Chemotherapy of Parasitic Infections

Chemotherapy of Parasitic Infections

• Chemotherapy is used to treat parasitic infections, including protozoal infections and helminth infections.
• Protozoal infections include malaria, amebiasis, giardiasis, trichomoniasis, and leishmaniasis.
• Helminth infections include nematodes (roundworms), cestodes (flatworms), and trematodes (flukes).

Malaria

• Five species of Plasmodium can cause human malaria: P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi.
• P. falciparum causes the most severe complications and deaths.
• Antimalarial agents have varying effectiveness against different parasite species and stages of the life cycle.

Parasite Life Cycle

• The parasite life cycle involves a mosquito vector, which becomes infected with the parasite's sexual form through human blood.
• Sporozoites develop in the mosquito and are inoculated into humans during the next feeding.
• In the exoerythrocytic stage, the sporozoites multiply in the liver to form tissue schizonts.
• Then, the parasites escape into the bloodstream as merozoites.

Anthelmintics

• Anthelmintics are used to treat helminthic infestations, which are a broad range of diseases caused by multicellular organisms.
• Helminths include intestinal nematodes, tissue-invading nematodes, cestodes, and trematodes.
• They enter the human host through contaminated food, insect bites, or direct skin penetration.

Nematode Infestations

• Intestinal nematodes include ascariasis (giant roundworm infestation), enterobiasis (pinworm infestation), trichuriasis (whipworm infestation), and hookworm infestation.
• Extra-intestinal nematodes include lymphatic filarial infestation and onchocerciasis (river blindness).

Cestode Infestations

• Cestode infestations include taeniasis (beef and pork tapeworm infestation) and trematode infestations (including schistosomiasis).

Anthelmintic Drugs

• Mebendazole is a synthetic benzimidazole with a wide spectrum of anthelminthic activity.

• It acts by inhibiting microtubule synthesis, preventing glucose uptake, and killing hookworm, Ascaris, and Trichuris eggs.

• It is used to treat ascariasis, trichuriasis, hookworm, and pinworm infections.

• Mebendazole is nearly free of adverse effects, but is contraindicated in pregnancy.

• Albendazole is a benzimidazole carbamate with a broad-spectrum of anthelminthic activity.

• It is used to treat onchocerciasis, strongyloidiasis, and W. bancrofti infestations.

• Adverse effects include fatigue, dizziness, nausea, vomiting, abdominal pain, and rashes.

• Piperazine is an alternative for the treatment of ascariasis, with cure rates over 90% when taken for 2 days.

• It is readily absorbed orally and acts by binding to muscle membrane GABA receptors, causing hyperpolarization and flaccid paralysis of the worm.

• Adverse effects include nausea, vomiting, diarrhea, abdominal pain, dizziness, and headache.

• Praziquantel is a synthetic isoquinoline-pyrazine derivative that increases the permeability of trematode and cestode cell membranes to calcium, resulting in paralysis and death.

• It is used to treat schistosomiasis, taeniasis, and other trematode and cestode infestations.

• Adverse effects are mild and transient.

• Diethylcarbamazine is a synthetic piperazine derivative used to treat filariasis, loiasis, and tropical eosinophilia.

• It immobilizes microfilariae and alters their surface structure, making them susceptible to destruction by host defense mechanisms.

• Thiabendazole is a benzimidazole compound used to treat strongyloidiasis.