Synthetic pyrethroids permethrin

Kolmodin-Hedman B, Swensson A, Akerblom M (1982) Occupational exposure to some synthetic pyrethroids (permethrin and fenvalerate). Arch Toxicol 50 27-33... 

Allan IJ, House WA, Parker A, Carter JE (2005) Diffusion of the synthetic pyrethroid permethrin into bed-sediments. Environ Sci Technol 39 523-530... 

Spehar, R.L., Tanner, D.K., Nordling, B.R. (1983) Toxicity of the synthetic pyrethroids, permethrin and AC 222, 705 and their accumulation in early life stages of fathead minnows and snails. Aquatic Toxicol. 3, 171-182. 

The majority of pyrethroid insecticides have low volatilities. The heavily used synthetic pyrethroid permethrin is classified as nonvolatile on the basis of its vapor pressure (1.3 x 10 kPa at 20 °C) and is rarely found in indoor air. However, it has recently been reported to be the major pesticide residue found in house dust (USEPA, 2000d). Cyper-methrin [( )-a-cyano-3-phenoxybenzyl-( )-cA,frani -3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] and cyfluthrin [cyano(4-fluoro-3-phenoxy-phenyl)methyl 3-(2,2-dichloro-ethenyl)-2,2-dimethylcyclopropanecarboxylate] are two other low-volatility pyrethroids commonly used for indoor flea and cockroach control. 

Pyrethrins and synthetic pyrethroids are among the safest of the topically applied ectoparasiticides, because of their selective toxicity for insects (mam-malian-to-insect toxic dose ratio is greater than 1000, compared with 33 for organophosphates and 16 for carbamate insecticides). In contrast to the very wide margin of safety for mammalian species, pyrethroids are toxic to fish. The synergistic action of pyrethrins and piperonyl butoxide (in combination preparations) is due to the inhibition by piperonyl butoxide of the microsomal enzyme system of some arthropods. Preparations of synthetic pyrethroids (permethrin, cypermethrin) often contain a mixture of drug isomers in varying proportions. 

Radiolabelled ( C) synthetic pyrethroids (permethrin, tefluthrin, cyper-methrin and lambdacyhalothrin Zeneca) were purified by radio thin layer chromatography (TLC) or radio high performance liquid chromatography (HPLC) to > 96% purity and dissolved in hexane as stock solutions. 

J.H. Skerritt, A.S. Hill, D.P. McAdam, L.H. Stanker, Analysis of the Synthetic Pyrethroids Permethrin and l(R)Phenothrin in Grain Using a Monoclonal Antibody-basedTest ,/. Agric. Food Chem., 40,1287-1292(1992). 

Concentrations of pyrethrins range from 0.05% to 0.2% in the ready-to-use products. Concentrates are marketed for dilution as a pour-on and are not greater than 2%. A practical method of providing a pyrethrin spray for a large dog is the use of a pour-on concentrate diluted in a commercial lawn/garden pressure sprayer. Many of pyrethrin-based products incorporate the use of synthetic pyrethroids (permethrin, resmethrin, sumithrin, D-trans-allethrin) which are added predominantly for residual effects. Permethrin is by far the most common pyrethroid used [40] in a range from 0.2 to 71.5 [4]. 

These synthetic pyrethroids mimic natural counterparts, of which the most important is pyrethrin 1 (10.265). Unfortunately, the natural products lack the photochemical and hydrolytic stability necessary for use as wool insect-resist agents. The synthetic products have the required stability, yet retain the low mammalian toxicity and low environmental retention of the natural products. Permethrin, however, is toxic to aquatic life and is therefore subject to increasingly severe discharge limits. There is some evidence that permethrin is less effective against larvae of a certain beetle. This can be compensated for by using a combination of permethrin with the hexahydropyrimidine derivative 10.264. Some possible alternative pyrethroids have been mentioned [517] as development products (10.266-10.269). 

Hansen, D.J., L.R. Goodman, J.C. Moore, and P.K. Higdon. 1983. Effects of the synthetic pyrethroids AC 222, 705, permethrin and fenvalerate on sheepshead minnows in early life stage toxicity tests. Environ. Toxicol. Chem. 2 251-258. 

