Avermectin and Ivermectin belong to the macrocyclic lactone class of antiparasitic medications, which are used to combat a wide range of parasites in animals and humans. Due to their similar names and related functions, they frequently cause confusion. Their relationship is that of a parent group (Avermectin) and one of its most successful, chemically refined descendants (Ivermectin).
Defining the Avermectin Compound Family
Avermectins represent a family of potent antiparasitic agents that are naturally derived from the fermentation process of the soil-dwelling bacterium Streptomyces avermitilis. This microorganism was first isolated from a soil sample in Japan in 1974. The discovery of this bacterium and its products, which showed activity against parasitic worms, earned its discoverers the Nobel Prize in 2015.
The compound produced by the bacterium is a complex composed of eight closely related molecules. These natural products are grouped into four pairs, designated A1, A2, B1, and B2, each with a major ‘a’ component and a minor ‘b’ component. This complex possesses broad-spectrum insecticidal and anthelmintic properties, meaning the compounds are effective against both insects and parasitic worms. Avermectin B1 became the foundation for further development due to its strong antiparasitic effect.
Ivermectin as a Specific Chemical Modification
Ivermectin is a semi-synthetic derivative created through the chemical modification of the naturally occurring Avermectin B1. Its creation involved subjecting Avermectin B1 to a targeted chemical reaction called hydrogenation. This process alters the structure of the molecule at a specific location.
Hydrogenation saturates the double bond located at the 22,23-position of the Avermectin B1 molecule, resulting in a new chemical structure. The resulting product is a mixture of 22,23-dihydroavermectin B1a and 22,23-dihydroavermectin B1b, which constitutes Ivermectin. This structural change was performed to enhance the drug’s pharmacological properties, improving stability, potency, and increasing the safety margin for use in warm-blooded animals and humans.
Divergent Applications and Practical Use
The chemical refinement that created Ivermectin resulted in a product with a safety and efficacy profile suitable for a wider range of applications than its natural parent compound. Ivermectin is primarily recognized for its widespread use in human medicine, where it is used globally to treat parasitic diseases like onchocerciasis, commonly known as river blindness, and lymphatic filariasis. Its improved safety profile also made it a major, broad-spectrum antiparasitic agent in veterinary medicine for livestock, horses, and dogs.
In contrast, other non-hydrogenated avermectin derivatives often maintain applications where higher toxicity is less of a concern or where topical application limits systemic exposure. For instance, Abamectin, which is essentially the natural Avermectin B1 product, is widely utilized as a powerful insecticide and acaricide in crop protection and pest control. Other semi-synthetic avermectin derivatives, such as Doramectin and Eprinomectin, are specialized for specific veterinary uses, capitalizing on their distinct chemical properties for targeted animal health applications.