PHARMACOLOGICAL PROPERTIES
Ivermectin is a mixture of two partially modified compounds of abamectin belonging to the avermectin family, which are a macrocyclic lactone group of
endectocides. Abamectin is a mixture of two fermentation products of the soil organism Streptomyces avermitilis.
ATC vet code: QP54AA01.
Therapeutic group: Endectocide, ivermectin
Pharmacodynamic properties
Ivermectin is a macrocyclic lactone derivative and acts by inhibiting nerve impulses. It binds 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 with hyperpolarization of the nerve or muscle cell, resulting in paralysis and death of the relevant parasites. 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 they do not readily cross the blood-brain barrier.
Pharmacokinetic particulars
In each of the target species the pharmacokinetic profile following subcutaneous administration was characterised as follows (pharmacokinetic parameters presented as mean values):
Following administration to cattle, Cmax was 51ng/ml, with a Tmax of 43 h, T1/2 of 129 h and an AUC of 7398 ng.h/ml.
Following two subsequent administrations seven days apart to sheep, Cmax was 14 ng/ml, with a Tmax of 202 h, T1/2 of 380 h and an AUC of 4686 ng.h/ml.
Following administration to pigs, Cmax was 6.35ng/ml, with a Tmax of 106 h, T1/2 of 219 h and an AUC of 1260 ng.h/ml.
Only about 2% of the drug is excreted in urine, faecal excretion being the major route of elimination. Tissue residues of radioactivity following subcutaneous administration of tritium-labelled ivermectin are highest in liver and fat; lowest levels are found in brain.
In cattle, the residual antiparasitic effect of ivermectin is due to its persistence which in turn is due in part to its long intrinsic half life and its relatively high protein binding (90%).
List of excipients
Benzyl alcohol
Ethanol 96 per cent
Water for injections
Propylene glycol