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2D Structure
Also known as: 121-75-5, Carbophos, Carbofos, Mercaptothion, Karbofos, Phosphothion
Molecular Formula
C10H19O6PS2
Molecular Weight
330.4  g/mol
InChI Key
JXSJBGJIGXNWCI-UHFFFAOYSA-N
FDA UNII
U5N7SU872W

A wide spectrum aliphatic organophosphate insecticide widely used for both domestic and commercial agricultural purposes.
Malathion is a Cholinesterase Inhibitor. The mechanism of action of malathion is as a Cholinesterase Inhibitor.
1 2D Structure

2D Structure

2 Identification
2.1 Computed Descriptors
2.1.1 IUPAC Name
diethyl 2-dimethoxyphosphinothioylsulfanylbutanedioate
2.1.2 InChI
InChI=1S/C10H19O6PS2/c1-5-15-9(11)7-8(10(12)16-6-2)19-17(18,13-3)14-4/h8H,5-7H2,1-4H3
2.1.3 InChI Key
JXSJBGJIGXNWCI-UHFFFAOYSA-N
2.1.4 Canonical SMILES
CCOC(=O)CC(C(=O)OCC)SP(=S)(OC)OC
2.2 Other Identifiers
2.2.1 UNII
U5N7SU872W
2.3 Synonyms
2.3.1 MeSH Synonyms

