Does Vermox (mebendazole) cause side effects?
Vermox (mebendazole) is a member of the benzimidazole class of antiparasitic agents used to treat tapeworms, roundworms, hookworms, threadworms, pinworms, pork worms, and whipworms.
Vermox, like other benzimidazoles, causes death of parasites by interfering with the function of tubulin, an important protein in parasites, and preventing glucose uptake.
Common side effects of Vermox include- abdominal pain,
- diarrhea,
- dizziness,
- drowsiness,
- headache,
- vomiting,
- chills,
- itching,
- flushing,
- hiccups,
- ringing in the ears,
- low blood pressure,
- bloody urine, and
- reduced number of blood cells.
Serious side effects of Vermox include
- signs of bone marrow suppression (sudden weakness or ill feeling, fever, chills, sore throat, mouth sores, red or swollen gums, trouble swallowing, easy bruising or bleeding) and
- severe skin reaction (swelling in your face or tongue; sores around your eyes, nose, mouth, or genitals; hives or skin rash that spreads and causes blistering and peeling).
Drug interactions of Vermox include metronidazole, due to the increased risk of rare but serious life-threatening skin conditions known as Stevens-Johnson syndrome and toxic epidermal necrolysis.
Carbamazepine, fosphenytoin, ethotoin, and phenytoin may interfere with successful treatment with Vermox by decreasing its blood levels. Cimetidine may increase Vermox levels and increase the risk of side effects from Vermox.
Adverse outcomes with use of Vermox in pregnancy have not been seen, however the Centers for Disease Control (CDC) recommends postponing pinworm therapy until the third trimester when possible.
While excretion of Vermox into breast milk is unlikely, caution should be used since data is not available on excretion of Vermox into breast milk. Consult your doctor before breastfeeding.
What are the important side effects of Vermox (mebendazole)?
Mebendazole may cause:
- abdominal pain
- diarrhea.
- dizziness,
- drowsiness,
- headache,
- vomiting,
- chills,
- itching,
- flushing,
- hiccups,
- ringing in the ears,
- low blood pressure,
- bloody urine, and
- a drop in number of blood cells.
Vermox (mebendazole) side effects list for healthcare professionals
Clinical Studies
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
The safety of mebendazole was evaluated in 6276 subjects who participated in 39 clinical trials for treatment of single or mixed parasitic infections of the gastrointestinal tract. In these trials, the formulations, dosages and duration of mebendazole treatment varied. Adverse reactions reported in mebendazole-treated subjects from the 39 clinical trials are shown in Table 2 below.
Table 2: Adverse Reactions Reported in Mebendazole-treated Subjects from 39 Clinical Trials*
Adverse Reaction(s) |
Gastrointestinal Disorders |
Anorexia |
Abdominal Pain |
Diarrhea |
Flatulence |
Nausea |
Vomiting |
Skin and Subcutaneous Tissue Disorders |
Rash |
* Includes mebendazole formulations, dosages and treatment duration other than Vermox™ 100 mg tablet |
Postmarketing Experience
The following adverse reactions have been identified in adult and pediatric patients postmarketing with mebendazole formulations and dosages other than the Vermox 100 mg chewable tablet. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
Table 3: Adverse Reactions Identified During Postmarketing Experience with Mebendazole*
Adverse Reaction(s) | |
Blood and Lymphatic System Disorders | Agranulocytosis, Neutropenia |
Immune System Disorders | Hypersensitivity including anaphylactic reactions |
Nervous System Disorders | Convulsions, Dizziness |
Hepatobiliary Disorders | Hepatitis, Abnormal liver tests |
Renal and Urinary Disorders | Glomerulonephritis |
Skin and Subcutaneous Tissue Disorders | Toxic epidermal necrolysis, Stevens-Johnson syndrome, Exanthema, Angioedema, Urticaria, Alopecia |
* Includes mebendazole formulations, dosages and treatment duration other than Vermox™ 100 mg chewable tablets |
Summary
Vermox (mebendazole) is a member of the benzimidazole class of antiparasitic agents used to treat tapeworms, roundworms, hookworms, threadworms, pinworms, pork worms, and whipworms. Common side effects of Vermox include abdominal pain, diarrhea, dizziness, drowsiness, headache, vomiting, chills, itching, flushing, hiccups, ringing in the ears, low blood pressure, bloody urine, and reduced number of blood cells. Adverse outcomes with use of Vermox in pregnancy have not been seen, however the Centers for Disease Control (CDC) recommends postponing pinworm therapy until the third trimester when possible. While excretion of Vermox into breast milk is unlikely, caution should be used.
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Related Disease Conditions
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Pinworms in Children and Adults
Pinworm infection is an intestinal infection caused by a pinworm, seatworm, or threadworm. Female pinworms leave the intestine through the ankus and deposit eggs on the skin around the anus while a person is asleep. Pinworm infection is the most common worm infection in the U.S. Symptoms include anal itching or vaginal itching. Pinworm infection is generally spread by inadequate handwashing from infected persons. Treatment is effective after a diagnosis is made with a pinworm test.
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Cysticercosis (Pork Tapeworm Infection)
Cysticercosis is an infection caused by Taenia solium, the pork tapeworm. Symptoms include seizures, lethargy, nausea and vomiting, headache, vision changes, weakness, and confusion. Treatment depends upon the individual's symptoms and the stage of the infection. Treatment may incorporate anthelmintics, corticosteroids, anticonvulsants, and/or surgery.
Treatment & Diagnosis
Medications & Supplements

Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.