Nithiazine and other members of the nitromethylene family
were shown at an early stage in their development to
be cholinergic agonists (and antagonists) by electrophysiology
(6). However, unlike nicotine, they mostly act as
partial agonists and are open channel blockers, a property
resulting from their partial positive charge.
Nithiazine is a useful building block and insecticide.
Nithiazine is used as an active ingredient in fly strips (e.g.,
QuickStrikes Fly Abatement Strip, Sandoz 9023 fly bait
station). The strips are most effective against houseflies (Musca
domestica). They can be placed in or around the house, animal
housing, recycling facilities, or other facilities where abundant
houseflies are a nuisance; however, the manufacturer currently
does not support residential uses.
Nithiazine is extremely unstable in sunlight due to the nitromethylene
chromophore. This group absorbs strongly in water at
365 nm with an extinction coefficient about 40 000M-1 cm-1.
Direct irradiation results in a loss of the insecticidal activity and
formation of a mixture of more than 40 degradation products.
The major products of nithiazine photoreduction and dimerization
from irradiation at 360 nm in water are nitrile, nitroso,
and oxim derivatives, and dimers. Consequently,
nithiazine half-time on foliage is only about 30min. Low photostability
is the primary reason that nithiazine is not used as an
insecticide for field and other environmental applications.
Nithiazine stability in aqueous environments is affected by pH.
Its half-time is greater than 3months at pH 7, while it is only 3 h
at pH 1.1.
Nithiazine is an agonist acting at the neural nicotinic acetylcholine
receptor – Na+/K+ ionophore in mammals and insects.
The nicotinic acetylcholine receptors regulate the flow of Na+
and K+ through the channels in the neural postsynaptic
membranes. Opening and closing of the channels by acetylcholine
maintains the dynamic ratio of the intracellular to
extracellular concentrations of Na+ and K+ needed for the
initiation of the signal in the postsynaptic neuron. The structural
differences between insect and mammalian receptors
determine the high selectivity of nithiazine toxicity to insects.
