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Mebendazole, 500 mg tablets

Drug formTablets

ATC categoryAntiparasitic agents

ATC subcategoryAntihelmintics

Brand nameMebendazole

Generic nameMebendazole

Composition

Each tablet contains:

active ingredient: mebendazole – 500 mg;

excipients:microcrystalline cellulose, maize starch, sodium starch glycolate, magnesium stearate, talc purified, sodium lauryl sulfate.

Pharmacological group and ATC code
Anthelmintic; P02CA01.

Chemical name and CAS number
Methyl-5-benzoyl-1H-benzimidazol-2-ylcarbamate; 31431-39-7.

Pharmacology

Mebendazole, a benzimidazole carbamate derivative, is an anthelmintic with activity against most nematodes and some other worms; activity against some larval stages and ova has also been demonstrated.

Mechanism of Action

Although the exact mechanism of anthelmintic activity of mebendazole has not been fully elucidated, the drug appears to cause selective and irreversible inhibition of the uptake of glucose and other low molecular weight nutrients in susceptible helminths; inhibition of glucose uptake appears to result in endogenous depletion of glycogen stores in the helminth. Mebendazole does not inhibit glucose uptake in mammals. Mebendazole appears to cause degenerative changes in the intestine of nematodes and in the absorptive cells of cestodes. The principal anthelmintic effect of the drug appears to be degeneration of cytoplasmic microtubules within these intestinal and absorptive cells. Microtubular deterioration results in inhibition of organelle movement and interferes with the absorptive and secretory function. As a result of excessive accumulation of intracellular transport secretory granules, hydrolytic and proteolytic enzymes are released and cause cellular autolysis. This irreversible damage leads to death of the parasite.

Mebendazole has no effect on blood glucose concentrations in humans, and examination of the intestine and other organs of treated animals has shown an intact microtubular system and normal subcellular organelles. The presence of food in the digestive tract of the definitive host does not affect the action of the drug during treatment of intestinal helminthic infections.

Pharmacokinetics

Absorption: mebendazole appears to be minimally absorbed from the GI tract following oral administration. Limited data indicate that about 2–10% of an oral dose is absorbed. Peak plasma concentrations of mebendazole occur approximately 0.5–7 hours after oral administration of the drug and exhibit wide interpatient variation.

Distribution: mebendazole is highly protein bound. It is not known if mebendazole is distributed into milk.

Elimination: the elimination half-life of mebendazole has been reported to be about 2.8–9 hours.

Although the exact metabolic fate of mebendazole has not been fully determined, the drug is metabolized via decarboxylation to 2-amino-5(6)-benzimidazolyl phenylketone; this metabolite does not have anthelmintic activity.

Approximately 2–10% of an oral dose of mebendazole is excreted in urine within 24–48 hours of administration, principally as unchanged drug and the 2-amino metabolite. The metabolic fate and rate of excretion of unabsorbed mebendazole have not been determined.

Uses and administration
Mebendazole, being poorly absorbed from the gastrointestinal tract, is used principally in the treatment of the intestinal nematode infections ascariasis (roundworm infection), enterobiasis (pinworm or threadworm infections), hookworm (ancylostomiasis and necatoriasis), and trichuriasis (whipworm infection). The drug’s broad spectrum of activity makes it useful in the treatment of mixed helminthic infections. During treatment with Mebendazole, migration of worms with expulsion through the mouth and nose has occurred in some patients heavily infected with Ascaris. Mebendazole is also used in the treatment of capillariasis and trichostrongyliasis and has been used in strongyloidiasis. Other nematode infections which may respond to Mebendazole are infection with the filarial nematode Mansonella perstans, and the tissue infections toxocariasis and trichinosis.

Administration

Mebendazole is given by mouth. The tablets may be crushed and mixed with food. Special diets, fasting, or purgation prior to administration of the drug is not necessary. Patients should be advised of hygienic precautions needed to minimize reinfection, such as wearing shoes, washing hands with soap and cleaning under fingernails often during the day (especially before eating and after using the toilet), and washing all fruits and vegetables thoroughly before eating them.

The usual dose for adults and children aged over 2 years with enterobiasis is 100 mg as a single dose, repeated if necessary after 2 to 3 weeks; for ascariasis, hookworm infections, and trichuriasis the usual dose in adults and children over 2 year is 100 mg twice daily for 3 days, although a single dose of 500 mg may be effective.

Adverse effects

At usual recommended dosages (i.e., 100–200 mg daily), Mebendazole appears to cause minimal adverse effects. Adverse effects appear to occur more frequently when higher dosages (e.g., those used in the treatment of extraintestinal infections such as hydatid disease) are used, and may be related to effects resulting from drug-induced killing of the parasites in some cases.

Since Mebendazole is poorly absorbed from the gastrointestinal tract at the usual therapeutic doses, adverse effects have generally been restricted to gastrointestinal disturbances, such as transient abdominal pain and diarrhoea, and have tended to occur in patients being treated for heavy intestinal infection. Headache and dizziness have been reported. Adverse effects have been reported more frequently with the high doses tried in echinococcosis and have included allergic reactions, raised liver enzyme values, alopecia, and bone marrow depression.

Acute Toxicity: overdosage of mebendazole may result in GI symptoms lasting up to a few hours. If acute overdosage of mebendazole occurs, vomiting and purging should be induced.

Contraindications
Patients receiving high doses of Mebendazole, such as those with echinococcosis, should be supervised closely with blood counts and liver function being monitored; such high-dose therapy may be inappropriate in those with hepatic impairment.

Mebendazole is contraindicated in patients who are hypersensitive to the drug.

Organ system function (including hematopoietic and hepatic) should be assessed periodically during prolonged mebendazole therapy.

Precautions

Safety of mebendazole in children younger than 2 years of age has not been established. Because of limited experience with mebendazole in children younger than 2 years of age, the drug should be used in such children only when the potential benefits justify the possible risks.

Overdosage

In patients treated at dosages substantially higher than recommended or for prolonged periods of time, the following adverse reactions have been reported rarely: alopecia, reversible liver function disturbances, hepatitis, agranulocytosis, neutropenia and glomerulonephritis. With the exception of agranulocytosis and glomerulonephritis, these also have been reported in patients who were treated with mebendazole at standard dosages .

Symptoms

In the event of accidental overdosage, abdominal cramps, nausea, vomiting and diarrhoea may occur.

Treatment

There is no specific antidote. Within the first hour after ingestion, gastric lavage may be performed. Activated charcoal may be given if considered appropriate.

Pregnancy and breastfeeding

Mebendazole is teratogenic in rats and there are no adequate and well controlled studies in human pregnancy. Mebendazole is therefore usually contra-indicated during pregnancy.

Since it is not known if mebendazole is distributed into milk, the drug should be used with caution in nursing women.

Drug interactions

Antiepileptics

Phenytoin or carbamazepine have been reported to lower plasma-mebendazole concentrations in patients receiving high doses for echinococcosis, presumably as a result of enzyme induction; valproate had no such effect.

Histamine H2-antagonists

Plasma concentrations of Mebendazole have been raised when the enzyme inhibitor cimetidine was also given, and this has resulted in the resolution of previously unresponsive hepatic hydatid cysts.

Identification

White with yellow tint cylindrical tablets with a few small darker spots, the end surface of which are flat .

Presentation

1 tablet in a plastic bottle .

Expiry date

3 years. Do not use after the expiration date.

Prescription status

To be dispensed with prescription.

Storage conditions

Store at a room temperature (15-250C), in a dry place, out of the reach of children. Protect from light.