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946.e2 Strychnine Toxicosis

Strychnine Toxicosis Client Education
Sheet
VetBooks.ir

BASIC INFORMATION
Concentration of strychnine in the bait varies
several hours of exposure). Urine may not
from 0.5% to 5%. washings) or urine early (within the first
Definition • Malicious/accidental toxicosis occurs contain detectable amounts of strychnine
A rapid-onset (30 minutes to 2 hours after when nontarget animals ingest strychnine- if samples are collected 1-2 days after the
ingestion), potentially fatal toxicosis is char- containing baits. exposure.
acterized by neurologic dysfunction (tremors, Mechanism of toxicosis: • Seal samples (stomach contents, liver, or
seizures). Toxicosis is rare and occurs most often • Strychnine competitively and reversibly kidney) in a plastic bag, freeze them, and
on the West Coast of the United States as a inhibits the inhibitory neurotransmitter submit to a veterinary diagnostic laboratory
malicious poisoning. glycine at postsynaptic neuronal sites in for strychnine analysis.
the spinal cord and medulla. This results
Synonyms in unchecked reflex stimulation of motor TREATMENT
Strychnine: Nux vomica neurons affecting all the striated muscles,
resulting in generalized rigidity and tonic- Treatment Overview
Epidemiology clonic seizures. Due to rapid progression of seizures, strychnine
SPECIES, AGE, SEX • Death usually results from respiratory arrest toxicosis is a medical emergency. A symptomatic
• All animals are susceptible; dogs are more and exhaustion from prolonged seizuring. patient presented early should be decontami-
commonly involved than cats. nated (emesis or lavage and activated charcoal).
• Male dogs are more commonly involved. DIAGNOSIS For symptomatic patients, the goals of treatment
are controlling central nervous system (CNS)
GENETICS, BREED PREDISPOSITION Diagnostic Overview signs (seizures), maintaining respirations, and
Younger, large-breed dogs are overrepresented. Strychnine toxicosis should be suspected based general supportive care. Because of severe
on suspected or witnessed history of exposure seizures, many patients require anesthesia for
GEOGRAPHY AND SEASONALITY and rapid onset of neurologic signs (muscular 24-48 hours.
• Year-round rigidity, seizures). Diagnosis can be confirmed
• Rural and urban dogs equally affected by identifying strychnine alkaloid in vomitus Acute General Treatment
• Most cases are reported in the western part or urine, but submission and turnaround time Control seizures and prevent asphyxia. Do not
of the United States. makes this confirmation clinically impractical. decontaminate a patient that is already showing
Given the rapid course of progression of this neurologic effects; stabilize the patient first.
Clinical Presentation disorder, treatment is initiated when strychnine Decontamination of patient (p. 1087):
HISTORY, CHIEF COMPLAINT intoxication is suspected or confirmed (e.g., • Induction of vomiting (p. 1188): useful
• Availability/presence of strychnine-containing container with label is available). within 30 minutes and only in asymptomatic
bait in pet’s environment; evidence of patients; contraindicated in symptomatic
exposure Differential Diagnosis patients because it can trigger seizures
• Rapid-onset (30 minutes to 2 hours) appre- • Other intoxications causing seizures: met- • Gastric lavage (p. 1117): used if emesis
hension, nervousness, chewing movements, aldehyde, tremorgenic mycotoxins/garbage cannot be induced or when suspected lethal
muscular rigidity, tonic-clonic seizures toxicosis, organochlorine, organophosphorus or doses have been ingested; intubate the patient
carbamate pesticides, zinc phosphide, nicotine with a cuffed endotracheal tube to reduce
PHYSICAL EXAM FINDINGS • Tetanus aspiration risk if the patient is unconscious.
• Hyperesthesia, apprehension, nervousness • Hypocalcemic tetany • Enterogastric lavage (through-and-through
initially • Hepatic encephalopathy lavage): induce general anesthesia and
• Muscle stiffness, rigidity protect airway; premedicate with atropine
• Hyperthermia (>40°C [>104°F]), caused by Initial Database 0.04 mg/kg IV to decrease vagal stimulation;
muscle activity (not febrile in origin) Because of the rapid onset of clinical signs, perform gastric lavage followed by an enema/
• Sawhorse stance no specific changes are expected on CBC, colonic irrigation under low pressure and
• Eventually, tetanic seizures, marked by serum biochemistry profile, or urinalysis at at body temperature; continue until fluids
violent, stiff limb movements presentation. Elevated creatine kinase (CK) exit through the gastric tube; used only if
○ Occur spontaneously or may be initiated level, metabolic acidosis and myoglobinuria known ingestion of potentially lethal dose
by external stimuli (touch, sound, sudden are possible as the toxicosis progresses. • Activated charcoal 1-2 g/kg, with a cathartic
bright light) such as sorbitol 5-10 mL/kg, 3% solution,
• Opisthotonos, mydriasis, exophthalmos, and Advanced or Confirmatory Testing PO or by stomach tube
cyanosis before death • On postmortem exam, no characteristic • Anticonvulsants
• Vomiting and hypersalivation (uncommon) lesions are seen. With prolonged convulsions ○ Diazepam 0.5-2 mg/kg IV, prn (various
before death, agonal hemorrhages of the heart degrees of success), or
Etiology and Pathophysiology and lungs and cyanotic congestion due to ○ Pentobarbital sodium 3-15 mg/kg IV to
Source: anoxia may be seen. effect; repeated as needed, or
• Strychnine is a bitter indole alkaloid from • Occasionally, poisoned animals may have ○ Propofol 3-6 mg/kg IV to effect, then
the seeds of the vinelike Southeast Asian or undigested red or green strychnine-laced 0.2-0.6 mg/kg/min IV constant-rate
Australian trees, Strychnos nux-vomica and grain (seed) based baits (wheat, milo, barley) infusion, or
Strychnos ignatii. in their stomach. ○ Gas anesthesia
• Since 1978 in the United States, strychnine • Strychnine alkaloid in the urine, vomitus, • Muscle relaxants
has been a restricted-use pesticide and stomach contents, liver, or kidney is consid- ○ Methocarbamol 100-200 mg/kg IV; repeat
rodenticide (licensed exterminators only) ered diagnostic. For living animals, submit as needed; maximum dose of 330 mg/kg
or has been banned in certain U.S. states. stomach contents (vomitus or stomach per day, or

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