Carbamate poisoning- Forensic medicine and toxicology

Carbamate poisoning

1. CARBAMATES

2. Carbamates are the class of compounds that reversibly inhibit the enzyme acetylcholinesterase. They are mostly used as insecticides. They are as popular as organophosphates and share a number of similarities with organophosphates.

3. COMMON CARBAMATES Aldicarb ( Temik ) Carbaryl ( Sevin 50) Propoxur ( Baygon ) Carbaryl + gamma BHC( Sevidol ) Physostigmine Neostigmine Pyridostigmine Edrophonium Ambenonium Carbofuran( Furadan ) Methomyl ( Lannate )

4. ACTION The primary mechanism of action of carbamates is inhibition of acetylcholinesterase or butyrylcholinesterase Carbamates will carbamylate the serene moiety at the active sites of AchE . This is a reversible type of binding ,hence symptoms are less severe and of shorter duration. They are spontaneously hydrolysed from the AChE enzyme site within 48 hrs.

5. Carbamates do not penetrate the CNS to the same extent as that of OPC, resulting in limited CNS toxicity. Carbamates are absorbed by many routes including transdermal, transconjunctival, inhalational, across the GIT and through direct injection. They are rapidly metabolized. Carbamates are eliminated rapidly by serum and liver enzymes

6. Fatal Dose: Carbofuran 10 - 30 gm Fatal Period: Carbofuran 2-6hrs.

7. SIGNS AND SYMPTOMS S alivation L acrimation, U rination, D iarrhea, G astrointestinal distress E mesis. D iaphoresis D iarrhea U rination M iosis B radycardia B ronchospasm B ronchorrhea E mesis, L acrimation S alivation

8. INVESTIGATIONS The estimation of Cholinesterase activity is not reliable because enzyme activity returns to normal within a few hours. So, blood is drawn and can be assayed for the detection of poison.

9. TREATMENT Atropine is the drug of choice in carbamate poisoning. Oximes are not recommended in carbamate poisoning since it is a reversible AChE inhibitor. It may form carbamylated oxime, especially with Carbaryl, which is more potent AChE inhibitor than carbamates. However, Oximes show antidotal properties in aliphatic carbamates (Aldicarb, Methomyl]). According to the latest view (WHO recommendations), oximes can be given along with atropine, especially, in mass casualties in which the exact nature of the insecticide is not known.

10. Postmortem appearance Face may be congested with congestion of conjunctivae. There will be froth at the mouth and nostrils. Stomach contents may have the smell of kerosene. The air passages contain froth. Lungs will be congested and edematous. Heart may have petechial hemorrhages on the pericardial surface. Brain may be congested and edematous. All the internal organs will be congested.

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