1. Carbafos

2. Carbofos

3. Carbophos

4. Cythion

5. Karbofos

6. Prioderm

7. Sadophos

2.3.2 Depositor-Supplied Synonyms

1. 121-75-5

2. Carbophos

3. Carbofos

4. Mercaptothion

5. Karbofos

6. Phosphothion

7. Carbetox

8. Ethiolacar

9. Maldison

10. Prioderm

11. Sadophos

12. Cythion

13. Oleophosphothion

14. Ovide

15. Chemathion

16. Sadofos

17. Carbetovur

18. Fosfothion

19. Fosfotion

20. Malagran

21. Malakill

22. Malaphos

23. Malaspray

24. Malathon

25. Moscarda

26. Cimexan

27. Fyfanon

28. Malafor

29. Malamar

30. Malatol

31. Malatox

32. Malphos

33. Sumitox

34. Taskil

35. Etiol

36. Emmatos Extra

37. Ortho Malathion

38. Siptox I

39. Extermathion

40. Forthion

41. Hilthion

42. Malacide

43. Malation

44. Mercaptotion

45. Kypfos

46. Malasol

47. Malathion E50

48. Malmed

49. Carbethoxy Malathion

50. Malamar 50

51. Kop-thion

52. Compound 4049

53. Insecticide No. 4049

54. Detmol Ma

55. Malathione

56. Emmatos

57. Malataf

58. Malathyl

59. Fosfotion 550

60. Malathion Lv Concentrate

61. Zithiol

62. Staeubol-puder

63. American Cyanamid 4,049

64. Mercaptosuccinic Acid Diethyl Ester

65. Latka 4049

66. Sf 60

67. Diethyl 2-dimethoxyphosphinothioylsulfanylbutanedioate

68. Experimental Insecticide 4049

69. Tm-4049

70. Nci-c00215

71. Ac 26691

72. Diethyl (dimethoxyphosphinothioylthio)succinate

73. Ent 17,034

74. El 4049

75. Four Thousand Forty-nine

76. O,o-dimethyldithiophosphate Diethylmercaptosuccinate

77. 8059hc

78. Dicarboethoxyethyl O,o-dimethyl Phosphorodithioate

79. O,o-dimethyl S-(1,2-dicarbethoxyethyl) Dithiophosphate

80. Nsc-6524

81. Mlt

82. Butanedioic Acid, ((dimethoxyphosphinothioyl)thio)-, Diethyl Ester

83. S-(1,2-dicarbethoxyethyl) O,o-dimethyldithiophosphate

84. Succinic Acid, Mercapto-, Diethyl Ester, S-ester With O,o-dimethyl Phosphorodithioate

85. O,o-dimethyl S-(1,2-dicarbethoxyethyl)phosphorodithioate

86. S-1,2-bis(ethoxycarbonyl)ethyl-o,o-dimethyl Thiophosphate

87. U5n7su872w

88. Calmathion

89. Cleensheen

90. Malathiazol

91. Camathion

92. Celthion

93. Dorthion

94. O,o-dimethyl S-1,2-di(ethoxycarbamyl)ethyl Phosphorodithioate

95. Flair

96. Diethyl Mercaptosuccinate, O,o-dimethyl Dithiophosphate, S-ester

97. S-(1,2-di(ethoxycarbonyl)ethyl) Dimethyl Phosphorothiolothionate

98. O,o-dimethyl-s-1,2-dikarbetoxylethylditiofosfat

99. Diethyl 2-[(dimethoxyphosphorothioyl)thio]succinate

100. Ent-17034

101. Kill-a-mite

102. Malation [polish]

103. O,o-dwumetylo-s-1,2-bis(karboetoksyetylo)-dwutiofosforan

104. S-(1,2-bis(carbethoxy)ethyl) O,o-dimethyl Dithiophosphate

105. Ncgc00091902-05

106. Ncgc00091902-08

107. Malathiozoo

108. ((dimethoxyphosphinothioyl)thio)butanedioic Acid Diethyl Ester

109. Malaphele

110. Organoderm

111. S-(1,2-bis(etossi-carbonil)-etil)-o,o-dimetil-ditiofosfato

112. Maltox

113. Vetiol

114. S-(1,2-bis(ethoxy-carbonyl)-ethyl)-o,o-dimethyl-dithiofosfaat

115. Vegfru Malatox

116. Butanedioic Acid, [(dimethoxyphosphinothioyl)thio]-, Diethyl Ester

117. Dithiophosphate De O,o-dimethyle Et De S-(1,2-dicarboethoxyethyle)

118. Dsstox_cid_791

119. S-(1,2-bis(ethoxycarbonyl)ethyl) O,o-dimethyl Phosphorodithioate

120. Mercaptotion [spanish]

121. Derbac-m

122. Hilthion 25wdp

123. Maltox Mlt

124. Diethyl 2-(dimethoxyphosphinothioylthio)succinate

125. Dsstox_rid_75791

126. Succinic Acid, Mercapto-, Diethyl Ester, S-ester With O,o-dimethylphosphorodithioate

127. Dsstox_gsid_20791

128. Latka 4049 [czech]

129. Sadofos 30

130. Kop-thionkypfosmalacide

131. Fog 3

132. [(dimethoxyphosphinothioyl)thio]butanedioic Acid Diethyl Ester

133. Malathyne

134. [(dimethoxyphosphinothioyl)thio]butanedioic Acid, Diethyl Ester

135. S-(1,o-dimethyl Phosphorodithioate

136. S-[1,o-dimethyl Phosphorodithioate

137. Malathion (usp)

138. Oms 1

139. Ifo 13140

140. Cas-121-75-5

141. Ccris 368

142. Hsdb 665

