Medication Summary
Therapy for parasitic infestations is based on the specific parasite and the particular phase of the disease. The treatment of classic hookworm infection has the following 2 components:
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Correcting the anemia, which is usually achieved by means of iron therapy and proper diet
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Expelling the intestinal parasites
In rare cases (eg, acute severe gastrointestinal [GI] hemorrhage), blood transfusion may be needed to correct anemia.
Anthelmintic drugs effective against hookworms include pyrantel pamoate and benzimidazoles (eg, albendazole, mebendazole). Benzimidazoles are the most convenient and effective drugs for treating hookworm disease. Other older agents are also effective but may have lower clearance rates.
Anthelmintics
Class Summary
Anthelmintics are poorly absorbed, relatively nontoxic broad-spectrum agents that act by inhibiting tubulin polymerization. They have shown high clearance rates.
Because biochemical pathways in these parasites differ from those in human hosts, toxicity is directed toward the parasite, egg, or larvae. The mechanism of action varies within the drug class. Antiparasitic actions may include the following:
- Inhibition of microtubules, causing irreversible block of glucose uptake
- Inhibition of tubulin polymerization
- Depolarizing neuromuscular blockade
- Cholinesterase inhibition
- Increased cell membrane permeability, resulting in intracellular calcium loss
- Vacuolization of the schistosome tegument
- Increased cell membrane permeability to chloride ions via alteration of chloride channels
Albendazole (Albenza)
Albendazole is a benzimidazole carbamate that inhibits tubulin polymerization, resulting in degeneration of cytoplasmic microtubules. It decreases production of adenosine triphosphate (ATP) in the worm, causing energy depletion, immobilization, and finally death. Albendazole is converted in the liver to its primary metabolite, albendazole sulfoxide; less than 1% of this metabolite is excreted in urine. The plasma level rises substantially (as much as 5-fold) when the drug is ingested after a high-fat meal.
Albendazole is approved by the US Food and Drug Administration (FDA) for treatment of hookworm infection but is considered investigational. A single 400-mg dose is the treatment of choice; it has a high eradication rate and is easy to administer. At such a dosage, albendazole is selectively toxic to parasites because binding to parasite β-tubulin occurs at a much lower concentration than binding to mammalian protein. Because the drug acts locally on worms within the GI tract, its action is not dictated by its systemic concentration.
Mebendazole (Vermox)
Mebendazole inhibits microtubule polymerization by binding to cytoplasmic β-tubulin. By affecting the intestinal cells of the parasite, it prevents the organism from using nutrients and thus essentially starves it to death.
Mebendazole is recommended for treating eosinophilic enteritis. A 3-day course has a reported cure rate of 95% and egg reduction rate of 99.9%. Single-dose therapy is often advocated but may not be as effective as single-dose albendazole. At recommended dosages, mebendazole is selectively toxic to parasites because binding to parasite β-tubulin occurs at a much lower concentration than binding to mammalian protein. Because the drug acts locally on worms within the GI tract, its action is not dictated by its systemic concentration.
Repeat stool examination with a concentration technique is recommended after 2 weeks; if the examination yields positive results, retreatment is indicated. No fasting or purging is required. The tablet may be chewed, swallowed, or crushed and mixed with food.
Pyrantel pamoate (Pin-X, Pamix, Reeses Pinworm Medicine)
Pyrantel pamoate is a depolarizing neuromuscular blocking agent that inhibits cholinesterases, resulting in spastic paralysis of the worm. It is FDA-approved for hookworm infection but is considered investigational for this condition.
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Adult hookworm attached to duodenal mucosa.
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Hookworm filariform larva. Courtesy of Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC).
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Adult Ancylostoma duodenale worm. Anterior end with mouth parts visible. Courtesy of Patrick W Hickey, MD.
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Adult Necator americanus worm. Anterior end with mouth parts visible. Courtesy of Patrick W Hickey, MD.
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Hookworm eggs examined on wet mount. Eggs of Ancylostoma duodenale and Necator americanus cannot be distinguished morphologically. Courtesy of Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC).
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Hookworm rhabditiform larva (wet preparation). Courtesy of Division of Parasitic Diseases, Centers for Disease Control and Prevention (CDC).
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Life cycle of hookworm. Courtesy of the Centers for Disease Control and Prevention (CDC) [https://www.cdc.gov/parasites/hookworm/biology.html].
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Hookworm egg in an unstained wet mount at 400x magnification. Courtesy of the Centers for Disease Control and Prevention (CDC) [https://www.cdc.gov/dpdx/hookworm/].
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Hookworm rhabditiform larva. Courtesy of the Centers for Disease Control and Prevention (CDC) [https://www.cdc.gov/dpdx/hookworm/].
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Side-by-side image of the mouth parts of each species of human-infecting hookworm. Courtesy of the Centers for Disease Control and Prevention (CDC) [https://www.cdc.gov/parasites/hookworm/biology.html].
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Cutaneous larva migrans. Courtesy of Wikipedia [WeisSagung, https://en.wikipedia.org/wiki/Cutaneous_larva_migrans].
Tables
Intensity |
Eggs per gram of feces |
Mild |
< 1,999 |
Moderate |
2,000-3,999 |
Heavy |
>4,000 |
Drug |
Adults |
Children (>24 months) |
Albendazole (preferred)* |
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|
Mebendazole |
|
|
Pyrantel pamoate |
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|
Thiabendazole |
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