, Question 1
A patient receiving high-dose fluconazole for cryptococcal meningitis develops
a supratherapeutic INR after warfarin initiation. Which mechanism best
explains this interaction?
A. Fluconazole induces CYP2C9, accelerating warfarin clearance and
requiring higher warfarin doses
B. Fluconazole inhibits CYP2C9 and CYP3A4, reducing warfarin
metabolism and increasing bleeding risk
C. Fluconazole displaces warfarin from albumin binding sites without
affecting hepatic metabolism
D. Fluconazole enhances renal tubular reabsorption of warfarin,
prolonging its half-life
Correct Answer: B - Fluconazole inhibits CYP2C9 and CYP3A4,
reducing warfarin metabolism and increasing bleeding risk
RATIONALE
Fluconazole is a potent inhibitor of CYP2C9 and CYP3A4, the
primary enzymes metabolizing S- and R-warfarin, respectively,
leading to elevated INR and bleeding risk. Induction (A) is incorrect
because azoles inhibit rather than induce these enzymes.
Protein-binding displacement (C) is clinically negligible and not the
dominant mechanism. Renal reabsorption (D) is not a recognized
warfarin interaction pathway.
Question 2
Which pharmacodynamic property distinguishes echinocandins from azoles in
the treatment of invasive candidiasis?
A. Echinocandins inhibit ergosterol synthesis, whereas azoles disrupt
-(1,3)-D-glucan synthesis
B. Echinocandins are fungicidal against Candida by inhibiting
-(1,3)-D-glucan synthase, while azoles are primarily fungistatic via
ergosterol synthesis inhibition
Page 2
, C. Echinocandins achieve higher cerebrospinal fluid concentrations than
azoles, making them first-line for Candida meningitis
D. Echinocandins require hepatic CYP450 activation, whereas azoles are
active prodrugs
Correct Answer: B - Echinocandins are fungicidal against
Candida by inhibiting -(1,3)-D-glucan synthase, while azoles are
primarily fungistatic via ergosterol synthesis inhibition
RATIONALE
Echinocandins (e.g., caspofungin, micafungin) inhibit -(1,3)-D-glucan
synthase, disrupting cell wall integrity and exerting fungicidal activity
against Candida. Azoles inhibit lanosterol 14-demethylase in the
ergosterol pathway and are generally fungistatic against Candida.
Option A reverses the mechanisms; C is false because echinocandins
have poor CNS penetration; D is false because echinocandins are not
CYP-activated prodrugs.
Question 3
A patient with onychomycosis and mild hepatic impairment is being
considered for oral terbinafine. Which monitoring parameter is most critical to
assess before and during therapy?
A. Serum creatinine and urinalysis
B. Complete blood count with differential
C. Liver function tests including ALT, AST, and bilirubin
D. Serum potassium and magnesium levels
Correct Answer: C - Liver function tests including ALT, AST, and
bilirubin
Page 3
, RATIONALE
Terbinafine is hepatically metabolized and can cause cholestatic
hepatitis or hepatic failure; baseline and periodic LFTs are essential,
especially with pre-existing hepatic impairment. Renal function (A) is
less critical as dose adjustment is not routinely required for mild renal
impairment. CBC (B) and electrolytes (D) are not the primary
monitoring parameters for terbinafine hepatotoxicity.
Question 4
Which statement best reflects the current role of therapeutic drug monitoring
(TDM) for voriconazole in invasive fungal infections?
A. Routine TDM is not recommended because voriconazole has a wide
therapeutic index
B. TDM is recommended for all patients, with a target trough of 0.5-1.0
mcg/mL to avoid toxicity
C. TDM is recommended in select patients (e.g., those with hepatic
dysfunction, CYP2C19 polymorphisms, or treatment failure) with a target
trough of 1-5.5 mcg/mL
D. TDM is only useful for oral therapy; intravenous voriconazole does
not require monitoring
Correct Answer: C - TDM is recommended in select patients (e.g.,
those with hepatic dysfunction, CYP2C19 polymorphisms, or
treatment failure) with a target trough of 1-5.5 mcg/mL
RATIONALE
Voriconazole exhibits wide interpatient variability due to CYP2C19
polymorphisms, hepatic impairment, and drug interactions; guidelines
recommend TDM in selected high-risk patients with a target trough of
1-5.5 mcg/mL. Option A is incorrect because the therapeutic index is
narrow. Option B's target range is too low for efficacy. Option D is
false because IV voriconazole also requires monitoring due to the
same pharmacokinetic variability.
