Difference between revisions of "Alpha-2 Agonists"

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Other systems affected by alpha-2 agonists include:
 
Other systems affected by alpha-2 agonists include:
* Cardiovascular System
+
* <u>Cardiovascular System</u>
 
** Post synaptic alpha-2 effects and non-selective action on alpha-1 receptors cause vasoconstriction, hypertension and reflex bradycardia.
 
** Post synaptic alpha-2 effects and non-selective action on alpha-1 receptors cause vasoconstriction, hypertension and reflex bradycardia.
 
** Pre-synaptic inhibition of noradrenaline release gives a reduced sympathetic outflow. This dexreases heart rate and offsets vasoconstriction.  
 
** Pre-synaptic inhibition of noradrenaline release gives a reduced sympathetic outflow. This dexreases heart rate and offsets vasoconstriction.  
* Respiratory System
+
* <u>Respiratory System</u>
 
** The drugs cause mild depression of the respiratory systsem.
 
** The drugs cause mild depression of the respiratory systsem.
 
** The response to hypercapnoea is reduced.
 
** The response to hypercapnoea is reduced.
* Gastrointestinal Tract
+
* <u>Gastrointestinal Tract</u>
 
** Alpha-2 agonists cause extreme vomitting in dogs and cats. [[#Xylazine|Xylazine]] is the worst culprit for this.
 
** Alpha-2 agonists cause extreme vomitting in dogs and cats. [[#Xylazine|Xylazine]] is the worst culprit for this.
 
** Huge reductions in gut motility occur following drug administration, as well as decreased salivation and secretion.
 
** Huge reductions in gut motility occur following drug administration, as well as decreased salivation and secretion.
* Endocrine System
+
* <u>Endocrine System</u>
 
** Alpha-2 agonists inhibit ADH, leading to diuresis.
 
** Alpha-2 agonists inhibit ADH, leading to diuresis.
 
** Insulin is also inhibited, causing hyperglycaemia which leads to osmotic diuresis. This, along with the aboce, causes excessive urination.
 
** Insulin is also inhibited, causing hyperglycaemia which leads to osmotic diuresis. This, along with the aboce, causes excessive urination.
 
** Growth hormone release is triggered by alhpa-2 agonists.
 
** Growth hormone release is triggered by alhpa-2 agonists.
* Urogenital Tract
+
* <u>Urogenital Tract</u>
 
** Uterine contraction occurs with alpha-2 agonist administration.
 
** Uterine contraction occurs with alpha-2 agonist administration.
  

Revision as of 15:53, 3 March 2009

Alpha-2 agonists have sedative, anxiolytic and analgesic effects.

Mechanism of Action

Alpha-2 agonists act on alpha-2 adrenoreceptors, and mimic the effects of the actual ligand binding. The sedative and anxiolytic effects arise from this process leading to pre-synaptic inhibition of noradrenaline release.

Actions

Alpha-2 agonists have a wide range of actions, due to the presence of alpha-2 receptors throughout the body. The actions most useful pharmacologically are sedation, anxiolysis and analgesia. The drugs also have a huge anaesthetic sparing effect, reducing MAC by 50-95%. They also give muscle relaxtion.

Other systems affected by alpha-2 agonists include:

  • Cardiovascular System
    • Post synaptic alpha-2 effects and non-selective action on alpha-1 receptors cause vasoconstriction, hypertension and reflex bradycardia.
    • Pre-synaptic inhibition of noradrenaline release gives a reduced sympathetic outflow. This dexreases heart rate and offsets vasoconstriction.
  • Respiratory System
    • The drugs cause mild depression of the respiratory systsem.
    • The response to hypercapnoea is reduced.
  • Gastrointestinal Tract
    • Alpha-2 agonists cause extreme vomitting in dogs and cats. Xylazine is the worst culprit for this.
    • Huge reductions in gut motility occur following drug administration, as well as decreased salivation and secretion.
  • Endocrine System
    • Alpha-2 agonists inhibit ADH, leading to diuresis.
    • Insulin is also inhibited, causing hyperglycaemia which leads to osmotic diuresis. This, along with the aboce, causes excessive urination.
    • Growth hormone release is triggered by alhpa-2 agonists.
  • Urogenital Tract
    • Uterine contraction occurs with alpha-2 agonist administration.

Side Effects and Contraindications

Drugs in this Group

Xylazine

Detomidine

Medetomidine

Romifidine