Page 253 - Cote clinical veterinary advisor dogs and cats 4th

110.e4 Barbiturates Toxicosis

aspirin, acetaminophen, caffeine, codeine, pharmacy; follow manufacturer instructions with mouth gag/speculum in place to
and anticholinergic alkaloids), hexobarbital for use). avoid tube chewing). Monitoring of
VetBooks.ir ○ Long-acting drugs: phenobarbital (Don- TREATMENT cleaning, deflating, and repositioning
(Nembutal),
pentobarbital
(Evipal),
tube and airway care are essential (tube
secobarbital (Seconal)
prn; avoid pressure injury from over-
natal in combination with anticholinergic
Treatment is aimed at decontamination of the
first.
alkaloids), primidone (metabolized to Treatment Overview inflated cuff). Can give antiemetics
phenobarbital) patient (emesis, activated charcoal) if no clinical ■ Positive-pressure ventilation
Mechanism of toxicosis: signs are seen. Supportive care—intravenous fluids
• Toxicosis occurs when animals accidentally to maintain blood pressure, thermoregulation, Drug Interactions
eat large amounts of prescription medication oxygen supplementation/assisted ventilation, • Drugs that can increase barbiturate
(e.g., phenobarbital), from an overdose or and enhanced elimination of barbiturates—is action: any CNS depressant, valproic acid,
accidental administration of injectable solu- implemented according to anticipated (ingested chloramphenicol
tion (e.g., pentobarbital, phenobarbital, dosage known to be large) or visible (marked • Decreased efficacy of oral anticoagulants,
euthanasia solution), or from eating flesh or clinical signs) severity of toxicosis. chloramphenicol, glucocorticoids, doxycy-
bone of an animal that had been euthanized cline, beta-blockers, quinidine, theophylline,
with a barbiturate. Acute General Treatment and metronidazole
• Barbiturates cause nonselective depression • Decontamination of patient:
of presynaptic and postsynaptic excitability ○ Emesis: useful within 2 hours with oral Possible Complications
by several mechanisms (GABA and glutamate exposure in asymptomatic dogs (3% • Aspiration pneumonia
receptors, sodium channels). hydrogen peroxide 2 mL/kg PO up to • Renal impairment secondary to hypotension
• Toxicosis is characterized by hyporeflexia, maximum of 45 mL/dose, repeat once if • Cardiorespiratory arrest
ataxia, hypothermia, hypotension, coma, no results within 15 minutes). Apomor-
slow shallow respirations, and death. phine may have additive CNS depressive Recommended Monitoring
effects. Oxygenation, blood pressure, body temperature,
DIAGNOSIS ○ Activated charcoal (1-2 g/kg PO once, mentation
with sorbitol or other cathartic); repeat-
Diagnostic Overview ing charcoal (half of the original dose; PROGNOSIS & OUTCOME
Barbiturate toxicosis is suspected from a omitting the cathartic) q 6-8h until
history of possible or confirmed exposure, improvement of depression helps decrease With coma, prognosis is guarded to
and suspicion is heightened by the presence severity and duration of signs. May be poor if intensive supportive care is not
of one of more overt signs (ataxia, depression, ingested by patient if conscious and stable pursued.
coma, hypothermia, hyporeflexia, and CV and or given by stomach tube in a recumbent
respiratory depression). In most instances, animal if the airway is protected. Monitor PEARLS & CONSIDERATIONS
this is sufficient to proceed to treatment and for hypernatremia and associated signs
monitoring. The diagnosis can be confirmed (tremor, ataxia, seizures). Comments
by identification of drug in bodily fluids or ○ Gastric lavage: consider if large toxic doses • Induction of emesis at home should be
tissues. have been ingested and emesis is not considered only if no clinical signs are
possible and the animal is not already present, if an observed ingestion took place,
Differential Diagnosis comatose. or if the pet was found with the open
• Toxicologic: alpha-2 agonists (e.g., amitraz, ○ Warm water enema: may help promote container.
detomidine, medetomidine, xylazine), benzo- gastrointestinal evacuation; administer 1-2 • Boiling/cooking or freezing of meat does
diazepines, ethanol or other alcohols, essential hours after administration of activated not destroy barbiturates. Barbiturate-con-
oils, ethylene glycol, isoxazole mushrooms, charcoal. taminated meat is a high-risk source of relay
ivermectin and other avermectins, marijuana, • Hemodialysis, charcoal hemoperfusion, or (secondary) toxicity for scavengers.
muscle relaxants (baclofen, methocarbamol), plasma exchange may be considered if • Acute signs of toxicosis (depending on the
opioids, phenothiazines, trazodone (tetracy- available. dose and the type of agent involved) can
clic antidepressant) • Intravenous lipid emulsion (p. 1127): last several days.
• Non-toxicologic disorders: hepatic encepha- intravenous administration of lipid emulsion • Repeated doses of activated charcoal are
lopathy, hypoglycemia, primary intracranial may decrease severity and duration of signs useful even when overdose occurs from
disorder (e.g., encephalitis, neoplasia), shock and may be considered in severe cases with barbiturate injection because plasma barbi-
(septic, hypovolemic), trauma coma and at risk for developing apnea. This turates diffuse into the acidic stomach
potentially can enhance elimination of environment. Be aware of possible hyper-
Initial Database lipophilic barbiturates; however, the efficacy natremia from multiple doses of activated
• CBC, serum chemistry profile varies significantly between cases. Risk of charcoal.
• Blood pressure: ± hypotension hyperlipidemia, pancreatitis, and hemolysis
• Heart rate and rhythm: ± bradycardia from therapy Prevention
• Acid-base status: monitor for acidosis • Supportive care: • Keep medications out of animal’s reach.
• Body temperature: ± hypothermia ○ Intravenous administration of isotonic • To prevent secondary acute poisoning,
crystalloid fluids (warmed if animal is animals euthanized with barbiturates should
Advanced or Confirmatory Testing hypothermic), rate titrated to support not be used for animal (or human)
Barbiturates can be analyzed antemortem blood pressure consumption.
in stomach contents/vomitus, urine, serum, ○ Thermoregulation: external warming, if • Proper disposal of euthanized carcasses
or plasma. Postmortem, barbiturates can hypothermic
be detected in liver, heart, or kidney. Some ○ If hypoventilating or apneic Client Education
over-the-counter illicit drug kits can detect ■ Supplemental oxygen • Control and monitor pet’s environment.
barbiturates in the urine even though they are ■ Cuffed endotracheal tube to protect • Do not feed barbiturate-contaminated meat/
not validated in animals (purchase at human airway and prevent aspiration (always euthanized animals to pets.

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