Carbamates Toxicity:

Compared to organophosphates, carbamate pesticides are of relatively recent origin and constitute another important group of pesticides.

• Carbamate insecticides, which are derivatives of carbamic acid are used as pesticides

. • In addition to their use as pesticides, carbamates are used as drugs of choice in human medicine against Alzheimer’s disease, myasthenia gravis and glaucoma and in veterinary medicine as parasiticides.

Toxcokinetics:

• Carbamates are absorbed through skin, lungs and gastointestinal tract.
• They are widely distributed in the body and are rapidly metabolised.
• Sulphate conjugation and glucuronide conjugation occur.
• Excreted in urine, faeces and milk. • Carbamates are less toxic to warm blooded animals.

Mechanism of action:

• Carbamates cause reversible inhibition of acetylcholinesterase (unlike organophosphorus compounds which cause irreversible inhibition). But in the insects this is not reversible because the enzyme is cleaved in the process of carbamylation.
• In addition they inhibit aliesterase enzyme in insects.
• Carbamate complexes with acetylcholinesterase and the complex is known as carbamylated enzyme.
• This undergoes hydrolysis or decarbamylation and the enzyme is released.

 Clinical symptoms

• The clinical symptoms are similar to organophosphorus compounds

. • But the symptoms are not long lasting.

 Treatment:

• Atropine adminstration and symptomatic treatment are useful.
• Oximes (enzyme reactivators) are not useful and they are contraindicated.
• Carbamates attach to both the anionic and esteratic site of acetylcholinesterase and this does not allow oximes site to attach. Oximes themselves are weak anticholinesterase agents and may add on to aggravation of symptoms.
• Hyderochlorothiazide diuretics are also said to be useful.

        Difference between carbamates and organophosphorus.