143. Ovide (tn)

144. Malathion [usp:ban]

145. Malathion ,s-(1,2-dicarbethoxyl)

146. Einecs 204-497-7

147. Brn 1804525

148. S-[1,2-bis(carbethoxy)ethyl] O,o-dimethyl Dithiophosphate

149. Unii-u5n7su872w

150. Gammaxine

151. Radotion

152. Ai3-17034

153. S-[1,2-bis(ethoxycarbonyl)ethyl] O,o-dimethyl Phosphorodithioate

154. Diethyl(dimethoxythiophosphorylthio)succinate

155. Malathion Ulv

156. Suleo M

157. Diethyl ((dimethoxyphosphinothioyl)thio)butanedioate

158. Phosphorodithioic Acid, O,o-dimethyl Ester, S-ester With Diethyl Mercaptosuccinate

159. O,o-dimethyl-s-1,2-dikarbetoxylethylditiofosfat [czech]

160. S-(1,2-dicarbethoxyethyl) O,o-dimethylphosphorodithioate

161. Spectrum_001795

162. Specplus_000386

163. Malathion [mi]

164. O,o-dimethyl S-(1,2-bis(ethoxycarbonyl)ethyl) Dithiophosphate

165. Malathion [hsdb]

166. Malathion [iarc]

167. O,o-dimethyl-s-1,2-(dicarbaethoxyaethyl)-dithiophosphat [german]

168. O,o-dwumetylo-s-1,2-bis(karboetoksyetylo)-dwutiofosforan [polish]

169. Spectrum2_001228

170. Spectrum3_000813

171. Spectrum4_000653

172. Spectrum5_001936

173. Malathion [vandf]

174. Diethyl Mercaptosuccinate S-ester With O,o-dimethylphosphorodithioate

175. S-(1,2-bis(ethoxy-carbonyl)-ethyl)-o,o-dimethyl-dithiofosfaat [dutch]

176. S-(1,2-bis(etossi-carbonil)-etil)-o,o-dimetil-ditiofosfato [italian]

177. Malathion [mart.]

178. Dithiophosphate De O,o-dimethyle Et De S-(1,2-dicarboethoxyethyle) [french]

179. S-(1,2-bis(aethoxy-carbonyl)-aethyl)-o,o-dimethyl-dithiophosphat [german]

180. Malathion [usp-rs]

181. Malathion [who-dd]

182. Schembl27358

183. Bspbio_002305

184. Kbiogr_001025

185. Kbioss_002288

186. S-(1,o-dimetil-ditiofosfato

187. S-1,o-dimethyl Thiophosphate

188. Divk1c_006482

189. Malathion, Analytical Standard

190. Diethyl Mercaptosuccinate, O,o-dimethyl Thiophosphate

191. Spbio_001076

192. S-(1,o-dimethyl-dithiofosfaat

193. 1,o-dimethyl Phosphordithioates

194. Chebi:6651

195. Malathion [orange Book]

196. O,2-dikarbetoxylethylditiofosfat

197. S-(1,o-dimethyl-dithiophasphat

198. Chembl1200468

199. Dtxsid4020791

200. Malathion [ep Monograph]

201. O,o-dimethyl-s-1,2-(dicarbaethoxyaethyl)-dithiophosphat

202. Bdbm85372

203. Jxsjbgjigxnwci-uhfffaoysa-

204. Kbio1_001426

205. Kbio2_002286

206. Kbio2_004854

207. Kbio2_007422

208. Kbio3_001805

209. S-[1,o-dimethyl Dithiophosphate

210. Diethyl Mercaptosuccinate, O,o-dimethyl Phosphorodithioate

211. Malathion [usp Monograph]

212. Nsc6524

213. Chebi:141474

214. 1,2-di(ethoxycarbonyl)ethyl O,o-dimethyl Phosphorodithioate

215. Diethyl Mercaptosuccinic Acid O,o-dimethyl Phosphorodithioate

216. Hms3264a04

217. Pharmakon1600-00330021

218. Hy-b0943

219. S-(1,2-bis(aethoxy-carbonyl)-aethyl)-o,o-dimethyl-dithiophosphat

220. Malathion 100 Microg/ml In Nonane

221. Tox21_111175

222. Tox21_400048

223. Ccg-39152

224. Nsc755848

225. Malathion 100 Microg/ml In Methanol

226. Akos015897264

227. Butanedioic Acid, ((dimethoxyphosphinothioyl)-thio)-, Diethyl Ester, (+-)-

228. Diethyl (+-)-mercaptosuccinate, S-ester With O,o-dimethyl Phosphorodithioate

229. Diethyl Mercaptosuccinic Acid, S-ester Of O,o-dimethyl Phosphorodithioate

230. Malathion 1000 Microg/ml In Acetone

231. Malathion 1000 Microg/ml In Toluene

232. O,2-dicarbethoxyethyl) Dithiophosphate

233. Tox21_111175_1

234. Cs-4416

235. Db00772

236. Nsc-755848

237. Malathion 100 Microg/ml In Cyclohexane

238. Ncgc00091902-01

239. Ncgc00091902-02

240. Ncgc00091902-03

241. Ncgc00091902-06

242. Ncgc00091902-07

243. Ncgc00091902-09

244. Ncgc00091902-11

245. O,2-dicarbethoxyethyl) Phosphorodithioate

246. As-13786

247. Cas_121-75-5

248. Malathion 1000 Microg/ml In Cyclohexane

249. O,2-dicarbethoxyethyl) Thiothionophosphate

250. Db-041629

251. Dithiophosphate De O,2-dicarboethoxyethyle)

252. Ft-0701077

253. Malathion, Vial Of 1 G, Analytical Standard

