The first step in the metabolism of carbamates is hydrolysis to carbamic acid, which decomposes to carbon dioxide (CO2) and the corresponding amine. The mechanism of hydrolysis is different for N -methyl and N -dimethyl derivatives. The N -methyl carbamates pass through an isocyanate intermediate, whereas in the hydrolysis of N - dimethylcarbamates, an addition product with a hydroxyl ion is formed yielding the alcohol and N -dimethyl substituted acid. The rate of hydrolysis by esterases is faster in mammals than in plants and insects. Apart from hydrolysis, oxidation also takes place including: hydroxylation of the aromatic ring, O -dealkylation, N -methyl hydroxylation, N -dealkylation, oxidation of aliphatic side chains, and sulfoxidation to the corresponding sulfone. Oxidation is associated with the mixed-function oxidase (MFO) enzymes. Conjugation leads to the formation of O - and N -glucuronides, sulfates, and mercapturic acid derivatives in mammals. Glycosides and phosphates are conjugation products more common in plants. /Carbamate Pesticides/
Basic treatment: Establish a patent airway. Suction if necessary. Aggressive airway control may be needed. Watch for signs of respiratory insufficiency and assist ventilations if necessary. Administer oxygen by nonrebreather mask at 10 to 15 L/min. Monitor for pulmonary edema and treat if necessary ... . Monitor for shock and treat if necessary ... . Anticipate seizures and treat if necessary ... . For eye contamination, flush eyes immediately with water. Irrigate each eye continuously with normal saline during transport ... . Do not use emetics. For ingestion, rinse mouth and administer 5 ml/kg up to 200 ml of water for dilution if the patient can swallow, has a strong gag reflex, and does not drool. Administer activated charcoal ... . /Carbamates and related compounds/
Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious. Positive pressure ventilation techniques with a bag valve mask device may be beneficial. Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start an IV with D5W /SRP: "To keep open", minimal flow rate/. Use lactated Ringer's if signs of hypovolemia are present. For hypotension if signs of hypovolemia are present, administer fluid cautiously. Watch for signs of pulmonary edema ... . Administer atropine. Correct hypoxia before administration ... . In severely poisoned patients, administer pralidoxime chloride (2 PAM). DIRECT PHYSICIAN ORDERS ONLY ... . Treat seizures with adequate atropinization and correction of hypoxia. Rarely is diazepam necessary ... . Use proparacaine hydrochloride to assist eye irrigation ... . /Carbamates and related compounds/
Artificial respiration (via a tracheal tube) should be started at the first sign of respiratory failure and maintained for as long as necessary. Cautious administration of fluids is advised as well as general supportive and symptomatic pharmacological treatment and absolute rest. /Carbamate pesticides/
Little information is available on the distribution of carbamates in the various organs and tissues in mammals following exposure by inhalation or the oral route. The organs in which residues have been reported are the liver, kidneys, brain, fat, and muscle. The half-life in the rat is of the order of 3-8 hr. ...It seems that the excretion of carbamates via urine is also rapid in man, and that the metabolic pathways in man are the same as those in the rat. /Carbamate Pesticides/