PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Pyrethrins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

Pesticides and the Third World.

Many developing countries are importing industrial processes that make use of toxic chemicals. By the same token, pesticides, which are toxic by design, are also used increasingly in agriculture and in public health programs to control pests and vector-borne diseases. Recent estimates suggest that pesticides account for more than 20,000 fatalities yearly, and that most of these will have occurred in developing countries. This may actually be a gross underreporting. Although organophosphate and carbamate insecticides are still responsible for many of those poisoning cases, herbicides such as paraquat are also increasingly being implicated in fatal poisoning cases. Newer pesticides such as the synthetic derivatives of pyrethrin, which were believed to be relatively safe to humans, now appear to be implicated in some serious cases of intoxication. Community-based pest control using locally available botanical pesticides could have severe consequences unless the toxicity of these compounds is carefully assessed relative to nontarget organisms. A high proportion of pesticide intoxications appear to be due to lack of knowledge, unsafe attitudes, and dangerous practices. The technology available to small farmers for pesticide application is often inappropriate: faulty sprayers, lack of protective equipment adapted to tropical conditions, nonexistent first-aid provisions. Agricultural extension is often not oriented to the transfer of information relative to the dangers inherent in the use of pesticides. The lack of information at all levels may be one of the most important causative factors of chemical intoxication in developing countries. Research should at this time concentrate on behaviors leading to chemical intoxication. This should be done concurrently with proper prospective and retrospective surveys of poisonings in developing country communities. More information should be sought relative to the decision processes of import, legislation, and licensing. Research and development efforts in appropriate technology and safety devices are also critically needed.

Animals↗

Pyrethroid insecticides: advances and challenges in biomonitoring.

Pyrethroid insecticides have a wide variety of applications throughout the world. They are structurally diverse chemicals that are synthetically derived from naturally occurring pyrethrin insecticides. Significant advances in analytical chemistry have led to the development of biomarkers of exposure to pyrethroids, and these methods are currently being applied to study exposure in the general population. This article reviews the chemistry and toxicology of pyrethroid insecticides, with an emphasis on the development of biomarkers to assess environmental exposure. Future challenges in the application of these biomarkers in epidemiological studies are explored, as is a need for improved understanding of the toxicokinetics of pyrethroids in humans.

Biomarkers↗

Pyrethrum allergic contact dermatitis in humans--real?, common?, or not documented? An evidence-based approach.

Pyrethrum has been reported to produce allergic contact dermatitis in humans. Moreover, it has been speculated that cross reactions occur in ragweed-sensitized people. This review presents the botany, contemporary chemistry, and case reports of alleged allergic contact dermatitis. Our interpretation suggests that the evidence presented in literature does not show that allergic contact dermatitis results from exposure to pyrethrum. Similarly, the data do not suggest cross reactions in ragweed-sensitized people. Changes in the chemical composition of the refined pyrethrins suggest the putative sensitizer is present at a lower level in today's refined extracts than in ground pyrethrum flowers or the extracts used earlier.

Allergens↗

Scabies and pediculosis pubis: an update of treatment regimens and general review.

The ectoparasites scabies and pediculosis pubis are common causes of skin rash and pruritus worldwide. They are transmitted primarily by person-to-person spread and are generally associated with low morbidity. The preferred treatment for scabies has generally been topical agents such as lindane and permethrin. Recently, ivermectin has demonstrated good efficacy in the treatment of scabies, and it may be of particular use in institutional outbreaks and in communities in which scabies is endemic. Combination treatment with topical agents and oral ivermectin may be necessary for crusted scabies. Treatment of pediculosis pubis is best accomplished with topical permethrin, lindane, or pyrethrins with piperonyl butoxide. Although resistance to these topical agents has been reported in head lice, decreased efficacy in the treatment of pediculosis pubis has not been reported.

Anthelmintics↗

Review of common therapeutic options in the United States for the treatment of pediculosis capitis.

