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Chapter 52: Antiprotozoal Drugs

Which statement about antiprotozoal drugs is most accurate?

(A) Chloroquine is an inhibitor of plasmodial dihydrofolate reductase

(B) Mefloquine destroys secondary exoerythrocytic schizonts

(C) Primaquine is a blood schizonticide and does not affect secondary tissue schizonts

(D) Proguanil complexes with double-stranded DNA, blocking replication

(E) Trimethoprim-sulfamethoxazole is the drug of choice for Pneumocystis jirovecii pneumonia

Proguanil (not chloroquine) is an inhibitor of dihydrofolate reductase. Primaquine (not mefloquine) is the drug that destroys secondary exoerythrocytic schizonts. TMP-SMZ is the drug of choice for Pneumocystis jirovecii pneumonia. The answer is E.

Plasmodial resistance to chloroquine is due to

(A) Change in receptor structure

(B) Decreased accumulation of the drug in the food vacuole

(C) Increased activity of DNA repair mechanisms

(D) Increased synthesis of dihydrofolate reductase

(E) Induction of drug-inactivating enzymes

Resistance to chloroquine in P falciparum can result from decreased accumulation of the drug in the food vacuole caused by the activity of a transporter system encoded by the pfcrt gene. The answer is B.

A 10-year-old American girl presented to the emergency department with fever, chills, lethargy, and splenomegaly. She had recently returned from Nigeria, where she had spent 3 weeks with her grandparents. She had previously received all standard childhood immunizations but no prophylactic travel medications because her parents had returned to Nigeria several times previously without any medical problems. Laboratory examination reveals low hematocrit and platelet count and elevated creatinine. Blood smear reveals parasites in the erythrocytes and a diagnosis of falciparum malaria is made.

The patient should have received prophylaxis for the prevention of malaria; what prophylactic regimen would have been most appropriate?

(A) Artesunate

(B) Chloroquine

(C) Mefloquine

(D) Quinidine

(E) Tetracycline

Mefloquine is a recommended drug for prophylaxis in regions of the world where chloroquine-resistant P falciparum is endemic. Quinidine is not indicated for prophylaxis. Doxycycline (not tetracycline) is an alternative drug for prophylaxis but must be given daily. The answer is C.

A 10-year-old American girl presented to the emergency department with fever, chills, lethargy, and splenomegaly. She had recently returned from Nigeria, ...

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