254. O,2-di(ethoxycarbamyl)ethyl Phosphorothioate

255. O,o-dimethyl S-1,2-di(ethoxycarbamyl)ethyl

256. 0,2-bis(ethoxycarbonyl)ethyl] Dithiophosphate

257. Malathion, Pestanal(r), Analytical Standard

258. C07497

259. D00534

260. Wln: 2ov1yvo2 & Sps & O1 & O1

261. Ab00053015_02

262. Diethyl 2-(dimethoxyphosphorothioylthio)succinate

263. O,o-dimethyl S-(1,2-bis(ethoxycarbonyl)ethyl)

264. 121m755

265. Diethyl (dimethoxyphosphinothioylthio) Butanedioate

266. Diethyl Mercaptosuccinate,o-dimethyl Thiophosphate

267. L001138

268. Q423005

269. Sr-01000942243

270. Diethyl [(dimethoxyphosphinothoiyl)thio]butanedioate

271. J-004630

272. O,o-dimethyl Dithiophosphate Diethylmercaptosuccinate

273. Sr-01000942243-1

274. 1,2-d.(ethoxycarbonyl)dimethyl Phosphorothiolothionate

275. Diethyl Mercaptosuccinate,o-dimethyl Phosphorodithioate

276. Malathion, Certified Reference Material, Tracecert(r)

277. O,o-dimethyl Dithiophosphate Of Diethyl Mercaptosuccinate

278. 1,2-di(ethoxycarbonyl)ethyl O,o-dimethyl Phosphordithioate

279. Diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]succinate #

280. Diethyl Mercaptosuccinic Acid,o-dimethyl Phosphorodithioate

281. Malathion, European Pharmacopoeia (ep) Reference Standard

282. O,o-dimethyl S-(1,2-dicarbethoxyethyl) Phosphorodithioate

283. O,o-dimethyl S-(1,2-dicarbethoxyethyl) Thiothionophosphate

284. O,o-dimethyl S-1,2-di(ethoxycarbamyl)ethyl Phosphorothioate

285. S-(1,2-dicarbethoxyethyl) O,o-dimethyl Phosphorodithioate

286. Diethyl 2-((dimethoxyphosphinothioyl)thio)butanedioate

287. Diethyl Mercaptosuccinate,o-dimethyl Dithiophosphate, S-ester

288. Malathion, United States Pharmacopeia (usp) Reference Standard

289. Mercaptosuccinic Acid Diethyl Ester,o-dimethyl Phosphorothioate

290. O,o-dimethyl S-[1,2-bis(ethoxy Carbonyl)ethyl]dithiophosphate

291. O,o-dimethyl-s-(1,2-di(ethoxycarbonyl)ethyl) Phosphorodithioate

292. S-(1,2-bis(aethoxy-carbonyl)-aethyl)-o,o-dimethyl-dithiophasphat

293. [(dimethoxyphophinothioyl)thio]butanedioic Acid, Diethyl Ester

294. Diethyl Mercaptosuccinate S-ester With O,o-dimethyl Phosphorodithioate

295. Succinic Acid, Diethyl Ester, S-ester With 0,0-dimethyl Phosphorodithioate

296. Succinic Acid, Diethyl Ester, S-ester With O,o-dimethyl Phosphorodithioate

297. 1,4-diethyl 2-{[dimethoxy(sulfanylidene)-$l^{5}-phosphanyl]sulfanyl}butanedioate

298. Butanedioic Acid, ((dimethoxyphosphinothioyl)-thio)-, Diethyl Ester, (+/-)-

299. Diethyl (+/-)-mercaptosuccinate, S-ester With O,o-dimethyl Phosphorodithioate

300. Malathion Solution, 100 Mug/ml In Cyclohexane, Pestanal(r), Analytical Standard

301. Mercaptosuccinic Acid Diethyl Ester, S-ester With O,o-dimethyl Phosphorothioate

302. Phosphorodithioic Acid,0-dimethyl Ester, S-ester With Diethyl Mercaptosuccinate

2.4 Create Date
2005-03-25
3 Chemical and Physical Properties
Molecular Weight 330.4 g/mol
Molecular Formula C10H19O6PS2
XLogP32.4
Hydrogen Bond Donor Count0
Hydrogen Bond Acceptor Count8
Rotatable Bond Count11
Exact Mass330.03606767 g/mol
Monoisotopic Mass330.03606767 g/mol
Topological Polar Surface Area128 Ų
Heavy Atom Count19
Formal Charge0
Complexity341
Isotope Atom Count0
Defined Atom Stereocenter Count0
Undefined Atom Stereocenter Count1
Defined Bond Stereocenter Count0
Undefined Bond Stereocenter Count0
Covalently Bonded Unit Count1
4 Drug and Medication Information
4.1 Drug Information
1 of 4  
Drug NameMalathion
PubMed HealthMalathion (On the skin)
Drug ClassesPediculicide
Drug LabelMalathion Lotion contains 0.005 g of malathion per mL in a vehicle of isopropyl alcohol (78%), terpineol, dipentene, and pine needle oil. The chemical name of malathion is () - [(dimethoxyphosphinothioyl) - thio] butanedioic acid diethyl ester. Mal...
Active IngredientMalathion
Dosage FormLotion
RouteTopical
Strength0.5%
Market StatusPrescription
CompanySuven Life

