Side Effects of Vermox (mebendazole)

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.

• 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.

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.

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*

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*

Concomitant use of mebendazole, including Vermox., and metronidazole should be avoided.