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Rambabu L, Mohamed F, Dhanarisi J, Gawarammana I, Raubenheimer J, Mackenzie L, Roberts MS, Buckley N, Eddleston M. Acute phenthoate self-poisoning: a prospective case series. Clin Toxicol (Phila) 2021; 60:214-220. [PMID: 33960866 DOI: 10.1080/15563650.2021.1917596] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
BACKGROUND The clinical characteristics following self-poisoning with organophosphorus (OP) insecticides differs according to the insecticide ingested. Phenthoate is a dimethoxy WHO Hazard Class II OP pesticide with limited literature on its clinical characteristics and outcome. We aimed to better understand its clinical characteristics by studying patients with phenthoate self-poisoning in Sri Lanka. METHODS We conducted a prospective cohort study of patients presenting with phenthoate self-poisoning to eight hospitals in Sri Lanka between 2002 and 2018. Clinical outcomes were recorded for each patient. Blood samples for measuring plasma phenthoate concentration, cholinesterase activity, and response to oximes were available for a very small number of patients recruited to a clinical trial. RESULTS Two hundred and ninety-two patients who ingested agricultural phenthoate formulations were included in the study. Median time to admission was 3.9 (IQR 2.4 - 6.8) h. Forty-two (14.4%) patients were intubated, mostly (30/37, 81%) within 24 h of ingestion (median time to intubation 7.2 [IQR 2.6-20.9] h). Median duration of intubation was 74.8 (IQR 26.8-232.5) h; the longest duration in a survivor was 592 h. Nineteen died (case fatality 6.5%, 95% CI 4.0-10.0); median time to death was 37 (IQR 16 - 101.7) h. Median plasma phenthoate concentration in patients with samples (n = 81) was 135 (IQR 62.7-356.5) ng/mL (0.42 µmol/mL [0.2 to 1.1 µmol/mL]). Five of six patients receiving pralidoxime chloride 2 g showed an initial increase in AChE and BuChE activity that was not sustained despite an infusion of pralidoxime. CONCLUSION Phenthoate self-poisoning has a 6.5% case fatality rate. Most patients who experience respiratory failure undergo early intubation; most deaths occurred among those patients who were intubated less than 24 h after ingestion. There was a non-sustained increase in cholinesterase activity with pralidoxime, but further studies are required to analyse the extent to which oximes are clinically effective in phenthoate self-poisoning.
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Affiliation(s)
- Lekaashree Rambabu
- National Health Service Tayside, Dundee, UK.,Edinburgh Medical School, The University of Edinburgh, Edinburgh, UK
| | - Fahim Mohamed
- South Asian Clinical Toxicology Research Collaboration, Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka.,Department of Pharmacy, Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya, Sri Lanka
| | - Jeevan Dhanarisi
- South Asian Clinical Toxicology Research Collaboration, Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka
| | - Indika Gawarammana
- South Asian Clinical Toxicology Research Collaboration, Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka
| | - Jacques Raubenheimer
- Faculty of Medicine and Health, Discipline of Biomedical Informatics and Digital Health, Clinical Pharmacology and Toxicology Research Group, The University of Sydney, Sydney, Australia
| | - Lorraine Mackenzie
- Therapeutics Research Centre, Clinical and Health Sciences, University of South Australia, Adelaide, Australia.,Basil Hetzel Institute for Translational Research, The Queen Elizabeth Hospital, Woodville, Australia
| | - Michael S Roberts
- Therapeutics Research Centre, Clinical and Health Sciences, University of South Australia, Adelaide, Australia.,Therapeutics Research Centre, Diamantina Institute, Translational Research Institute, The University of Queensland, Brisbane, Australia
| | - Nicholas Buckley
- Clinical Pharmacology and Toxicology Research Group, Discipline of Pharmacology, University of Sydney, Sydney, Australia
| | - Michael Eddleston
- Pharmacology, Toxicology, & Therapeutics, University/BHF Centre for Cardiovascular Science, Edinburgh, UK.,Centre for Pesticide Suicide Prevention, University of Edinburgh, Edinburgh, UK
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Eddleston M. Novel Clinical Toxicology and Pharmacology of Organophosphorus Insecticide Self-Poisoning. Annu Rev Pharmacol Toxicol 2019; 59:341-360. [DOI: 10.1146/annurev-pharmtox-010818-021842] [Citation(s) in RCA: 62] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Organophosphorus insecticide self-poisoning is a major global health problem, killing over 100,000 people annually. It is a complex multi-organ condition, involving the inhibition of cholinesterases, and perhaps other enzymes, and the effects of large doses of ingested solvents. Variability between organophosphorus insecticides—in lipophilicity, speed of activation, speed and potency of acetylcholinesterase inhibition, and in the chemical groups attached to the phosphorus—results in variable speed of poisoning onset, severity, clinical toxidrome, and case fatality. Current treatment is modestly effective, aiming only to reactivate acetylcholinesterase and counter the effects of excess acetylcholine at muscarinic receptors. Rapid titration of atropine during resuscitation is lifesaving and can be performed in the absence of oxygen. The role of oximes in therapy remains unclear. Novel antidotes have been tested in small trials, but the great variability in poisoning makes interpretation of such trials difficult. More effort is required to test treatments in adequately powered studies.