Page 4
A patient receiving high-dose fluconazole for cryptococcal meningitis develops
a supratherapeutic INR after warfarin initiation. Which mechanism best
explains this interaction?
A. Fluconazole induces CYP2C9, accelerating warfarin clearance and
requiring higher warfarin doses
B. Fluconazole inhibits CYP2C9 and CYP3A4, reducing warfarin
metabolism and increasing bleeding risk
C. Fluconazole displaces warfarin from albumin binding sites without
affecting hepatic metabolism
D. Fluconazole enhances renal tubular reabsorption of warfarin,
prolonging its half-life
Correct Answer: B - Fluconazole inhibits CYP2C9 and CYP3A4,
reducing warfarin metabolism and increasing bleeding risk
RATIONALE
Fluconazole is a potent inhibitor of CYP2C9 and CYP3A4, the
primary enzymes metabolizing S- and R-warfarin, respectively,
leading to elevated INR and bleeding risk. Induction (A) is incorrect
because azoles inhibit rather than induce these enzymes.
Protein-binding displacement (C) is clinically negligible and not the
dominant mechanism. Renal reabsorption (D) is not a recognized
warfarin interaction pathway.
Question 2
Which pharmacodynamic property distinguishes echinocandins from azoles in
the treatment of invasive candidiasis?
A. Echinocandins inhibit ergosterol synthesis, whereas azoles disrupt
-(1,3)-D-glucan synthesis
B. Echinocandins are fungicidal against Candida by inhibiting
-(1,3)-D-glucan synthase, while azoles are primarily fungistatic via
ergosterol synthesis inhibition
Page 2
, C. Echinocandins achieve higher cerebrospinal fluid concentrations than
azoles, making them first-line for Candida meningitis
D. Echinocandins require hepatic CYP450 activation, whereas azoles are
active prodrugs
Correct Answer: B - Echinocandins are fungicidal against
Candida by inhibiting -(1,3)-D-glucan synthase, while azoles are
primarily fungistatic via ergosterol synthesis inhibition
RATIONALE
Echinocandins (e.g., caspofungin, micafungin) inhibit -(1,3)-D-glucan
synthase, disrupting cell wall integrity and exerting fungicidal activity
against Candida. Azoles inhibit lanosterol 14-demethylase in the
ergosterol pathway and are generally fungistatic against Candida.
Option A reverses the mechanisms; C is false because echinocandins
have poor CNS penetration; D is false because echinocandins are not
CYP-activated prodrugs.
Question 3
A patient with onychomycosis and mild hepatic impairment is being
considered for oral terbinafine. Which monitoring parameter is most critical to
assess before and during therapy?
A. Serum creatinine and urinalysis
B. Complete blood count with differential
C. Liver function tests including ALT, AST, and bilirubin
D. Serum potassium and magnesium levels
Correct Answer: C - Liver function tests including ALT, AST, and
bilirubin
Page 3
, RATIONALE
Terbinafine is hepatically metabolized and can cause cholestatic
hepatitis or hepatic failure; baseline and periodic LFTs are essential,
especially with pre-existing hepatic impairment. Renal function (A) is
less critical as dose adjustment is not routinely required for mild renal
impairment. CBC (B) and electrolytes (D) are not the primary
monitoring parameters for terbinafine hepatotoxicity.
Question 4
Which statement best reflects the current role of therapeutic drug monitoring
(TDM) for voriconazole in invasive fungal infections?
A. Routine TDM is not recommended because voriconazole has a wide
therapeutic index
B. TDM is recommended for all patients, with a target trough of 0.5-1.0
mcg/mL to avoid toxicity
C. TDM is recommended in select patients (e.g., those with hepatic
dysfunction, CYP2C19 polymorphisms, or treatment failure) with a target
trough of 1-5.5 mcg/mL
D. TDM is only useful for oral therapy; intravenous voriconazole does
not require monitoring
Correct Answer: C - TDM is recommended in select patients (e.g.,
those with hepatic dysfunction, CYP2C19 polymorphisms, or
treatment failure) with a target trough of 1-5.5 mcg/mL
RATIONALE
Voriconazole exhibits wide interpatient variability due to CYP2C19
polymorphisms, hepatic impairment, and drug interactions; guidelines
recommend TDM in selected high-risk patients with a target trough of
1-5.5 mcg/mL. Option A is incorrect because the therapeutic index is
narrow. Option B's target range is too low for efficacy. Option D is
false because IV voriconazole also requires monitoring due to the
same pharmacokinetic variability.
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