Antiprotozoal agents
Antiprotozoal agents treat malaria, leishmaniasis, toxoplasmosis, babesiosis, trypanosomiasis, and luminal protozoal infections; the parasite species and disease stage, not one universal drug, dictate the regimen. Artemisinin combination therapy is first-line for malaria, liposomal amphotericin B for visceral leishmaniasis, and pyrimethamine-sulfadiazine-leucovorin for toxoplasmic encephalitis.
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What this article covers
- Overview
Antiprotozoal agents treat infections from single-celled eukaryotic parasites: Plasmodium (malaria), Leishmania, Toxoplasma gondii, Babesia microti, Trypanosoma species, and the luminal protozoa Giardia, Entamoeba, and Trichomonas.
- Epidemiology
Malaria drives most antiprotozoal prescribing worldwide, concentrated in sub-Saharan Africa, South Asia, and South America; most United States cases are imported.
- Risk factors
Travel to an endemic area without chemoprophylaxis: the leading risk factor for imported malaria in a nonimmune host.
- Pathophysiology
4-aminoquinolines (chloroquine, hydroxychloroquine): block detoxification of heme into inert hemozoin in the plasmodial digestive vacuole; free heme accumulates and is toxic.
- Clinical features
Effects and adverse profiles vary widely by agent.
- Differential diagnosis
Agent selection is a differential among competing drugs, each chosen for a specific discriminator.
- Diagnosis
Species identification and disease staging drive drug choice more than any laboratory parameter.
- Management
Uncomplicated malaria, first-line: Artemether-lumefantrine 4 tablets PO as a 5-day, 10-dose course (initial dose, second dose 8 hours later, then twice daily on days 2-5).
- Complications
Toxicity clusters by mechanism: hemolysis with 8-aminoquinolines in G6PD deficiency, QT prolongation with quinine, mefloquine, and antimonials, marrow suppression with pyrimethamine.
- Prognosis
With prompt species-appropriate therapy, uncomplicated malaria, giardiasis, amebiasis, and trichomoniasis resolve without sequelae.
- Prevention
Malaria chemoprophylaxis for travelers: atovaquone-proguanil daily, started 1 to 2 days before travel and continued 7 days after leaving; or mefloquine weekly, started 1 to 2 weeks before and…
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Related articles
- Malaria
Malaria is a Plasmodium infection acquired from Anopheles mosquito bites, most often diagnosed in returning travelers from sub-Saharan Africa, and severe Plasmodium falciparum disease is a medical emergency treated with IV artesunate.
- Leishmaniasis
Leishmaniasis is a sand fly-transmitted protozoan infection causing either destructive cutaneous ulcers or visceral disease (kala-azar) with hepatosplenomegaly and pancytopenia, diagnosed by direct visualization of amastigotes and treated with liposomal amphotericin B or miltefosine.
- Toxoplasmosis
Toxoplasmosis is infection with the protozoan Toxoplasma gondii, acquired from undercooked meat or cat feces, causing a mononucleosis-like illness in immunocompetent hosts, reactivation encephalitis with ring-enhancing brain lesions in advanced HIV, and a severe congenital syndrome after maternal primary infection in pregnancy. Diagnosis in CNS disease is largely presumptive on serology, imaging, and empiric treatment response, and management is pyrimethamine-sulfadiazine-leucovorin, with prevention centered on CD4-based prophylaxis and food/cat-litter precautions in pregnancy.
- Babesiosis
Babesiosis is caused by the intraerythrocytic protozoan Babesia microti, transmitted by the blacklegged deer tick or by blood transfusion, producing a hemolytic febrile illness diagnosed on thin blood smear and treated first-line with atovaquone plus azithromycin.
- Chagas disease
Chagas disease is chronic infection with Trypanosoma cruzi, transmitted by the triatomine (kissing bug) vector in Latin America, that after a mild acute phase and a long silent latency destroys the myenteric plexus and cardiac conduction system, producing megaesophagus, megacolon, and dilated cardiomyopathy decades later. Diagnosis is by blood smear or PCR in acute disease and two different serologic assays in chronic disease, and treatment is benznidazole or nifurtimox, most effective when given early, while established organ disease is managed symptomatically.
- Trichomonas vaginalis infection
Trichomonas vaginalis is a flagellated protozoan sexually transmitted infection that presents with malodorous frothy yellow-green discharge and a strawberry cervix but is frequently asymptomatic, especially in men. Diagnosis rests on nucleic acid amplification testing of vaginal secretions, and treatment is a single 2 g oral dose of metronidazole or tinidazole with partner treatment and retesting in 3 months for high reinfection rates.