Anthelmintics: Generic and Brand Names
- Anthelmintics
- albendazole (Albenza)
- ivermectin (Stromectol)
- mebendazole (Vermox)
- praziquantel (Biltricide)
- pyrantel (Antiminth)
Disease Spotlight: Helminthic Infections
Helminthic infections are worm infestations in the GI tract or other tissues. Soil-transmitted helminths alone infect more than 1.5 billion people, roughly 24% of the world's population, which makes them among the most common infections worldwide (WHO). Infestations are common in tropical and subtropical areas, and travelers carry them home where the worms can infect others. The most common infectious helminths are nematodes (roundworms) and platyhelminthes (flatworms), which invade the intestines and tissues.
Therapeutic Action
Anthelmintics act on metabolic pathways that exist in the worm but are absent or very different in the human host. The benzimidazoles, mebendazole and albendazole, bind selectively to the parasite's beta-tubulin, which immobilizes and kills the worm; albendazole is better absorbed, so it is preferred for systemic infections like echinococcosis and cysticercosis (StatPearls).
Indications
Each drug targets a different set of worms. Albendazole treats active lesions from pork tapeworm and cystic disease of the liver, lungs, and peritoneum from dog tapeworm. Ivermectin treats threadworm disease (strongyloidiasis) and onchocerciasis (river blindness). Mebendazole treats pinworms, roundworms, whipworms, and hookworms. Praziquantel treats a wide range of schistosomes (flukes). Pyrantel treats pinworms and roundworms.
Culture the suspected worm before starting any drug. In children, albendazole, ivermectin, and praziquantel are more toxic and are avoided, so a chewable mebendazole preparation is usually given instead, and children can develop serious GI effects, so nutrition and hydration are the focus. Adults may be repulsed by the diagnosis and reluctant to discuss the lifestyle changes and treatment, so communicate clearly. Pregnant and nursing women should not use these drugs unless the benefit clearly outweighs the risk. Older adults, especially those with hepatic or renal dysfunction, are more prone to GI and CNS effects.
Pharmacokinetics
Here are the characteristic interactions of anthelmintics and the body in terms of absorption, distribution, metabolism, and excretion:
| Route | Onset | Peak | Duration |
|---|---|---|---|
| Oral | Slow | 2-4 h | N/A |
| Half-life (T1/2) | Metabolism | Excretion |
|---|---|---|
| 2.5-9 h | Liver | Colon (feces) |
Contraindications and Cautions
Known allergy to the drug, to prevent hypersensitivity. Lactation, since the drug can enter breast milk. Renal and hepatic disease, which interfere with metabolism and excretion. Severe diarrhea and malnourishment, which can alter the drug's effect on the intestine and on existing helminths. Pyrantel has not been established as safe in children younger than 2 years.
Adverse Effects
- GI: abdominal discomfort, diarrhea, pain
- CNS: headache, dizziness
- Immunologic: fever, shaking, chills, malaise, rash, pruritus, hair loss
- Albendazole is associated with severe bone marrow depression and renal failure.
Interactions
Dexamethasone, praziquantel, and cimetidine increase the toxic effects of albendazole.
Nursing Considerations
Nursing Assessment
Screen for the cautions and contraindications (allergy, hepatorenal dysfunction, pregnancy, lactation). Do a baseline physical exam covering other medications, reflexes and muscle strength, and skin color, temperature, and texture so you can gauge effectiveness and catch adverse effects. Check liver function, including liver function tests, for appropriateness of therapy and toxicity. Obtain a stool culture for ova and parasites to identify the worm and set the right treatment. Assess the abdomen for changes tied to the infection and for adverse effects.
Nursing Diagnoses
- Acute pain related to GI, CNS, and skin effects of the drug
- Imbalanced nutrition: less than body requirements related to GI effects of the drug
Implementation with Rationale
Arrange culture and sensitivity testing before therapy so the drug matches the infecting worm. Give the complete course for full effect. Monitor hepatic function and perform an ophthalmologic exam before and periodically during treatment so you catch failing liver function or deteriorating vision early and can stop the drug. If CNS effects appear, use side rails and assist with ambulation when dizziness or weakness is present. Provide oral hygiene and ready bathroom access for GI effects. Teach the regimen to support understanding and compliance.
Evaluation
Watch for resolution of the infestation and improvement in signs and symptoms. Monitor for adverse effects (orientation and affect, nutritional state, skin color and lesions, hepatic function, abdominal discomfort and pain). Confirm the patient can name the drug, its indication, and the adverse effects to watch for. Track compliance.
Frequently Asked Questions
Why confirm the worm before treating? Each drug targets a different set of worms, so the right choice depends on the species. Obtain a stool culture for ova and parasites first; matching the drug to the worm is what makes treatment work.
How do anthelmintics kill worms without harming the patient? They act on metabolic pathways found in the worm but absent or very different in humans. The benzimidazoles (mebendazole, albendazole) bind the worm's beta-tubulin, immobilizing and killing it (StatPearls).
When is albendazole used instead of mebendazole? Mebendazole is generally preferred for pinworm and roundworm. Albendazole is better absorbed, so it is favored for systemic infections such as echinococcosis (hydatid disease) and cysticercosis (StatPearls).
Why are children treated differently? Albendazole, ivermectin, and praziquantel are more toxic in children and are usually avoided, so a chewable mebendazole preparation is often used instead. Children develop serious GI effects easily, so nutrition and hydration become the priority.
Does the whole household need treatment for pinworms? Pinworms spread easily, so providers often treat household contacts and stress hygiene, handwashing, and laundering of bedding and clothing to prevent reinfection. Follow the prescriber's guidance.
What monitoring matters most during therapy? Check liver function and, with prolonged albendazole, perform periodic eye exams, since the drug is linked to bone marrow depression and can affect the liver. Finish the complete course for full effect.