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Toxicokinetics of permethrin in the rat.

The toxicokinetics of permethrin after single 460 mg/kg oral and 46 mg/kg intravenous doses were studied in male Sprague-Dawley rats. Serial blood samples after oral and intravenous dosage, and brain, medulla oblongata, sciatic nerve, and liver samples after oral administration were collected. Plasma, hypothalamus, cerebellum, frontal cortex, caudate putamen, hippocampus, medulla oblongata, sciatic nerve, and liver concentrations of permethrin and its metabolites, m-phenoxybenzyl alcohol and m-phenoxybenzoic acid, were determined by a high-performance liquid chromatographic assay. The permethrin plasma profile could be adequately described by a two-compartment open model. For permethrin, the elimination half-life (t1/2 beta) and the mean residence time from plasma were 8.67 and 11.19 hr after i.v. and 12.37 and 17.77 hr after po administration. The total plasma clearance was not influenced by dose concentration or route and reached a value of 0.058 liter/hr. After the single oral dose, permethrin was absorbed slowly with a Tmax of 3.52 hr. The maximum plasma concentration was 49.46 micrograms/ml. The oral bioavailability of permethrin was found to be 60.69%. The plasma concentration-time data for permethrin metabolites as well as the tissue concentration-time data for permethrin and its metabolites after an oral dose of permethrin were found to fit a one-compartment open model. The elimination half-life (t1/2el) of permethrin was greater for the hippocampus, medulla oblongata, frontal cortex, and sciatic nerve (23.10, 22.36, 13.86, and 16.27 hr, respectively) than for plasma (t1/2 beta, 12.37 hr). The maximum amounts of permethrin in cerebellum, hippocampus, caudate putamen, frontal cortex, hypothalamus, and sciatic nerve were about 1.5, 2, 2, 2.7, 4.8, and 7.5 times higher than in plasma, respectively, indicating an accumulation of pyrethroid by nervous tissue itself. Nervous tissue accumulation of permethrin was also reflected by the area under the concentration curve ratios of tissue/plasma (1.16, 3.71, 1.57, 4.27, 3.48, and 8.77, respectively). The metabolites of permethrin, m-phenoxy-benzyl alcohol and m-phenoxybenzoic acid, were detected in plasma and in all selected tissues for 48 hr after dosing, suggesting that a combination of metabolism by the tissues and diffusion into it from the blood may be present.

Administration, Oral

Permethrin-impregnated curtains against phlebotomine sandflies (Diptera: Psychodidae): laboratory and field studies.

The efficacy of permethrin-impregnated nets against vectors of leishmaniases was evaluated in laboratory and field studies. Permethrin-impregnated curtains were tested at different dosages in experimental tunnel against Phlebotomus perniciosus and P. papatasi. The influence on feeding behaviour and the mortality rate post contact with the impregnated curtain were investigated. The vapour effect of permethrin on P. perniciosus adults confined less than 1 cm away from a treated net was also evaluated. From laboratory studies it seems that permethrin shows low or any barrier effect against sandfly species tested, and that the high insecticidal activity (mortality rate greater than 90%, 24 hours after the contact with treated net, 1 g/m2) and the reduction of biting rate observed (between 53.56% and 85.24%) are the main effects that make permethrin-impregnated nets very effective for sandfly control. In field studies carried out in cutaneous leishmaniasis foci of Italy, it was demonstrated that permethrin-impregnated curtains around windows and around CDC light traps, reduce the number of sandflies entering the stables and traps. In Burkina Faso, indoor use of wide-mesh cotton curtains impregnated with permethrin 1 g/m2 almost completely eliminate the occurrence of endophilic sandfly species. In conclusion the use of permethrin-impregnated curtains could be an alternative to residual house-spraying for the control of endophilic vectors of leishmaniases.

Animals

Chronic toxicity and carcinogenic evaluation of permethrin in rats and mice.

