Item |
Information |
Drug Groups
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approved; investigational |
Description
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A wide spectrum aliphatic organophosphate insecticide widely used for both domestic and commercial agricultural purposes. [PubChem] |
Indication |
For patients infected with Pediculus humanus capitis (head lice and their ova) of the scalp hair. |
Pharmacology |
Malathion is an organophosphate insecticide commonly used to control mosquitos and other flying insects. Pharmaceutically, malathion is used to eliminate head lice. The principal toxicological effect of malathion is cholinesterase inhibition, due primarily to malaoxon and to phosphorus thionate impurities. |
Toxicity |
Malathion is slightly toxic via the oral route, with reported oral LD50 values of 1000 mg/kg to greater than 10,000 mg/kg in the rat. It is also slightly toxic via the dermal route, with reported dermal LD50 values of greater than 4000 mg/kg in rats. Moderate poisoning can result in chest tightness, difficulty breathing, bradycardia, tachycardia, tremor/ataxia, blurred vision, and confusion. Severe, life-threatening signs include coma, seizures, respiratory arrest, and paralysis. Malathion may also be irritating to the skin and eyes. |
Affected Organisms |
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Biotransformation |
The major metabolites of malathion are the diacid and monoacid metabolites, namely, malathion dicarboxylic acid (DCA) and malathion monocarboxylic acid (MCA). Malaoxon, the active cholinesterase-inhibiting metabolite of malathion, is a minor metabolite. Both malathion and malaoxon are detoxified by carboxyesterases leading to polar, water-soluble compounds that are excreted. |
Absorption |
Malathion in an acetone vehicle has been reported to be absorbed through normal human skin only to the extent of 8% of the applied dose. Absorption may be increased when malathion is applied to damaged skin. Malathion is rapidly and effectively absorbed by practically all routes including the gastrointestinal tract, skin, mucous membranes, and lungs. However, it is readily excreted in the urine, and does not accumulate in organs or tissues. |
Half Life |
8-24 hours |
References |
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Baker EL Jr, Warren M, Zack M, Dobbin RD, Miles JW, Miller S, Alderman L, Teeters WR: Epidemic malathion poisoning in Pakistan malaria workers. Lancet. 1978 Jan 7;1(8054):31-4.
[Pubmed]
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Bonner MR, Coble J, Blair A, Beane Freeman LE, Hoppin JA, Sandler DP, Alavanja MC: Malathion exposure and the incidence of cancer in the agricultural health study. Am J Epidemiol. 2007 Nov 1;166(9):1023-34. Epub 2007 Aug 23.
[Pubmed]
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Edwards JW, Lee SG, Heath LM, Pisaniello DL: Worker exposure and a risk assessment of malathion and fenthion used in the control of Mediterranean fruit fly in South Australia. Environ Res. 2007 Jan;103(1):38-45. Epub 2006 Aug 17.
[Pubmed]
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External Links |
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