Milbemycin

A class of macrocyclic lactone compounds used as antiparasitic agents

Chemical structure of Milbemycins

Milbemycin is a class of macrocyclic lactone compounds that are primarily used as antiparasitic agents in veterinary medicine. These compounds are derived from the fermentation products of the bacterium Streptomyces hygroscopicus subsp. aureolacrimosus. Milbemycins are structurally related to avermectins, another group of macrocyclic lactones, but they differ in their chemical structure and spectrum of activity.

Chemical Structure

Milbemycins are characterized by a 16-membered macrocyclic lactone ring. The core structure of milbemycins lacks the disaccharide moiety found in avermectins, which contributes to their distinct pharmacological properties. The chemical structure of milbemycins allows them to bind to glutamate-gated chloride channels in the nervous system of parasites, leading to paralysis and death of the parasite.

Mechanism of Action

Milbemycins exert their antiparasitic effects by increasing the permeability of cell membranes to chloride ions through binding to glutamate-gated chloride channels. This action results in hyperpolarization of the nerve or muscle cell, leading to paralysis and eventual death of the parasite. This mechanism is similar to that of avermectins, although milbemycins may have a broader spectrum of activity against certain parasites.

Uses in Veterinary Medicine

Milbemycins are widely used in veterinary medicine to control a variety of parasitic infections in animals. They are effective against a range of endoparasites and ectoparasites, including:

• Heartworms (Dirofilaria immitis)
• Roundworms (Toxocara canis, Toxascaris leonina)
• Hookworms (Ancylostoma caninum)
• Whipworms (Trichuris vulpis)
• Mites (Demodex canis)

Milbemycins are often formulated in combination with other antiparasitic agents to broaden their spectrum of activity and enhance their efficacy.

Common Formulations

Milbemycins are available in various formulations, including oral tablets, topical solutions, and injectables. Some common veterinary products containing milbemycins include:

• Milbemycin oxime: Often combined with other agents such as lufenuron or praziquantel for broader antiparasitic coverage.
• Moxidectin: Used in both small and large animals for the prevention and treatment of parasitic infections.

Safety and Side Effects

Milbemycins are generally well-tolerated in animals when used according to the prescribed dosage. However, some animals, particularly certain breeds of dogs such as Collies, may be more sensitive to these compounds due to a genetic mutation in the MDR1 gene that affects drug metabolism. Side effects can include neurological symptoms such as ataxia, tremors, and in severe cases, coma.

Related Pages

• Avermectin
• Antiparasitic drug
• Macrocyclic lactone
• Veterinary medicine