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TOXICOLOGY > 16 – CNS Depressants > Flashcards

16 – CNS Depressants Flashcards

1
Q

Opioids

A
  • Alkaloids from poppy plant
  • Agonists, partial agonists, antagonists
    o Most worried about the pure mu-opioid agonists
  • First line therapy for pain management in vet med
  • Minimum lethal dose varies by drug
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2
Q

Opioids: exposure scenarios

A
  • Calculation errors
  • Narcotics detection dogs
  • Ingestion of fentanyl patches
  • Consumption of human drugs
  • Animal cruelty
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3
Q

Opioids: mechanism

A
  • Interaction with opioid receptors in spinal cord, limbic system and brain
    o Mu receptors: analgesia, sedation, respiratory depression, bradycardia
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4
Q

Opioids: target organs

A
  • CNS
  • CV
  • Respiratory
  • GI
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5
Q

Opioids: relevant toxicokinetic

A
  • Some are more lipophilic: heroin, fentanyl, buprenorphine
  • Some metabolized via glucuronidation
  • Renal excretion
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6
Q

Opioids: onset

A
  • Within minutes of injection
  • Within 30mins of ingestion
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7
Q

Opioids: clinical features

A
  • Vomiting, constipation
  • Depression/sedation (dogs), excitation (cats)
  • Bradycardia, sinus arrythmias
  • Miosis (dogs), mydriasis (cats)
  • Hypothermia (dogs), hyperthermia (cats)
  • *severe: RESPIRATORY DEPRESSION, cyanosis, constipation, seizures, coma
    o Cause of death: hypoxia, respiratory failure
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8
Q

Opioids: management

A
  • Decontamination: if injected=no, but if ingested=maybe
  • *Antidote: naloxone (pure mu-opioid antagonist)
    o What if no naloxone? Butorphanol
  • Monitor for CNS and respiratory depression
  • Blood gas: ventilation, pulse oximeter
  • CV monitoring: ECG, BP
  • Thermoregulation
  • Serotonin syndrome: cyproheptadine
  • *make sure you are wearing proper PPE
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9
Q

Opioids: diagnosis

A
  • Working dog ADR after completing a search
  • Overdose in clinic
  • Access to owner drugs
    o urine drug test
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10
Q

Opioids: prognosis

A
  • Good with rapid recognition of toxicity, naloxone and appropriate supportive care
  • Guarded with delayed intervention or hypoxemia
  • Positive response to therapy=good prognostic indicator
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11
Q

Benzodiazepines

A
  • Diazepam, midazolam (pam or lam drugs)
  • First line treatment for seizure control
    o Sedatives, anxiolytics, muscle relaxants
    o VM: treat anxiety, phobias, behavioural disorders
  • Toxicity: generally low due to wide margin of safety
    o Exception: oral diazepam in CATS
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12
Q

Benzodiazepines: exposure scenarios

A
  • Ingestion of huma prescription medication
  • Overdose in clinical setting
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13
Q

Benzodiazepines: mechanism

A
  • *Enhance binding of GABA to receptors in CNS = CNS depression
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14
Q

Benzodiazepines: onset

A
  • 30-60mins after ingestion/exposure
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15
Q

Benzodiazepines: clinical features

A
  • CNS depression
  • Bradycardia, hypotension
  • Vomiting
  • Tremors, hypothermia, weakness
  • Paradoxical excitation and hyperactivity possible
  • Severe overdose, respiratory depression, coma, seizures
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16
Q

Benzodiazepines: CATS clinical features

A
  • Fulminant liver failure with repeated oral diazepam
    o Exact mechanism is unknown (related to glucuronidation)
    o Anorexia and lethargy
    o Clin path: increased liver enzyme, indicators of liver failure
  • Management: acute liver failure=hepatoprotectants, lactulose, vitamin K, metronidazole
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17
Q

Benzodiazepines: management

A
  • Decontamination if oral ingestion
  • **antidote: FLUMAZENIL
    o Short half life (may need to treat again)
  • Supportive care measures: thermoregulation, IVFT, maybe IVLE
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18
Q

Benzodiazepines: diagnosis

A
  • History of ingestion
  • Overdose in clinical setting
  • Analysis in blood and urine
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19
Q

Benzodiazepines: prognosis

A
  • Good with antidote and adequate supportive care
    o Oral diazepam in cats=guarded to poor
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20
Q

Barbiturates

A
  • Phenobarbital (long acting) vs. pentobarbital (short acting)
    o Pheno: epilepsy in dogs
  • Therapeutic use: sedatives, anticonvulsants
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21
Q

Barbiturates: exposure scenarios

A
  • Accidental ingestion of medication
  • Iatrogenic overdose
  • Accidental administration of euthanasia solution
  • Ingestion of tissue of euthanized animals
22
Q

Barbiturates: mechanism

A
  • Activation of GABA receptors
  • Inhibition of glutamine receptors
  • Inhibition of NE and ACh release
  • *CNS depression
    o Suppression of hypoxic drive and chemoreceptor drive
23
Q

