Mebendazole is a broad-spectrum anthelmintic medication primarily used to treat parasitic worm infections. First synthesized in the 1970s, it belongs to the benzimidazole class of drugs, which also includes albendazole and thiabendazole. Mebendazole is widely recognized for its effectiveness against common intestinal nematodes such as pinworms (Enterobius vermicularis), roundworms (Ascaris lumbricoides), whipworms (Trichuris trichiura), Laliqua.es) and hookworms (Ancylostoma duodenale and Necator americanus). Its mechanism of action, pharmacokinetics, clinical applications, safety profile, and emerging research make it a cornerstone in global public health efforts to control soil-transmitted helminthiases.

Mechanism of Action
Mebendazole exerts its anthelmintic effects by selectively binding to β-tubulin in parasitic cells, inhibiting microtubule polymerization. This disrupts glucose uptake and energy metabolism, leading to the depletion of intracellular glycogen stores and ultimately causing immobilization and death of the worm. Because mammalian tubulin binds mebendazole with much lower affinity, the drug has a favorable therapeutic index. The slow onset of action typically results in worm expulsion within one to three days after administration.

Pharmacokinetics
Mebendazole is administered orally and has poor aqueous solubility, which limits its absorption. Its bioavailability is increased when taken with fatty foods. The drug undergoes extensive first-pass metabolism in the liver, primarily via cytochrome P450 enzymes, and is converted to inactive metabolites that are excreted in bile and urine. The plasma half-life is approximately three to six hours. For intestinal infections, systemic absorption is minimal, but higher doses used in hydatid disease achieve therapeutic serum levels.

Clinical Uses
The primary indication for mebendazole is the treatment of single or mixed intestinal helminth infections. The standard dose for most infections is 100 mg twice daily for three days, or a single 500 mg dose for enterobiasis. It is also used in the management of trichinosis, though alternatives may be preferred. For cystic hydatid disease caused by Echinococcus granulosus, prolonged high-dose therapy (e.g., 400–600 mg three times daily for one to six months) may be given, often adjunct to surgical or percutaneous intervention. Mebendazole is included on the World Health Organization’s Model List of Essential Medicines and is frequently employed in mass drug administration programs in endemic regions.

Side Effects and Contraindications
Mebendazole is generally well tolerated. Adverse effects are uncommon and usually mild, including abdominal pain, diarrhea, nausea, vomiting, headache, and rash. Rarely, transient elevation of liver enzymes occurs. High-dose, prolonged treatment has been associated with hepatitis, alopecia, bone marrow suppression, and agranulocytosis. Contraindications include hypersensitivity to benzimidazoles, pregnancy (particularly first trimester) due to embryotoxicity in animal studies, and severe hepatic impairment. The drug is not recommended in children under two years of age unless benefit clearly outweighs risk.

Drug Interactions
Mebendazole may interact with cimetidine, which can increase its plasma levels, and with anticonvulsants (phenytoin, carbamazepine) that may reduce its efficacy through enzyme induction. Co-administration with metronidazole has been associated with Stevens-Johnson syndrome in rare reports.

Resistance and Limitations
Resistance to mebendazole has been documented in veterinary use and is emerging in human populations, particularly where mass drug administration is widespread. Genetic mutations in β-tubulin can reduce drug binding. Combination therapy with other anthelmintics like ivermectin or albendazole may help delay resistance and improve efficacy against mixed infections.

Emerging Research and Repurposing
Beyond its anthelmintic role, mebendazole has attracted attention for potential anticancer properties. Preclinical studies and case reports suggest that mebendazole may inhibit microtubule formation in cancer cells, induce apoptosis, reduce angiogenesis, and sensitize tumors to chemotherapeutic agents. In vitro and in vivo activity has been reported against glioblastoma, melanoma, colorectal, lung, and breast cancer lines. However, large-scale clinical trials are lacking, and its use for this indication remains investigational. Additionally, mebendazole is being studied for neuroprotection in neurodegenerative diseases due to its anti-inflammatory and anti-tubulin effects.

Public Health Importance
Soil-transmitted helminthiases affect over 1.5 billion people globally, primarily in tropical and subtropical regions with poor sanitation. Mebendazole, along with albendazole, forms the backbone of preventive chemotherapy campaigns targeting school-age children and at-risk populations. Its low cost, single-dose regimen for some infections, and safety profile make it suitable for large-scale distribution. Integrated with water, sanitation, and hygiene (WASH) interventions, such programs have reduced worm burdens and morbidity significantly.

Conclusion
Mebendazole remains a vital and safe anthelmintic drug with established efficacy against major intestinal nematodes. Its mechanism, pharmacokinetics, and clinical applications are well understood. While resistance and off-label investigations present ongoing challenges, its public health impact is substantial. Future research may broaden its therapeutic utility, but for now, mebendazole continues to serve as an essential tool in combating parasitic infections worldwide.