Lewisite 2-chlorovinyl-dichloroarsine Vesicants

1. Lewisite (2-chlorovinyl-dichloroarsine) Vesicants

2. Vesicants / Blistering Agents Lewisite

3. Overview: Lewisite Lewisite (2-chlorovinyl-dichloroarsine) Colorless, odorless, oily liquid Impurities give it a brown to blue-black color and the odor of geraniums Hydrolyzes rapidly Maintaining biologically active concentrations in high humidity is difficult

4. Overview: Toxicity Less likely than mustard to be used by terrorists Acute toxicity levels not well defined Dermal exposure 0.05 - 0.1 mg/cm2 produces erythema 0.2 mg/cm2 produces vesication ~ 30 drops (2.6 mg) can kill an average man through systemic toxicity

5. Overview: Toxicity Ocular exposure 15-minute exposure to a vapor concentration of 10 mg/m3 produces conjunctivitis Inhalation exposure LCt50 is estimated to be about 1500 mg min/m3

6. Protective Equipment Ordinary clothing and surgical gear offer little or no protection Respirator, impermeable protective clothing, gloves and over-boots are required

7. Detection Cannot be detected by automated chemical agent detectors Arsenic forms colored products with reagents Draeger� tubes available that react with organic arsenicals Gas-chromatographic techniques can be used for identification

8. Decontamination Efficient and quick -- serious damage occurs within minutes Skin Absorbing powders: Fullers earth, talcum powder Chemical inactivation Efficacy of water is unclear and may spread the agent

9. Decontamination Mucous Membranes and Eyes Flush affected mucous membranes immediately with water Flush eyes with water, saline or isotonic sodium bicarbonate

10. Signs and Symptoms Dependent upon affected areas Unlike the mustards, lewisite has no latency period and causes immediate pain Less severe injuries than those from mustards

11. Signs and Symptoms Eyes Animal tests: edema of the lids, conjunctivae, and cornea, early meiosis Severe exposures Involvement of iris and ciliary body Depigmentation, atrophy of iris stroma Immediate blepharospasm and edema helps prevent prolonged exposure

12. Signs and Symptoms Eyes Serious injuries Pannus formation, massive necrosis, and blindness A 0.001 ml droplet can perforate and destroy the eye

13. Signs and Symptoms Dermal Liquid or vapor form burns upon contact Erythema within 15-30 minutes Painful vesication within a few hours Blisters start small and expand to cover entire erythematous area Taking up to 4 days to occur Blister roof contains entire epidermal layer

14. Signs and Symptoms Dermal Liquid exposure Pigment changes do not occur and minor lesions heal Coagulative necrotic lesions Large, deep lewisite burns may show necrosis, gangrene and slough

15. Signs and Symptoms Respiratory Tract Immediate irritation and congestion from the nasal cavity to the lower airways Symptoms start with rhinorrhea Obstruction caused by airway secretions and fragments of necrotic epithelium

16. Signs and Symptoms Respiratory Tract Severe cases Pseudomembrane formation and pulmonary edema Avoid bronchopneumonia Inhaled dose Victim dies in a few days Pulmonary edema Mechanical asphyxia due to obstruction Sepsis

17. Signs and Symptoms Systemic Action Liver toxicity and systemic arsenic toxicity �Lewisite shock� Result of protein and plasma leakage from the capillaries

18. Signs and Symptoms Systemic Action Subnormal body temperature, restlessness, hypotension, and T-wave elevations Generalized weakness, muscle cramping, and red or green colored urine Gastrointestinal symptoms

19. Treatment No specific treatment available Arsenic toxicity must be addressed Aim of therapy is to relieve symptoms, prevent infection, promote healing

20. Treatment Indications for systemic treatment Cough with dyspnea or sign of pulmonary edema Skin burn the size of the palm of the hand or larger Skin contamination covering 5% or more of the body surface, Immediate damage or where erythema develops over the area within 30 minutes

21. Treatment Dimercaprol is used to chelate arsenic Deep, intramuscular injection Standard dose: 3-5 mg/kg IM every 4 hours for four doses Reserved for severe exposure exhibiting pulmonary edema or shock

22. Treatment Caveats Eyes Do not use topical anesthetics or bandages Use systemic, narcotic analgesics Skin Hospitalization for presence of deep, severe burns Ingestion Do not induce vomiting Activated charcoal is of no use Milk will help hydrolyze the agent

23. Long Term Medical Sequelae Lacking data from which to predict Chronic pulmonary disease and persistence of acute, severe injuries to the eye Does not appear to be mutagenic, teratogenic, or carcinogenic

24. Environmental Sequelae 7 times less persistent than the mustard agents in the environment Hydrolyzes rapidly Not found in soil Lewisite oxide Found in the soil demonstrates legacy contamination

25. Summary Less likely than mustards to be used by terrorists Only military-grade protective gear can prevent exposure Immediate decontamination is critical Signs and symptoms are dependent upon affected areas

26. Summary Pain and physical signs are immediate No specific antidote or treatment Aim of therapy is to relieve symptoms, prevent infection, and promote healing Systemic arsenic treated with dimercaprol (BAL) chelation