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Probable topical permethrin-induced neck dystonia.

A 28-year-old Caucasian man who applied topical 5% permethrin cream once for the treatment of scabies infestation experienced a severe dystonic reaction on the left side of his neck. Assessment of causality using the Naranjo algorithm revealed a probable relationship between this adverse drug event and application of topical permethrin. Dystonic or musculoskeletal adverse reactions, including muscle spasms, have been reported with pyrethroid insecticides only after inappropriate occupational dermal exposure. These reported reactions occurred 4-48 hours after exposure and lasted from a few days to a few weeks. The mechanism behind these adverse effects may be related to permethrin's ability to delay sodium channel closure within nerve cells. This may result in a lowered threshold of nerve fibers to activation of further action potentials, leading to repetitive firing and hyperexcitation of the nervous system. Clinicians should be aware of this rare but potential adverse effect of permethrin.

Administration, Topical↗

Evaluation of three methods for detecting permethrin resistance in adult and nymphal Blattella germanica (Dictyoptera: Blattellidae).

The insecticide resistance status of the German cockroach, Blattella germanica (L.), against permethrin was evaluated with three different bioassay methods. The LT50 and KT50 in adults were measured by glass jar test, the LT50 and KT50 in nymphs were assessed by glass petri dish-test, and the LD50 in adults and nymphs was measured by topical application. The results indicate that in all three bioassays, cockroaches showed different degrees of resistance to permethrin. Resistance ratios of 6.7-, 12.8-, and 7.5-fold for KT50, LD50, and LT50, respectively, were obtained for adult cockroaches compared with those from a susceptible strain. Similarly, resistance ratio values of 17-fold for KT50, 8-fold for LD50, and 6.4-fold for LT50 were obtained for nymphs compared with those from a susceptible strain. Although both adults and nymphs exhibited a similar level of susceptibility to permethrin, adults showed a higher degree of susceptibility to topical application than to the other exposure method. The order of sensitivity (based on resistance ratio values) was topical application (LD50) > LT50 > KT50 in adults. For nymphs, the resistance ratio in the knockdown test was higher than in other tests (resistance ratio = 17-fold). Therefore, the order of test sensitivity based on comparisons of resistance ratio values was KT50 > topical application (LD50) > LT50 in nymphs. Topical application exhibited a higher sensitivity than the LT and KT methods in adults. Thus, the results suggest that topical application and knockdown testing methods are the most sensitive assays for measuring resistance of adult and nymphal German cockroaches, respectively, to permethrin.

Animals↗

Permethrin-impregnated mattress liners: a novel and effective intervention against house dust mites (Acari: Pyroglyphididae).

This study tested the efficacy of permethrin-impregnated mattress liners in reducing house dust mites in the homes of volunteers with no previous recorded history of asthma, atopic eczema, or perennial rhinitis. The field trial using permethrin-impregnated (450 mg/m2 of pure permethrin in polyester netting weighing 35 g/m2) mattress liners (n = 9) was conducted for 27 mo. The permethrin-impregnated bedding significantly reduced house dust mites in mattresses for at least 27 mo. Allergen concentrations were significantly lowered at 15-mo postintervention. No adverse side-effects were reported. This is a promising development in house dust mite control.

Animals↗

Susceptibility of Haematobia irritans (Diptera: Muscidae) to permethrin in dairies in Aguascalientes, Mexico.

The purpose of this study was to conduct a survey for the susceptibility of the horn fly, Hematobia irritans (L.), populations to permethrin on dairy cattle from Aguascalientes, Mexico. Samples of populations of horn flies at 25 dairies were exposed to two discriminating doses (2.5 and 6.0 microg/cm2) on permethrin-treated filter papers and the percentage of mortality was compared with that of a susceptible strain treated with same doses of permethrin. The results show that there was a difference in the mortality from two discriminating doses and the mortality of the susceptible strain. Therefore, horn fly populations at all dairies tested in Aguascalientes, Mexico, were susceptible to permethrin. This insecticide, as well as other pyrethroids, could continue to be used to provide satisfactory control of horn flies in the study region.

Animals↗

Prevalence and levels of permethrin resistance in Pediculus humanus capitis De Geer (Anoplura: Pediculidae) from Buenos Aires, Argentina.

