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Pharmacology Test 2 > Sedatives and Anesthetics Part 1 > Flashcards

Sedatives and Anesthetics Part 1 Flashcards

1
Q

Name the alpha 2 drugs?

A
  • Dexmedetomidine
  • Medetomidine
  • Xylazine
  • Yohimbine
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2
Q

Alpha 2 effects on nociception?

A

Perception, Modulation, and Transmission

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3
Q

Describe some general info on alpha 2 agonist receptors?

A
  • Brain & spinal cord
  • Vascular endothelium
  • Endocrine organs

↓ Insulin
↓ Renin
↓ NE release
↓ Pancreatic secretion

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4
Q

Which alpha 2 agonist do we use for Dogs, cats, exotics?

A

Dexmedetomadine

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5
Q

Which alpha 2 agonist do we use for horses, deer, and elk?

A

Xylazine

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6
Q

Name the alpha 2 antagonists and which alpha 2 drug they antagonize?

A

Atipamezole (antagonizes dexmedetomidine)

Yohimbine (antagonizes xylazine)

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7
Q

Name the alpha 2 agonists?

A

Dexmedetomidine

Xylazine

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8
Q

Name the mechanism of action for sedative and analgesic effects?

A

Competitive agonism of the alpha 2 receptors (located in the brain/spinal cord)

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9
Q

Name the mechanism of action for ANS effects?

A

Competitive agonism of α1-receptors (vasculature–> vasoconstriction)

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10
Q

Varying degrees of α1-adrenergic receptor agonism can cause these two reactions?

A

Paradoxical CNS excitement

Peripheral vasoconstriction

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11
Q

Out of the alpha 2 drugs who is most selective and who is least selective?

A
  1. Dexmedetomidine

2. Xylazine

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12
Q

Most common routes of adm.?

A

IV or IM are the most common routes of administration

  • Also can be given as a CRI and epidurally
  • Oral transmucosal administration
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13
Q

Do they cross the BBB?

A

yes! Widely distributed to all tissues

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14
Q

Describe the onset and duration of action of Xylazine? What about Medetomidine and detomidine?

A

Xylazine onset of action is rapid within min IV

-15 minutes IM)

Duration of sedation ~1–2 hr

Analgesia ~15 to 30 min recovery up to 4 hr

Medetomidine & detomidine slightly longer

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15
Q

Describe the metabolism and elimination?

A

Rapid hepatic metabolism (short T1/2) followed by urinary excretion

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16
Q

Alpha 2 agonism main effects in the CNS?

A
  • Sedation (alpha 2 receptors in the brain, CNS excitation in large doses)
  • Pain Modulation and Analgesia (α2 receptors in brain and spinal cord)
  • Muscle relaxation (spinal cord interneurons)
  • Emesis (Stimulation of α2 receptors in the emetic center & CRTZ)
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17
Q

What is the drug of choice for emetic effects in cats?

A

Xylazine

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18
Q

What is unique about their cardiovascular effect? Name the phases

A

It’s a BIPHASIC Effect

Phase I – Peripheral Phase

Phase II – Central Phase

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19
Q

Describe the Phase 1 - Peripheral Phase

A
  • Mediated by α1 receptors
  • Peripheral vasoconstriction (↑ systemic vascular resistance (SVR) causes transient ↑ in mean arterial blood pressure (MAP) causes reflex bradycardia
  • HR drops to maintain constant cerebral perfusion pressure (CPP)

if anticholinergics are given at this time they will force the heart to beat faster against the high SVR

Contraindicated - will cause ↑ myocardial workload and oxygen demand, can exacerbate pre-existing heart disease, can cause or worsen arrhythmias

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20
Q

Describe Phase II – Central Phase?

A

Mediated by α2 receptors

Decreased sympathetic tone (↓ NE)  heart rate stays low

↓ Dronotropy (rate of conduction) & ↓ SA node firing

Peripheral vasodilation due to central effects on vasomotor center + low catecholamine levels

Often results in hypotension and bradycardia

Cardiac output can decrease 30-50% with α2 - agonists

21
Q

Summary of the Cardiovascular effects?

A

↓ Cardiac output due to ↑ BP and reflex bradycardia

Bi-phasic effect due to initial vasoconstriction and hypertension followed by vasodilation and hypotension due to CNS depression

Bradyarrhythmias (incomplete AV block (2◦ most common)

Myocardial depression

Sensitizes myocardium to catecholamines tachyarrhythmias also possible

All effects are reversible

22
Q

Alpha 2 agonist other effects respiratory effects?

