Is Mebendazole (anthelmintic medication) 10mg/kg/dose twice daily for 3 days an effective treatment for pinworm/threadworm and roundworm infections in a patient, presumably a child or adult, without any contraindications?

Mebendazole 10mg/kg/dose Twice Daily for 3 Days is NOT the Recommended Dosing for Pinworm or Roundworm

You have significantly overdosed mebendazole—the correct dose is 100 mg as a single dose (not weight-based), repeated in 2 weeks, for both pinworm and roundworm infections. 1

Correct Dosing for Pinworm (Enterobius vermicularis)

• The American Academy of Pediatrics recommends mebendazole 100 mg as a single oral dose, with a repeat dose in 2 weeks. 1
• This is a standardized dose across all age groups, including young children—it is NOT weight-based. 1
• The 100 mg single dose is equally effective and safe as albendazole 400 mg for pinworm treatment. 1
• The repeat dose at 2 weeks is essential to eradicate any newly hatched worms from eggs that survived the initial treatment. 1, 2

Correct Dosing for Roundworm (Ascaris lumbricoides)

• Mebendazole is effective for roundworm at the same 100 mg single dose regimen used for pinworm. 3
• For roundworm specifically, some sources support mebendazole as a drug of choice, though the exact dosing may vary by indication. 3
• The weight-based dosing you used (10 mg/kg twice daily for 3 days) is NOT standard for these common intestinal nematodes. 1, 2

Why Your Dosing is Problematic

• A 10 mg/kg dose twice daily for 3 days represents a massive overdose compared to the standard 100 mg single dose. For example, in a 20 kg child, you gave 200 mg twice daily for 3 days (total 1,200 mg) versus the recommended 100 mg once (repeated once at 2 weeks).
• The higher multi-day dosing regimen (300 mg twice daily for 3 days) has been studied for tapeworm infections (Taenia species), not for pinworm or roundworm. 4
• Mebendazole is generally safe, but prolonged use beyond 14 days requires monitoring for hepatotoxicity and leukopenia. 1 While your 3-day course is shorter than 14 days, the excessive dose is unnecessary and increases risk without added benefit.

Clinical Monitoring After Overdose

• Monitor the patient for gastrointestinal side effects (abdominal pain, diarrhea, nausea), though mebendazole is generally well-tolerated even at higher doses. 2
• Watch for signs of hepatotoxicity (jaundice, dark urine, right upper quadrant pain) or hematologic effects (unusual bruising, bleeding), though these are rare with short-term use. 1
• Treatment failure is rare with correct dosing, and persistent symptoms usually indicate reinfection rather than medication resistance. 1

Preventing Reinfection

• Treat all household members simultaneously, especially if there are multiple or repeated symptomatic infections. 2, 5
• Emphasize hand hygiene (frequent handwashing after bowel movements and before meals), nail clipping, and avoidance of nail-biting and scratching the perianal area. 2, 5
• Wash underwear and nightwear daily to destroy eggs, and have the patient wear pajamas or pants at night to prevent scratching. 5

Key Takeaway

For future cases, use mebendazole 100 mg as a single dose, repeated in 2 weeks—this is the evidence-based standard for both pinworm and roundworm infections. 1, 2 The patient you treated likely received an excessive but probably safe dose; monitor for side effects and ensure proper hygiene measures to prevent reinfection.