Absorption, Distribution and Excretion
Pyrethrins are absorbed from the gastrointestinal tract following oral administration. Studies in male rats receiving 3 mg/kg orally resulted in almost complete absorption and metabolism within 100 hours. No pyrethrin was observed in urine, although substantial quantities of metabolites were present. In feces, small quantities of the parent pyrethrin were observed, again accompanied by metabolites.
Pyrethrins are absorbed through intact skin when applied topically. When animals were exposed to aerosols of pyrethrins with piperonyl butoxide being released into the air, little or none of the combination was systemically absorbed. /Pyrethrins/
The pyrethrins or their metabolites are not known to be stored in the body or to be excreted in the milk...
Following a single oral pyrethrin II dose to rats, 53% of the admin dose appeared as CO2 & 7% appeared in urine. After an equivalent dose of pyrethrin I, 0.3% could be accounted for as CO2 & 46% of the dose was eliminated in urine.

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Metabolism / Metabolites
Pyrethrins are extensively metabolized, the residues of the parent compound in feces and urine representing only 10%. Six metabolites were identified and two major metabolic pathways were suggested, the first involving oxidation of the double-bond and/or the methyl groups and the second involving hydrolysis of the ester bond. Pyrethrins I are metabolized mainly through oxidative processes, while pyrethrins II are metabolized through a combination of hydrolytic and oxidative processes.
... Within 48 hr of oral admin of (14)C-pyrethrin II to rats, 53% of the (14)C was recovered as exhaled carbon dioxide ... . The ... (14)C recovered from urine ... /was/ 7% ... some of the orally admin material is excreted in feces, at least partially in metabolized form. Three compounds have been isolated from urine & identified by NMR & mass spectra. All three are produced by ... pyrethrin I & II. All three are the result of oxidation of ... the acid & alcoholic moieties leaving the main structure of the molecule intact.
The oral administration of radio-labelled pyrethrin I, or pyrethrin II, to rats produced several urinary metabolites. Each contained a trans-2-carboxyprop-1-enyl side chain resulting from oxidation of the chrysanthemate isobutenyl group or hydrolysis of the pyrethrate methoxy-carbonyl group. Also, the cis-2',4'-pentadienyl side chain of pyrethrin I and pyrethrin II was oxidized at the penta-2,4-dienyl group to give a cis-4',5'-dihydroxypent-2'-enyl group, a 4' conjugate of this diol, or a trans-2',5'-dihydroxypent-3'-enyl group.
The 2-methylpropenyl group of (S)-bioallethrin (A) and the pentadienyl group of pyrethrin II are selectively oxidized by m-chloroperoxybenzoic acid in dichloromethane to yield the 7,8-epoxide (1) from A and a mixture of the 8',9'- and 10',11'-epoxides (7 and 8) from pyrethrin II. These epoxides are hydrated in aqueous acid to the corresponding diols and other hydroxy derivatives produced by opening of the cycloprophyl ring or migration of the adjacent double bond. The epoxy and hydroxy derivatives are identified by two dimensional NMR techniques. Mouse liver enzymes do not detectably hydrate epoxide 1 but quickly hydrate epoxides 7 and 8 without migration of the double bond. HPLC analyses of the microsomal metabolites of pyrethrins I and II identify the 10',11'-diols as major metabolites and the 8',9'-diols as minor products.
For more Metabolism/Metabolites (Complete) data for PYRETHRIN II (12 total), please visit the HSDB record page.

Interactions
Piperonyl butoxide potentiates /insecticidal activity/ of pyrethrins by inhibiting the hydrolytic enzymes responsible for pyrethrins' metabolism in arthropods. When piperonyl butoxide is combined with pyrethrins, the insecticidal activity of the latter drug is increased 2-12 times /Pyrethrins/
At dietary level of 1000 ppm pyrethrins & 10000 ppm piperonyl butoxide ... /enlargement, margination, & cytoplasmic inclusions in liver cells of rats/ were well developed in only 8 days, but ... were not maximal. Changes were proportional to dosage & similar to those produced by DDT. Effects of the 2 ... were additive. /Pyrethrins/
There is no evidence that synergists incr toxicity of the pyrethrins to mammals. /pyrethrins/
Antioxidants used to help protect insecticidal residues of pyrethrins include minute concn of pyrocatechol, pyrogallol, & hydroquinone; 1-benzene-azo-2-naphthol is used to protect against the effects of sunlight.
/LABORATORY ANIMALS: Developmental or Reproductive Toxicity/ ... Extract containing pyrethrum & piperonyl butoxide /was applied/ to chorio-allantoic membrane /of chick embryo/ & produced damaged testes with absence of gonadocytes in the surviving chicken embryo. /Pyrethrum extract/

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Non-Human Toxicity Values
LD50 Rat male oral greater than 600 mg/kg
LD50 Mouse intraperitoneal less than 240 mg/kg
LD50 Cat female intravenous 1 mg/kg
LD50 Rat oral 1.2 g/kg
For more Non-Human Toxicity Values (Complete) data for PYRETHRIN II (8 total), please visit the HSDB record page.