Groups of Alpk:AP (Wistar-derived) rats were fed diets containing 0, 500, 1000 or 2500 ppm permethrin for 2 years and Swiss-derived mice were maintained for their lifetime (80% mortality) on diets containing 0, 250, 1000, or 2500 ppm permethrin. Changes of toxicological significance were confined to the top dose level of 2500 ppm permethrin in both species. Tremors and hypersensitivity to noise were noted in rats at this dose during the first 2 weeks of study but such signs were not seen in mice. Pathological examination of the central and peripheral nervous systems did not reveal abnormalities attributable to permethrin administration. The effect on mice at 2500 ppm permethrin was shown by decreased body weight gain. Liver hypertrophy, associated with increase in liver weight, microsomal enzyme activity, and proliferation of smooth endoplasmic reticulum occurred in the rat with similar but less marked changes in the mouse. This was considered to be an adaptive response of no toxicological significance. No evidence of a carcinogenic effect was seen in the rat study. In the mouse study a slight elevation in benign lung tumor incidence in males only at 2500 ppm permethrin was observed but was not considered to represent a carcinogenic effect.

Animals

Permethrin transfer from treated cloth to the skin surface: potential for exposure in humans.

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease-bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with 14C-labeled permethrin were applied to the backs of rabbits for 1 wk. Permethrin migration was quantitated by measuring the fate of the 14C label. Conditions that could affect leaching and/or absorption were also evaluated, that is, varying environments, the presence of sweat, different fabric types, and the effects of prelaundering. Results showed that fabric treated with permethrin at a rate of 0.125 mg/cm2 lost the substance to the skin surface at an average rate of 0.49%/d. At the end of the 7-d exposures in rabbits, about 3.2% of the available permethrin had reached the skin, 2% having been recovered from excreta (absorbed) and 1.2% remaining on the skin surface. Prelaundering the treated fabric had little effect on migration rate, nor did the other variables tested. Exposure dose to humans from wearing permethrin-treated (0.125 mg/cm2) military clothing is predicted to be 6 x 10(-4) mg/kg/d.

Animals

Comparative study of 5% permethrin cream and 1% lindane lotion for the treatment of scabies.

A multicenter, randomized, investigator-blind controlled trial was conducted to compare the safety and efficacy of a single, whole-body application of 5% permethrin cream with that of 1% lindane lotion for the treatment of scabies in 467 patients. At 14 +/- 3 days after treatment, the mean active lesion count decreased from pretreatment levels of 85 (range, 4 to 600) in both treatment groups to 14 (range, 0 to 133) in the permethrin group and to 15 lesions (range, 0 to 500) in the lindane group. At 28 +/- 7 days after treatment, complete resolution had occurred in 181 (91%) of 199 patients treated with permethrin and in 176 (86%) of 205 patients given lindane. Pruritus due to scabies persisted at 28 +/- 7 days in 14% of the permethrin group and in 25% of the lindane group. The most frequent adverse effects were new or increased pruritus and mild, transient burning or stinging; the latter was slightly more frequent following permethrin treatment and appeared to be related to severity of infestation. Because of a lower potential for neurologic toxicity, permethrin may be preferable to lindane for the treatment of scabies particularly in children.

Adolescent

[Pyrethrin and pyrethroid (permethrin) in the treatment of scabies and pediculosis].

The history and development of pyrethrum, the natural pyrethrins and synthetic pyrethroids and their insecticidal properties, chemical structure and toxic and allergic side-effects are reported. Permethrin is stressed as a photostable insecticide that is very effective against a large variety of insects and mites with low mammalian toxicity and virtually no allergic side-effects. Only 10-20 min after application, permethrin (1% cream rinse or 0.5% in ethanol) proved to be safe, reliable and cosmetically acceptable in the treatment of infestations with head lice and the prevention of reinfestations, and also in failures with lindane owing to the development of tolerance in the lice. The same was true of 5% permethrin cream (2.5% in children below 5 years of age) used in the treatment of scabies. Permethrin is absorbed percutaneously in only small amounts, is metabolized rapidly in the skin and excreted in the urine. A single "head to toe" application is ideal for eradication programmes allowing lice to be targetted and the prevalence of secondary bacterial infections decreased at the same time. Benzyl benzoate has an irritant potential, and lindane has been reported to exert CNS toxicity in a few anecdotal cases, in particular in small children or after repeated applications in patients with scabies crustosa, and permethrin was distinctly superior to both of these. This is documented by the results obtained in the treatment of 48 children and 56 adults suffering from scabies. Permethrin is recommended in scabies therapy in premature infants, small children, patients with seizures and neurological complications, in treatment failures with lindane entailing the need to repeat the therapy, in scabies crustosa and in pregnant women and nursing mothers.