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Affiliation(s)
- Michael Eddleston
- Pharmacology, Toxicology, and Therapeutics Unit, Centre for Cardiovascular Science, and Centre for Pesticide Suicide Prevention, University of Edinburgh, Edinburgh EH16 4TJ, United Kingdom
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Eddleston M. Are Oximes Still Indicated for Acute Organophosphorus Insecticide Self-Poisoning? J Med Toxicol 2018; 14:1-2. [PMID: 29388062 DOI: 10.1007/s13181-018-0651-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 01/09/2018] [Indexed: 12/19/2022] Open
Affiliation(s)
- Michael Eddleston
- Pharmacology, Toxicology, & Therapeutics, and Centre for Pesticide Suicide Prevention, University of Edinburgh, Edinburgh, UK.
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Wilhelm CM, Snider TH, Babin MC, Jett DA, Platoff GE, Yeung DT. A comprehensive evaluation of the efficacy of leading oxime therapies in guinea pigs exposed to organophosphorus chemical warfare agents or pesticides. Toxicol Appl Pharmacol 2014; 281:254-65. [PMID: 25448441 DOI: 10.1016/j.taap.2014.10.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 10/14/2014] [Accepted: 10/15/2014] [Indexed: 11/28/2022]
Abstract
The currently fielded pre-hospital therapeutic regimen for the treatment of organophosphorus (OP) poisoning in the United States (U.S.) is the administration of atropine in combination with an oxime antidote (2-PAM Cl) to reactivate inhibited acetylcholinesterase (AChE). Depending on clinical symptoms, an anticonvulsant, e.g., diazepam, may also be administered. Unfortunately, 2-PAM Cl does not offer sufficient protection across the range of OP threat agents, and there is some question as to whether it is the most effective oxime compound available. The objective of the present study is to identify an oxime antidote, under standardized and comparable conditions, that offers protection at the FDA approved human equivalent dose (HED) of 2-PAM Cl against tabun (GA), sarin (GB), soman (GD), cyclosarin (GF), and VX, and the pesticides paraoxon, chlorpyrifos oxon, and phorate oxon. Male Hartley guinea pigs were subcutaneously challenged with a lethal level of OP and treated at approximately 1 min post challenge with atropine followed by equimolar oxime therapy (2-PAM Cl, HI-6 DMS, obidoxime Cl₂, TMB-4, MMB4-DMS, HLö-7 DMS, MINA, and RS194B) or therapeutic-index (TI) level therapy (HI-6 DMS, MMB4-DMS, MINA, and RS194B). Clinical signs of toxicity were observed for 24 h post challenge and blood cholinesterase [AChE and butyrylcholinesterase (BChE)] activity was analyzed utilizing a modified Ellman's method. When the oxime is standardized against the HED of 2-PAM Cl for guinea pigs, the evidence from clinical observations, lethality, quality of life (QOL) scores, and cholinesterase reactivation rates across all OPs indicated that MMB4 DMS and HLö-7 DMS were the two most consistently efficacious oximes.
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Affiliation(s)
| | - Thomas H Snider
- Battelle, 505 King Avenue, JM-7, Columbus, OH 43201-2693, USA.
| | - Michael C Babin
- Battelle, 505 King Avenue, JM-7, Columbus, OH 43201-2693, USA.
| | - David A Jett
- National Institutes of Health/National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA.
| | - Gennady E Platoff
- National Institutes of Health/National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA.
| | - David T Yeung
- National Institutes of Health/National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892, USA.
