Tox.Osweiler Flashcards
Ammonia/urea
MOA
Characteristics
Ammonia or other nitrogenous waste products stimulate CNS; inhibits TCA cycle causing cerebral energy deficit
Seizures accompanied by excitement, belligerence, tremors; urination and bloat occur in cattle; most commonly affect ruminants
Amphetamines
MOA
Characteristics
Promote catecholamine release from CNS and adrenals
Seizures accompanied by stimulation of respiratory center, cerebral cortex, reticular activating system; excitement, hyperreflexia and tremors predominate
4Aminopyridine
MOA
Characteristics
Increases acteylcholine release and inhibits repolarization by potassium current
Seizures accompanied by hyperexcitablity; tremors, tachycardia, arrhythmia; used as an acivide
Bromethalin
MOA
Characteristics
Uncouples oxidative phospohorylation in the CNS, leading to loss of energy metbaolismand decreasing the actiivty of the sodium pump, causes cerebral edema
Dose-dependent; low dosages cause depression, tremors, posterior weakness, ataxia; high dosages may cause seizures, tremors, occasiona paralysis
Caffeine
MOA
Characteristics
Inhibits adenosine receptors and phosphodiesterase, increasing cAMP production; enhances catecholamine release and effects
Excitement and hyperreflexia predominate; accompanied by tachycardia, cardiac arrhythmia and hyperthermia
Cocaine
MOA
Characteristics
Inhibits reuptake of actecholamines at nerve terminal,e hancing sympathetic stimulation
CNS signs range from excitement to depression; often accompanied by vomiting, salivation and tachycardia
Crimidine
MOA
Characteristics
Vitamin B6 antagonist primarily affecting CNS; occasionally used as a rodenticide
Acute, convulsive seizures
Cyanide
MOA
Characteristics
Inhibits cytochrom oxidase in electron transport system, leading to cerrebral energy deficit
Generalized seizures and hyperpnea followed initially by weakness
Ergot
MOA
Characteristics
Lysergic acid diethylamide (LSD-type alkaloids)
Excitement and hallucinations accompanied by tremors
Fluoracetate.
MOA
Characteristics
Inihibits aconitate hydratase in TCA cycle, causing cerebral enerngy deficit and accumulation of citrate and lactate
Clonic seizures accompanied by wild running, barking, urination, defecation; very rare
Hexaclorophene
MOA
Characteristics
Uncouples oxidative phosphorylation, leading to cerebral edema
Seizures accompanied by excitement, tremors, hypermetria; response to lower dosages or chronic exposure include blindness, posterior ataxia
Lead
MOA
Characteristics
Not well-characterized; inhibits several enzymes; causes cerebral edema and neuronal degenreation; inhibits the inhibitory neurotransmitter GABA
CNS signs highly variable: termors, excitability, hysteria (in dogs) accompanied by anorexia, GI stasis, mild anemia with regenerative response
Metaldehyde
MOA
Characteristics
Metabolized to acetaldehyde; toxicosis correlated with dec in 5-hydroxytrptamine (5-HT, serotonin) and GABA in the brain
Continuous seizures; include prominent mm tremors and incoordination, salivation and tachycardia; not induced by stimuli
4-MI (methyl imidazole)
MOA
Characteristics
Directly toxic to CNS; mechanism unclear
Excitement, tremors, running (Cattle)
Nitrofurazone
MOA
Characteristics
Inhibits oxidative phosphorylation and energy metabolisim in the brain; calves highly susceptible
Acute seizures, facial tremors, hyperexcitability, paddling
Organochlorine inseciticides
MOA
Characteristics
Diphenyl aliphatics: inhibits both trning off the inward sodium current and turning on the outward potassium current, decreasing the action potential threshold and stimulating nervous activity
Cyclodiene insecticides: inhibit receptor binding of the inhibitor GABA, promoting excitatory transmission in the CNS
Grand mal seizures, accompnaied by paddling, chewing, opisthotonos, refractory interictal phase, hyperthermia
Pyrethrins
MOA
Characteristics
