How Long Does It Take For Mebendazole To Work?

In our latest question and answer, the pharmacist discusses how long it takes mebendazole (Emverm, Vermox, Ovex) to start working.

May 10, 2018

Jojo asked

My daughter took Ovex on Monday and she still has worms today how long will it be till they have gone?


Mebendazole (brand names Emverm, Vermox and Ovex) is an anti-parasitic, more specifically an anthelmintic, medication used to treat a variety of gastrointestinal infections including:

  • Roundworms
  • Whipworms
  • Pinworms
  • Hookworms

For pinworms, mebendazole is usually given as a single dose, however the dose may need be repeated again in 2 weeks. The second dose is given because mebendazole prevents the growing and reproduction of only the living worms, but not the eggs, which will mature between 2 to 3 weeks.

After the initial dose of mebendazole, it beings to work quickly, within a few days at most. As mebendazole immobilizes and causes the death of infectious worms, you may begin to notice them in the stool. However, as mebendazole does not kill eggs, you may not be symptom free for one to three weeks. This is why a second dose is often recommended.

According to the CDC, one dose of these mebendazole is over 90% effective in killing pinworms. A second dose has close to 100% efficacy.

GI Helminth Infections

In many cases, it is recommended that each person in the household is treated if it is possible to prevent spreading of the infection.

Advice to prevent the spread of infection or re-infection:

  • Keep nails short and clean
  • Avoid nail biting
  • Wear pajamas or underclothes to bed
  • Wash area each morning
  • Do not share towels within the house
  • Regularly wash clothes and bed linen
  • Thoroughly wash hands and nails after using the toilet and before meals (CDC Handwashing)
  • Treat everyone in the family at the same time

Ovex Package Insert

Emvem Package Insert

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