Adolescent

Cytogenetic effects of permethrin in cultured human lymphocytes.

The pyrethroid insecticide permethrin was tested for its ability to induce sister chromatid exchanges (SCE), micronuclei (MN) and structural chromosome aberrations (CA) in cultured human peripheral blood lymphocytes. Permethrin was tested in the range of 5-500 micrograms/ml in the absence and in the presence of a rat liver activation system (S9 mix). Small elevations in the SCE frequencies were found and even though statistically significant may have no biological meaning, the more so since there was no dose-effect relationship. Permethrin induced both MN and CA when it was evaluated in the absence of a metabolic activation system. Nevertheless, it cannot be said that S9 mix suppressed the activity in itself. The effect of permethrin seemed to be time of exposure dependent. Permethrin could be characterized as a S-phase independent agent with greater potential for inducing chromosomal damage than sister chromatid exchanges.

Animals

Impact of permethrin-treated bednets on malaria transmission by the Anopheles gambiae complex in The Gambia.

Malaria vector mosquitoes belonging to the Anopheles gambiae complex were studied in four hamlets in The Gambia. All inhabitants were given bednets treated either with a placebo (milk) in two hamlets or with the pyrethroid insecticide permethrin (500 mg/m2) in two other hamlets. Malaria transmission occurred mainly during a few weeks of the rainy season, in September and October 1987. The indoor resting densities of mosquitoes in permethrin-treated hamlets were reduced, and we estimated over 90% reduction in biting on man by An. gambiae Giles sensu stricto in these hamlets. No mosquitoes were found under permethrin-treated bednets compared with eighty-one recovered from placebo-treated bednets. Mosquitoes exited more readily from rooms where permethrin-treated bednets were used than from rooms with placebo-treated nets. The annual mean probability that a child would receive an infective bite was estimated to be 0.09 in hamlets with insecticide-treated bednets, compared with 1.9 where placebo-treated bednets were used. Permethrin-treated bednets are therefore recommended as a means of effectively reducing the risk of exposure to malaria transmission, particularly in areas of low seasonal transmission.

Animals

Evaluations of permethrin-impregnated clothing and three topical repellent formulations of deet against tsetse flies in Zambia.

Permethrin-impregnated clothing and three topical repellent formulations of deet (diethyltoluamide) were field tested against natural populations of tsetse flies, mostly Glossina morsitans centralis Machado, in central Zambia. Volunteers wore different combinations of clothing impregnated with permethrin 0.125 mg ai/cm2 and repellents while riding in a vehicle that was driven slowly (4-6 km/h), with the windows and rear door open, through fly-infested areas. The mean rate of tsetse bites was about twenty per 75 min for unprotected people. The treatment combination of permethrin-impregnated clothing (blue cotton coveralls) and either of two controlled-release deet formulations on exposed skin of face and arms provided 91% mean protection, but this was not significantly better (P greater than 0.05) than wearing deet repellent alone (76-87% protection). No significant differences of protection were observed between the three repellent treatments, although the two controlled-release formulations (intended to be more persistent) were applied at approximately half the dosage of the standard 75% deet. Wearing permethrin-impregnated coveralls alone provided relatively poor protection (34%) for the untreated and exposed skin of head and hands. However, olive drab mesh jackets treated with permethrin reduced the tsetse biting rate by 75%.

Animals

Postmarketing surveillance study of permethrin creme rinse.

BACKGROUND: An observational, epidemiological study was undertaken to evaluate the safety of permethrin 1% creme rinse (Nix) for treatment of head lice infestations. METHODS: Thirty-seven local public health departments enrolled a total of 38,160 patients for 47,578 treatments with permethrin or other pediculicides from September 1, 1986, through January 31, 1988. Follow-up safety information was collected between 7 and 14 days following treatment via return visit or telephone contact. RESULTS: One hundred three adverse events were reported among 41,955 evaluable treatments. The rates of reported adverse events were 2.2 per 1000 treatments among permethrin treatments, 3.4 per 1000 treatments among lindane treatments, and 1.5 per 1000 treatments among other over-the-counter treatments. No serious, unexpected adverse events were detected in the 18,950 patients treated with permethrin. CONCLUSIONS: This study confirmed the safety profile of permethrin in conditions of general use, as seen in clinical trials. Postmarketing safety monitoring in public health departments of drugs used to treat public health conditions was shown to be feasible.

