Organophosphate poisoning
Organophosphate poisoning is poisoning due to organophosphates (OPs). Organophosphates are used as insecticides, medications, and nerve agents. Symptoms include increased saliva and tear production, diarrhea, vomiting, small pupils, sweating, muscle tremors, and confusion. While onset of symptoms is often within minutes to hours, some symptoms can take weeks to appear. Symptoms can last for days to weeks.
Organophosphate poisoning occurs most commonly as a suicide attempt in farming areas of the developing world and less commonly by accident. Exposure can be from drinking, breathing in the vapors, or skin exposure. The underlying mechanism involves the inhibition of acetylcholinesterase (AChE), leading to the buildup of acetylcholine (ACh) in the body. Diagnosis is typically based on the symptoms and can be confirmed by measuring butyrylcholinesterase activity in the blood. Carbamate poisoning can present similarly.
Prevention includes banning very toxic types of organophosphates. Among those who work with pesticides the use of protective clothing and showering before going home is also useful. In those who have organophosphate poisoning the primary treatments are atropine, oximes such as pralidoxime, and diazepam. General measures such as oxygen and intravenous fluids are also recommended. Attempts to decontaminate the stomach, with activated charcoal or other means, has not been shown to be useful. While there is a theoretical risk of health care workers taking care of a poisoned person becoming poisoned themselves, the degree of risk appears to be very small.
OPs are one of the most common causes of poisoning worldwide. There are nearly 3 million poisonings per year resulting in two hundred thousand deaths. Around 15% of people who are poisoned die as a result. Organophosphate poisoning has been reported at least since 1962.
Organophosphate poisoning
A number of measurements exist to assess exposure and early biological effects for organophosphate poisoning. Measurements of OP metabolites in both the blood and urine can be used to determine if a person has been exposed to organophosphates. Specifically in the blood, metabolites of cholinesterases, such as butyrylcholinesterase (BuChE) activity in plasma, neuropathy target esterase (NTE) in lymphocytes, and of acetylcholinesterase (AChE) activity in red blood cells. Due to both AChE and BuChE being the main targets of organophosphates, their measurement is widely used as an indication of an exposure to an OP. The main restriction on this type of diagnosis is that depending on the OP the degree to which either AChE or BuChE are inhibited differs; therefore, measure of metabolites in blood and urine do not specify for a certain OP. However, for fast initial screening, determining AChE and BuChE activity in the blood are the most widely used procedures for confirming a diagnosis of OP poisoning. The most widely used portable testing device is the Test-mate ChE field test, which can be used to determine levels of Red Blood Cells (RBC), AChE and plasma (pseudo) cholinesterase (PChE) in the blood in about four minutes. This test has been shown to be just as effective as a regular laboratory test and because of this, the portable ChE field test is frequently used by people who work with pesticides on a daily basis.