Chapter 12: Antiprotozoal Agents

The foremost protozoal infection discussed is malaria, a serious systemic disease caused by the Plasmodium parasite, which completes its essential life cycle in the Anopheles mosquito before transmission to humans. The acute, characteristic signs of malaria, including cyclic fever and chills, are a result of merozoites bursting from ruptured red blood cells. Pharmacological intervention for malaria typically involves combination therapy using drugs such as chloroquine, mefloquine, primaquine, and quinine, which are designed to attack the parasite at varying life stages—schizonticidal, gametocytocidal, or sporontocidal—by mechanisms that include inhibiting protein synthesis or blocking DNA replication. Addressing growing drug resistance, fixed-combination agents like Malarone (atovaquone and proguanil) and Coartem (artemether and lumefantrine) are utilized. Beyond malaria, the chapter covers other key protozoal diseases: amebiasis (amebic dysentery caused by Entamoeba histolytica from contaminated food or water); giardiasis (Giardia lamblia), the most commonly diagnosed intestinal parasite in the United States; trichomoniasis (a sexually transmitted cause of vaginitis); leishmaniasis (sand fly transmission); and trypanosomiasis, which includes African sleeping sickness and Chagas disease. Agents such as metronidazole, tinidazole, and pentamidine are primary treatments for these other infections, generally working by interfering with the protozoal cell's ability to synthesize DNA. Nursing considerations for all antiprotozoal drugs emphasize extensive assessment for contraindications, including liver dysfunction, alcoholism, pregnancy, and lactation, and close monitoring for adverse effects like visual or retinal damage, hepatic toxicity, and CNS effects such as dizziness and headache. Patients must be monitored for potential hemolytic crisis if they have Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency, especially when taking chloroquine or primaquine, and advised to strictly avoid alcohol with specific drugs like metronidazole or tinidazole.