Antihelminthic drugs have diverse chemical structures, mechanisms of action, and properties. Many act against specific parasites, and few are devoid of significant toxicity to host cells. In addition to the direct toxicity of the drugs, reactions to dead and dying parasites may cause serious toxicity in patients. In the text that follows, the drugs are divided into 3 groups on the basis of the type of helminth primarily affected (nematodes, trematodes, and cestodes). The drugs of choice and alternative agents for selected important helminthic infections are listed in Table 53–1.
TABLE 53–1Drugs for the treatment of helminthic infections. ||Download (.pdf) TABLE 53–1 Drugs for the treatment of helminthic infections.
|Infecting Organism ||Drugs of Choice ||Alternative Drugs |
|Nematodes || || |
| Ascaris lumbricoides (roundworm) ||Albendazole or mebendazole or pyrantel pamoate ||Ivermectin, piperazine |
| Necator americanus and Ancylostoma duodenale (hookworm) ||Pyrantel pamoate or albendazole or mebendazole || |
| Trichuris trichiura (whipworm) ||Albendazole or mebendazole ||Ivermectin |
| Strongyloides stercoralis (threadworm) ||Ivermectin ||Albendazole, thiabendazole |
| Enterobius vermicularis (pinworm) ||Mebendazole or pyrantel pamoate ||Albendazole |
| Trichinella spiralis (trichinosis) ||Mebendazole (+/– corticosteroids) ||Albendazole |
| Cutaneous larva migrans ||Albendazole or ivermectin ||Thiabendazole |
| Wuchereria bancrofti and Brugia malayi (filariasis) ||Diethylcarbamazine ||Ivermectin |
| Onchocerca volvulus (onchocerciasis) ||Ivermectin || |
|Trematodes (flukes) || || |
| Schistosoma haematobium ||Praziquantel ||Metrifonate |
| Schistosoma mansoni ||Praziquantel ||Oxamniquine |
| Schistosoma japonicum ||Praziquantel || |
| Paragonimus westermani ||Praziquantel ||Bithionol |
| Fasciola hepatica (sheep liver fluke) ||Bithional or triclabendazole || |
| Fasciolopsis buski (large intestinal fluke) ||Praziquantel or niclosamide || |
|Cestodes (tapeworms) || || |
| Taenia saginata (beef tapeworm) ||Praziquantel or niclosamide ||Mebendazole |
| Taenia solium (pork tapeworm) ||Praziquantel or niclosamide || |
| Cysticercosis (pork tapeworm larval stage) ||Albendazole ||Praziquantel |
| Diphyllobothrium latum (fish tapeworm) ||Praziquantel or niclosamide || |
| Echinococcus granulosus (hydatid disease) ||Albendazole || |
DRUGS THAT ACT AGAINST NEMATODES
The medically important intestinal nematodes responsive to drug therapy include Enterobius vermicularis (pinworm), Trichuris trichiura (whipworm), Ascaris lumbricoides (roundworm), Ancylostoma and Necator species (hookworms), and Strongyloides stercoralis (threadworm). More than 1 billion persons worldwide are estimated to be infected by intestinal nematodes. Pinworm infections are common throughout the United States, and hookworm and threadworm are endemic in the southern United States. Tissue nematodes responsive to drug therapy include Ancylostoma species, which cause cutaneous larva migrans. Species of Dracunculus, Onchocerca, Toxocara, and Wuchereria bancrofti (the cause of filariasis) are responsive to drug treatment. The number of persons worldwide estimated to be infected by tissue nematodes exceeds 0.5 billion.
The action of albendazole is thought to involve inhibition of microtubule assembly. The drug is larvicidal in ascariasis, cystercercosis, hookworm, and hydatid disease and is ovicidal in ascariasis, ancylostomiasis, and trichuriasis.