2 of 4  
Drug NameOvide
PubMed HealthMalathion (On the skin)
Drug ClassesPediculicide
Drug LabelOVIDE Lotion contains 0.005 g of malathion per mL in a vehicle of isopropyl alcohol (78%), terpineol, dipentene, and pine needle oil. The chemical name of malathion is () - [(dimethoxyphosphinothioyl) - thio] butanedioic acid diethyl ester. Malathi...
Active IngredientMalathion
Dosage FormLotion
RouteTopical
Strength0.5%
Market StatusPrescription
CompanyTaro Pharms North

3 of 4  
Drug NameMalathion
PubMed HealthMalathion (On the skin)
Drug ClassesPediculicide
Drug LabelMalathion Lotion contains 0.005 g of malathion per mL in a vehicle of isopropyl alcohol (78%), terpineol, dipentene, and pine needle oil. The chemical name of malathion is () - [(dimethoxyphosphinothioyl) - thio] butanedioic acid diethyl ester. Mal...
Active IngredientMalathion
Dosage FormLotion
RouteTopical
Strength0.5%
Market StatusPrescription
CompanySuven Life

4 of 4  
Drug NameOvide
PubMed HealthMalathion (On the skin)
Drug ClassesPediculicide
Drug LabelOVIDE Lotion contains 0.005 g of malathion per mL in a vehicle of isopropyl alcohol (78%), terpineol, dipentene, and pine needle oil. The chemical name of malathion is () - [(dimethoxyphosphinothioyl) - thio] butanedioic acid diethyl ester. Malathi...
Active IngredientMalathion
Dosage FormLotion
RouteTopical
Strength0.5%
Market StatusPrescription
CompanyTaro Pharms North

4.2 Therapeutic Uses

Malathion Lotion is indicated for patients infected with Pediculus humanus capitis (head lice and their ova) of the scalp hair. /Included in US product label/

US Natl Inst Health; DailyMed. Current Medication Information for OVIDE (malathion) lotion (December 2011). Available from, as of January 30, 2012: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=2024030e-b00d-4fcc-b51d-45dc86933749


Malathion is used for the topical treatment of pediculosis capitis (head lice infestation). The drug also has been used for the topical treatment of pediculosis pubis (pubic lice infestation), pediculosis corporis (body lice infestation), and scabies (mite infestation).

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3535


Pediculicide

O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Cambridge, UK: Royal Society of Chemistry, 2013., p. 1059


(VET): Ectoparasiticide

O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Cambridge, UK: Royal Society of Chemistry, 2013., p. 1059


For more Therapeutic Uses (Complete) data for MALATHION (8 total), please visit the HSDB record page.


4.3 Drug Warning

Malathion Lotion is contraindicated for neonates and infants because their scalps are more permeable and may have increased absorption of malathion. Malathion Lotion should also not be used on individuals known to be sensitive to malathion or any of the ingredients in the vehicle.

US Natl Inst Health; DailyMed. Current Medication Information for OVIDE (malathion) lotion (December 2011). Available from, as of January 30, 2012: https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=2024030e-b00d-4fcc-b51d-45dc86933749


Malathion 0.5% lotion is contraindicated in patients with a history of hypersensitivity to the drug or any ingredient in the formulation. The lotion is also contraindicated in neonates and infants. Some clinicians suggest that the malathion preparation commercially available in the US be avoided in patients with asthma and in small children to prevent exposure to fumes from the isopropyl alcohol vehicle.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3536


Slight stinging or burning has been reported following application of malathion 0.5% lotion, which may be due to the effects of the isopropyl alcohol vehicle. Adverse local effects may include irritation of the skin and scalp, dryness of the hair, and a transient increase in dandruff.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3536


The manufacturer states that it is not known whether malathion 0.5% lotion has the potential to cause allergic contact sensitization. However, dermatitis of the scalp has been reported in at least one individual following topical application of malathion 5% lotion (10 times the usually recommended dosage) and contact dermatitis has been reported in individuals exposed to agricultural formulations of malathion.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3536


For more Drug Warnings (Complete) data for MALATHION (10 total), please visit the HSDB record page.