Permethrin has been used extensively for control of Pediculus humanus capitis De Geer (Anoplura: Pediculidae) in Argentina since 1990, resulting in the development of resistance to this and other pyrethroids. This resistance was first detected in some field populations in 1997. A survey for resistance in Buenos Aires in 2001 revealed significant resistance levels in lice on children at 24 of 26 (92.3%) schools. When compared with a previously unexposed reference population, resistance ratios (RRs) obtained by exposing the insects to filter papers impregnated with permethrin ranged from 2 to 60 in 10 (39%) of the schools. RRs in the remaining 14 (61%) populations were too great to not be measured with the filter paper method (RR > 88.7). As an alternative, we used topical applications of 0.1 microl of acetone solution of permethrin on the dorsal abdomen of adults and third instars. This topical method, which has not been previously reported for head lice, was capable of quantifying higher levels of resistance. Highly resistant populations had RRs from 162.5 to 655.2. When applied to populations with low and intermediate levels of resistance, results from the filter paper and topical application methods were highly correlated, and RRs from topical application were higher than those from the filter paper method. Results from the combination of the two methods indicated that head lice among Buenos Aries school children are highly resistant to permethrin, and the resistance is widespread.

Animals↗

Pyridostigmine, diethyltoluamide, permethrin, and stress: a double-blind, randomized, placebo-controlled trial to assess safety.

OBJECTIVE: To determine whether short-term human exposure to pyridostigmine bromide, diethyltoluamide, and permethrin, at rest or under stress, adversely affects short-term physical or neurocognitive performance. PARTICIPANTS AND METHODS: A multicenter, prospective, double-blind, placebo-controlled crossover trial exposing 64 volunteers to permethrin-impregnated uniforms, diethyltoluamide-containing skin cream, oral pyridostigmine, and corresponding placebos was performed. Each participant had 4 separate sessions, ensuring exposure to all treatments and placebos under both stress and rest conditions in random order. Outcomes Included physical performance (handgrip strength and duration, stair climbing, and pull-ups [males] or push-ups [females]), neurocognitive performance (computerized tests), and self-reported adverse effects. RESULTS: Permethrin was undetectable in the serum of all participants; pyridostigmine levels were higher Immediately after stress (41.6 ng/mL; 95% confidence Interval, 35.1-48.1 ng/mL) than rest (23.0 ng/mL; 95% confidence Interval, 19.2-26.9 ng/mL), whereas diethyltoluamide levels did not significantly differ by stress condition. Heart rate and systolic blood pressure increased significantly with stress compared with rest but did not vary with treatment vs placebo. Physical and neurocognitive outcome measures and self-reported adverse effects did not significantly differ by exposure group. CONCLUSION: Combined, correct use of pyridostigmine, diethyltoluamide, and permethrin is well tolerated and without evidence of short-term physical or neurocognitive impairment.

Adult↗

Susceptibility of adult field strains of Aedes aegypti and Aedes albopictus in Singapore to pirimiphos-methyl and permethrin.

The susceptibilities of field strains (Fl) of Aedes aegypti and Ae. albopictus adult females to pirimiphos-methyl and permethrin were investigated and compared with a susceptible laboratory strain (S) by using a filter paper (12 x 15 cm) impregnation method. The resistance ratio between the 50% lethal concentration values (RR50) of the Fl and the S strains shows that the RR50 of Fl Ae. aegypti for pirimiphos-methyl was 1.5 and the RR50 of Fl Ae. aegypti for permethrin was 12.9. The RR50 of Fl Ae. albopictus for pirimiphos-methyl was 1.4, and that for permethrin was 1.8. This indicates that the field strain Ae. aegypti, but not Ae. albopictus, has developed resistance to permethrin. However, both species are still susceptible to pirimiphos-methyl. Therefore, control with pirimiphos-methyl will still be effective.

Aedes↗

Repellency and efficacy of 65% permethrin and selamectin spot-on formulations against Ixodes ricinus ticks on dogs.

