect is most likely?
A. Severe hypertension
B. Prolonged sedation
C. Digoxin toxicity
D. Nephrotoxicity
b
duh
Ketoconazole inhibits metabolism of midazolam, causing prolonged and excessive sedation.
Which pairing is INCORRECT?
A. Isoniazid — mycolic acid synthesis
B. Rifampin — RNA polymerase
C. Ethambutol — arabinosyl transferase
D. Pyrazinamide — DNA gyrase
Answer: D.
Why it's correct
DNA gyrase is inhibited by moxifloxacin, not pyrazinamide.
A 69-year-old man with end-stage renal disease on hemodialysis develops herpes zoster. His physician plans to prescribe acyclovir at the standard adult dose.
What is the biggest concern?
A. The dose should be increased because dialysis removes the drug.
B. Acyclovir requires renal dose adjustment to avoid toxicity.
C. Acyclovir is contraindicated in patients with kidney disease.
D. Acyclovir is ineffective against herpes zoster.
Answer: B
Why it's correct
Acyclovir is primarily eliminated by the kidneys. Patients with renal impairment require dose adjustment to reduce the risk of toxicity (including neurotoxicity).
A 68-year-old man with chronic kidney disease is admitted for sepsis. The physician wants to start gentamicin. His serum creatinine is 3.2 mg/dL.
Which adverse effect is he at particularly high risk for?
A. Pulmonary fibrosis
B. Nephrotoxicity and ototoxicity
C. Bone marrow suppression
D. Tendon rupture
Answer: B. nephro and nephrotoxicity
Aminoglycosides are nephrotoxic and ototoxic. Patients with impaired renal function accumulate the drug, making toxicity more likely.
A patient develops optic neuritis while receiving tuberculosis therapy.
Which drug most likely caused this adverse effect?
A. Isoniazid
B. Ethambutol
C. Rifampin
D. Pyrazinamide
Answer: B. Ethambutol
Why it's correct
Ethambutol inhibits arabinosyl transferase, preventing arabinogalactan synthesis in the mycobacterial cell wall.
Optic neuritis is its classic toxicity.
A 63-year-old woman with pulmonary tuberculosis is taking rifampin. She develops blastomycosis, and her physician considers itraconazole.
What is the biggest concern?
A. Increased QT interval
B. Antifungal inefficacy
C. Increased bleeding
D. Severe hypoglycemia
Why it's correct
Rifampin is a potent enzyme inducer that dramatically lowers azole concentrations, making itraconazole ineffective.
A patient cannot tolerate ethambutol.
Which component of the mycobacterial cell wall will no longer be targeted?
A. Mycolic acids
B. RNA polymerase
C. Arabinogalactan
D. DNA gyrase
Answer: C. Arabinogalactan
Why it's correct
Ethambutol inhibits arabinosyl transferase, preventing arabinogalactan synthesis.
A patient is prescribed enfuvirtide for multidrug-resistant HIV.
What is its mechanism?
A. Reverse transcriptase inhibitor
B. Protease inhibitor
C. Fusion inhibitor
D. Integrase inhibitor
Answer: C
Why it's correct
Enfuvirtide prevents HIV from fusing with the host cell membrane.
A transplant patient has multidrug-resistant CMV.
The provider orders cidofovir.
why is this drug affective against CMV?
adverse affects? what is commonly prescribed along it?
A physician prescribes pyrazinamide.
Which statement best describes its mechanism?
A. Inhibits RNA polymerase
B. Active in acidic environments and disrupts mycobacterial membrane energetics
C. Inhibits mycolic acid synthesis
D. Inhibits arabinogalactan synthesis
Answer: B.
Why it's correct
Pyrazinamide is converted to pyrazinoic acid and is most active in acidic environments within macrophages.
A liver transplant recipient takes tacrolimus. Fluconazole is added for candidemia.
Which laboratory value requires the closest monitoring?
A. Hemoglobin
B. Tacrolimus concentration
C. Platelet count
D. INR only
Why it's correct
Azoles increase tacrolimus serum levels, increasing the risk of nephrotoxicity.
A 37-year-old kidney transplant recipient develops CMV retinitis.
Which medication works by the same mechanism as acyclovir but has greater activity against CMV?
A. Ganciclovir
B. Oseltamivir
C. Maraviroc
D. Enfuvirtide
a
Answer: A
Why it's correct
Ganciclovir is a nucleoside analog DNA polymerase inhibitor used for CMV.
A patient with HIV has a virus that uses the CCR5 receptor to enter CD4 cells.
Which medication specifically blocks this receptor?
A. Enfuvirtide
B. Maraviroc
C. Zidovudine
D. Efavirenz
Answer: B
Why it's correct
Maraviroc blocks the CCR5 co-receptor, preventing HIV entry.
A physician wants to prescribe clindamycin for a patient who has had three previous episodes of Clostridioides difficile infection.
Which concern is most important?
A. QT prolongation
B. High risk of recurrent C. difficile infection
C. Pulmonary fibrosis
D. Nephrotoxicity
Why it's correct
Clindamycin is one of the antibiotics most strongly associated with C. difficile infection.
Why the others are wrong
The remaining adverse effects are associated with other drug classes.
Teaching Point: History of C. diff → think twice before clindamycin.
A patient is prescribed the new 2025 four-month regimen for drug-susceptible pulmonary TB.
Which medication in the regimen works by inhibiting DNA gyrase?
A. Rifapentine
B. Pyrazinamide
C. Isoniazid
D. Moxifloxacin
Answer: D. Moxifloxacin
Why it's correct
Moxifloxacin is a fluoroquinolone that inhibits DNA gyrase (and topoisomerase IV).
A 70-year-old man with atrial fibrillation takes warfarin. He is started on fluconazole for oral candidiasis.
What adverse effect is most likely?
A. Pulmonary fibrosis
B. Enhanced anticoagulant effect
C. Tendon rupture
D. Ototoxicity
Why it's correct
Azoles inhibit warfarin metabolism, increasing INR and bleeding risk.
Why the others are wrong
The remaining toxicities are unrelated.
Teaching Point: Warfarin + azoles = monitor INR closely.
A college student develops a cold sore before a wedding and wants an OTC medication.
Which medication inhibits viral entry rather than DNA synthesis?
A. Acyclovir
B. Valacyclovir
C. Docosanol (Abreva)
D. Ganciclovir
Answer: C
Why it's correct
Docosanol works by preventing viral entry into host cells.