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NABP NAPLEX Exam - Topic 1 Question 123 Discussion

A patient with multibacillary leprosy is on dapsone, clofazimine, and rifampin. Which of the following is true regarding the mechanism of action of the medications listed?
E) Rifampin is bactericidal by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase
A) Dapsone is bacteriostatic because of its inhibitory effects on dihydrofolate reductase
B) Dapsone is bacteriostatic because of its inhibitory effects on myeloperoxidase
C) Clofazimine is bactericidal by directly inhibiting bacterial DNA polymerase
D) Rifampin is bacteriostatic by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase

NABP NAPLEX Exam - Topic 1 Question 123 Discussion

Actual exam question for NABP's NAPLEX exam
Question #: 123
Topic #: 1
[All NAPLEX Questions]

A patient with multibacillary leprosy is on dapsone, clofazimine, and rifampin. Which of the following is true regarding the mechanism of action of the medications listed?

Show Suggested Answer Hide Answer
Suggested Answer: E

A, B -- false -- dapsone inhibits bacterial synthesis of dihydrofolic acid, via competition with para- aminobenzoate for the active site of dihydropteroate synthetase. Dapsone is both bacteriostatic and weakly bactericidal against M. leprae. Neither of the listed mechanisms are the cause of these effects. C -- False -- A substance with both anti-leprosy and anti-inflammatory activity, clofazimine is weakly bactericidal against M. leprae by binding to the guanine bases of bacterial DNA, not DNA polymerase directly. D -- False -- See below. E -- True -- Rifampin is bactericidal by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase.


by Leota at Jun 27, 2026, 01:13 PM

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Nathalie
3 days ago
Wait, is rifampin really bactericidal? That seems off.
upvoted 0 times
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Louisa
8 days ago
Totally agree, A is the correct answer!
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Tenesha
14 days ago
Dapsone inhibits dihydrofolate reductase, right?
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Paris
19 days ago
A little surprised by the details on dapsone!
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Loreta
24 days ago
I thought clofazimine was more about DNA than just bactericidal effects.
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Daren
29 days ago
Wait, isn't rifampin bactericidal, not bacteriostatic?
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Ludivina
1 month ago
Totally agree, A is the correct answer!
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Maia
1 month ago
Dapsone inhibits dihydrofolate reductase, right?
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Daren
1 month ago
I practiced a question like this before, and I think dapsone's action is linked to dihydrofolate reductase, but I might be mixing it up.
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Paul
2 months ago
Clofazimine sounds familiar, but I can't recall if it directly inhibits DNA polymerase or has a different action.
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Minna
2 months ago
I think rifampin is definitely bactericidal, but I get confused about its exact mechanism with RNA synthesis.
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Precious
2 months ago
I remember dapsone is related to folate synthesis, but I'm not sure if it's bacteriostatic or bactericidal.
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