4.4 Minimum/Potential Fatal Human Dose

The lethal dose in mammals is ~1 g/kg.

Brunton, L. Chabner, B, Knollman, B. Goodman and Gillman's The Pharmaceutical Basis of Therapeutics, Twelth Edition, McGraw Hill Medical, New York, NY. 2011, p. 243


4.5 Drug Indication

For patients infected with Pediculus humanus capitis (head lice and their ova) of the scalp hair.


FDA Label


5 Pharmacology and Biochemistry
5.1 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.


5.2 MeSH Pharmacological Classification

Insecticides

Pesticides designed to control insects that are harmful to man. The insects may be directly harmful, as those acting as disease vectors, or indirectly harmful, as destroyers of crops, food products, or textile fabrics. (See all compounds classified as Insecticides.)


Cholinesterase Inhibitors

Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system. (See all compounds classified as Cholinesterase Inhibitors.)


5.3 FDA Pharmacological Classification
5.3.1 Active Moiety
MALATHION
5.3.2 FDA UNII
U5N7SU872W
5.3.3 Pharmacological Classes
Cholinesterase Inhibitors [MoA]; Cholinesterase Inhibitor [EPC]
5.4 ATC Code

P03AX03

S76 | LUXPHARMA | Pharmaceuticals Marketed in Luxembourg | Pharmaceuticals marketed in Luxembourg, as published by d'Gesondheetskeess (CNS, la caisse nationale de sante, www.cns.lu), mapped by name to structures using CompTox by R. Singh et al. (in prep.). List downloaded from https://cns.public.lu/en/legislations/textes-coordonnes/liste-med-comm.html. Dataset DOI:10.5281/zenodo.4587355


P - Antiparasitic products, insecticides and repellents

P03 - Ectoparasiticides, incl. scabicides, insecticides and repellents

P03A - Ectoparasiticides, incl. scabicides

P03AX - Other ectoparasiticides, incl. scabicides

P03AX03 - Malathion


5.5 Absorption, Distribution and Excretion

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.


Concentrations of pesticides and selected metabolites in rat urine and amniotic fluid were determined as biomarker upon oral administration of Wistar rats to two pesticide mixtures consisting of three to five pesticides (bitertanol, propiconazole, cypermethrin, malathion, and terbuthylazine). The pesticides and their metabolites were found in rat amniotic fluid and urine, generally in dose-response concentrations in relation to dosage. The measurement of the substances in the amniotic fluid indicated that the fetus was exposed to the pesticides as well as their metabolites. Moreover, the pesticides detected in urine demonstrated the exposure as well as the ability of the rat to excrete these compounds.

PMID:23736656 Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3717736 Bossi R et al; Int J Environ Res Public Health 10 (6): 2271-81 (2013)


O,O,S-Trimethyl phosphorothioate (OOS-TMP) is an impurity present in widely used organophosphorus insecticides such as malathion. Oral treatment of rats with the compound produces prominent bronchiolar epithelial necrosis. Following the administration of [(3)H]OOS-TMP to rats, substantial amounts of radiolabeled material were covalently bound to lung with a concomitant depletion of glutathione (GSH). Other organs showing significant covalently bound radioactivity were liver, kidneys, and ileum. The maximal accumulation occurred in the tissues within 6 hr, and reached a plateau between 6 and 12 hr. Pretreatment of rats with either phenobarbital or piperonyl butoxide decreased the level of radiolabeled material bound in lung, GSH depletion, and the toxicity of OOS-TMP. These results suggest that the covalent binding is due to a metabolite(s) of OOS-TMP and that the metabolite(s) is involved in the mechanism of toxicity of OOS-TMP. ... /(3)H-O,O,S-trimethyl phosphorothioate/

PMID:6710498 Imamura T, Hasegawa L; Toxicol Appl Pharmacol 72 (3): 476-83 (1984)


... /The/ objective was to determine the percutaneous absorption of chronically applied malathion in man and to compare chronic absorption to single-dose absorption. The experimental design was to first topically apply [(14)C]malathion to human male volunteers. This procedure was followed by repeated administration of nonradioactive malathion to the same site of application (ventral forearm). [(14)C]Malathion was reapplied (Day 8) when urinary excretion of radioactivity from the first application reached minimum detectable levels. The first [(14)C]malathion absorption was compared to the second [(14)C]malathion application. The percutaneous absorption from the first [(14)C]malathion application was 4.48 +/- 1.3% (SD) of the applied dose. The absorption from the second [(14)C]malathion administration was 3.53 +/- 1.0%, a value not significantly (p greater than 0.05) different from the first application. Therefore, for malathion the single-dose application data are relevant for predicting the toxic potential for longer-term exposure.