Barbiturates: onset

A
  • Within minutes to several hours post-exposure
24
Q

Barbiturates: clinical features

A
  • Weakness
  • CNS depression
  • Hypothermia
  • Hypoventilation
  • CV: tachycardia or bradycardia
    o *high doses: myocardial depression
    o *death due to respiratory depression
  • Hepatoxicosis in patients on long-term PB treatment for idiopathic epilepsy
    o **HEPATIC CIRRHOSIS
25
Barbiturates: management
- No specific antidote - Recent ingestion: emesis with A/C - Respiratory monitoring and support - CV monitoring and support - IVFT - IVLE - Long acting: prolonged treatment required (phenobarbital)
26
Barbiturates: diagnosis
- Accidental administration of euthanasia solution - Ingestion of euthanized animal - Overdose of prescribed medication - *human OTC urine drug test, analysis in stomach contents and blood
27
Barbiturates: prognosis
- Good with early management
28
Veterinarians and pentobarbital
- Responsibility to INFORM clients about proper disposal of animals euthanized with pentobarbital - MUST be documented in medical record or on a SIGNED CONSENT FORM - A vet may be liable if the client WAS NOT informed of the risks
29
Local anesthetics
- Lidocaine, bupivacaine - Therapeutic use: local anestic, antiarrhythmic, prokinetic - Human OTC and Rx products
30
Local anesthetics: exposure scenarios
- Clinical setting: accidental IV injection, overdose during local block - Consumption of topical ointments
31
Local anesthetics: target organs
- CNS - CV - *lidocaine: more neurotoxic - *bupivacaine: more cardiotoxic
32
Local anesthetics: mechanism
- Block voltage gated Na channels in nerves and myocardium
33
Local anesthetics: clinical features
- *see CNS first o Sedation, weak o Muscle twitching to seizures - CV o Bradycardia, decreased contractility o Can progress to cardiac arrest - Bupivacaine: more cardiotoxic (CNS and CV signs occur concurrently)
34
Local anesthetics: management
- *Antidote: IVLE - Supportive care
35
Local anesthetics: prognosis
- Dictated by severity of clinical signs and response to medical management - Good with lidocaine - Guarded with bupivacaine
36
Marijuana
- Cannabis - Lots of cannabinoids - Most exposures result from owner’s use (ex. edibles, vapes, smoke inhalation, human feces) - Therapeutic uses of marijuana for animals is an active area of research o No vet products currently approved for use - *very common poisoning o Decriminalization, accessibility o Mostly in dogs
37
Marijuana: mechanism
- Binds to CB1 and CB2 receptors in CNS - Relevant toxicosis: lipophilic, different hepatic metabolism between dogs and humans
38
Marijuana: toxicity
- NOT acutely toxic - Behaviour effects occur at 1000x less than minimum lethal oral dose
39
Marijuana: onset
- Within 30mins of ingestion
40
Marijuana: clinical features
Marijuana: clinical features - Vomiting possible - Tachycardia or bradycardia - Dullness/depression - **ataxia - Weakness - *hyperesthesia - *mydriasis and urinary incontinence
41
Marijuana: management
- No specific antidote - Decontamination if not contraindicated - Symptomatic and supportive care o Monitor HR and temperature o Low stimulation environment o Antiemetics - Severe: atropine, intubation and mechanical ventilation, IVLE
42
Marijuana: diagnosis
- History of exposure and clinical signs - *human OTC urine test=FALSE NEGATIVES
43
Marijuana: prognosis
- Good to excellent
44
What is the treatment protocol for marijuana intoxication?
- Emesis induction: apomorphine (within 2 hrs of ingestion) - Activated charcoal - IVFT if vomiting and for temperature regulation - Monitor heart rate, temperature, respiratory rate - Antiemetics for persistent vomiting - Severely poisoned animals: considered IVLE
45
Xylazine
- Alpha-2 agonist (large animal for sedation and pain management) - *emerging public health issue: ADULTERANT IN STREET DRUGS
46
Xylazine: exposure scenarios
- Administration of ‘wrong’ xylazine - Miscalculation - Exposure to illicit drugs laced with xylazine (working canines)
47
Xylazine: mechanism
- Alpha-2 adrenergic receptor agonist
48
Xylazine: target organs
- CNS, CV o Therapeutic: sedation, muscle relaxation, analgesia o Overdose: profound sedation
49
Xylazine: clinical features
- Similar to opioid overdose and LACK OF RESPONSE TO NALOXONE o Bradycardia, vasodilation, hypotension o Progressive CNS depression, can proceed to respiratory depression o Muscle twitching, miosis, hypothermia o Intracarotid administration=convulsions
50
Xylazine: management
- *antidote: ATIPAMEZOLE (also yohimbine) o IM better, but intra-nasal did work (50% bioavailability) - Supportive care: BP support, oxygen, ventilation support o Frequent monitoring of CV and respiratory systems - Decontamination if not contraindicated

TOXICOLOGY (20 decks)

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