Numerous therapies are available in both over-the-counter and prescription formulations for the treatment of head lice infestation. We summarize treatment recommendations from published literature and from a recent meta-analysis from the Cochrane Database of Systematic Reviews that describe the efficacy, safety, and resistance patterns of monotherapies available in the United States. If treatment with pyrethrin or permethrin fails to eradicate the infestation, the treatment of choice is malathion. However, because of malathion's flammability, it should be a second-line therapy. Orally administered ivermectin has been reported to be efficacious, but it is not currently a US Food and Drug Administration-approved pediculicide. Alternative therapies are also discussed, in addition to indications for prophylaxis, resistance reporting, and the social impact of infestation.

Animals↗

Use of household pesticides and the risk of aplastic anaemia in Thailand. The Aplastic Anemia Study Group.

BACKGROUND: Aplastic anaemia is a severe blood dyscrasia that is more common in Thailand than in Western countries. Its a etiology remains poorly understood. METHODS: A case-control study was conducted in Bangkok and two rural regions of Thailand. The effect of household pesticides was evaluated among 253 incident cases of aplastic anaemia and 1174 hospital controls. RESULTS: A total of 54% of the cases and 61% of the controls were exposed 1-6 months previously. For most individual household pesticides and for groups classified according to chemical type (organophosphates, pyrethrins, and organochlorines), the relative risk (RR) estimates approximated 1.0; upper 95% confidence limits were below 2.0 for many comparisons. A significant association was observed for exposure to combination products containing dichlorvos and propoxur, with an overall RR estimate of 1.7 (95% confidence interval [CI]: 1.1-2.6); the estimate for regular use was 1.6 (95% CI: 0.9-2.9). CONCLUSIONS: The absence of a higher risk for the regular use of dichlorvos/propoxur reduces the credibility of the apparent association, which could well have been an artefact of multiple comparisons. We conclude that most household pesticides used in Thailand do not appear to increase the risk of aplastic anaemia.

Adult↗

Susceptibility of house flies (Diptera: Muscidae) and five pupal parasitoids (Hymenoptera: Pteromalidae) to abamectin and seven commercial insecticides.

Assays of five commercial insecticides applied as residual sprays at label rates to plywood indicated the most toxic insecticide overall for pteromalid parasitoids of house flies, Musca domestica L., was Atroban (permethrin), followed by Ciodrin (crotoxyphos), Rabon (tetrachlorvinphos), Ectrin (fenvalerate), and Cygon (dimethoate). Insecticide-susceptible house flies were susceptible to all five insecticides (mortality, 62-100%). Flies that were recently colonized from populations on dairy farms in New York were susceptible only to Rabon. Urolepis rufipes (Ashmead) was the most susceptible parasitoid species overall to these insecticides, followed by Muscidifurax raptor Girault & Sanders, Nasonia vitripennis Walker, Pachycrepoideus vindemmiae (Rondani), and Spalangia cameroni Perkins. Compared with susceptible flies, newly colonized flies showed moderate resistance to avermectin B1a (abamectin). Abamectin was more toxic to all of the parasitoids except N. vitripennis and S. cameroni than to newly colonized house flies when exposed for 90 min to plywood boards treated with 0.001-0.1% abamectin. Space sprays with Vapona (dichlorvos) killed all of the parasitoids and susceptible flies and 64% of the newly colonized flies when insects were placed directly in the path of the spray; mortality was substantially lower among flies and parasitoids protected under 5 cm of wheat straw. Space sprays with Pyrenone (pyrethrins) killed greater than 86% of all insects exposed to the spray path except for the newly colonized flies (1% mortality); mortality of insects protected under straw was low (less than 12%) except for S. cameroni (76%). Because responses of the five parasitoids to the different insecticides varied considerably, general conclusions about parasitoid susceptibility to active ingredients, insecticide class, or method of application were not possible.

Animals↗

Decline of pyrethroid resistance in the absence of selection pressure in a population of German cockroaches (Dictyoptera: Blattellidae).

