It is used for the treatment and control of internal parasitosis (gastrointestinal and pulmonary nematodes), ticks and mange (and other ectoparasites). Doramectin is a derivative of ivermectin. Its spectrum includes:Haemonchus spp., Ostertagia spp., Trichostrongylusspp., Cooperia spp., Oesophagostomum spp., Dictyocaulus viviparus, Dermatobia hominis, Boophilus microplus, Psoroptes bovis, among many other internal and external parasites. 
Doramectin is effective against the major parasitic roundworms: gastrointestinal and pulmonary. It is also effecive against most mites and lice species, and against numerous myiases (e.g. those caused by screwworm flies, bot flies and warble flies) usually regardless of the delivery form As all macrocyclic lactone doramectin acts as agonist of the GABA (gamma-aminobutyric acid) neurotransmitter in nerve cells and also binds to glutamate-gated chloride channels in nerve and muscle cells of invertebrates. In both cases it blocks the transmission of neuronal signals of the parasites, which are either paralyzed and expelled out of the body, or they starve. It also affects the reproduction of some parasites by diminishing oviposition or inducing an abnormal oogenesis.