What is the treatment for roundworm (Toxocariasis or Ascariasis) infection resistant to albendazole?

Treatment of Albendazole-Resistant Roundworm Infection

For roundworm (Ascaris lumbricoides) infections resistant to albendazole, switch to mebendazole 500 mg as a single oral dose or ivermectin 200 μg/kg as a single oral dose. 1

Species-Specific Considerations

For Ascariasis (Common Roundworm)

• Mebendazole 500 mg orally as a single dose is the primary alternative treatment when albendazole resistance is suspected 1
• Ivermectin 200 μg/kg orally as a single dose is equally effective as an alternative 1
• Mebendazole has demonstrated a 95% cure rate for ascariasis in FDA-approved labeling 2
• Both alternatives have shown 100% cure rates in clinical studies for Ascaris infections 3

For Toxocariasis (Visceral Larva Migrans)

• Albendazole 400 mg twice daily for 5 days is the standard treatment 4
• If true resistance is documented (rare in Toxocara), consider extending treatment duration or adding corticosteroids for symptomatic management 4
• Note that Toxocara infections often require longer treatment courses than intestinal roundworms, so apparent "resistance" may actually reflect inadequate treatment duration rather than true drug resistance 5

Critical Pre-Treatment Safety Screening

Before administering ivermectin, you must exclude Loa loa infection in any patient who has traveled to endemic regions (Central/West Africa), as severe adverse reactions including encephalopathy can occur 1

Monitoring for Extended Treatment

• If treatment extends beyond 14 days with any benzimidazole (albendazole or mebendazole), monitor for hepatotoxicity and leukopenia 1, 6
• Check liver function tests and complete blood count at baseline and every 2 weeks during prolonged therapy 1

Follow-Up Strategy

• Repeat stool examination 2-3 weeks after treatment to confirm cure 6
• If symptoms persist despite alternative therapy, consider:
  • Reinfection from environmental exposure 6
  • Mixed parasitic infections requiring different treatment 6
  • Alternative diagnoses beyond parasitic infection 6

Common Pitfall to Avoid

The most common error is assuming treatment failure represents true drug resistance when the actual issue is inadequate dosing or treatment duration. For intestinal Ascaris, single-dose therapy is appropriate, but tissue-dwelling larvae (as in Toxocariasis) require multi-day regimens 4. Always confirm the specific roundworm species before declaring resistance and switching therapy.