Block 10 Antiprotozoal Drugs

10 Questions | By Chachelly | Last updated: Mar 19, 2022 | Total Attempts: 544

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1.

A 41-year-old woman, coming back from a trip to Kenya, was admitted to the hospital because of malaise, myalgia, abdominal pain and fever (104E F). The recent history of the patient was significant for two paroxysmal attacks of chills, fever and vomiting. The first attack lasted a day and was followed by a second 36 hours later. Physical examination revealed an acutely hill patient complaining of severe abdominal pain. Palpation showed a tender, soft and enlarged spleen. Examination of a stained blood specimen revealed ringlike and crescent-like forms within the RBCs. Which of the following pairs of drugs would be appropriate for this patient?
- A.
  
  Quinidine and doxycycline
- B.
  
  Primaquine and clindamycin
- C.
  
  Pyrimethamine and metronidazole
- D.
  
  Chloroquine and paromomycin
- E.
  
  Mefloquine and ciprofloxacin
2.

A 34-year-old black man permanent US is planning to visit his seriously ill father who lives in Uganda. He will be accompanied by his wife and son. Knowing that chloroquine-resistant strains of malaria are present in Uganda, which of the following drugs used alone should be administered to the man, his wife and son before entering Uganda?
- A.
  
  Primaquine
- B.
  
  Metronidazole
- C.
  
  Pyrimethamine
- D.
  
  Mefloquine
- E.
  
  Chloroquine
- F.
  
  Quinine
3.

A 33-year-old man was planning a vacation to sub-Saharan Africa where chloroquineresistant strains of P. falciparum are present. Which of the following drugs combinations would be appropriate to prevent infection in this man?
- A.
  
  Primaquine-quinine
- B.
  
  Mefloquine-metronidazole
- C.
  
  Pyrimethamine-sulfadoxine
- D.
  
  Doxycycline-iodoquinol
- E.
  
  Chloroquine-paromomycin
4.

A 31-year-old man, coming back from a trip to Malaysia, was admitted to the hospital with a two day history of fever, chills and bouts of diarrhea. A Giemsa blood smear demonstrated P. Vivax trophozoites. The patient was placed on chloroquine for 5 days, then he was instructed to take another drug for 14 days. Which of the following drugs was most likely prescribed?
- A.
  
  Primaquine
- B.
  
  Mefloquine
- C.
  
  Quinidine
- D.
  
  Pyrimethamine
- E.
  
  Doxycycline
- F.
  
  Sulfadoxine
5.

A 45-year-old black man referred to his physician that few days ago he noticed a persistent yellow color in his eyes . One week before, coming back from a trip to central America, the man had started a treatment which included primaquine. A blood test disclosed the following: RBC count: 3.8 x 106/ mm3 (normal: 4-5.5) Hb: 9 g/dL (normal: > 12) Reticulocytes: 3.7% of red cells (normal 0.5-1.5%) WBC count 12000/mm3 (normal: 3200-9800) The physician told the patient that he probably had a genetically induced enzyme defect. Which of the following enzymes was most likely abnormal?
- A.
  
  Thymidylate synthase
- B.
  
  Uroporphyrinogen decarboxylase
- C.
  
  Pyruvate kinase
- D.
  
  Dihydrofolate reductase
- E.
  
  Glucose-6-phosphate-dehydrogenase
6.

A 55-year-old man, who was about to leave for a vacation trip to central Africa, started a treatment with mefloquine. Which of the following plasmodia cells can be effectively killed by the drug?
- A.
  
  P. Vivax hypnozoites
- B.
  
  P. Falciparum gametocytes
- C.
  
  P. Vivax tissue schizonts
- D.
  
  P. Falciparum hypnozoites
- E.
  
  P. Malarie blood schizonts
- F.
  
  P. Malarie tissue schizonts
7.

A 35-year-old woman was planning a trip to malaria endemic regions of central America. She was advised by her physician to take a tablet of pyrimethamine-sulfadoxine (fansidar) in case of fever and then to obtain as soon as possible medical attention. The antimalarial efficacy of pyrimethamine is most likely mediated by the inhibition of which of the following protozoal enzymes?
- A.
  
  Purine phosphoribosyl transferase
- B.
  
  Ornithine decarboxylase
- C.
  
  Ferredoxin oxidoreductase
- D.
  
  Dihydropteroate synthetase
- E.
  
  Dihydrofolate reductase
8.

A 43-year-old man is about to leave for a vacation trip to central America. He is advised by his physician to take mefloquine as a prophylactic measure, since he knew that chloroquine resistance was widespread and increasing. Which of the following phrase best explains the likely mechanism of plasmodial resistance to chloroquine?
- A.
  
  Increased inactivation of the drug
- B.
  
  Increased activity of DNA repair mechanism
- C.
  
  Increased drug transport outside plasmodia cells
- D.
  
  Decreased chloroquine binding sites on plasmodia cells
- E.
  
  Decreased of conversion of free heme into hemozoin
9.

A 45-year-old reporter who was about to leave for Honduras, started a prophylactics antimalarial treatment with chloroquine. Which of the following molecular actions most likely mediate the therapeutic effect of this drug?
- A.
  
  Inhibition of dihydropteroate synthase
- B.
  
  Blockade of translocation of peptidyl-tRNA
- C.
  
  Incorrect amino acid incorporation into the polypeptide chain
- D.
  
  Inhibition of DNA-dependent RNA polymerase
- E.
  
  Prevention of polymerization of free heme into hemozoin
10.

A 24-year-old woman, who was 22-week pregnant, presented with a 5-day history of loose stools containing bloody mucus. Her past medical history was significant for an optic neuritis one month ago, apparently due to a viral infection. Upon physical examination her abdomen was soft but nontender. The exam of fresh stools showed E. histolytica trophozoites. A CT scan was negative for gut wall or liver amebiasis. Which of the following drugs would be appropriate for this patient?
- A.
  
  Metronidazole
- B.
  
  Chloroquine
- C.
  
  Clindamycin
- D.
  
  Paromomycin
- E.
  
  Pyrimethamine
- F.
  
  Sulfadoxine