I. Pharmacological Action of Albendazole

Albendazole, a benzimidazole derivative, is a broad-spectrum, highly efficient, and low-toxicity anthelmintic drug. It exhibits high efficacy against various nematodes in multiple animals and also has strong expelling effects on certain trematodes and tapeworms. This drug is insoluble in water, highly lipophilic, and more readily absorbed from the digestive tract compared to other drugs of the same class. Its hepatic metabolite, albendazole sulfoxide, possesses anti-parasitic activity. Effective against gastrointestinal nematodes, lungworms, liver flukes, and tapeworms in ruminants, horses, pigs, dogs, and poultry, Albendazole can effectively expel various parasitic worms in animals with mixed infections. It has a strong expelling effect on intestinal nematodes, kidney worms, esophageal worms, roundworms, whipworms, strongyles, and stomach bots in ruminants, as well as roundworms and Ascaridia galli in chickens. It is effective against tapeworms, liver flukes, both pre- and post-teat flukes, and Fasciola hepatica in cattle. Particularly effective against cysticercosis in pigs and cattle, Albendazole is a promising drug for treating this condition. Clinically, it is mainly used for nematodiasis, cestodiasis, and trematodiasis in animals.

II. Mechanism of Action

Albendazole, a benzimidazole derivative, is rapidly metabolized in the body to albendazole sulfoxide, sulfoxide alcohol, and 2-aminosulfoxide. It selectively and irreversibly inhibits the polymerization of the cytoplasmic microtubule system of parasite intestinal wall cells, blocking their absorption of various nutrients and glucose. This leads to the depletion of endogenous glycogen in the worms and inhibits the fumarate reductase system, preventing the production of adenosine triphosphate (ATP), thereby rendering the worms unable to survive and reproduce. Similar to thiabendazole, Albendazole can also cause degeneration of the worm's intestinal cell cytoplasm and bind to its microtubule proteins, causing cellular transport blockage. This results in the accumulation of secretory granules in the Golgi apparatus and gradual cytoplasmic dissolution, leading to complete cellular degeneration and worm death.

III. Combination and Contraindications

1. Pyrantel: Combined use can increase the plasma concentration of Albendazole.

2. High-fat foods: Fat can enhance the absorption of Albendazole.

3. Cimetidine: Can increase the concentration of Albendazole in bile and cystic fluid.

4. Ivermectin: Combined use can broaden the range of antiparasitic effects.

IV. Precautions for Using Albendazole

1. Prolonged continuous use may lead to worm resistance and potential cross-resistance with other benzimidazole drugs.

2. Sensitive animals such as horses, rabbits, and cats should avoid using this drug; alternative dewormers are recommended.

3. Albendazole has embryotoxic and teratogenic effects. It should be avoided in cattle and sheep within 45 days of pregnancy and in pigs within 30 days of pregnancy. It is not advisable to use it in other animals during pregnancy or lactation.

4. There is no specific antidote for this drug. In case of overdose, induce vomiting or gastric lavage and provide symptomatic supportive treatment immediately.

5. Avoid using in animals with acute enteritis, and use with caution in animals with a history of epilepsy.

6. Use with caution in animals with impaired liver function.

7. Withdrawal period: 14 days for cattle, 4 days for sheep, 7 days for pigs, and 4 days for poultry; discard milk for 60 hours.

In conclusion, Albendazole is best administered on an empty stomach, as controlled fasting facilitates the full efficacy of the drug. Dewormers like Albendazole, when administered under controlled fasting conditions, result in higher drug concentrations in the intestines, facilitating direct contact between the drug and the parasites, thus enhancing efficacy. Therefore, controlled fasting is recommended for optimal efficacy.