Alpha Blockers Flashcards
What do alpha receptors do?
receptors in the vasculature that activate smooth muscle, thereby producing vasoconstriction both in skeletal muscle and in skin and splanchnic vessels.
What are some alpha blockers that have a much higher specificity for a1 than a2?
-Doxazosin-Terazosin-Prazosin
What are some alpha blockers that have relatively equal specificity for a1 and a2?
-Phenoxybenzamine (slightly more from a1)-Phentolamine (equal)
What is yohimbine?
an alpha-2 antagonist used in treatment of erectile dysfunction
What are the types of alpha-1 receptors?
a, b, and d
What are alpha-1 receptors involved in?
smooth muscle contraction
Where are the subtypes of alpha-1 receptors located in the body?
b and d- vasculaturea- prostate mostly
Blockade of alpha-1a receptors in the bladder neck and prostate can do what?
improve urine flow rate and reduce symptoms of benign prostatic hypertrophy (BPH)
What is Alfuzosin?
more specific drug for alpha-1a receptors than other alpha-1 antagonists used for BPH
Where are alpha-1 and alpha-2 receptors located in relation to muscular junctions?
alpha-1 receptor on the post-synapticmembrane where it mediates downstream events, and the alpha-2 receptor on thepresynaptic terminal, where it functions as an auto-receptor to terminate furtherrelease of endogenous NE
What do alpha-1 receptors do?
activation of the receptor decreases production go cAMP leading to an inhibition of further release of norepinephrine from the neuron
What do alpha-2 receptors do?
activation of the receptor increases production go DAG and IP3, leading to an increase of intracellular calcium
Side effects of alpa-2 stimulation?
-bradycardia and hypotension (due to stimulation of vagal activity.)-sedation-analgesia-reduced anesthetic requirements
What does block of alpha-1 receptors result in?
leads to hypotension, by preventing NE-stimulatedsmooth muscle contraction in the vasculature.
Norepinephrine is an agonist for which receptors?
a1, a2, B1
Epinephrine is an agonist for which receptors?
a1, a2, B1, B2
Isoproterenol is an agonist for which receptors?
B1, B2
What does Isoproterenol do to BP?
decreases via beta receptor stimulation
What do Norepinephrine and Epinephrine do to BP?
increases via primarily alpha receptor stimulation
What would pre-treatment someone with an a-blocker and giving epi result in?
the a-blockers would block the alpha receptors so the major effect would be a decrease in BP even though if given alone the epinephrine would raise BP this is called epinephrine reversal
How would the a-blocker/epi combo affect CV?
- increase in HR and renal blood flow - `decrease in totalperipheral resistance (TPR), BP and effective refractory period (ERP) in the heart
What would pre-treatment someone with a nonspecific b-blocker and giving epi result in?
Blocking the b-receptors would leave only a receptors and that would manifest in a spike in BP and there would be no CV effects upon the heart
What are the side effects of alpha-blockers?
-first dose orthostatic hypotension (most common in prazosin)-sinus tach (angina, palpitations)-syncope-vertigo
T or F. Non-specific alpha-blockers like phentolamine are more likely than the alpha- 1 selective agents to produce tachycardia.
T, by virtue of the action augmenting the release of endogenous NE
