Tau-fluvalinate is a pyrethroid insecticide. A pyrethroid is a synthetic chemical compound similar to the natural chemical pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids are common in commercial products such as household insecticides and insect repellents. In the concentrations used in such products, they are generally harmless to human beings but can harm sensitive individuals. They are usually broken apart by sunlight and the atmosphere in one or two days, and do not significantly affect groundwater quality except for being toxic to fish. Insects with certain mutations in their sodium channel gene may be resistant to pyrethroid insecticides. (3, 2)
belongs to the class of organic compounds known as diphenylethers. These are aromatic compounds containing two benzene rings linked to each other through an ether group.
Pyrethroids exert their effect by prolonging the open phase of the sodium channel gates when a nerve cell is excited. They appear to bind to the membrane lipid phase in the immediate vicinity of the sodium channel, thus modifying the channel kinetics. This blocks the closing of the sodium gates in the nerves, and thus prolongs the return of the membrane potential to its resting state. The repetitive (sensory, motor) neuronal discharge and a prolonged negative afterpotential produces effects quite similar to those produced by DDT, leading to hyperactivity of the nervous system which can result in paralysis and/or death. Other mechanisms of action of pyrethroids include antagonism of gamma-aminobutyric acid (GABA)-mediated inhibition, modulation of nicotinic cholinergic transmission, enhancement of noradrenaline release, and actions on calcium ions. (7, 4)
Metabolism
The major metabolic pathways are cleavage of ester linkage and oxidation at the acid and alcohol moieties. Ester hydrolysis leads to formation of anilino acid. The anilino acid is further conjugated with amino acids (glycine, serine, threonine, and valine), bile acids (cholic, taurochoric, and taurochenodeoxycholic), and glycerols (oleoyl- and linoleoylglycerol). In addition, an amide derivative of anilino acid was found. These conjugation reactions of anilino acid with bile acid (cholic acid, taurocholic acid, and taurochenodeoxycholic acid) and with glycerol and monoglycerides have rarely been reported as conjugates with xenobiotics. The major urinary metabolites are anilino acid, its hydroxymethyl derivative, its glycine conjugate, haloaniline, and sulfate conjugate of hydroxyhaloaniline. On the other hand, the major fecal metabolites are anilino acid, its amide derivative, and several conjugates of anilino acid with several endogenous components. An unexpected difference between fluvalinate and other pyrethroids is the minimal amount of hydroxylation at the 4'-position of the alcohol moiety. (9)
At high doses, signs of poisoning attributable to tau-fluvalinate include profuse salivation and pulmonary edema, clonic seizures, opisthotonos (i.e., the spine is bent forward such that a supine body rests on its head and heels), coma, and death. At lower doses, commonly observed effects include paresthesia and erythema. (5)
Symptoms
Following dermal exposure to tau-flavulinate, feelings of numbness, itching, burning, stinging, tingling, or warmth may occur, that could last for a few hours. Dizziness, headache, nausea, muscle twitching, reduced energy, and changes in awareness can result from inhalation or ingestion of large amounts of tau-fluvalinate. Paralysis can occur after exposure. (4)
Treatment
Following oral exposure, the treatment is symptomatic and supportive and includes monitoring for the development of hypersensitivity reactions with respiratory distress. Provide adequate airway management when needed. Gastric decontamination is usually not required unless the pyrethrin product is combined with a hydrocarbon. Following inhalation exposure, move patient to fresh air. monitor for respiratory distress. If cough or difficulty breathing develops, evaluate for respiratory tract irritation, bronchitis, or pneumonitis. Administer oxygen and assist ventilation as required. Treat bronchospasm with inhaled beta2 agonist and oral or parenteral corticosteroids. In case of eye exposure, irrigate exposed eyes with copious amounts of room temperature water for at least 15 minutes. If irritation, pain, swelling, lacrimation, or photophobia persist, the patient should be seen in a health care facility. If the contamination occurs through dermal exposure, remove contaminated clothing and wash exposed area thoroughly with soap and water. A physician may need to examine the area if irritation or pain persists. Vitamin E topical application is highly effective in relieving parenthesis. (8)