The level of resistance to seven pyrethroids was followed in a laboratory-selected population of Blattella germanica (L.) for 15 generations, during which time it was not exposed to any insecticide. As estimated by LT50 resistance ratios (RRs), resistance declined in a stepwise manner to preselection levels with all of the pyrethroids except pyrethrins. I also compared the levels of resistance as indicated by RRs and by gene frequency (GF) estimates. Results showed that GF estimates provide a more precise indication of the changes in resistance that occur over time than do RRs alone, especially when combined with RR and end-point mortality data. I discuss my results from the standpoints of the number of genetic mechanisms involved in pyrethroid resistance in this insect, and what the declines in resistance mean for future cockroach control.

Animals↗

Stimulation of vitellogenesis by pyrethroids in mated and virgin female adults, male adults, and fourth instar females of Ornithodoros moubata (Acari: Argasidae).

The effects of several pyrethroids on vitellogenesis, i.e., vitellogenin (Vg) synthesis and ovarian development in unfed mated female adults of Ornithodoros moubata were investigated. Survival of ticks treated with pyrethrin, resmethrin, and etophenprox was very low. Ticks treated with cypermethrin (CyM), fenvalerate (Fev), and flucythrinate (Flu) survived even when high concentrations were used. Vg titer in the hemolymph of unfed mated females was the same level on day 5 and about three times higher on day 10 after treatment with CyM, Fev, and Flu, as that of engorged adult females. CyM was the most effective in inducing vitellogenesis and was further evaluated in unfed virgin females, males, and fourth instars. CyM was shown to stimulate vitellogenesis in unfed virgin females adults. Oviposition did not occur but ovaries were well developed. CyM also was shown to stimulate Vg in the hemolymph of unfed and fed adult males; however, the Vg levels were very low compared to that of engorged adult females. Extremely high concentrations of Vg were observed in the hemolymph of female nymphs (fourth instar), particularly engorged nymphs, treated with CyM (10 micrograms). No ovarian development was observed in these nymphs. Vg stimulated by CyM was shown to be immunologically and electrophoretically the same as that of normal engorged females.

Animals↗

Videodermatoscopy enhances the ability to monitor efficacy of scabies treatment and allows optimal timing of drug application.

BACKGROUND: Videodermatoscopy (VD) is a noninvasive diagnostic tool that has recently been advanced as an alternative technique for the diagnosis of scabies, based on studies showing its ability to detect mites in vivo with results comparable to those obtained by traditional skin scraping. OBJECTIVE: In this study we evaluated a group of patients undergoing topical treatment with a thermosensible foam containing 0.165% pyrethrins and 1.65% piperonyl butoxide to determine whether VD would enhance monitoring of the clinical response to treatment and indicate the optimal timing of drug application. MATERIALS AND METHODS: Twenty patients (12 M, 8 F; age 1-65 years) affected by scabies (diagnosis confirmed by VD), and who were treatment naïve, were included in the study. The foam was applied to the entire body once a day at bedtime for two consecutive days. To detect treatment response, VD evaluation of two targeted skin sites for each patient was performed at baseline and at 12, 24, 36 and 48 h. A video microscope system equipped with a zoom lens that allowed skin observation with incident light at magnifications ranging from x 20 to x 600 was used. RESULTS: In all patients, VD showed active mite migration within burrows at 12 h. At 24 h, there was no evidence of active mite migration, and a majority of patients reported that itching had subsided. At 48 h, the mites were no longer visible in appreciable amounts by VD, and an amorphous material, probably resulting from mite decomposition, was detectable at one end of an empty burrow in the majority of patients. Skin scraping at 48 h, followed by standard microscopic observation, also showed only mite remnants in all patients. None of the 20 patients showed signs of infestation by VD at targeted skin sites at a 2-week post baseline follow-up visit. CONCLUSIONS: VD enhances the monitoring of clinical response to treatment and allows optimal timing of drug application. This may be particularly important in minimizing risk of overtreatment, reducing the potential for side-effects, and enhancing patient compliance.

