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Questions and Answers
Which receptor do alpha-2 adrenergic receptor agonists selectively bind to?
Where are most alpha-2 receptors located?
What can peripheral alpha-2 receptor inhibition affect?
What are the clinical effects of alpha-2 adrenergic receptor agonists?
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What is the mechanism of action of alpha-2 adrenergic receptor agonists?
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What can withdrawal from even short-term use of alpha-2 adrenergic receptor agonists trigger?
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Where do centrally-acting alpha-2 agonists spread throughout?
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Which drug is primarily excreted unchanged in the urine and has a terminal half-life of approximately 12-16 hours?
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Which drug is known for its selective alpha 2 receptor potency with a preference ratio of 1,600:1 for alpha 2 receptors over alpha 1 receptors?
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Which drug is commonly used in the ICU and OR as a sedative and analgesic due to its central sympatholytic effects?
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Which drug has dose-dependent reductions in heart rate and blood pressure and is clinically used for treating resistant hypertension, tremors associated with central stimulant medications, and opioid withdrawal?
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Which drug has a loading dose of 0.5-1 mcg/kg over 10 minutes and an infusion range of 0.2-0.7 mcg/kg/hr, with an onset of 5-10 minutes and an offset of 30-60 minutes?
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Which drug is known for its potent and highly selective action for alpha 2 receptors, with a preference ratio of 1,620:1, and has a higher affinity for alpha 2 receptors than clonidine?
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Which drug can lead to physiological dependence, resulting in withdrawal symptoms such as tachycardia, hypertension, and anxiety after just a few days of administration?
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Which drug has a relatively short terminal elimination half-life of 2 hours and is primarily administered intravenously as an infusion?
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Study Notes
Alpha-2 Adrenergic Receptor Agonists
- Alpha-2 adrenergic receptor agonists selectively bind to alpha-2 receptors.
- Most alpha-2 receptors are located in the pancreas, kidney, and adipose tissue.
Peripheral Effects
- Peripheral alpha-2 receptor inhibition can affect insulin secretion, sodium reabsorption, and lipolysis.
Clinical Effects
- Alpha-2 adrenergic receptor agonists can cause sedation, analgesia, and a decrease in sympathetic outflow, leading to decreased blood pressure and heart rate.
Mechanism of Action
- Alpha-2 adrenergic receptor agonists work by inhibiting the release of norepinephrine, which decreases sympathetic activity.
Withdrawal
- Withdrawal from even short-term use of alpha-2 adrenergic receptor agonists can trigger rebound hypertension, tachycardia, and anxiety.
Central Action
- Centrally-acting alpha-2 agonists spread throughout the brain, including the hypothalamus, amygdala, and brainstem.
Clonidine
- Clonidine is primarily excreted unchanged in the urine and has a terminal half-life of approximately 12-16 hours.
- It is known for its selective alpha-2 receptor potency with a preference ratio of 1,600:1 for alpha-2 receptors over alpha-1 receptors.
Dexmedetomidine
- Dexmedetomidine is commonly used in the ICU and OR as a sedative and analgesic due to its central sympatholytic effects.
- It has a loading dose of 0.5-1 mcg/kg over 10 minutes and an infusion range of 0.2-0.7 mcg/kg/hr, with an onset of 5-10 minutes and an offset of 30-60 minutes.
Guanfacine
- Guanfacine has dose-dependent reductions in heart rate and blood pressure and is clinically used for treating resistant hypertension, tremors associated with central stimulant medications, and opioid withdrawal.
Tizanidine
- Tizanidine is known for its potent and highly selective action for alpha-2 receptors, with a preference ratio of 1,620:1, and has a higher affinity for alpha-2 receptors than clonidine.
- It has a relatively short terminal elimination half-life of 2 hours and is primarily administered intravenously as an infusion.
Dependence and Withdrawal
- Alpha-2 adrenergic receptor agonists can lead to physiological dependence, resulting in withdrawal symptoms such as tachycardia, hypertension, and anxiety after just a few days of administration.
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Description
Test your knowledge of Alpha-2 adrenergic receptor agonists with this quiz. Explore their mechanism of action, receptor location, and impact on sympathetic outflow and blood pressure. See how well you understand their role in the central nervous system and potential effects on insulin.