Two topically applied spot-on products used for flea and tick control on dogs, 65% permethrin (Defend EXspot Treatment for Dogs, Schering-Plough Animal Health Corp., Union, NJ) and selamectin (Revolution [United States] or Stronghold [Europe], Pfizer Animal Health, New York, NY), were evaluated for repellency and efficacy against Ixodes ricinus, the primary vector of Lyme disease in Europe. Eighteen dogs were evenly and randomly allocated to the following treatments: 1) 65% permethrin, 2) selamectin, 3) untreated control. Dogs were treated by topical application of the assigned product in accordance with product label directions on Day 0. At 7, 14, 21, 28, and 35 days after treatment, each dog was exposed for 2 hours to 50 unfed, adult ticks in a cage with a carpet that covered approximately 70% of the floor area. After the exposure period, dogs were removed from the cages and live and dead ticks were counted on the dogs and in the cages. The number of live ticks recovered was reduced by 90.3% to 99.5% for dogs treated with 65% permethrin (P <.0001 versus controls and selamectin), compared with 10.9% to 31.1% for dogs treated with selamectin (P >.05 versus controls). The repellency of 65% permethrin was 63.4% to 80.2% against I. ricinus ticks (P <.0001 versus controls, P <.0007 versus selamectin), compared with 0% to 10.9% repellency for selamectin (P >.05 versus controls).

Administration, Cutaneous↗

Efficacy of three dose volumes of topically applied 65% permethrin against Ctenocephalides felis and Rhipicephalus sanguineus on dogs weighing 30 kg or more.

Twenty-five dogs were evenly and randomly allocated by weight to five treatment groups: untreated control, 2 ml 65% permethrin (dogs weighing 15 to 29 kg, "average dogs"), and 2, 3, or 4 ml 65% permethrin (dogs weighing > or = 30 kg, "big dogs"). Each dog was infested with 125 unfed, adult cat fleas, Ctenocephalides felis, and 50 unfed, adult brown dog ticks, Rhipicephalus sanguineus, on Days -3 (ticks only), -2 (fleas only), 3, 7, 14, 17, 21, 24, and 28. Fleas and ticks were counted 1 and 3 or 4 days after each infestation. The duration of efficacy (defined as >90%) against C. felis was 28 to 31 days. The efficacy against fleas 31 days after application of 2, 3, or 4 ml on big dogs ranged from 79.1% (2 ml) to 100% (4 ml). Big dogs that received either 3 or 4 ml of 65% permethrin had significantly (P < or = .05) fewer fleas at several evaluations between 15 and 31 days after treatment. The duration of efficacy against R. sanguineus was 15 (2 ml for big dogs) to 28 (2 ml for average dogs) days. The efficacy against R. sanguineus 28 days after treatment ranged from 79.1% (2 ml on big dogs) to 94.1% (2 ml on average dogs). Significantly (P < or = .05) fewer ticks were present at several evaluations after treatment on big dogs that received 3 or 4 ml than were present on big dogs treated with 2 ml. No significant differences were detected between the 3- and 4-ml groups from Days 10 to 31; however, the geometric mean number of ticks in the group treated with 4 ml was numerically lower than that for dogs treated with 3 ml on several occasions. These data indicate that a dose volume of 3 or 4 ml of 65% permethrin is needed to obtain an adequate level and duration of efficacy against both C. felis and R. sanguineus on dogs weighing 30 kg or more.

Administration, Cutaneous↗

An episode of resistance to permethrin in larvae of Simulium squamosum (Diptera: Simuliidae) from Cameroon, after 3 1/2 years of control.

Because of the biting nuisance from females of Simulium squamosum, a 30 km section of the Sanaga River (Cameroon) was treated since 1987 with permethrin for the control of larval populations. In 1990, resistance to permethrin occurred in a small proportion of the larvae, with a resulting 2-4x increase of the LC95 for dead larvae (moribund larvae considered as live). In 1991, after a 6-month interruption of the treatments, susceptibility to permethrin returned to the initial level, and was similar to the susceptibility of S. squamosum larvae from a non-treated section of the Sanaga. In the context of a small-scale control program, resistance to permethrin can be reversible, and it can be avoided by rotation with other types of insecticides such as Bacillus thuringiensis serovar, israelensis.

Animals↗

Repellency and efficacy of a 65% permethrin spot-on formulation for dogs against Aedes aegypti (Diptera: Culicidae) mosquitoes.