Adolescent

Comparative Effectiveness of Oral Ivermectin, 1% Permethrin Shampoo, and 4% Dimethicone Liquid Gel in Treatment of Pediculosis Capitis among School Children in Chachoengsao Province, Thailand.

Pediculosis capitis remains a persistent public health issue, especially in developing countries where resistance to standard neurotoxic pediculicides like permethrin is increasingly prevalent. This study aimed to compare the effectiveness of alternative treatment options against the standard care in a resource-limited setting. We conducted a single-blind randomized controlled trial involving three primary schools in Chachoengsao Province, Thailand (ClinicalTrials.gov: NCT06332872). Eighty-five female participants ages 6-13 years with active infestations were enrolled. Schools were randomly assigned to three treatment arms: 1) oral ivermectin (200 &#xb5;g/kg) on Days 0 and 7; 2) 1% permethrin shampoo on Days 0 and 7, or 3) 4% dimethicone liquid gel as a single dose on Day 0. The primary outcome was the cure rate, defined as the absence of live lice and viable nits upon clinical assessment on Day 9. Of the 66 participants included in the final per-protocol analysis, oral ivermectin achieved a cure rate of 95.5% (21/22), which was significantly higher than that of the 1% permethrin standard of care (37.0%; 10/27) and the 4% dimethicone physical suffocant (29.4%; 5/17) (P <0.001). Although dimethicone achieved high initial parasitic clearance on Day 0 (88.2%), a rapid reinfestation rate of 58.8% was observed by Day 9, indicating that a single-dose protocol may be clinically insufficient. Adverse events were mild and temporary across all groups. Oral ivermectin appears significantly more effective than both 1% permethrin and single-dose 4% dimethicone in this population. These findings suggest that permethrin resistance is clinically prevalent and relevant in this area.

Humans

Efficacy and transdermal absorption of permethrin in scabies patients.

The clinical efficacy and transdermal absorption of permethrin, a new synthetic insecticide was investigated in ten scabies patients. All patients were successfully treated with one application of a cream, containing 5% permethrin. Apart from mild postscabies dermatitis no side-effects were observed. The mean weight of cream used per patient was 25 g (range 21-32; mean content of permethrin 1250 mg). The degree of permethrin absorption was assessed indirectly by determination of conjugated and unconjugated cis- and trans-CVA (a metabolite of permethrin) excretion in urine using two dimensional gas chromatography mass spectrometry. It was found that during the first 48 hours the mean estimated absorption was 6 mg (range 3-11), which is approximately 0.5% of the total dose.

Adult

Effectiveness of controlled-release personal-use arthropod repellents and permethrin-impregnated clothing in the field.

Two topical controlled-release personal-use arthropod repellent formulations of diethyl methylbenzamide (deet) and permethrin-impregnated clothing were tested on human volunteers in a tropical rain forest near Innisfail, Queensland, Australia. The field trials were arranged in a four-way factorial design which compared fabric types, permethrin treatment and repellent treatments over a 14-hour test period. An analysis of variance with each factor treated as a fixed effect indicated that treatment of the clothing with permethrin and use of topical repellents were effective in preventing bites. The controlled release formulations were not significantly better than the current U.S. Army formulation of deet under field conditions. The repellent formulations and the permethrin-treated clothing used as one system provided better protection than the repellent formulations or permethrin-treated clothing used separately.

Administration, Cutaneous

Comparative effects of synthetic insecticides--endosulfan, phosalone and permethrin--on Chlamydomonas reinhardtii algal cells.

Presence of insecticide-endosulfan, phosalone or permethrin in the growth medium caused concentration dependent inhibition in the vegetative growth of Chlamydomonas reinhardtii algal cells. The rate of inhibition produced by endosulfan was two-fold higher than that of phosalone or permethrin. Endosulfan affected the cell growth completely at 100 times less concentration as compared to that of phosalone or permethrin. Non-dividing cell populations encountered significant losses in cells during their exposure (2 h) to endosulfan and did not show further loss in the 72 h post-treatment period. The populations treated with phosalone exhibited losses of considerable magnitude in the post-treatment period. Permethrin treated non-diving cell populations did not lower the cell number, either after the treatment period (2 h) or the post-treatment period (72 h). However, these populations showed reduced levels of chlorophyll following the exposure of the insecticide and did not display recovery or further reduction in the levels in the post-treatment period. The chlorophyll levels of endosulfan or phosalone treated cell populations remained unaffected. The cells remaining intact after the treatment (2 h) of endosulfan or phosalone exhibited significant decreases in their post treatment vegetative growth abilities. The growth ability of such permethrin exposed cells was similar to that of untreated cells.

