Pharmacotherapeutic group: Ectoparasiticides for topical use, organophosphorus compounds. ATC Vet code: QP53AF03.
Pharmacodynamic properties
Dimpylate (Diazinon) is an organophosphorus compound. It is effective against a wide range of insects. Organophosphorus insecticides are both contact and stomach poisons. They act by combining with the neutralising cholinesterase at the nerve ganglion of the insect. Cholinesterases remove acetylcholine. Two types of this enzyme are recognised, the first, true acetylcholinesterase, is largely specific in its action and is found mainly in erythrocytes, in muscles and in the nervous system. The second, pseudocholinesterase, a non-specific enzyme capable of hydrolysing a wide variety of esters, occurs in plasma and the nervous system. Some organophosphorus compounds inhibit one of these enzymes more than the other but few are entirely specific.
Used as a sheep dip at a concentration of 0.025%, Dimpylate (Diazinon) is active locally in the skin and wool. Owing to their lipid solubility, they are rapidly absorbed into the oily secretions on wool and the skin surface and persists at concentrations effective against mites, lice and blowfly for at least 60 days.
Pharmacokinetic properties
Parenterally absorbed organophosphates are metabolised by hydrolysis and oxidation and excreted mainly via the urine.