Dasgupta S, Cheplick JM, Denton DL, Troyan JJ, Williams WM (2008) Predicted runoff loads of permethrin to the Sacramento river and its tributaries. In Gan J, Spurlock F, Hendley P, Weston DP (eds) Synthetic pyrethroids. Occurrence and behavior in aquatic environments, Chap 11. ACS Symposium Series 991, American Chemical Society, Washington DC, pp 223-237... 

Papers from the symposium on the chemistry, biochemistry, and insecticidal action of natural and synthetic pyrethroids (Helsinki 1974, Third I.U.P.A.C. International Congress on Pesticide Chemistry) and the proceedings of a symposium on synthetic pyrethroids held at the 172nd A.C.S. Meeting (San Francisco, 1976) have been published. Other pyrethroid papers of interest include C n.m.r. spectra of synthetic pyrethroids (cf. Vol. 7, p. 20), gd.c. analysis of permethrin and bioresmethrin, further work (Vol. 7, p. 10) on permethrin metabolism in rats ... 

Figure 8.3. Separation of synthetic pyrethroids (0.8 ng of each) on a 25 m OV-101 WCOT capillary column. Peaks 1 = cis-methrin 2 = bioresmethrin 1 + 2 = resmethrin 4 and 5 = phenothrin 6 = cis-permethrin 7 = trans-permethrin 8, 9, 10 and 11 = cypermethrin 12 and 13 = fenvalerate and 14 and 15 = deltamethrin. From [80]...

Some pyrethroids have as many as eight different isomers, and there are several different types. Acute toxicity of a mixture of two isomers depends on the ratio of the amounts of isomers in the formulation. For example, the female rat s acute oral LD50 of permethrin increases from 224 mg/kg to 6,000 mg/kg as the proportion of transisomer increases from 20% to 80%. The route of exposure also is critical in assessing the acute toxicity of a synthetic pyrethroid. Like DDT and many other registered insecticides, naturally occurring pyrethrins and the synthetic pyrethroids are nerve poisons. 

The synthetic pyrethroid principal mechanism of action is believed to be the disruption of the permeability of nerve membranes to sodium atoms.3 Organo-phosphates and carbamates also are nerve poisons, but they do not attack the human peripheral (in addition to our central) nervous system, as do DDT and synthetic pyrethroids. The half-life of pyrethroids in soils ranges from 1 day to 16 weeks. (It is amazing that people apply them annually for termite control, even though permethrin is supposedly effective against termites in the very same soil for 1 to 5 years). 

Permethrin, a synthetic pyrethroid, exhibits similar antiectoparasitic activity and may be the drug of choice owing to its slower cutaneous absorption, fast hydrolytic inactivation, and rapid renal elimination. 

Agricultural pesticides were found to be effective insect resist agents when applied in emulsion form to wool dyebaths. Dieldrin (Fig. 16.2a), one of the original nerve poisons, is also highly toxic to mammals and aquatic life and its use has been banned in most countries. Products based on permethrin (Fig. 16.2b), a synthetic pyrethroid, are very effective against moth larvae, but have less effect on Anthrenus beetles. To overcome this disadvantage, combination products of permethrin and hexahydropyrimidine derivatives (Fig. 16.2c) have been introduced. 

Synthetic pyrethroids (cypermethrin, deltamethrin, fenvalerate, flumethrin, permethrin) are available in a variety of dosage forms for topical application to... 

Synthetic pyrethroids cypermethrin, deltamethrin, fenvalerate, flumethrin, permethrin. 

Synthetic pyrethroids are geometric isomers with cis, trans configurations. Commercially available preparations of cypermethrin contain a mixture of cis and trans isomers in various proportions, for example, 60 40 and 80 20. Cypermethrin (cis trans 60 40) 2.5% solution is equivalent to cypermethrin (ids trans 80 20) 1.25% solution for pour-on application to sheep. Permethrin, which is the active ingredient incorporated in ear tags for cattle and insecticidal collars for dogs and cats, contains a mixture of cis and trans isomers in the proportion 40 60. 

Synthetic pyrethroids (cypermethrin, permethrin) and natural pyrethrins (pyrethrum extract) combined with piperonyl butoxide constitute the most important class of insecticide applied topically to horses (Table 5.7). The liquid concentrate containing cypermethrin which, after dilution, is applied to horses by spray contains a mixture of the isomers in equal proportion (cis trans 50 50). 

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