A topically applied 65% permethrin spot-on (Defend EXspot Treatment for Dogs, Schering-Plough Animal Health) used for flea and tick control on dogs was evaluated for repellency and efficacy against the yellow fever mosquito, Aedes aegypti, a vector of canine filariasis. Six dogs were randomly assigned to receive a single application of 65% permethrin on Day 0 (n=3) or to remain untreated as controls (n=3). Dogs were anesthetized and exposed to 100 unfed, female mosquitoes in screened cages for 2 hours on Days -6, -4, -1, 0, 1, 7, 14, 21, and 28. Mosquito landing rates, engorgement rates, and mortality were determined for each mosquito challenge. Cages were thoroughly cleaned after each mosquito challenge. Treatment of dogs with 65% permethrin reduced the mosquito landing rates by 96.3% 6 hours after treatment and by 82.5% on Day 1. Mosquito mortality, relative to the control group, was 28.2% 6 hours after treatment, ranged from 84.0% to 90.9% through Day 21, and declined to 50.3% 28 days after treatment. Successful feeding by mosquitoes was significantly (P=.05) reduced on Days 1 through 28. The 65% permethrin spot-on treatment killed and repelled significantly (P =.05) more mosquitoes on treated dogs versus untreated dogs for 28 days after treatment.

Administration, Cutaneous↗

Increased monooxygenase activity associated with resistance to permethrin in Pediculus humanus capitis (Anoplura: Pediculidae) from Argentina.

We studied the profile of permethrin resistance in populations of head lice infesting children 6-12 yr old in schools and their homes in and around Buenos Aires, Argentina. Five permethrin-resistant populations with different levels of resistance were collected: Hogar Loyola (HL), Republica de Turquia (RT), Hogar Mitre (HM), Guardia de Honor (GH), and Ricardo Guiraldes (RG). One susceptible population, Bandera Argentina (BA), also was collected. Their level of resistance was evaluated, and results showed resistance ratios of 13 for HL, 16 for RT, 22 for HM, 61 for GH, and 69 for RG. To elucidate the possible involvement of the cytochrome P450 monooxygenase system in conferring permethrin resistance, ethoxycoumarin-O-deethylase (ECOD) activity was measured in abdomens of individual third instars and adults by using a fluorometric assay. The ECOD activity was lower in the susceptible BA population (4.7 ng per louse) than in the resistant ones (13.7 ng per louse for RG, 12.3 ng per louse for GH, 8.6 ng per louse for RT, and 8.2 ng per louse for HL). ECOD activity was significantly correlated with the level of resistance in the field populations (r = 0.97, P = 0.0009), suggesting a role for cytochrome monooxygenase P450 system in permethrin resistance by head louse, Pediculus humanus capitis De Geer.

7-Alkoxycoumarin O-Dealkylase↗

[Study on the biological characteristics of permethrin-resistant and susceptible strains of Culex pipiens pallens].

OBJECTIVE: To compare the biological characteristics of Culex pipiens pallens between permethrin-resistant strain and the susceptible strain. METHODS: In laboratory, the biological characteristics about bloodsucking, reproduction and development of permethrin-resistant and susceptible strains were observed and recorded. Life table of the experimental populations was constituted. RESULTS: The bloodsucking rate of resistant strain was lower than susceptible strain and the difference was significant. The life-span of adults of resistant strain and the developmental duration of eggs, larvae and pupae were longer than susceptible strain and the difference was significant. The death rate of eggs of resistant strain was higher than that of susceptible strain and the difference was significant. The permethrin-resistant strain showed a fitness value of 0.58 relative to the susceptible strain. CONCLUSION: The permethrin resistance of Culex pipiens pallens may result in a disadvantage to its reproduction and development.

Animals↗

Permethrin and dimethyl phthalate as tent fabric treatments against Aedes aegypti.

