Poisoning by organophosphorus pesticides results from inhibition of acetylcholinesterase. The outcome and optimum treatment depend on properties which differ among individual compounds. Treatment consists of supportive care, especially aimed at respiratory complications, and specific antidotal treatment. Treatment with atropine and diazepam is well established, but there is controversy concerning treatment with oximes capable of forcing reactivation of inhibited acetylcholinesterase. Although all parameters have not been fully established, initial bolus doses followed by continuous intravenous infusion to achieve plasma concentrations of 85–170 μmol/L of pralidoxime or 10–20 μmol/L of obidoxime have been recommended. These are well above concentrations that were likely to have been achieved by many of the ineffective regimens reported in the literature. Several independent reasons for failure of attempts at oxime therapy are discussed in this overview. If nothing else, it is likely that maintenance of adequate levels of oxime will shorten the period that a patient requires assisted ventilation with its associated risks. Topics for further laboratory and clinical research are listed. It is important to seek further understanding and the introduction of better practice because death rates from this type of poisoning remain significant.

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Ricin is a naturally occurring toxin derived from the beans of the castor oil plant Ricinus communis. It is considered a potential chemical weapon. Ricin binds to cell surface carbohydrates, is internalised then causes cell death by inhibiting protein synthesis. Oral absorption is poor and absorption through intact skin most unlikely; the most hazardous routes of exposure being inhalation and injection. Features of toxicity mainly reflect damage to cells of the reticuloendothelial system, with fluid and protein loss, bleeding, oedema and impaired cellular defence against endogenous toxins. It has been estimated that in man, the lethal dose by inhalation (breathing in solid or liquid particles) and injection (into muscle or vein) is approximately 5-10 micrograms/kg, that is 350-700 micrograms for a 70 kg adult. Death has ensued within hours of deliberate subcutaneous injection. Management is supportive. Prophylactic immunisation against ricin toxicity is a developing research initiative, although presently not a realistic option in a civilian context.

The management of methanol poisoning includes standard supportive care, the correction of metabolic acidosis, the administration of folinic acid, the provision of an antidote to inhibit the metabolism of methanol to formate, and selective hemodialysis to correct severe metabolic abnormalities and to enhance methanol and formate elimination. Although both ethanol and fomepizole are effective, fomepizole is the preferred antidote for methanol poisoning.