Poisons affecting the neurological system
Abstract
The brain is susceptible to a variety of poisons. Sedating drugs and chemicals can cause central nervous system (CNS) depression while other substances can cause CNS stimulation, including seizures. These are of particular concern since intractable seizure activity may cause complications, with pyrexia resulting in secondary damage to other organs. The common poisons discussed here that cause neurological effects are metaldehyde and tremorgenic mycotoxins, which can cause rapid onset seizures; cannabis, which can cause prolonged sedation in companion animals; permethrin, which is associated with prolonged seizures, particularly in cats; and ivermectin, which can cause CNS depression, blindness and seizures. Treatment is supportive in most cases; care should be taken when considering the use of emetics since there is a risk of aspiration in seizuring animals. Control of seizure activity is a priority, while intravenous lipid emulsion may also be useful.
Many different substances can cause a variety of neurological effects following overdose or accidental exposure. These effects can range from central nervous system (CNS) depression to CNS stimulation and seizures. Complications of prolonged seizure activity include severe pyrexia, which can result in rapid cellular necrosis; rhabdomyolysis, which can lead to acute kidney injury; and disseminated intravascular coagulation (DIC). These complications can lead to multi-organ failure.
Neurological effects from poisons can occur through direct effects on receptors, or as a result of metabolic disturbances. There are species and breed-specific factors that may influence susceptibility to some poisons. Some of the common poisons associated with neurological effects are discussed below; other substances that can cause neurological effects in companion animals are listed in Box 1.
Box 1.Other potential toxicological causes of neurological effects in companion animals
Lipid emulsion may be useful in the management of poisoning with some substances affecting the neurological system, since many are lipophilic. A measure of lipophilicity is the log P; the higher the log P the more lipophilic a compound. If the log P is >1 then lipid emulsion may be useful, although it is not used for substances with a long biological half-life, even if lipophilic.
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