Administration, Topical↗

Pediculosis capitis: why prefer a solution to shampoo or spray?

Two hundred and sixty-eight children with pediculosis capitis took part in a comparative study to test the efficacy of five different pediculocides commonly used in Israel. The preparations used were pyrethrin shampoo, pyrethroid spray, malathion solution, carbaryl shampoo and carbaryl lotion. Carbaryl lotion and malathion solution were much more efficient when compared to the shampoo and spray preparations.

Carbaryl↗

Toxins that modulate the sodium channel gating mechanism.

A variety of toxins and chemicals has been shown to modulate the gating kinetics of the sodium channel. Studies of batrachotoxin, grayanotoxins and pyrethroids are summarized here as examples. Batrachotoxin and grayanotoxins eliminate the sodium channel inactivation thereby causing a prolonged, steady-state sodium current to flow during a depolarizing step. The sodium channel activation kinetics are not affected markedly. Batrachotoxin appears to bind to a site in the sodium channel to which the inactivation gate normally binds, thus causing an inhibition of sodium inactivation. Single channel recording experiments have shown that the mean open time of individual sodium channels is greatly prolonged by batrachotoxin. It appears that individual sodium channels are modified by batrachotoxin in an all-or-none manner. Pyrethroids which are synthetic derivatives of pyrethrins also modify the kinetics of sodium channels in a very drastic manner. In the presence of type I pyrethroids which lack a cyano group at the alpha position (e.g., allethrin and tetramethrin), a large steady-state sodium current appears during a step depolarization and a large slowly decaying sodium tail current appears upon repolarization. Thus both the activation and inactivation kinetics are slowed. Type II pyrethroids which contain an alpha-cyano group (e.g., deltamethrin, cyphenothrin, and fenvalerate) exert effects on sodium channels qualitatively similar to those of type I pyrethroids. However, the amplitudes of the steady-state sodium current and sodium tail current are smaller and the time constant of tail current decay is much longer. The mean open time of single sodium channels is greatly prolonged by the pyrethroids, and the effect is much more pronounced in type II than in type I pyrethroids. A high degree of stereospecificity has been found among four isomers of tetramethrin, (+)-trans and (+)-cis isomers being highly active and (-)-trans and (-)-cis isomers almost totally inactive. The inactive isomers bind to the sodium channel sites, thus preventing the action of the active isomers. Because of the unique action of pyrethroids in modulating the sodium channels, they are becoming useful tools for channel physiology and pharmacology.

Action Potentials↗

Systematic review of clinical efficacy of topical treatments for head lice.

OBJECTIVES: To collect and evaluate all trials on clinical efficacy of topical treatments for head lice. DESIGN: Systematic review of randomised trials identified from following data sources: Medline, International Pharmaceutical Abstracts, Science Citation Index, letters to key authors and companies, and hand search of journals. SETTING: Trials in schools or communities. SUBJECTS: Patients infested with lice. MAIN OUTCOME MEASURE: Cure rate (absence of live lice and viable nits) on day 14 after treatment. RESULTS: Total of 28 trials were identified and evaluated according to eight general and 18 lice specific criteria. Of the 14 trials rated as having low to moderate risk of bias, seven were selected as they used the main outcome measure. These seven trials described 21 evaluations of eight different compounds and placebo (all but two evaluations were of single applications). Only permethrin 1% creme rinse showed efficacy in more than two studies with the lower 95% confidence limit of cure rate above 90%. CONCLUSIONS: Only for permethrin has sufficient evidence been published to show efficacy. Less expensive treatments such as malathion and carbaryl need more evidence of efficacy. Lindane and the natural pyrethrines are not sufficiently effective to justify their use.

Administration, Topical↗

Oestradiol potentiates the effects of certain pyrethroid compounds in the MCF7 human breast carcinoma cell line.

