PHARMACOLOGICAL PROPERTIES
Pharmacotherapeutic group: antiparasitic products, insecticides and repellents
ATCvet code: QP53AX17
Pharmacodynamic properties
Imidacloprid, 1-(6-Chloro-3-pyridylmethyl)-N-nitro-imidazolidin-2-ylideneamine
* is an ectoparasiticide belonging to a new group of chloronicotinyl compounds. Chemically, it is more accurately described as a chloronicotinyl nitroguanidine.
The substance has a high affinity for the nicotinergic acetylcholine receptors in the post-synaptic region of the central nervous system (CNS). The ensuing inhibition of cholinergic transmission in insects results in paralysis and death. Due to the weak nature of the interaction with mammalian nicotinergic receptor sites and the postulated poor penetration through the blood/brain barrier in mammals, it has virtually no effect on the mammalian CNS. The minimal pharmacological activity in mammals is supported by safety studies involving systemic administration of sub-lethal doses to rabbits, mice and rats.
In further studies, in addition to the adulticide flea efficacy of imidacloprid, a larvicidal flea efficacy in the surroundings of the treated pet has been demonstrated. Larval stages in the pet’s surroundings are killed following contact with a treated animal.
Pharmacokinetic particulars
Oral studies in the rat show imidacloprid to be absorbed rapidly from the gastro-intestinal tract. Almost complete absorption (95%) occurs within 48 hours. Peak plasma concentrations are observed within 2.5 hours following administration. Tissue distribution is also rapid with the lowest levels recorded in the brain. The active ingredient undergoes extensive metabolism with only 10-16% remaining as parent compound. Almost complete (96%) elimination occurs within 48 hours, approximately 75% being removed by the kidneys and 21% with the faeces.
The product is indicated for cutaneous administration. Following topical application in dogs, the solution is quickly distributed over the animal. Acute dermal studies in the rat and target animal overdose and serum kinetic studies have established that systemic absorption is very low, transient and not relevant for the clinical efficacy. This has been further demonstrated by a study in which fleas were not killed after having fed on previously treated animals once the animal’s skin and fur had been cleaned of all active material.