Pyrethroid insecticides: poisoning syndromes, synergies, and therapy.
ABSTRACT BACKGROUND: Pyrethroid insecticides are widely used, but there have been relatively few reports of systemic poisoning. These reports have, however, shown that pharmacotherapy is difficult and that the duration of poisoning can be unexpectedly long. Pyrethroids are ion channel toxins prolonging neuronal excitation, but are not directly cytotoxic. Two basic poisoning syndromes are seen. Type I pyrethroids produce reflex hyperexcitability and fine tremor. Type II pyrethroids produce salivation, hyperexcitability, choreoathetosis, and seizures. Both produce potent sympathetic activation. Local effects are also seen: skin contamination producing paresthesia and ingestion producing gastrointestinal irritation. The slow absorption of pyrethroids across the skin usually prevents systemic poisoning, although a significant reservoir of pyrethroid may remain bound to the epidermis. Carboxyesterase inhibitors can enhance pyrethroid toxicity in high-dose experimental studies. Hence, the unauthorized pyrethroid/organophosphate mixtures marketed in some developing countries may precipitate human poisoning. Pyrethroid paresthesia can be treated by decontamination of the skin, but systemic poisoning is difficult to control with anticonvulsants. Pentobarbitone, however, is surprisingly effective as therapy against systemic type II pyrethroid poisoning in rats, probably due to its dual action as a chloride channel agonist and a membrane stabilizer.
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ABSTRACT: Context. Pyrethroids are synthetic pyrethrin analogues that induce sodium-channel depolarization and hyperexcitation. Severe pyrethroid poisoning is manifested by a "Tremor Syndrome" (Type I cyano-agents) or a "Choreoathetosis/Salivation Syndrome" (Type II non cyano-agents). Very few reports of neurotoxic effects caused by Type I pyrethroids ingestion are available, and no human data concerning Type I pyrethroid blood levels in pediatric poisoning are reported in the medical literature. Case details. A 19-month-old female patient presented with irritability and inconsolable crying that rapidly worsened to tonic-clonic seizures and coma (GCS 6). On admission vital signs including BP 110/70 mmHg, HR 110 beats/min, and SpO2 98% on room air were normal. Orotracheal intubation, oxygen administration, and midazolam infusion (4 μg/kg/min) were performed. Intravenous thiopental sodium, up to 18 mg/kg/hour, was administered to control convulsions. An inquiry revealed that 9 h before presentation the patient had ingested an unknown amount of an insecticide containing 7% piperonyl-butoxide and a mixture of the Type I pyrethroids bifenthrin (5%) and esbiothrin (3%). Consequently, gastric lavage was performed, followed by administration of activated charcoal and cathartics. On the subsequent 48 h, the patient returned progressively alert; she was extubated on day 4 and discharged asymptomatically 12 days after hospitalization. After 9, 48, and 72 h of ingestion, the plasma levels were 500, 95, and 40 ng/mL for bifenthrin and 1,640, 640, and 165 ng/mL for piperonyl-butoxide respectively. Discussion. This pediatric case showed severe pyrethroid neurotoxicity associated with measurable plasma levels of bifenthrin and piperonyl-butoxide. In pediatric pyrethroid poisoning, coma and seizures may represent the main life-threatening features. First-aid therapy including airway maintenance and control of muscle fasciculation and seizures is of major importance. Benzodiazepines and high-dose thiopental sodium were effective treatments for convulsion.Clinical Toxicology 06/2013; · 2.59 Impact Factor
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ABSTRACT: Bellamya bengalensis (Gastropoda: Prosobranchia) and Lamellidens marginalis (Bivalvia: Eulamellibranchiata) are the molluscs of Indian freshwater ecosystem and important biological resources. These edible species bear economical, ecological, nutritional and medicinal importance. Natural habitat of these organisms is under the ecological threat of contamination by cypermethrin and fenvalerate, the common pyrethroid pesticides of India. Hemocytes are chief immunoeffector cells of molluscs which exhibit responsiveness against environmental toxins and perform diverse immunological functions including phagocytosis, encapsulation and cytotoxicity. Experimental exposure of cypermethrin and fenvalerate resulted in significant shift in density and morphological damage in hemocytes of B. bengalensis and L. marginalis respectively. Pyrethroid induced fragility and destabilization of hemocyte lysosomal membrane was recorded and proposed as an indication of toxin induced stress in molluscs. Apoptosis is an immunologically important cellular response which is modulated by environmental toxins. Pyrethroid exposure suppressed the physiological level of apoptosis and necrosis in hemocytes of B. bengalensis and L. marginalis indicating possible impairment of apoptosis mediated immunoprotection. Differential responses of B. bengalensis and L. marginalis hemocytes may be due to species specificity, toxin specificity, nonidentical immune strategies of Gastropoda and Bivalvia, specific habitat preference and related ecological niches.Fish & Shellfish Immunology 05/2013; · 2.96 Impact Factor
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ABSTRACT: Excluding disinfectants, pyrethrins and pyrethroids are the pesticides used most commonly in and around homes. Respiratory effects and paresthesia are among the concerns about pyrethrin/pyrethroid exposures. Acute pesticide-related illness/injury cases were identified from the Sentinel Event Notification System for Occupational Risks-Pesticides Program and the California Department of Pesticide Regulation from 2000-2008. Characteristics and incidence rates were determined for acute pyrethrin/pyrethroid-related illness/injury cases. Logistic regression analyses were performed to determine odds of respiratory and dermal symptoms in persons with illness/injury following pyrethrin/pyrethroid exposure compared to persons with illness/injury following exposure to other pesticides. A total of 4,974 cases of acute pyrethrin/pyrethroid-related illness were identified. Incidence rates increased over time, reaching 8 cases/million population in 2008. The majority of cases were low severity (85%) and 34% were work-related. Respiratory effects were the most common symptoms reported (48%). Risk of acute respiratory effects were significantly elevated among persons exposed only to pyrethrins (adjusted odds ratio [aOR] 1.79; 95% confidence interval [95% CI]: 1.49-2.16), only to pyrethroids (aOR 1.99 95% CI: 1.77-2.24), to a mixture of pyrethroids (aOR 2.36; 95% CI: 1.99-2.81) or to a mixture containing both pyrethrins and pyrethroids (aOR 2.99; 95% CI: 2.33-3.84) compared to those with illness arising from exposure to other pesticides. The most common factors contributing to pyrethrin/pyrethroid-related illness included exposure from spills/splashes, improper storage, and failure to evacuate during pesticide application. The magnitude of acute pyrethrin/pyrethroid-related illness/injury is relatively low but is increasing. As such, additional measures to prevent them are needed. Am. J. Ind. Med. 9999:1-16, 2013. © 2013 Wiley Periodicals, Inc.American Journal of Industrial Medicine 06/2013; · 1.97 Impact Factor