Pyrethroids are the most widely used insecticides for indoor pest control, so human exposure to them is common. The main target of pyrethroids is the nervous system, but their endocrine disrupting capabilities may also be of toxicological concern. In the present study, the proliferation of the breast cancer cell line, MCF7, was studied after a 7-day exposure to various concentrations of pyrethrin, permethrin and cypermethrin. The effects of oestradiol and the combined effects of oestradiol (0.10 nM) and pyrethroids (0.1-100 microM) on MCF7 cell proliferation were also evaluated. Proliferation and cell toxicity were studied by measuring the ATP content with a luminescence method, and mitochondrial metabolic enzyme activity with the WST-1 test. In the ATP test, low concentrations (0.1-1 microM) of pyrethroids in co-exposure with oestradiol caused a clear statistically significant increase in the proliferation of MCF7 cells. This was evident when compared to the proliferative effect caused by 0.1 nM oestradiol alone. High concentrations were cytotoxic, and the greatest cell toxicity was that of cypermethrin, which has a cyano group in its molecular structure.

Adenosine Triphosphate↗

Evaluation of safety and efficacy of acaricides for control of the African tortoise tick (Amblyomma marmoreum) on leopard tortoises (Geochelone pardalis).

Nine acaricides (amitraz, carbaryl, chlorpyrifos, cyfluthrin, fipronil, lindane, permethrin, phenothrin, and pyrethrins) were studied for their efficacy in killing the African tortoise tick (Amblyomma marmoreum). Only four of the acaricides (chlorpyrifos, cyfluthrin, lindane, and permethrin) produced 100% mortality within 24 hr of application, and only two (cyfluthrin and permethrin) continued to cause 100% mortality when diluted to as low as 1:10,000. Five of the acaricides (amitraz, carbaryl, chlorpyrifos, cyfluthrin, and permethrin) were studied for toxicity to the leopard tortoise (Geochelone pardalis), the most common host of A. marmoreum. The results indicate that cyfluthrin and permethrin, which were herein found to be the two most effective acaricides for control of A. marmoreum, are also the safest acaricides for use on leopard tortoises.

Animals↗

Accudosetm aerosol--an effective house fly (Diptera; Muscidae: Musca domestica L.) adulticide control system for cage type poultry houses.

An automatic piped aerosol system (Accudose TM) using 0.7% synergized pyrethrin insecticide, was tested at a typical narrow cage poultry farm for the control of adult house flies, Musca domestica L. A similar narrow cage poultry farm was used as a control with all house fly control measures left up to the cooperating poultryman. AccudoseTM was compared with other house fly control methods at other similar farms which included three types of man-portable ultra volume (ULV) generators and an integrated (biological-chemical) program. Results of the five month test demonstrated that the AccudoseTM system suppressed house fly populations better than other control methods.

Aerosols↗

[Synthetic pyrethroid insecticides and development of resistance to them].

After the structures of pyrethrins, the insecticidal components of pyrethrum flowers, were determined, syntheses of derivatives of them were undertaken, and first generation synthetic pyrethroids, such as allethrin, resmethrin and phenothrin, were produced. Due to lack of photostability in these compounds, their use was limited to the control of sanitary or household pests. The syntheses of second generation synthetic pyrethroids, i.e., permethrin and fenvalerate, overcame a lack of photostability. These are now widely employed in the areas of agriculture and public health. Development of resistance in insect pests is the only difficulty to the future success of ideal insecticides, or synthetic pyrethroides. In this review, information regarding the development of pyrethroid resistance is summerized, and also the importance of nerve insensitivity to the chemicals, as a mechanism of resistance in insects pests, is pointed out.

Animals↗

Urticaria due to airborne permethrin exposure.

Although naturally derived pyrethrins are well recognized sensitizers, there is currently some degree of controversy regarding the sensitizing potential of synthetic pyrethroids. The literature is briefly reviewed, and an outbreak of several cases of urticaria occurring in children from 1 household and associated with airborne exposure to permethrin is reported.

Adult↗