NABP North American Pharmacist Licensure Examination NAPLEX Question # 26 Topic 3 Discussion
NAPLEX Exam Topic 3 Question 26 Discussion:
Question #: 26
Topic #: 3
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?
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
E.
Rifampin is bactericidal by inhibiting RNA synthesis by blocking DNA-dependent RNA polymerase
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.
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