Prolong sodium influx and reduce potassium efflux, enhancing of the action potential and promote repetitive discharge
Hyperexcitability and tremors dominate; actual seizures are less common
Sodium ion toxicosis
MOA
Characteristics
Interferes with aerobic glycolysis, reducing the activity of sodium pump and resulting in sodium-related accumulation of water, cerebral edema and seizures
Sterotypical of cranial to caudal clonic seizures; blindness and cerebral malacia occur as sequelae to acute seizures often assoc with water deprivation
Strychnine
MOA
Characteristics
Inhibits the action of inhibitory aa glycine in the CNS, preventing the actiono of inhibitory interneurons in the spinal cord
Acute hyperesthesia, hyperreflexia, tetanic seizures; severe extensor rigidity
Water hemlock (Cicuta, cicutoxin)
MOA
Characteristics
Mechanism is not characterized
Violent acute tetanic siezures, mm twitching, extensor ridigidity
Zinc phosphide
MOA
Characteristics
Phosphine (PH3) is released in stomach and presumably absorbed; mechanisms related to CNS effects are unclear
Clonic spasm of head and neck, paddling, generalized tremors; animals are not hyperesthetic; vomiting, acidosis, liver damage often occur
Avocado (persea)
MOA
Characteristics
Unknown
Depression or mild tremors assoc with depression and other systemic signs
Barbiturates
MOA
Characteristics
Y-Aminobutyric acid (GABA)- like action results in inhibition of transmission
CNS depression, general anesthesia, slowed respiratory rate and coma
Bracken fern
MOA
Characteristics
Thiaminase principle induces thiamine deficiency in equids
Peripheral neuropathy with progressive posterior weakness, incoordination, ataxia
Bromethalin
MOA
Characteristics
Uncouples oxidative phosphorylation in the CNS, leading to loss of energy metabolism and decreasing the acitivity of the sodium pump and causing cerebral edema
Dose dependent:
Low dose: depression, tremors possterior weakness, ataxia
High dose: seizures, tremors, occasional paralysis
Carbon monoxide
MOA
Characteristics
Forms carboxyhemoglobin, leading to severe anoxia, which causes anoxic degeneration and necrosis of neurons
Fumonisin
MOA
Characteristics
Inhibits the enzymatic conversion of spinganine to sphingosine; this emcahnism is not proven in horses
Leukocenphaldmalacia (horses): produces CNS signs of severe depression, paralysis of tongue and facial mm, blindness, prostration and death
Hydrogen sulfide
MOA
Characteristics
Inhibits cytochrome c oxidase and electron transport; rapidly affects respiratory center
Respiratory paralysis, acute CNS depression, loss of consciousness
Ivermectin
MOA
Characteristics
Stimulates presynaptic release and postsynaptic binding of GABA, enhancing the inhibitory effects of GABA in the CNS; primarily affects collie breeds b/c drug cross the BBB in these breeds
Depression, ataxia, blindness, coma; signs in noncollie breeds occur only at excessive dosages
Lead
MOA
Characteristics
Not well-characterized; inhibits several enzymes; causes cerebral edema and neuronal degeneration; inhibits the inhibitory neurotransmitter GABA
May also be dose depednent; depression, coma, and blinddness occur intermittently with excitement or seizures
Mercury (alkyl form)
MoA
Characteristics
Interrupts sufhydryle enzymes of protein syntehsis in the cerebral cortex and possibly, the cereballum; causes fibrinoid degneration ofmedial layer of cerebral artieries
Severe depression, coma, tremors, hypermetria, abnormal postures, blindness
Opiates
MOA
Characteristics
Interact with variety of receptors in the CNS
Primary response to overdose include: CNS depression, coma, respiratory depression
Yellow star thistle (Centaurea)
MOA
Characteristics
Unknown toxin causes nigropallidal encelphalomalacia, with poss release of CNS from inhibitory control of brain neuclei
Mild tremors of face and lips; paralysis of tongue in horses