Cell Count

Permethrin and its two metabolite residues in seven agricultural crops.

Metabolite residues of permethrin are not reported in the literature for most agricultural crops. This paper reports residues of permethrin and its 2 metabolites (dichlorovinyl acid and metaphenoxybenzyl alcohol) in 7 different agricultural crops (Chinese cabbage, spinach, asparagus, raspberries, green peas, turnip roots, and turnip greens). Permethrin residues declined approximately 85% within 7 days after treatment in all crops. In most cases, the acid metabolite residues peaked at 3 days, and declined after that. Translocation of residues into turnip roots was very slight; the average was less than 0.05 ppm for permethrin and alcohol metabolite residues and none was detected for the acid metabolite residue. Permethrin residues in the turnip greens averaged approximately 2 ppm for the 0.112 kg ai/ha treatment, and 6 ppm for the 0.224 kg ai/ha treatment.

Food Contamination

Acute toxicity of permethrin to four size classes of red swamp crayfish (Procambarus clarkii) and observations of post-exposure effects.

The mean static acute 96-h LC50 of permethrin [(3-phenoxybenzyl (+) cis, trans, 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate)] to red swamp crayfish (Procambarus clarkii) 8-12 mm (0.017 g), 25-35 mm (0.64 g), 45-55 mm (2.45 g), and 65-75 mm total length (8.98 g) was 0.44, 0.85, 1.30, and 0.81 micrograms/L, respectively. Permethrin toxicity did not differ among immature or mature male and female P. clarkii. Crayfish surviving permethrin exposures exhibited no differences in post-exposure growth, survival, onset of sexual maturity, or the reproduction of viable young when compared to non-exposed controls. Teratogenesis was not observed in third-instar crayfish produced from permethrin-exposed parents.

Animals

A trial of permethrin-treated bed nets in the prevention of malaria in Gambian children.

A trial was undertaken in a rural area of The Gambia to investigate the impact of permethrin-treated bed nets on malaria. Two groups of children, matched for age, sex, and malaria exposure, were followed through the rainy season of 1985 for illness and febrile episodes. One group of 205 children slept under permethrin-treated bed nets (0.5 g/m2); 184 children who slept under placebo-treated nets formed the control group. At the end of the rains the children were examined for splenomegaly and blood samples were taken for determination of packed cell volume (PCV) and parasitaemia. Permethrin treatment of bed nets was well accepted and was without side-effects. Children who slept under treated nets had significantly fewer episodes of clinical malaria than control children. However, at the end of the rains there was no significant difference in the prevalence of splenomegaly or parasitaemia or in the mean PCV between the groups. It is suggested that permethrin treatment of nets may have a greater effect on the duration of probing by mosquitoes for a blood meal than on the number of bites received.

Animals

Permethrin 5% dermal cream: a new treatment for scabies.

Permethrin 5% dermal cream (Burroughs Wellcome Co.) was compared in an investigator-blinded, randomized study against lindane 1% lotion (Kwell) for the treatment of microscopically confirmed scabies. Eleven of twenty-three patients treated with permethrin cream were cured in 2 weeks (48%). Only two patients had scabies 1 month following a single treatment with this product, giving a cure rate of 91%. One of these two patients was considered to have a reinfestation. Only three of twenty-three (13%) patients treated with 1% lindane lotion (Kwell) were free of scabies 2 weeks after a single treatment and fifteen of twenty-three (65%) were cured at 1 month. The unusually high percentage of treatment failures (35%) following lindane therapy may have been related to extensive use of this agent for head lice and scabies in this village during the preceding 5 years. The higher cure rate at 1 month seen with permethrin cream was significant (p less than 0.025). Permethrin 5% dermal cream offers a new, cosmetically elegant alternative to lindane therapy and was effective in a community in which lindane demonstrated an unacceptable level of treatment failures.

Administration, Topical