Organophosphates and carbamates are potent cholinesterase inhibitors capable of causing severe cholinergic toxicity following cutaneous exposure, inhalation, or ingestion. Although structurally distinct (figure 1), organophosphates and carbamates exhibit similar clinical manifestations with toxicity and require similar management following overdose.
An overview of organophosphate and carbamate poisoning will be presented here. A summary table to facilitate emergent management is provided (table 1). A general approach to suspected drug intoxication is discussed separately. (See "General approach to drug poisoning in adults".)
EPIDEMIOLOGY AND SOURCES OF EXPOSURE
Organophosphates have been used as insecticides worldwide for more than 50 years. The use of these agents has declined in the last 10 to 20 years, in part due to the development of carbamate insecticides, which are associated with similar toxicities . Medical applications of organophosphates and carbamates include reversal of neuromuscular blockade (neostigmine, pyridostigmine, edrophonium) and treatment of glaucoma, myasthenia gravis, and Alzheimer disease (echothiophate, pyridostigmine, tacrine, and donepezil).
Worldwide, an estimated 3,000,000 people are exposed to organophosphate or carbamate agents each year, with up to 300,000 fatalities [2,3]. In the United States, there were more than 8000 reported exposures to these agents in 2008, resulting in fewer than 15 deaths . Toxicity generally results from accidental or intentional ingestion of, or exposure to, agricultural pesticides [2,5]. Other potential causes of organophosphate or carbamate toxicity include ingestion of contaminated fruit, flour, or cooking oil, and wearing contaminated clothing [5,6]. (See "Information and educational resources for occupational and environmental health issues in the United States".)
Specific agents linked to human poisoning include both carbamate (methomyl and aldicarb) and organophosphate (parathion, fenthion, malathion, diazinon, and dursban) insecticides. Chlorpyrifos, the organophosphate agent of dursban, is found in some popular household roach and ant sprays, including Raid® and Black Flag® (figure 2). The United States Environmental Protection Agency (EPA) banned many household uses of chlorpyrifos in 2001, and has restricted its use on certain crops including tomatoes, apples, and grapes .