Leptophos

Maria Yukiko KomiyamaChristopher Louis P. OrquizaIII-BSCTChemical and Molecular Toxicology

Leptophos

C13H10BrCl5O2PS

O-(4-bromo-2,5-dichlorophenyl) O-methyl phenylphosphonothioate

Organophosphate Compound

Leptophos

Stable white, crystalline solid at room temperature

a.k.a Phosvel, Abar and Vcs 506

Used as pesticide and fungicide for rice, cotton, fruit and vegetables

First discovered to be toxic in 1974 when more than 1000 water buffaloes died after exposure to leptophos in Egypt

Discontinued for use by the year 1975

ToxicityModerately toxic with LD50 values in excess of 50 mg/kg and less than 500 mg/kg.

Stable to photodegradation under atmospheric conditions

Stable in acidic medium but hydrolyzes at strong basic conditions

Efficiently absorbed by inhalation, ingestion, and skin penetration

Metabolism in mice

Mode of ActionInhibits acetylcholinerase (AChE) through phosphorylation of the esteratic site.

Causes increase in levels of acetylcholine (ACh)

Mode of ActionHigh ACh concentrations in:

Smooth muscles and gland cells: muscle contraction and secretion, respectively.

Skeletal muscle junctions: excitatory (cause muscle twitching), but may also weaken or paralyze the cell

High ACh concentrations in:

Central Nervous System: sensory and behavioral disturbances, incoordination, depressed motor function, and respiratory depression

Signs and SymptomsInhalation results in the fastest appearance of toxic symptoms.

Tightness of chest and wheezing

Increased in bronchial secretion, salivation, sweating, gastrointestinal tone

Peristalsis with consequent development of nausea, vomiting, abdominal cramps, diarrhea & bradycardia

Signs and Symptoms

Easy fatigue and mild weakness

Involuntary twitching and muscular weakness that may affect respiratory muscles causing dyspnea and cyanosis

Cause of death is asphyxia

Treatment

Airway protection

Atropine Sulfate (antagonist for excess acetylcholine)

Skin and Gastrointestinal Decontanimation

Monitoring of pulmonary and cardiac status

Referenceshttp://toxipedia.org/display/toxipedia/Leptophoshttp://nepis.epa.gov/Exe/ZyNET.exe/20013S5N.txt?ZyActionD=ZyDocument&Client=EPA&Index=1976%20Thru%201980&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&UseQField=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5CZYFILES%5CINDEX%20DATA%5C76THRU80%5CTXT%5C00000009%5C20013S5N.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p%7Cf&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=3&ZyEntry=1http://www.inchem.org/documents/jmpr/jmpmono/v075pr25.htm

References

Katzung, Pharmacology Ebook