Treatment of Ascaris lumbricoides Infection
For a patient infected with Ascaris lumbricoides, treat with a single oral dose of either albendazole 400 mg, mebendazole 500 mg, or ivermectin 200 μg/kg. 1
First-Line Treatment Options
All three medications are equally effective as single-dose therapy:
- Albendazole 400 mg orally as a single dose 1, 2
- Mebendazole 500 mg orally as a single dose 1, 2
- Ivermectin 200 μg/kg orally as a single dose 1, 2
These regimens achieve cure rates exceeding 95% and egg reduction rates over 99% 3, 4. The tablet may be chewed, swallowed, or crushed and mixed with food 5.
Alternative Mebendazole Dosing (FDA-Approved)
If the single 500 mg dose is unavailable, the FDA-approved alternative is mebendazole 100 mg twice daily for 3 consecutive days, which achieves a 98% cure rate 5. This multi-day regimen is equally effective but less convenient for mass treatment programs 3.
Clinical Considerations Before Treatment
Diagnosis Confirmation
- Concentrated stool microscopy is the primary diagnostic test 1, 2
- Fecal PCR offers higher sensitivity when available 1, 2
- Direct visualization of adult worms (earthworm-sized, pink or white) passed in stool or occasionally regurgitated is diagnostic 1
Assess for Complications Requiring Urgent Intervention
- Intestinal obstruction (more common in children with heavy worm burden) 1, 2
- Biliary obstruction (more common in adults) 1, 2
- Loeffler's syndrome (fever, dry cough, wheezing, urticarial rash during larval migration phase) 1
If obstruction is present, surgical consultation is essential alongside anthelmintic therapy 2.
Special Clinical Scenario: Loeffler's Syndrome
When Ascaris presents with Loeffler's syndrome during the tissue migration phase (prepatent period of 2-3 months):
- Treat with standard single-dose albendazole 400 mg or mebendazole 500 mg 1
- Consider repeating treatment one month after resolution of pulmonary symptoms 6
- Stool microscopy may be negative during this early phase since eggs are not yet being produced 1
- Serology becomes positive at 4-8 weeks but has limited clinical utility 1
Important Caveats
No Special Preparation Required
- No fasting or purging is necessary before or after treatment 5
Treatment Failure
- If the patient is not cured three weeks after treatment, repeat the same regimen 5
- Failure rates are low but can range from 0% to 30.3% with albendazole, 0% to 22.2% with mebendazole, and 0% to 21.6% with ivermectin 3
Coinfection Considerations
- Screen for Strongyloides stercoralis before using corticosteroids in patients with eosinophilia, as hyperinfection syndrome can be fatal 6, 1
- Multiple helminth infections are common in migrants and may require additional targeted therapy 1
Safety Profile
- All three medications are safe with minimal adverse events 3
- Most common side effects are mild and transient: nausea, vomiting, abdominal pain, diarrhea, headache, and fever 3
- No serious adverse events have been reported in clinical trials 3