PMID:6845371 Wester RC et al; Toxicol Appl Pharmacol 68 (1): 116-9 (1983)


Eight autopsy samples from an individual who had ingested a large amount of malathion were analyzed. ... The highest concentrations were found in gastric contents (8621 ppm) and adipose tissue (76.4 ppm). Malaoxon was identified in some tissues at very low levels; a significant amount was found only in fat (8.2 ppm). Malathion monocarboxylic acid & malathion dicarboxylic acid were found in greater abundance: 221 ppm in bile, 106 ppm in kidney, and 103 ppm in the gastric contents.

PMID:7143485 Morgade C, Barquet A; J Toxicol Environ Health 10 (2): 321-5 (1982)


For more Absorption, Distribution and Excretion (Complete) data for MALATHION (20 total), please visit the HSDB record page.


5.6 Metabolism/Metabolites

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.


Malathion is either oxidized in the liver to malaoxon by microsomal cytochrome P450 enzymes or to monoacids by a microsomal carboxyesterase. ... The other products of malathion and malaoxon metabolism are detoxification products. Malaoxon is also subject to hydrolysis and carboxyesterase. There is evidence that the linkage at P-S is enzymatically broken by another cytosolic esterase as well (A-esterase) and forms O,O-dimethyl phosphorothioate. There is some evidence that the monoacids can then be S-methylated, and that the C-S bond of either malaoxon or malathion can be further hydrolyzed.

Bingham, E.; Cohrssen, B.; Powell, C.H.; Patty's Toxicology Volumes 1-9 5th ed. John Wiley & Sons. New York, N.Y. (2001)., p. V7 867


Malathion is rapidly metabolized in vivo principally by hydrolysis of the carboxyl ester linkage to inactive metabolites by carboxylesterases. Because this detoxification reaction occurs much more rapidly in mammals than in susceptible insects, malathion exhibits a relative degree of selective toxicity in insects.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3538


Malathion ... is oxidized by the hepatic microsomal monooxygenase system to malaoxon, an active, toxic metabolite. Metabolism of malaoxon typically occurs at a faster rate than its formation from malathion, and little accumulation of this highly toxic metabolite occurs in mammals.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3538


Malathion is metabolically converted to its structurally similar metabolite, malaoxon (oxidation of the P=S moiety to P=O), in insects and mammals. Both malathion and malaoxon are detoxified by carboxyesterases leading to polar, water-soluble, compounds that are excreted. Mammalian systems show greater carboxyesterase activity, as compared with insects, so that the toxic agent malaoxon builds up more in insects than in mammals. This accounts for the increased toxicity of malathion in insects.

EPA/Office of Pollution Prevention and Toxic Substances; Malathion: Updated Revised Human Health Risk Assessment for the Reregistration Eligibility Decision Document (RED) EPA-HQ-OPP-2004-0348-0004. Available from, as of February 2, 2012: https://www.regulations.gov/#!home


For more Metabolism/Metabolites (Complete) data for MALATHION (16 total), please visit the HSDB record page.


5.7 Biological Half-Life

8-24 hours


In a patient who injected about 1.8 g of malathion as a 50% solution IV, the apparent half-life was 2.9 hours.

American Society of Health-System Pharmacists 2016; Drug Information 2016. Bethesda, MD. 2016, p. 3538


Among male volunteers, approximately 90% of an intravenous dose of malathion was excreted in the urine within 5 days and the elimination half-life was 3 hours.

Bingham, E.; Cohrssen, B.; Powell, C.H.; Patty's Toxicology Volumes 1-9 5th ed. John Wiley & Sons. New York, N.Y. (2001)., p. V7 867


In rats given malathion orally, it is distributed to blood, adipose tissue, muscle, liver, and brain and then eliminated from these tissues at half-lives of 1.4, 2.4, 3.7, 19.4, and 17.6 days, respectively.

Bingham, E.; Cohrssen, B.; Powell, C.H.; Patty's Toxicology Volumes 1-9 5th ed. John Wiley & Sons. New York, N.Y. (2001)., p. V7 866


5.8 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.


