Ivermectin is derived from the avermectin, a family of the
highly active broad-spectrum, anti-parasitic agents which are
produced from fermentation of Streptomyces Avermitilis.
In roundworms, ivermectin stimulates the release of GABA from
nerve endings and enhances binding of GABA to special receptors
at nerve junctions, thus interrupting nerve impulses,
paralyzing and killing the parasite.The enhancement of the GABA
effect in arthropods resembles that in roundworms except that
nerve impulses are interrupted between the nerve ending and the
muscle cell.
Ivermectin has no measurable effect against flukes or
tapeworms, presumably because they do not have GABA as a nerve
impulse transmitter.
Recommended doses of ivermectin have a wide safety margin in
livestock. The principal peripheral neurotransmitter in
mammals, acetyl choline is unaffected by ivermectin.
Ivermectin does not readily penetrate the central nervous
system of mammals.