[1].Residual determination of pyrethrins in Lycium barbarum (goji) by GC-MS/MS and a dietary risk assessment of Chinese goji consumption. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2020 Mar;37(3):478-487.

Pyrethrin II is a member of pyrethrins. It is functionally related to a pyrethrin I.

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Mechanism of Action
The symptoms of pyrethrin poisoning follow the typical pattern ... : (1) excitation, (2) convulsions, (3) paralysis, and (4) death. The effects of pyrethrins on the insect nervous system closely resemble those of DDT, but are apparently much less persistent. Regular, rhythmic, and spontaneous nerve discharges have been observed in insect and crustacean nerve-muscle preparations poisoned with pyrethrins. The primary target of pyrethrins seems to be the ganglia of the insect central nervous system although some pyrethrin-poisoning effect can be observed in isolated legs. /Pyrethrins/
Electrophysiologically, pyrethrins cause repetitive discharges and conduction block. /Pyrethrins/
The primary site of action for pyrethrins ... is the sodium channel of nerve cells. Using a variety of methods, including voltage clamp and patch clamp techniques, it has been shown that pyrethrins ... slow the closing of sodium channel gates following an initial influx of sodium during the depolarizing phase of an action potential, which results in a prolonged sodium tail current.
Following absorption through the chitinous exoskeleton of arthropods, pyrethrins stimulate the nervous system, apparently by competitively interfering with cationic conductances in the lipid layer of nerve cells, thereby blocking nerve impulse transmissions. Paralysis & death follow. /Pyrethrins/
The interactions of natural pyrethrins and 9 pyrethroids with the nicotinic acetylcholine (ACh) receptor/channel complex of Torpedo electronic organ membranes were studied. None reduced (3)H-ACh binding to the receptor sites, but all inhibited (3)H-labeled perhydrohistrionicotoxin binding to the channel sites in presence of carbamylcholine. Allethrin inhibited binding noncompetitively, but (3)H-labeled imipramine binding competitively, suggesting that allethrin binds to the receptor's channel sites that bind imipramine. The pyrethroids were divided into 2 types according to their action: type A, which included allethrin, was more potent in inhibiting (3)H-H12-HTX binding and acted more rapidly. Type B, which included permethrin, was less potent and their potency increased slowly with time. The high affinities that several pyrethroids have for this nicotinic ACh receptor suggest that pyrethroids may have a synaptic site of action in addition to their well known effects on the axonal channels. /Pyrethrins and Pyrethroids/

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Therapeutic Uses
... The insecticide has been considered so innocuous that an ointment containing 0.75% pyrethrin was recommended for treatment of scabies, and such use led to only a few cases of dermatitis, some of doubtful relation to the treatment. Pyrethrins have been used extensively for the control of human body lice.
Head lice can be treated with pyrethrin 0.3% plus 3% piperonyl butoxide.

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Drug Warnings
Because commercial formulations are irritating to the eyes and mucous membranes, they should not be used to treat P. pubis infestations of the eyelashes.
Individuals sensitive to ragweed have shown cross-sensitivity to unrefined but not to refined pyrethrins; however, manufacturers of pyrethrins combinations warned that these products should not be used by ragweed-sensitive patients. /Pyrethrins/
Local irritation incl erythema, pruritus, urticaria, edema, eczema, & slight corneal erosion & stromal edema may occur & ... contact with face, eyes, mucous membranes, & urethral meatus should be avoided. ... Pyrethrins with piperonyl butoxide should not be applied to acutely inflamed skin or raw, weeping surfaces. ... The drug should not be used more than twice in 24 hours. /Pyrethrins/

C22H28O5

372.45

372.193

121-29-9

5281555

Light yellow to yellow liquid

1.1±0.1 g/cm3

473.7±45.0 °C at 760 mmHg

203.8±28.8 °C

0.0±1.2 mmHg at 25°C

1.528

4.43

0

5

9

27

751

3

CC1=C(C(=O)C[C@@H]1OC(=O)[C@@H]2[C@H](C2(C)C)/C=C(\C)/C(=O)OC)C/C=C\C=C

VJFUPGQZSXIULQ-XIGJTORUSA-N

InChI=1S/C22H28O5/c1-7-8-9-10-15-14(3)18(12-17(15)23)27-21(25)19-16(22(19,4)5)11-13(2)20(24)26-6/h7-9,11,16,18-19H,1,10,12H2,2-6H3/b9-8-,13-11+/t16-,18+,19+/m1/s1

[(1S)-2-methyl-4-oxo-3-[(2Z)-penta-2,4-dienyl]cyclopent-2-en-1-yl] (1R,3R)-3-[(E)-3-methoxy-2-methyl-3-oxoprop-1-enyl]-2,2-dimethylcyclopropane-1-carboxylate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO :~100 mg/mL (~268.49 mM; with sonication)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.71 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween-80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one),clear solution.
For example, if 1 mL of working solution is to be prepared,you can add 100 μL of 25.0 mg/mL clear DMSO stock solution and add it to 400 μL PEG300 and mix well. Then add 50 μL Tween-80 to the above system and mix well. Then continue to add 450 μL of physiological saline to make up to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)