A

Centrally mediated decrease in respiratory rate

Mild respiratory depression compared to other drugs

Cats may be more sensitive

23
Q

Sheep and goats and horses

A

Increased respiratory rate, airway pressures (resistance) and; pulmonary elastance

Activation of pulmonary macrophages

Leading to ↑ CO2, hypoxemia, pulmonary edema

Also seen in unborn, near term lambs (these drugs cross the placenta!)

24
Q

What do they do to the GI?

A

↓ GI motility (esp. large intestine)

↓ acid secretion

25
Q

What are their effects on the renal system?

A

Diuresis by reducing ADH release and function

26
Q

WHat are their effects on the Uterus?

A

Simulate myometrial contractions

May cause abortion (ruminants)

27
Q

Hyperglycemic effects?

A

↓ Release of insulin leading to transient hyperglycemia

Typically not clinically significant

Should not ↑ [glucose] over renal threshold (~180mg/dL in dogs and horses)

More pronounced in ruminants and horses

28
Q

Hypothermia effects?

A

Reduction in vasoconstrictive and shivering thresholds

29
Q

Clinical uses?

A
  • Sedation (Procedural sedation) (laceration/wound repair, bandage changes, etc) Recovery from anesthesia (anxiolytic) Mechanical ventilation
  • Pre-anesthetic: MAC-sparing effect, Muscle relaxation (useful with ketamine)
  • Analgesia: Combined with other drugs – e.g. neuroleptanalgesia CRI (fentanyl, diazepam, etc), epidural anesthesia (bupivacaine + morphine) Colic in horses, Goats are most sensitive to sedative and analgesic effects, swine are least sensitive

Emetic: cats > dogs

Behavioral: Chemical restraint for out-patient procedures/examination. Treatment of noise/storm phobias (Sileo®) Chemical ejaculation in stallions

30
Q

Precautions?

A

Cardiovascular disease/instability

Emesis

Liver disease

Kidney disease

Seizure disorder

31
Q

Do not use alpha 2 agonists with these drugs?

A

epinephrine and atropine

32
Q

Contraindicated in?

A

critically ill and patients with shock syndrome

33
Q

Name the 2 drugs that are competitive alpha 2 antagonists?

A

Atipamezole

Yohimbine

34
Q

Details about Atipamezole?

A

Approved in dogs

Reverses sedation and analgesic effects of
dexmedetomidine and medetomidine

Most selective for alpha 2 receptors

35
Q

Details about Yohimbine?

A

Approved in dogs, deer, and elk

Reverses sedation and analgesic effects of xylazine

36
Q

Describe the best route of administration for atipamezole and yohimbine?

A

Recommend IM administration due to greater possibility of side effects if given IV, including CV collapse

Can be given IV in emergency

37
Q

Describe the selectivity of atipamezole and yohimbine?

A

Atipamezole (8526:1)

Yohimbine (40:1)

38
Q

Main effects of alpha 2 antagonists in the CNS?

A

Antagonizes α2 receptor agonist to reverse sedative effects

Analgesia will also be reversed!!

Administration of α2 antagonist alone will cause CNS excitement

Adverse effect: CNS excitement/stimulation

39
Q

Main effects of alpha 2 antagonists in the Cardiovascular system?

A

Can reverse cardiovascular effects of α2 agonist

Administration without α2 agonist will cause tachycardia and hypotension

Adverse effect: tachycardia and hypotension due to vasodilation

40
Q

Main effects of alpha 2 antagonists in the Respiratory ?

A

Antagonizes respiratory depression of α2 agonist

GI side effects: salivation, diarrhea

41
Q

Alpha 2 antagonists therapeutic used to reverse?

A

Used to reverse alpha 2 agonist toxicity

Specific antidote

Mitoban toxicity

Amitraz tick collars

42
Q

Describe the effectiveness of sedation for alpha 2 agonists?

A

Very good sedation

43
Q

Describe the effectiveness of muscle relaxation for alpha 2 agonists?

A

Good muscle relaxation

44
Q

Describe the effectiveness of analgesia for alpha 2 agonists?

A

Good/moderate but short lived analgesia

45
Q

Describe the effectiveness of Cardiovascular/Respiratory effects for alpha 2 agonist?

A

Biphasic cardiovascular effects

Mild respiratory depression (more sig. issues in sheep)

46
Q

WHich drug has the most selectivity for the alpha 2 receptor?

A

Dexmedetomidine

47
Q

Alpha 2 agonist often cause _______ and the most common is called?

A

bradycardia (most common is atrioventricular block 2* degree)

48
Q

What is significant about yohimbine?

A

specific reversal agent for xylazine

Pharmacology Test 2 (7 decks)

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