Treatment of Ascariasis
For ascariasis (Ascaris lumbricoides infection), treat with a single oral dose of albendazole 400 mg, mebendazole 500 mg, or ivermectin 200 μg/kg. 1
First-Line Treatment Options
All three medications below are equally recommended as single-dose therapy and achieve cure rates exceeding 95%:
- Albendazole 400 mg orally as a single dose 1, 2, 3
- Mebendazole 500 mg orally as a single dose 1, 2, 3
- Ivermectin 200 μg/kg orally as a single dose 1, 3
The tablet may be chewed, swallowed whole, or crushed and mixed with food for ease of administration. 4
Evidence Quality and Efficacy
The 2025 UK guidelines from the Journal of Infection provide the most current recommendations, establishing these three options as equivalent first-line choices. 1 Albendazole demonstrates 100% cure rates for Ascaris at the 400 mg single dose in clinical trials, with complete egg reduction. 5 Mebendazole achieves 98% cure rates for ascariasis according to FDA labeling data. 4 Both medications are highly effective against Ascaris even when less effective against other helminths like Trichuris. 5, 6
Alternative FDA-Approved Dosing for Mebendazole
If using the alternative FDA-approved regimen rather than the single 500 mg dose, mebendazole can be given as one tablet (100 mg) twice daily (morning and evening) for 3 consecutive days. 4 However, the single 500 mg dose recommended by current guidelines is more practical for treatment and mass therapy programs. 1
Special Clinical Scenario: Loeffler's Syndrome
When ascariasis presents as Loeffler's syndrome (pulmonary phase with fever, dry cough, wheezing, urticarial rash, and migratory pulmonary infiltrates):
- Treat with the same regimen: albendazole 400 mg or mebendazole 500 mg as a single dose 2, 3
- Consider repeating treatment one month after resolution of pulmonary symptoms 2
- Exercise caution with corticosteroids if Strongyloides co-infection is possible, as steroids can precipitate hyperinfection syndrome with Strongyloides 2
When to Retreat
If the patient remains infected three weeks after initial treatment (confirmed by repeat stool examination), administer a second course using the same regimen. 4 No special preparation such as fasting or purging is required before treatment. 4
Treatment Rationale
Even asymptomatic patients with confirmed ascariasis warrant treatment to prevent serious complications including intestinal obstruction (especially in children), biliary obstruction (more common in adults), appendicitis, and rarely hepatobiliary or pancreatic invasion. 3, 7, 8 The goal is to eliminate adult worms before migration causes these mechanical complications. 8
Common Pitfalls to Avoid
- Do not withhold treatment from asymptomatic patients—they still require anthelminthic therapy to prevent future complications from worm migration 3, 8
- Do not use fluconazole or other antifungals—these have no activity against helminths and the evidence provided about aspergillosis and candidiasis is irrelevant to ascariasis treatment 1
- Ensure adequate follow-up in endemic areas—reinfection occurs within months in most treated patients living in areas with poor sanitation, necessitating repeat treatment or mass deworming programs 8