Thursday, January 21, 2010


Abamectin is a mixture of avermectins containing > 80% avermectin B1a and <>


Abamectin is used to control insect and mite pests of a range of agronomic, fruit, vegetable and ornamental crops, and it is used by homeowners for control of fire ants. Abamectin is also used as a veterinary antihelmintic. Resistance to abamectin based antihelmintics, although a growing problem, is not as common as to other classes of veterinary antihelmintics.


Abamectin is a highly toxic material, however most formulated products containing abamectin are of low toxicity to mammals. Emulsifiable concentrate formulations may cause moderate eye irritation and mild skin irritation. Symptoms of poisoning observed in laboratory animals include pupil dilation, vomiting, convulsions and/or tremors, and coma .

Abamectin acts on insects by interfering with neural and neuromuscular transmission. It acts on a specific type of synapse located only within the brain and is protected by the blood-brain barrier. However, at very high doses, the mammalian blood-brain barrier can be penetrated, causing symptoms of CNS depression such as incoordination, tremors, lethargy, excitation and pupil dilation. Very high doses have caused death from respiratory failure.

Abamectin is not readily absorbed through skin. Tests with monkeys show that less than 1% of dermally applied abamectin was absorbed into the bloodstream through the skin . Abamectin does not cause allergic skin reactions.

The amount of a chemical that is lethal to one-half (50%) of experimental animals fed the material is referred to as its acute oral lethal dose fifty, or LD50. The oral LD50 for abamectin in rats is 11 mg/kg, and in mice range from 14 to > 80 mg/kg. The dermal LD50 for technical abamectin on rats and rabbits is > 330 mg/kg. The oral LD50 for the product Affirm 0.011% Fire Ant Bait in rats is > 5,000 mg/kg, and its dermal LD50 on rabbits is > 2,000 mg/kg. The oral LD50 for the 1.8% w/v Abamectin EC product in rats is 300 mg/kg, and the dermal LD50 for this product on rabbits is > 2,000 mg/kg .


In a 1-year study with dogs given oral doses of 0, 0.25, 0.5, or 1 mg/kg/day, there were no changes in tissue at any dose level. However, some dogs at the 0.5 and 1 mg/kg/day levels had pupillary dilation, weight loss, lethargy, tremors and recumbency. The NOEL for this study was 0.25 mg/kg/day. Similar results were seen in a 2-year study with rats fed 0, 0.75, 1.5, or 2 mg/kg/day. No changes in the nervous or muscular systems were observed, but rats in all the dosage levels exhibited body weight gains significantly higher than the controls. A few individuals in the high dose group exhibited tremors .

When mice were fed 8 mg/kg/day, the highest dose tested, for 94 weeks, the males developed dermatitis and changes in blood formation in the spleen, while females exhibited tremors and weight loss.


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