What is the first‑line therapy for pinworm (Enterobius vermicularis) infection, including dosing, repeat dose, and recommendations for children, pregnant or lactating patients, and household contacts?

Treatment for Pinworms (Enterobius vermicularis)

Give albendazole 400 mg as a single oral dose, repeated in 2 weeks, for all patients aged 2 years and older, including adults. 1, 2, 3

First-Line Medication Options

• Albendazole 400 mg is the preferred first-line treatment, given as a single oral dose with a mandatory repeat dose at 2 weeks 1, 2, 3
• Mebendazole 100 mg is equally effective as an alternative, also given as a single dose repeated in 2 weeks 1, 2
• Pyrantel pamoate 11 mg/kg (maximum 1 g) is a third option, particularly useful in pregnancy, given as a single dose repeated in 2 weeks 4, 5

The 2-week repeat dose is essential because these medications kill adult worms but may not eliminate all eggs; the second dose eradicates any newly hatched worms from eggs that survived initial treatment. 1, 4

Dosing Across Age Groups

• Adults and children ≥2 years: Albendazole 400 mg or mebendazole 100 mg—the dose is standardized across all ages 1, 2
• Children 12-24 months: Expert consultation is recommended before initiating albendazole; the same 400 mg dose applies if treatment proceeds 2, 3
• Children <12 months: Defer to expert consultation for appropriate management 3

Special Populations

Pregnancy and Lactation

• Pyrantel pamoate is preferred during pregnancy over albendazole and mebendazole due to better safety data 4
• Ivermectin (not typically used for pinworms but mentioned in broader helminth guidelines) is considered low-risk and probably compatible with breastfeeding 2

Household Contacts

• Treat all household members simultaneously, especially when there are multiple or repeated symptomatic infections, because reinfection is extremely common even with effective medication 4, 5
• Asymptomatic household contacts should be treated when index cases are identified to break the transmission cycle 4

Monitoring and Safety

• Short-course treatment (single dose × 2) requires no laboratory monitoring 1
• If albendazole is used for >14 days (not typical for pinworms but relevant for other helminths), monitor liver function tests and complete blood count for hepatotoxicity and leukopenia 1, 2
• Treatment failure is rare; persistent symptoms after appropriate therapy almost always indicate reinfection rather than drug resistance 1

Diagnostic Confirmation

• Perianal adhesive tape test (cellophane tape test) is the preferred diagnostic method, performed in the morning before bathing or defecation 6, 3, 4
• Sensitivity of a single tape test is ~50%, but increases to ~90% when performed on three consecutive mornings 4
• Stool examination is not recommended because pinworms and eggs are rarely passed in stool 1, 3, 4
• Direct visualization of adult worms in the perianal area, particularly at night, confirms diagnosis 3

Clinical Presentation to Recognize

• Nocturnal perianal itching is the most common symptom, occurring in 60-70% of infected patients 1, 3
• 30-40% of infected children are completely asymptomatic 1, 4
• Other symptoms include irritability, weight loss, diarrhea, abdominal pain, and restlessness 1, 3, 4
• In girls, vaginal discharge may occur from female genital tract colonization when worms migrate into the vagina 1, 3

Common Pitfalls and How to Avoid Them

• Failing to repeat the dose at 2 weeks is the most common cause of apparent treatment failure; the second dose is mandatory, not optional 1, 2, 4
• Treating only the symptomatic child without treating household members leads to rapid reinfection 4, 5
• Expecting immediate symptom resolution: Pruritus may persist for several days after successful treatment due to local inflammation 4
• Recurrent infections are usually reinfection, not resistance: Emphasize hygiene measures including frequent handwashing, clipping fingernails short, avoiding nail-biting and finger-sucking, and daily morning bathing to remove eggs 4

Refractory Cases

• In the rare case of truly refractory vaginal pinworm infection despite standard 2-dose therapy, consider 3-dose albendazole at 2-week intervals (given at weeks 0,2, and 4) 7
• Ensure all household members are treated simultaneously and hygiene measures are strictly followed before concluding treatment has failed 4, 7