Pharmacotherapeutic group: Endectocide. ATC vet code QP54AA01.
Ivermectin is a member of the macrocyclic lactone class of endectocides. Compounds of the class bind selectively and with high affinity to glutamate-gated chloride ion channels which occur in invertebrate nerve and muscle cells. This leads to an increase in the permeability of the cell membrane to chloride ions and hyperpolarization of the nerve or muscle cell, resulting in paralysis and death of the parasite. Compounds of this class may also interact with other ligand-gated chloride channels, such as those gated by the neurotransmitter gamma-aminobutyric acid (GABA).
The margin of safety for compounds of this class is attributable to the fact that mammals do not have glutamate-gated chloride channels, the macrocyclic lactones have a low affinity for other mammalian ligand-gated chloride and they do not readily cross the blood-brain barrier.
Pharmacokinetic Properties
Following administration of Bimectin, ivermectin is rapidly absorbed to reach peak plasma concentration in several hours. This peak falls off gradually over several days. Ivermectin is eliminated primarily via the faeces. The highest residues are found in the fat.
At a dose rate of 0.2mg ivermectin per kilogram of bodyweight, plasma levels of ivermectin reach a mean Cmax concentration of 40.44ng/ml and a mean Tmax at 8.35 hours. This peak falls off gradually to an average level of 3ng/ml at 10 days.