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Pharmacological particulars
Pharmacotherapeutic Group
Endectocide, macrocyclic lactones
ATCVet code: QP54AA01
Pharmacodynamic Properties
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 the permeability of the cell membrane to chloride ions with hyperpolarization of the nerve or muscle cell, which results 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 channels, and macrocyclic lactones do not readily cross the blood-brain barrier.
Pharmacokinetic Particulars
Following oral administration of the recommended dose to horses, a mean peak plasma concentration (Cmax) of 33 ng/ml was achieved within 24 hours.
Ivermectin is well absorbed into the systemic circulation following administration. Only about 2% of the drug is excreted in urine, faecal excretion being the major route of elimination.
Ivermectin passes readily into milk.