1. B. The drug of choice for clinical cure of P. vivax malaria is oral chloroquine. The only isolated reports of chloroquine-resistant P. vivax are from the western Pacific, not Central and South America. The patient should become afebrile in 24 to 48 hours, and parasitemia should decline in 72 hours. Since P. vivax, known as benign tertian malaria, responds well to chloroquine, there is no need to resort to parenteral quinine or quinidine or oral mefloquine; these agents have cardiotoxic and neu-rotoxic side effects. P. vivax also does not respond as well to the sulfonamides. In P. vivax and P. ovale infections, treatment with a blood schizonticide will result only in clinical cure, but radical cure requires additional treatment with a tissue schizonticide, pri-maquine, to destroy exoerythrocytic stages responsible for relapses. The patient should be checked for glucose 6-phosphate dehydrogenase deficiency before taking primaquine. Also, primaquine is not effective against erythrocytic schizonts at pharmacological levels, so it cannot be used in place of chloroquine.

2. C. The first-line drug for cutaneous or mucocuta-neous leishmaniasis is sodium stibogluconate (Pentostam) or meglumine antimonate (Glucan-time). Antimonials have not been approved by the U. S. Food and Drug Administration, but sodium sti-bogluconate is obtained from the Centers for Disease Control and Prevention. Clinical response is determined by species and resistance patterns of Leishmania and by host immunity. These drugs are given by intravenous or intramuscular injection. Phlebitis and pain are reduced when these drugs are given intravenously. In advanced mucocutaneous leishmaniasis amphotericin B may be an alternative, especially in areas of resistance to antimony drugs. Liposomal amphotericin B is the drug of choice for visceral leishmaniasis and has been used successfully in the treatment of cutaneous and mucocutaneous disease. Pentamidine, ketoconazole, and itraconazole have been used effectively to treat the cutaneous but not visceral form of leishmania-sis. Pyrantel pamoate is a roundworm treatment and not indicated here. Primaquine phosphate is used to prevent relapses in tertian malaria, and praziquantel is the drug of choice in treating tapeworm and fluke infections. Pyrimethamine-sulfadoxine is used to treat malaria and is sometimes combined with quinine sulfate in chloroquine resistance. It is also used to treat toxoplasmosis when it is accompanied by leucovorin (folinic acid).

3. C. Suramin is the drug of choice for the hemolym-phatic stage of T. rhodesiense and T. gambiense with a normal CSF examination. This drug is almost 100% effective in eliminating trypanosomes from the blood of patients in the early stage of disease. Epidemiologically this patient appears to have East African trypanosomiasis caused by T. rhodesiense. Pentamidine isethionate results in lower cure rates in T. rhodesiense infections than those with suramin. Suramin does not cross the blood-brain barrier, so it is not effective for patients with meningoencephalo-pathic involvement. Somnolence, or inability to concentrate, may be seen before the CNS is involved. Treatment for CNS late-stage trypanosomiasis is melarsoprol; however, because of potential toxicity, this drug is reserved for late-stage disease only. Metronidazole is used to treat amebiasis, not try-panosomiasis. Sulfadoxine-pyrimethamine and chloroquine are antimalarial and are not used for this indication. Sulfadoxine-pyrimethamine with leucovorin (folinic acid) can also be used to treat Toxoplasma gondii.

4. D. Metronidazole is the drug most frequently recommended for treatment of this infection. Quin-acrine has been used in the past, but because of tox-icity and lack of availability it is not a first choice. Albendazole, not mebendazole, has been used with a good outcome in giardiasis. Mebendazole is used to treat roundworm infections. Melarsoprol is used to treat advanced-stage CNS African trypanosomia-sis. Mefloquine is an oral drug used to treat chloro-quine-resistant malaria. Meglumine antimonate (Glucantime) or sodium stibogluconate (Pentostam) is used to treat cutaneous or mucocutaneous leish-maniasis by the IV route. Giardiasis, which may be chronic and the cause of malabsorption, sometimes requires multiple stool examinations or a duodenal aspirate. Infection may be through contaminated food or beverages or may be acquired through surface water contaminated by mammals such as beavers. The risk of human infection appears increased in those with reduced gastric acid production.

5. A. Liposomal amphotericin B was approved by the U.S. Food and Drug Administration to treat visceral leishmaniasis. Pentavalent antimony compounds, pentamidine, amphotericin B, and aminosi-dine (paromomycin) have all been demonstrated efficacious here. The liposomal amphotericin appears to be better taken up by the reticuloendothe-lial system, where the parasite resides, and partitions less in the kidney, where amphotericin B traditionally manifests its toxicity. In addition to being better tolerated by patients, it has proved to be very effective in India, where resistance to antimony drugs is widespread. This patient appears to have acquired his infection there, where many infected patients develop darkening of the skin, hence the name kala-azar, or black sickness. Albendazole, an anthelmintic, has no role here. Atovaquone, a naphthoquinone, is used to treat malaria, babesiosis, and pneumocystosis. Pyrimethamine-sulfadoxine is used to treat malaria and toxoplasmosis. Proguanil inhibits the dihydro-folate reductase of malaria parasites and is used in combination with atovaquone.

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