Neonicotinoids

Neonicotinoids (sometimes shortened to neonics /ˈniːoʊnɪks/) are a class of neuro-active insecticides chemically similar to nicotine. In the 1980s Shell and in the 1990s Bayer started work on their development. The neonicotinoid family includes acetamiprid, clothianidin, imidacloprid, nitenpyram, nithiazine, thiacloprid and thiamethoxam. Imidacloprid is the most widely used insecticide in the world. Compared to organophosphate and carbamate insecticides neonicotinoids cause less toxicity in birds and mammals than insects. Some breakdown products are also toxic to insects.

In the late 1990s neonicotinoids came under increasing scrutiny over their environmental impact. Neonicotinoid use was linked in a range of studies to adverse ecological effects, including honey-bee colony collapse disorder (CCD) and loss of birds due to a reduction in insect populations. In 2013, the European Union and a few non EU countries restricted the use of certain neonicotinoids.

The precursor to nithiazine was first synthesized by Henry Feuer, a chemist at Purdue University, in 1970;Shell researchers found in screening that this precursor showed insecticide potential and refined it to develop nithiazine. In 1984 nithiazine's mode of action was found to be as a postsynaptic acetylcholine receptor agonist, the same as nicotine. Nithiazine does not act as an acetylcholinesterase inhibitor, in contrast to the organophosphate and carbamate insecticides. While nithiazine has the desired specificity (i.e. low mammalian toxicity), it is not photostable—that is, it breaks down in sunlight, thus is not commercially viable.

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