Introduction

• Carbamates: derived from carbamic acid, thiocarbamic acid or dithiocarbamic acid. Used as: fungicides, herbicides, insecticides and molluscicides.
• LD50 of 25 mg/kg in the dog (Methiocarb).
• Mechanism of poisoning similar to organophosphate poisoning.
• Signs: vomiting, tremor and convulsions.
• Diagnosis: history, clinical signs.
• Treatment: atropine to effect. Control nervous signs with diazepam (valium).
  Do not administer barbiturates or other cardiorespiratory depressants.
• Prognosis: excellent if treated early.

Pathogenesis

Etiology

• Carbamates vary widely in their toxicity, generally they are considered relatively safe.
• Exceptions are: aldicarb, oxamyl, methiocarb, carbofuran, isolan, methomyl, formetanate, aminocarb, cloethocarb, bendiocarb.

Pathophysiology

• Cholinesterase action → accumulation of acetylcholine → neuromuscular blockade.
• Death, when it occurs, is due to respiratory failure.
• The most toxic carbamates are aldicarb (LD50 5-10 mg/kg), carbofuran (LD50 19 mg/kg).

• Carbamates are cholinesterases → accumulation of acetylcholine.
• Fat soluble, diffuse readily into tissues.
• Toxicity varies according to the compound involved.
• Incomplete blockade of acetylcholinesterase → less toxic than organophosphates.

• Increase in all body secretions, eg hypersalivation.
• Vomiting and diarrhea.
• Colic.
• Incontinence due to relaxation of the sphincters.
• Myosis, sometimes very prominent.

• Predominantly neuromuscular.
• Muscle fasciculations.
• Clonic spasms.
• Weakness/paralysis.

• Depression.
• Convulsive episodes.
• Coma.

Timecourse

• Signs of poisoning occur soon after ingestion or exposure to the poison.
• Death due to respiratory failure may occur within a few hours to several days (according to the compound involved).
• Occasionally → rapidly fatal asphyxia.

Diagnosis

Treatment

Outcomes