Anticholinesterases
Kenneth J. Broadley in Autonomic Pharmacology, 2017
The organophosphorus compounds are highly lipid-soluble liquids, the less volatile agents such as parathion and malathion having been developed as insecticides for crop protection. They are dispersed by spraying as aerosols or dusts, their high lipid solubility allowing ready penetration of the insect cuticle. Death of the insect arises from respiratory paralysis. Malathion selectively inhibits insect cholinesterase because it is metabolized in mammals by hydrolysis of the carboxyl ester linkage. In insects, oxidation to the active metabolite is the preferred route. In addition to agricultural uses, it is widely used to treat infestations of body lice (Pediculus humanus); the adult forms, larvae and eggs are all susceptible. Carbaryl has also become a widely used topical insecticide for the treatment of head and body lice. Being a carbamate, it has a reversible action and has low toxicity to humans via the dermal route.
Carcinogenicity of Agricultural Pesticides in Adults and Children
Ana Maria Osorio, Lynn R. Goldman in Proceedings from the Medical Workshop on Pesticide-Related Illnesses from the International Conference on Pesticide Exposure and Health, 2017
Among the occupational studies of farmers, 18 of 29 studies, showed an excess of non-Hodgkin's lymphoma compared to the general population.26 In a meta-analysis of 6 studies examining the association between non-Hodgkin's lymphoma and farming in the central United States the overall estimated relative risk is 1.34 (95% Confidence interval = 1.17-1.55).125 The various studies which attempted to assess the associations between specific pesticides and non-Hodgkin's lymphoma, however, do not yet offer a clear etiologic picture. Among a series of population-based case-control studies, NHL was linked to organochlorine pesticides. 126-129 In a multi-center population-based incident study in Canada127 several chemical classes of pesticides were associated with non-Hodgkin's lymphoma including phenoxy and benzoic acid herbicides and to carbamate and organophosphate insecticides, to amide fumigants and to the fumigant carbon tetrachloride. Carbaryl, a carbamate insecticide, was found to be a risk factor for NHL in a pooled analysis.130 A trace contaminant, dioxin, formed during the manufacture of several chemicals including the phenoxyherbicides 2,4,5 T and 2,4,5, TP has also been suggested to play a role in the etiology of non-Hodgkin's lymphoma.131 Additional studies are needed that have the capability of identifying a association of a specific pesticide with NHL are need, since NHL is a grouping of more than 20 phenotypes, it may be necessary for future studies to distinguish between these phenotype in etiologic studies as well.132
Genital itching
Manu Shah, Ariyaratne de Silva in The Male Genitalia, 2018
For eradication of the lice, lotions are more effective than shampoos and should be applied to all body hair. A second application within one week may be required. The treatment options are: malathion 0.5%. Apply to dry hair and wash off after 12 hours orcarbaryl 0.5%. Apply to dry hair and wash off after two hours (not licensed for pubic lice in the UK) orphenothrin 0.2%. Apply to dry hair and wash off after two hours orpermethrin 1% cream. Apply to damp hair and wash off after 10 minutes.
Pyrethroid based pesticides – chemical and biological aspects
Published in Critical Reviews in Toxicology, 2021
Anandha Rao Ravula, Suresh Yenugu
CAs are derived from carbamic acid and the first one among this class, carbaryl, was introduced in 1956 as a lawn and garden insecticide. Its broad-spectrum insect control activity and low toxicity to mammals allowed it to be a preferred choice. CAs are less persistent in the environment unlike OPs and OCs and are rapidly detoxified in animal tissues. The mode of action of CAs is similar to that of OPs as both are inhibitors of acetylcholinesterase (AChE). While CAs inhibit AChE activity by phosphorylation resulting in the formation of a reversible complex, OPs form an irreversible complex (Darvesh et al. 2008). Since CAs are considered to be safer than OPs, as they exhibit reversible action on AChE and do not cause severe poisoning in cholinergic pathway (Silva et al. 2013), they are proposed as therapeutic drugs (physostigmine derived from Physostigma venenosum) for neuromuscular disorders such as myasthenia gravis.
Acute organophosphate and carbamate pesticide poisonings – a five-year survey from the National Poison Control Center Of Serbia
Published in Drug and Chemical Toxicology, 2023
Žana M. Maksimović, Jasmina Jović-Stošić, Slavica Vučinić, Nataša Perković-Vukčević, Gordana Vuković-Ercegović, Ranko Škrbić, Miloš P. Stojiljković
Clinical studies show that the mortality rate associated with intentional poisonings with carbofuran is around 2.2% and that it is lower compared to other CPs and OPPs (Lamb et al.2016). Methomyl poisoning was recorded in 6 patients, half of whom had severe intoxications. The majority of developed countries prohibited the usage of methomyl due to its high toxicity, but cases of methomyl poisoning are still being recorded even in countries where its usage is prohibited (Boucaud-Maitre et al.2019). Sri Lanka, a country where pesticides are the most common cause of suicidal poisonings, has prohibited the use of carbofuran, carbaryl, dimethoate, and chlorpyrifos in 2014, reducing the morbidity and mortality rate of pesticide poisonings by 50% within 3 years (Rathish et al.2018). Likely, other, less toxic OPPs will replace them and become more commonly used. The case fatality from OPP poisonings is higher compared to other pesticides in the same WHO Hazard Class, such as neonicotinoids, pyrethroids, and other non-cholinesterase pesticides (Rambabu et al. 2021). AChE inhibited by CP will be spontaneously reactivated and oxime administration is not recommended. In carbaryl intoxication, oximes even potentiate its toxicity (Faragó 1969, Lieske et al.1992).
Effects of anatomical location on in vivo percutaneous penetration in man
Published in Cutaneous and Ocular Toxicology, 2020
Jordan L. Bormann, Howard I. Maibach
Maibach et al.12 quantified percutaneous penetration of organophosphate chemicals frequently used as pesticides, malathion and parathion. Each pesticide was applied in several anatomic sites and left in place for 24 h. The radiolabeled pesticide’s absorption was then measured via 5 day urine analysis. Only parathion was tested on the scrotum; this anatomical location proved most penetrable of all sites tested and was 11 times more penetrable than forearm. Malathion was placed on the forearm, palm, ball of foot, abdomen, hand dorsum, forehead, and axilla. Of all locations, malathion was most penetrable in the axilla (Table 1). Carbaryl was tested on the forearm and jaw angle; however, it was nearly completely absorbed at both sites (Table 1)12.
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