Albendazole

Introduction

Albendazole is a broad-spectrum anthelmintic medication belonging to the benzimidazole class. It is widely used to treat various parasitic worm infestations by inhibiting the growth and reproduction of helminths. Due to its efficacy and safety profile, Albendazole is included in the World Health Organization’s List of Essential Medicines.

Chemical structure

Key Chemical Information:

• IUPAC Name: Methyl 5-(propylthio)-1H-benzimidazol-2-ylcarbamate

• Molecular Formula: C₁₂H₁₅N₃O₂S

• Molecular Weight: 265.33 g/mol

• SMILES Notation: CCCSc1ccc2nc(NC(=O)OC)[nH]c2c1

This structure illustrates the benzimidazole core with a propylthio substituent and a methyl carbamate group, which are essential for Albendazole’s anthelmintic activity.

Mechanism of Action

Albendazole exerts its anthelmintic effect by binding to the β-tubulin of parasitic worms, inhibiting microtubule polymerization. This disruption impairs glucose uptake and depletes glycogen stores, leading to energy depletion and eventual death of the parasite. The active metabolite, albendazole sulfoxide, is primarily responsible for this activity.

Pharmacokinetics

Absorption

Albendazole has poor oral bioavailability (<5%) due to its low solubility. However, taking it with a high-fat meal can increase absorption significantly. (Wikipedia, MedicinesFAQ)

Distribution

After absorption, albendazole is widely distributed throughout the body, including the liver, bile, cyst wall, cyst fluid, and cerebrospinal fluid (CSF). Approximately 70% of albendazole sulfoxide binds to plasma proteins.

Metabolism

Albendazole is rapidly converted in the liver to its active metabolite, albendazole sulfoxide, which is further metabolized to albendazole sulfone and other oxidative metabolites. (Drugs.com)

Elimination

Albendazole and its metabolites are primarily excreted via the bile. Less than 1% of albendazole sulfoxide is detectable in urine. The elimination half-life of albendazole sulfoxide ranges from 8 to 12 hours. (PharmaconAid.com)

Indications

Albendazole is indicated for the treatment of various parasitic infections, including:

• Neurocysticercosis: Caused by Taenia solium (pork tapeworm) larvae.
• Hydatid disease: Due to Echinococcus granulosus (dog tapeworm).
• Strongyloidiasis: Caused by Strongyloides stercoralis.
• Ascariasis: Due to Ascaris lumbricoides.
• Hookworm infections: Caused by Ancylostoma duodenale and Necator americanus.
• Enterobiasis (Pinworm infection): Caused by Enterobius vermicularis.
• Trichuriasis: Due to Trichuris trichiura.
• Clonorchiasis: Caused by Clonorchis sinensis.
• Gnathostomiasis: Due to Gnathostoma spp.
• Microsporidiosis: Caused by microsporidia.
• Cutaneous and visceral larva migrans: Due to various nematode larvae.

Dosage and Administration

General Guidelines

Albendazole should be taken with food, preferably a high-fat meal, to enhance absorption. The dosage varies depending on the type of infection, patient’s age, and weight.

Specific Dosages

• Ascariasis, Hookworm, Trichuriasis, Enterobiasis:
  • Adults and children over 2 years: 400 mg as a single dose.
• Strongyloidiasis, Taeniasis:
  • Adults and children over 2 years: 400 mg once daily for 3 consecutive days.
• Neurocysticercosis:
  • Adults and children over 60 kg: 400 mg twice daily for 8 to 30 days.
  • Adults and children under 60 kg: 15 mg/kg/day divided into two doses for 8 to 30 days.
• Hydatid Disease:
  • Same dosing as neurocysticercosis, administered in 28-day cycles with 14-day drug-free intervals, up to 3 cycles.
• Clonorchiasis:
  • 10 mg/kg daily for 7 days.
• Gnathostomiasis, Microsporidiosis:
  • 400 mg twice daily for 21 days.(Pediatric Oncall)
• Cutaneous Larva Migrans:
  • 400 mg once daily for 3 days.
• Visceral Larva Migrans:
  • 400 mg twice daily for 5 days.

Adverse Effects

Common Side Effects

• Abdominal pain
• Nausea and vomiting
• Headache
• Dizziness(
• Elevated liver enzymes
• Fever
• Hair loss (reversible)

Rare but Serious Side Effects

• Leukopenia
• Agranulocytosis
• Pancytopenia
• Hepatitis
• Acute liver failure
• Hypersensitivity reactions (rash, itching) (PharmEasy)

Contraindications

• Known hypersensitivity to albendazole or benzimidazole derivatives.
• Pregnancy, especially during the first trimester.
• Caution in patients with liver disease or biliary obstruction.

Drug Interactions

• Cimetidine: May increase albendazole plasma concentrations by inhibiting its metabolism.
• Carbamazepine, Phenytoin, Phenobarbital: May decrease albendazole plasma concentrations by inducing hepatic enzymes.
• Grapefruit Juice: May increase albendazole bioavailability; patients should maintain consistent intake levels. (Wikipedia)

Use in Specific Populations

Pregnancy

Albendazole is classified as Pregnancy Category C. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Lactation

It is unknown whether albendazole is excreted in human milk. Caution is advised when administering to breastfeeding women. (Medical Dialogues)

Pediatric Use

Albendazole is generally safe for use in children over 2 years of age. Limited data are available for children under 2 years.

Geriatric Use

Limited experience exists for patients aged 65 years or older. No specific dose adjustments are recommended.

Monitoring Parameters

• Liver Function Tests: Monitor before and during prolonged therapy.
• Complete Blood Count (CBC): Monitor for signs of bone marrow suppression.
• Pregnancy Testing: Recommended before initiating therapy in women of childbearing potential.

Patient Counseling Information

• Take albendazole with food to enhance absorption.
• Inform your healthcare provider if you are pregnant, planning to become pregnant, or breastfeeding.
• Report any signs of liver dysfunction (e.g., yellowing of the skin or eyes, dark urine) or unusual bleeding/bruising.
• Regular monitoring of liver function and blood counts may be necessary during prolonged therapy.

Summary

Summary of the Article on Albendazole:

Albendazole is a broad-spectrum anthelmintic from the benzimidazole class, widely used to treat a variety of parasitic worm infections. It works by inhibiting microtubule formation in parasites, which disrupts glucose uptake and depletes energy, ultimately killing the worms. Though it has low oral bioavailability, this increases significantly when taken with fatty food. After metabolism in the liver, its active form—albendazole sulfoxide—acts systemically and is eliminated primarily via bile.

Albendazole is effective against neurocysticercosis, hydatid disease, strongyloidiasis, ascariasis, hookworm, trichuriasis, and more. Dosage varies depending on the type and severity of the infection, with treatment ranging from a single dose to 30-day regimens. Common side effects include gastrointestinal discomfort, headache, and liver enzyme elevation; rare but serious effects include bone marrow suppression and liver failure.

Albendazole is contraindicated in pregnancy and liver disease, and may interact with drugs like cimetidine and phenytoin. Caution is advised in lactating and elderly patients, and monitoring liver function and blood counts during long-term use is essential. Albendazole’s inclusion in the WHO’s Essential Medicines list underscores its importance in global health, particularly in managing neglected tropical diseases.