Brands, Medical Use, Clinical Data
- Cholinesterase Inhibitors
Brands / Synonyms
Calmathion; Carbethoxy malathion; Carbetovur; Carbetox; Carbofos; Carbophos; Celthion; Chemathion; Cimexan; Cleensheen; Compound 4049; Cythion; Derbac-M; Detmol MA; Emmatos; Emmatos extra; Ethiolacar; Etiol; Experimental insecticide 4049; Extermathion; Fog 3; Formal; Forthion; Fosfothion; Fosfotion; Fosfotion 550; Four thousand forty-nine; Fyfanon; Hilthion; Hilthion 25wdp; Insecticide no. 4049; Karbofos; Kop-thion; Kop-Thionkypfosmalacide; Kypfos; Latka 4049; Lice Rid; Malacide; Malafor; Malagran; Malakill; Malamar; Malamar 50; Malaphele; Malaphos; Malasol; Malaspray; Malathion 60; Malathion E50; Malathion LV Concentrate; Malathione; Malathiozoo; Malathon; Malation; Malatol; Malatox; Maldison; Malmed; Malphos; Maltox; Maltox MLT; Mercaptosuccinic acid diethyl ester; Mercaptothion; Mercaptotion; MLT; Moscarda; Mychel; Mycinol; Oleophosphothion; OMS 1; Organoderm; Ortho Malathion; Ovide; Phosphothion; Prioderm; Sadofos; Sadofos 30; Sadophos; Siptox I; Staeubol-Puder; Suleo-M; Sumitox; TAK; Taskil; Vegfru malatox; Vetiol; Zithiol
For patients infected with Pediculus humanus capitis (head lice and their ova) of the scalp hair.
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.
Mechanism of Action
Malathion is a nonsystemic, wide-spectrum organophosphate insecticide. It inhibits acetylcholinesterase activity of most eukaryotes. Malathion is toxic to aquatic organisms, but has a relatively low toxicity for birds and mammals. The major metabolites of malathion are mono- and di-carboxylic acid derivatives, and malaoxon is a minor metabolite. However, it is malaoxon that is the strongest cholinesterase inhibitor. Cholinesterases catalyze the hydrolysis of the neurotransmitter acetylcholine into choline and acetic acid, a reaction necessary to allow a cholinergic neuron to return to its resting state after activation. Because of its essential function, chemicals that interfere with the action of cholinesterase are potent neurotoxins, causing muscle spasms and ultimately death.
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.
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.
Biotrnasformation / Drug Metabolism
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.
OVIDE Lotion is contraindicated for neonates and infants because their scalps are more permeable and
may have increased absorption of malathion. OVIDE Lotion should also not be used on individuals known to be sensitive
to malathion or any of the ingredients in the vehicle.
No information available.