Drug of Choice for Nematodes and Platyhelminths
There is no single drug that is the drug of choice for ALL nematodes and platyhelminths—the optimal agent depends on the specific parasite, but albendazole 400 mg PO has the broadest spectrum of activity across both groups and serves as the most versatile first-line agent for most common infections. 1, 2, 3
Algorithmic Approach by Parasite Class
For Nematodes (Roundworms)
Albendazole 400 mg PO single dose is the preferred broad-spectrum agent for most intestinal nematodes 1, 2, 3:
- Ascaris lumbricoides: Albendazole 400 mg, mebendazole 500 mg, or ivermectin 200 μg/kg as single dose 1, 3
- Hookworm (Ancylostoma, Necator): Albendazole 400 mg daily for 3 days 1, 2
- Enterobius (pinworm): Albendazole 400 mg or mebendazole 100 mg, repeat in 2 weeks 1, 4
- Strongyloides: Ivermectin 200 μg/kg daily for 2 days is preferred over albendazole 1, 5
- Trichuris (whipworm): Mebendazole 100 mg twice daily PLUS ivermectin 200 μg/kg daily for 3 days (combination improves cure rates in heavy infections) 1
For Platyhelminths (Flatworms)
Praziquantel is the drug of choice for most flatworm infections, with dosing varying by species 1:
Cestodes (Tapeworms):
- Taenia saginata: Praziquantel 10 mg/kg single dose 1
- Taenia solium (intestinal): Niclosamide 2 g single dose preferred (praziquantel contraindicated unless neurocysticercosis excluded) 1
- Hymenolepis: Praziquantel 25 mg/kg single dose 1
Trematodes (Flukes):
- Schistosoma: Praziquantel 60 mg/kg in two divided doses 1
Critical Clinical Pitfalls
When Albendazole Fails or Is Inadequate:
- Trichuris requires combination therapy (mebendazole + ivermectin) due to low cure rates with single agents 1
- Strongyloides requires ivermectin as first-line; albendazole is inferior 1, 5
- Monitor for hepatotoxicity and leukopenia if albendazole used >14 days 2, 4
When Praziquantel Is Contraindicated:
- Never use praziquantel for T. solium without excluding neurocysticercosis—can precipitate CNS inflammation 1
- Use niclosamide 2 g as safer alternative for intestinal tapeworms when species uncertain 1
Empiric Treatment for Unidentified Infections
For suspected but undiagnosed helminth infections (e.g., eosinophilia with negative stool studies):
- Albendazole 400 mg PLUS ivermectin 200 μg/kg as single doses covers most nematodes 2
- This combination addresses the limitation that stool microscopy misses many infections 2
Evidence Quality Considerations
The 2025 UK guidelines from the Journal of Infection 1 provide the most comprehensive and current treatment algorithms, superseding older research 6, 7, 8. The benzimidazoles (albendazole, mebendazole) work by blocking parasite microtubule systems, leading to glucose uptake inhibition and cell death 6, 9. Albendazole's superior absorption compared to mebendazole makes it more effective for tissue infections 6.
Drug resistance is emerging in hookworm, Trichuris, possibly Ascaris, and Giardia, which may explain treatment failures 6. In such cases, consider combination therapy or alternative agents rather than assuming reinfection.