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RUSVM Pharmacology I > Alpha-2 agonists > Flashcards

Alpha-2 agonists Flashcards

1
Q

A2 adrenergic drugs - List of agonists

A

Xylazine - Detomidine - Dexmedetomidine - Romifidine - Clinidine

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2
Q

A2 adrenergic drugs - List of antagonists (reversals)

A

Yohimbe - Atipamezole (most A2 selective) - Tolazoline (least a2 selective)

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3
Q

Xylazine - species used, sensitivities

A

Best for horses, deer, elk - Sensitivity: Cattle > camelids > small ruminants > cat/dog/horse > Swine > Rodents (not used in dog/cats much)

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4
Q

Detomidine

A

Horses (sublingual gel option) & Cattle

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5
Q

Dexmedetomidine / Medetomidine

A

Dogs, cats, exotics

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6
Q

Romifidine

A

Horses (maybe less ataxia than with xylazine)

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7
Q

Clonidine

A

Humans for blood pressure

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8
Q

A2 agonists mechanism of action

A

G-protein coupled receptor activation - Reduce cAMP activity - Increase K+ efflux - Hyperpolarization - Decreased NE release

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9
Q

A2 receptor location

A

Throughout body: Pre & Postsynaptic (neurons & tissues) - Extrasynaptically in vasculature, platelets

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10
Q

A2 agonist effect on A1 receptors

A

Varying degrees of effects - Paradoxical excitement - A2:A1 selectivity is known for most drugs

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11
Q

A2 agonist & imidazoline ring

A

Most contain imidazoline ring (I2 receptors)

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12
Q

Different I receptors

A

I1 = blood pressure, I2= pain modulation, I3=insulin (no I2 activity with xylazine)

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13
Q

a2:a1 Selectivities : In order most selective to least

A

Dexmedetomidine > Romifidine > Detomidine > Xylazine

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14
Q

A2 agonist effects overview

A

Sedative - some muscle relaxation - mild analgesia - Biphasic CV effects - Mild respiratory depression (especially sheep) - Emetic in cats

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15
Q

A2 agonist sedation receptor location

A

a2 receptors in brain

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16
Q

A2 agonist analgesia receptor location

A

a2 receptors in brain & spinal cord

17
Q

A2 agonist muscle relaxation receptor location

A

Spinal cord interneurons

18
Q

A2 agonist emesis receptor location

A

especially in cats - stimulation of a2 receptors in emetic center & CRTZ

19
Q

A2 agonist CV effects on initial peripheral phase

A

Initial peripheral phase : peripheral vasoconstriction - reflex increase in parasympathetic tone (vagal) - Bradycardia - AV block may be seen

20
Q

A2 agonist Anticholinergics

A

Atropine / Glycopyrrolate -Not generally used - Measure blood pressure - Can lead to hypertension & dysrhythmias - increase workload & oxygen demand of heart

21
Q

A2 agonist CV effects on subsequent/central phase

A

Cardiac output can decrease 30-50% - Decreased sympathetic flow (NE) heart rate stays low - peripheral vasodilation (central effects on vasomotor center) low catecholamine levels - Hypotension & Bradycardia -

22
Q

A2 agonist respiratory effects

A

Centrally mediated decrease in resp rate (but mild)- Sheep and goats anomaly

23
Q

Sheep and goat respiratory effect of a2 agonist

A

Increased respiratory rate, airway pressures & elastase - activation of pulmonary macrophages - Increases in CO2, hypoxemia, pulmonary edema - Unboarn, near term lambs (drugs cross placenta!)

24
Q

A2 agonist typical administration

A

IV or IM (avoid intra-arterial!)

25
Q

What happens if you inject an A2 agonist intra-arterially?

A

Seizures may occur (especially intracarotid injection in horse)

26
Q

Alternative A2 administration

A

SQ (but immediate vasoconstriction, low distribution) - CRI/Epidurally - Some transmucosal (detomidine gel for horse)

27
Q

A2 agonist distribution

A

Wide - Cross BBB/CNS and Placenta

28
Q

A2 agonist metabolism & excretion

A

Metab in liver, excreted in urine

29
Q

Effects of A2 agonist @ GI

A

Reduce GI motility - Reduced acid secretion

30
Q

Effects of A2 agonist @ Renal

A

Decreased ADH –> diuresis

31
Q

Effects of A2 agonist @ Uterus

A

Stimulate contractions –> abortion in ruminants

32
Q

Hyperglycemic effects of A2 agonist

A

Minor. Decreased insulin release –> increased blood sugar

33
Q

Hypothermic Effects of A2 agonist

A

Sparks shivering response in response to body temp - Increased by a’terations in vascular

34
Q

A2 agonist cautions

A

Avoid if cardiovascular/liver/kidney dz or pregnancy present - Less effective in excitable patients - Seizures with intra-arterial injections - Caution with Epi or atropine - Caution with sheep (pulmonary changes) & deer (delayed HS)

35
Q

Amitraz

A

a2 agonist - Sign of toxicity=sedation - Reverse with amitraz (Mitaban)

36
Q

A2 antagonist adverse effects

A

CNS excitement - Hypotension/Bradycardia - Salivation - Diarrhea

RUSVM Pharmacology I (19 decks)

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