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Estévez J, Barril J, Vilanova E. Kinetics of inhibition of soluble peripheral nerve esterases by PMSF: a non-stable compound that potentiates the organophosphorus-induced delayed neurotoxicity. Arch Toxicol 2012; 86:767-77. [DOI: 10.1007/s00204-012-0817-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2011] [Accepted: 02/07/2012] [Indexed: 11/28/2022]
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Worek F, Aurbek N, Herkert NM, John H, Eddleston M, Eyer P, Thiermann H. Evaluation of medical countermeasures against organophosphorus compounds: the value of experimental data and computer simulations. Chem Biol Interact 2009; 187:259-64. [PMID: 19917271 DOI: 10.1016/j.cbi.2009.11.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 11/07/2009] [Accepted: 11/09/2009] [Indexed: 10/20/2022]
Abstract
Despite extensive research for more than six decades on medical countermeasures against poisoning by organophosphorus compounds (OP) the treatment options are meagre. The presently established acetylcholinesterase (AChE) reactivators (oximes), e.g. obidoxime and pralidoxime, are insufficient against a number of nerve agents and there is ongoing debate on the benefit of oxime treatment in human OP pesticide poisoning. Up to now, the therapeutic efficacy of oximes was mostly evaluated in animal models but substantial species differences prevent direct extrapolation of animal data to humans. Hence, it was considered essential to establish relevant experimental in vitro models for the investigation of oximes as antidotes and to develop computer models for the simulation of oxime efficacy in different scenarios of OP poisoning. Kinetic studies on the various interactions between erythrocyte AChE from various species, structurally different OP and different oximes provided a basis for the initial assessment of the ability of oximes to reactivate inhibited AChE. In the present study, in vitro enzyme-kinetic and pharmacokinetic data from a minipig model of dimethoate poisoning and oxime treatment were used to calculate dynamic changes of AChE activities. It could be shown that there is a close agreement between calculated and in vivo AChE activities. Moreover, computer simulations provided insight into the potential and limitations of oxime treatment. In the end, such data may be a versatile tool for the ongoing discussion of the pros and cons of oxime treatment in human OP pesticide poisoning.
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Affiliation(s)
- Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany.
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Paradox findings may challenge orthodox reasoning in acute organophosphate poisoning. Chem Biol Interact 2009; 187:270-8. [PMID: 19883634 DOI: 10.1016/j.cbi.2009.10.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/17/2009] [Accepted: 10/20/2009] [Indexed: 12/15/2022]
Abstract
It is generally accepted that inhibition of acetylcholinesterase (AChE) is the most important acute toxic action of organophosphorus compounds, leading to accumulation of acetylcholine followed by a dysfunction of cholinergic signaling. However, the degree of AChE inhibition is not uniformly correlated with cholinergic dysfunction, probably because the excess of essential AChE varies among tissues. Moreover, the cholinergic system shows remarkable plasticity, allowing modulations to compensate for dysfunctions of the canonical pathway. A prominent example is the living (-/-) AChE knockout mouse. Clinical experience indicates that precipitous inhibition of AChE leads to more severe poisoning than more protracted yet finally complete inhibition. The former situation is seen in parathion, the latter in oxydemeton methyl poisoning. At first glance, this dichotomy is surprising since parathion is a pro-poison and has to be activated to the oxon, while the latter is still the ultimate inhibitor. Also oxime therapy in organophosphorus poisoning apparently gives perplexing results: Oximes are usually able to reactivate diethylphosphorylated AChE, but the efficiency may be occasionally markedly smaller than expected from kinetic data. Dimethylphosphorylated AChE is in general less amenable to oxime therapy, which largely fails in some cases of dimethoate poisoning where aging was much faster than expected from a dimethylphosphorylated enzyme. Similarly, poisoning by profenofos, an O,S-dialkyl phosphate, leads to a rapidly aged enzyme. Most surprisingly, these patients were usually well on admission, yet their erythrocyte AChE was completely inhibited. Analysis of the kinetic constants of the most important reaction pathways, determination of the reactant concentrations in vivo and comparison with computer simulations may reveal unexpected toxic reactions. Pertinent examples will be presented and the potentially underlying phenomena discussed.
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Isidori M, Caterino E, Criscuolo E, Fatigati V, Liguori G, Parrella A. Antimutagenic and antigenotoxic effects of vegetable matrices on the activity of pesticides. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2009; 26:1049-62. [DOI: 10.1080/02652030902896194] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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