Muscle dysfunction in acute organophosphorus (OP) poisoning is a cause of death in human. The present study was conducted to identify the mechanism of action of OP in terms of muscle mitochondrial dysfunction. Electromyography (EMG) was conducted on rats exposed to the acute oral dose of malathion (400 mg/kg) that could inhibit acetylcholinesterase activity up to 70%. The function of mitochondrial respiratory chain and the rate of production of reactive oxygen species (ROS) from intact mitochondria were measured. The bioenergetic pathways were studied by measurement of adenosine triphosphate (ATP), lactate, and glycogen. To identify mitochondrial-dependent apoptotic pathways, the messenger RNA (mRNA) expression of bax and bcl-2, protein expression of caspase-9, mitochondrial cytochrome c release, and DNA damage were measured. The EMG confirmed muscle weakness. The reduction in activity of mitochondrial complexes and muscular glycogen with an elevation of lactate was in association with impairment of cellular respiration. The reduction in mitochondrial proapoptotic stimuli is indicative of autophagic process inducing cytoprotective effects in the early stage of stress. Downregulation of apoptotic signaling may be due to reduction in ATP and ROS, and genotoxic potential of malathion. The maintenance of mitochondrial integrity by means of artificial electron donors and increasing exogenous ATP might prevent toxicity of OPs.

PMID:23774768 Karami-Mohajeri S et al; Hum Exp Toxicol 33 (3): 251-63 (2014)


... The current study investigates the influence of malathion on insulin signaling pathways and the protective effects of N-acetylcysteine (NAC). Malathion (200 mg/kg) and NAC (2 g/L) were administered orally to rats, during 28 consecutive days. Malathion increases plasma glucose, plasma insulin and glycated hemoglobin levels. Further, we observed an increase of insulin resistance biomarkers and a decrease of insulin sensitivity indices. The GP, GSK3beta and PEPCK mRNA expressions were amplified by malathion while, the expression of glucokinase gene is down-regulated. On the basis of biochemical and molecular findings, it is concluded that malathion impairs glucose homeostasis through insulin resistance and insulin signaling pathways disruptions in a way to result in a reduced function of insulin into hepatocytes. Otherwise, when malathion-treated rats were compared to NAC supplemented rats, fasting glucose and insulin levels, as well as insulin resistance indices were reduced. Furthermore, NAC restored liver GP and PEPCK expression. N-acetylcysteine showed therapeutic effects against malathion-induced insulin signaling pathways disruption in liver. These data support the concept that antioxidant therapies attenuate insulin resistance and ameliorate insulin sensitivity.

PMID:25449180 Lasram MM et al; Gen Comp Endocrinol 215: 88-97 (2015)


The cardiovascular actions of antic-ChE agents are complex, since they reflect both ganglionic and postganglionic effects of accumulated ACh on the heart and blood vessels and actions in the CNS. The predominant effect on the heart from the peripheral action of accumulated ACh is bradycardia, resulting in a fall in cardiac output. Higher doses usually cause a fall in blood pressure, often as a consequence of effects of anti-ChE agents on the medullary vasomotor centers of the CNS. /Anticholinesterase agents/

Brunton, L. Chabner, B, Knollman, B. Goodman and Gillman's The Pharmaceutical Basis of Therapeutics, Twelth Edition, McGraw Hill Medical, New York, NY. 2011, p. 246


/LABORATORY ANIMALS: Acute Exposure/ It was established in experiments on noninbred albino rats that acute intoxication with malathion (0.75 LD50) /administered instramuscularly/ reduced the function of Th1 cells more significantly than the function of Th2 lymphocyte, decreases the activity of B cells and NK cells, blood levels of TNFa, IL-1b and IL-6, IFN-g, IL-2, and IL-4, while not significantly affecting the concentration of IL-10 and IL-13. Atropine (10 mg/kg) under conditions of acute malathion intoxication improved the function of T cells and B lymphocytes, NK cells, as well as the synthesis of immunoregulatory cytokines IFN-g, IL-2, and IL-4. At the same time, atropine in malathion intoxicated rats had no effect on suppression of the synthesis of proinflammatory cytokines TNF, IL-1g and IL-6 as well as the content of anti-inflammatory cytokines IL-10 and IL-13.

PMID:26591203 Zabrodskii PF et al; Eksp Klin Farmakol 78 (7): 20-3 (2015)