What is the treatment for pinworm (Enterobius vermicularis) infection?

Treatment of Pinworm Infection

The first-line treatment for pinworm (Enterobius vermicularis) infection is either albendazole 400 mg or mebendazole 100 mg as a single oral dose, with a mandatory repeat dose in 2 weeks to eliminate newly hatched worms. 1, 2

Medication Options and Dosing

First-Line Agents

• Albendazole 400 mg as a single oral dose, repeated after 2 weeks 1, 2
• Mebendazole 100 mg as a single oral dose, repeated after 2 weeks 1, 2, 3
• Both medications are equally effective and safe, with cure rates for mebendazole reaching 95% 3
• The dosing is standardized across all age groups, including young children as young as 2 years old 1

FDA-Approved Dosing Details

• Mebendazole tablets may be chewed, swallowed whole, or crushed and mixed with food 3
• No special procedures such as fasting or purging are required 3
• If the patient is not cured three weeks after treatment, a second full course of treatment is advised 3

Alternative Agent

• Pyrantel pamoate 11 mg/kg (maximum 1 g) as a single dose, repeated in 2 weeks 4
• This is the preferred option in pregnant women, as it is adulticidal only (not ovicidal like albendazole and mebendazole) 4

Why the Two-Week Repeat Dose is Critical

The repeat dose at 2 weeks is essential because these medications kill adult worms but may not eliminate all eggs 1. The two-week interval allows any eggs present at initial treatment to hatch into adult worms, which are then killed by the second dose, breaking the cycle of autoinfection 1, 4.

Clinical Presentation to Recognize

• Nocturnal perianal itching is the hallmark symptom and most common presentation 1, 2, 4
• However, 30-40% of infected children are completely asymptomatic 1
• Additional symptoms may include weight loss, irritability, diarrhea, and abdominal pain 1, 2
• In girls, vaginal discharge may occur from female genital tract colonization 1, 2

Diagnostic Approach

• The cellophane tape test (also called "sellotape test") is the preferred diagnostic method 1, 2
• Apply adhesive tape to the perianal skin in the morning before bathing or defecation to collect eggs 2
• A single test has only 50% sensitivity, but performing the test on three different mornings increases sensitivity to approximately 90% 4
• Do not examine stool samples, as pinworms and eggs are not usually passed in stool 1, 4

Treatment of Household Contacts

Treat all household members simultaneously, especially when there are multiple or repeated symptomatic infections, as reinfection is extremely common 4, 5. This includes sexual partners in adults 5. Failure to treat all contacts is a major cause of treatment failure and recurrence 5.

Monitoring and Safety Considerations

• For standard pinworm treatment (single dose repeated once), no special monitoring is required 1
• Only monitor for hepatotoxicity and leukopenia if albendazole is used for more than 14 days, which would be unusual for pinworm but relevant for other helminthic infections 6, 1

Managing Recurrent Infections

Understanding Treatment Failure vs. Reinfection

• True treatment failure is rare; persistent symptoms usually indicate reinfection rather than medication resistance 1
• Recurrences are common due to repeated cycles of autoinfection, given the short life span of adult pinworms 4

For Recurrent Cases

• For recurrent infections despite standard treatment, consider prolonged "pulse scheme" treatment for up to 16 weeks 5
• Ensure all household members are treated simultaneously 4, 5
• Reinforce hygiene measures (see below) 4, 5

Rare Ectopic Infections

• In girls with recurrent vaginal symptoms despite complete treatment and negative stool samples, the vagina may serve as a reservoir for pinworms through ascending migration 7
• This may require extended treatment courses (e.g., mebendazole 100 mg for 3 days, repeated at 3-week intervals over 3 months) 7

Essential Hygiene Measures to Prevent Reinfection

These non-pharmacologic measures are critical to prevent the cycle of autoinfection and reinfection 4, 5:

• Frequent handwashing, especially after bowel movements and before meals 4
• Clip fingernails short to reduce egg accumulation under nails 4
• Avoid finger-sucking, nail-biting, and scratching the anogenital area 4
• Ensure supervised body hygiene in young children 5
• Wash bedding and clothing in hot water 5

Common Pitfalls to Avoid

• Failing to give the repeat dose at 2 weeks is a major cause of treatment failure 1
• Not treating all household members simultaneously leads to ongoing transmission 4, 5
• Examining stool samples is not useful for pinworm diagnosis 1, 4
• Assuming treatment failure when symptoms recur without considering reinfection as the more likely cause 1