Tests were conducted to determine the persistence of compounds applied to tents to protect against mosquitoes. Interiors of 2 camping tents were treated by the manufacturer--one with the repellent dimethyl phthalate (DMP) and one with the insecticide permethrin. A third tent was untreated. Tents were set up outdoors and exposed to weathering for one year. Weekly tests were conducted by releasing Aedes aegypti into the tents, then recording knockdown (KD) and biting behavior during a 3-h period. Weather data were collected 24 h/day during the study. Year-long mean KD of mosquitoes exposed in the tent to permethrin was 58.6%, to DMP 2.7% and the control 0.9%. Mean biting was 11.9, 43.8 and 58%, respectively. Under constant exposure to weathering, the permethrin-treated tent gave best results with average protection from bites greater than 96% for 9 months (DMP was less than 31%). Although preliminary, the data suggest permethrin would be effective as a tent treatment to reduce annoyance of mosquitoes.

Aedes↗

Deet and permethrin as protectants against malaria-infected and uninfected Anopheles stephensi mosquitoes.

Deet and permethrin were evaluated as protectants against Plasmodium falciparum-infected, P. berghei-infected and uninfected Anopheles stephensi mosquitoes. Deet 50% effective dose (ED50) values were 3.2 micrograms/cm2 for P. falciparum-infected and 1.9 micrograms/cm2 for uninfected mosquitoes; permethrin values were 0.5 micrograms/cm2 and 0.6 micrograms/cm2, respectively. Deet ED50 values were 2.3 micrograms/cm2 for P. berghei-infected and 1.3 micrograms/cm2 for uninfected mosquitoes; the permethrin values were both 0.5 micrograms/cm2. There were no significant differences in the protective efficacy of deet or permethrin between malaria-infected and uninfected An. stephensi mosquitoes.

Animals↗

Treatment of scabies with permethrin versus lindane and benzyl benzoate.

This open clinical study was designed to evaluate and compare the efficacy and side effects of lindane (1% and 0.3%), benzyl benzoate (20% and 10%) and permethrin (5% and 2.5%) after two, three, and one application at bedtime, in the treatment of scabies in 114 adults and 80 children aged between 0 and 5 years. Treatment failures were registered after lindane in 3 adults and 2 children, whereas benzyl benzoate and permethrin cured all patients as assessed after a 3-week follow-up. The number of irritations and post-scabious eczematous reactions was increased after benzyl benzoate treatment. Permethrin proved to be very reliable and exhibited few side effects when applied once at bedtime. Because of the percutaneous absorption and neurotoxicity of lindane, the application of permethrin can be recommended as a useful alternative in premature infants and small children, patients with seizures and neurological complications, in cases of therapeutic failure with lindane the treatment needs to be repeated, in scabies crustosa, as well as in children, pregnant women and nursing mothers.

Adult↗

[The treatment of scabies with permethrin in comparison with lindane and benzyl benzoate].

This open clinical study was designed to evaluate and compare the efficacy and side-effects of lindane (1% and 0.3%), benzyl benzoate (20% and 10%) and permethrin (5% and 2.5%) after twice-, three times- and once application at bedtime, respectively, in the treatment of scabies in 104 adults and 70 children aged between 0 and 5 years. Treatment failures were registered afer lindane in 3 adults and 2 children, while benzyl benzoate and permethrin cured all patients as assessed after 3 weeks follow-up. The number of irritations and postscabious eccematous reactions was increased after benzyl benzoate. Permethrin revealed to be very reliable and exhibited only a few side-effects when applied once at bedtime. Because of the risk of the percutaneous absorption and neurotoxicity of lindane, the application of permethrin can be recommended as an useful alternative in premature infants and small children, patients with seizures and neurological complications, in cases of treatment failures of lindane with the need to repeat the therapy, in scabies crustosa as well as in children, pregnant woman and nursing mothers.

Administration, Topical↗

Effects of weathering on fabrics treated with permethrin for protection against mosquitoes.

Permethrin-impregnated and untreated fabrics were evaluated for their toxic and repellent effects against Anopheles stephensi and Aedes aegypti after both types of fabrics were subjected to accelerated weathering for 9 weeks, under a simulated wet/tropical environment. The toxic (knockdown) effect of permethrin-impregnated fabrics against both species of mosquitoes diminished rapidly after 1 week compared to the repellent effect. After 6 weeks of weathering, the remaining low amounts of permethrin provided fair protection from mosquito bites; however, no knockdown was observed at those levels. Permethrin-treated fabric was effective in providing protection from mosquito bites and appears to be a means of attenuating both the nuisance effects and, possibly, disease transmission by mosquitoes.

Animals↗