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49 Cards in this Set
- Front
- Back
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What is the only alpha receptor antagonist that is not competitive?
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Phenoxybenzamine (PBZ)
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What receptor mediates the clinical response of alpha antagonists?
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A1
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What is the effect of A2 on the vagal nerve?
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increases vagal tone and parasympathetic outflow
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What is the effect of A2 receptor activation on platelet aggregation?
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increases
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What is the effect of A2 on the nerve terminal?
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Repolarization to decrease neurotransmitter release
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What is the effect of A2 on metabolic regulation of insulin and lipolysis?
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Causes a decrease in lipolysis and insulin release.
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What is the effect of an A1-blocker on arterioles and veins?
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Drives BP down. Much more significantly when upright rather than supine, due to the reflex action of the baroreceptors.
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What is the expected baroreflex after an A1 blocker has been administered?
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Increased rate and CO, can be dramatic if A2 is also blocked, causing B1 response.
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Will A2 antagonists increase or decrease NE release in the periphery? Why?
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Will increase NE due to the removal of feedback inhibition system.
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What is the CNS effect of an A2 antagonist?
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Will increase NE release causing A1 and B1 activation, results in increased BP and pulse rate.
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What is the target for phenoxybenzamine?
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Nonselective alpha blocker
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WHy is phenoxybenzamine different from other antagonists?
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Irreversably binds the receptor. Restoration of function requires the synthesis of new receptors
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What are the major effects of phenoxybenzamine?
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1. progressive decrease in peripheral resistance
2. Tachycardia with increased CO |
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What is the effect of epinephrine if phenoxybenzamine is on board?
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Dangerous hypotension due to unopposed B2 activation
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Explain by the effects of phenoxybenzamine are so much more dramatic when standing.
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Baroreflex tries to maintain blood pressure when moving from a supine position to a standing position, but because A1 receptors are blocked, pressure cannot be regulated.
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What is the effect of high dose phenoxybenzamine?
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irreversible inhibition of serotonin, histamine, and ACh
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What is the half-life and duration of impact for phenoxybenzamine?
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half-life is 24 hours, but the impact of action is much longer. Receptors have to be re-synthesized.
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What are the therapeutic uses for phenoxybenzamine?
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Used to treat pheochromocytoma and BPH.
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Who will receive long-term phenoxybenzamine therapy?
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non-operable pheochromocytoma patients
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What are the adverse effects associated with phenoxybenzamine?
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Hypotension
Congestion Miosis Sexual dysfunction |
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What is the molecular target for phentolamine?
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Nonselective alpha blocker
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What are the GI effects of phentolamine?
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Stimulates GI smooth muscle and enhances gastric acid secretion
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What are the therapeutic uses for phentolamine?
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Pheochromocytoma
Bowel obstruction Raynauds Limit dental necrosis following alpha agonist use Clonidine withdrawl Following tyrosine-rich food with MAO-I Impaired erection |
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What nonselective alpha blocker can exacerbate peptic ulcers?
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Phentolamine, due to GI action and increased gastric acid secretion
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What is the molecular target of prazosin?
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Selective A1 with 1000x greater affinity for A1 than A2.
Inhibitor of phophodiesterases |
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How does prazosin effect pulse rate?
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Does not,
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What are prazosin effects on lipids?
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decrease LDL and increase in HDL, decrease in triglycerides
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Why do some selective A1 antagonist work for patients with BPH?
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increases apoptosis of prosthatic smooth muscle
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How is prazosin administered? What is the bioavailability and half life?
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Orally
50-70% bioavail 2-3 hour half life due to extensive metabolism by the liver. |
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What are the therapeutic uses for prazosin?
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HTN
CHF BPH Possibly use for hypolipid effects |
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What is unique about the first dose of prazosin?
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postural hypotension and syncope
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What is the clinical use for tamsulosin?
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BPH, with little effect on BP.
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What is the molecular target for tamsulosin?
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Selective A1 blocker with A1a-d affinity.
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What is the side effect associated with tamsulosin?
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abnormal ejaculation
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What is the molecular target for Yohimbine?
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Selective alpha 2 blocker (similar to reserpine)
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What are the effects of yohimbine use?
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increased BP
increased CO and pulse rate Increased motor activity and tremors |
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What was yohimbine historically used to treat?
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ED
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What is the short term effect of beta blocker use?
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Decrease in CO and peripheral resistance
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What is the long term effect of beta blocker use?
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Peripheral resistance returns back to normal levels, with B1 subclass of antagonist CO can be maintained with a decrease in peripheral resistance.
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What is the effect of beta blockers on chronotropy and dromotropy of the heart?
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Decreases pulse rate and slows conduction through the SA and AV nodes as well as the purkinje fibers. (decrease in the slope of phase 4 depolarization).
Causes an increase in the refractory period of the AV node |
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What property of beta blockers allow them to stabilize arrhythmias?
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local anesthetic effects: block voltage-dependent Na channels
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What is the mechanism that leads to a decrease in blood pressure with longterm beta blocker use?
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1. decrease in CO
2. decrease of renin from the kidney (B1) |
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Why are beta blocker good as antianginals?
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improve cardiac reserve be decreasing CO and O2 consumption.
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What can happen if a COPD patient is placed on a beta blocker?
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If the compound has B2 activity, it can cause dangerous constriction of the bronchials.
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How is insulin sensitivity effected by beta blockers?
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Decreased... bad for diabetics
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What is the effect of nonselective beta blockers on lipid metabolism? What is the effect of B1 blockers?
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Decrease in HDL, increase in LDL and triglyceride levels...General decrease in hormone-mediated lipase activity and release of FFA from adipose.
B1 produce opposite results. |
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What are some side effects associated with beta blocker usage?
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Tiredness, dizziness, vivid dreams, insomnia, hallucinations, depression
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What drugs can be used to treat an overdose on beta blockers?
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Isoproterenol
An alpha agonist Atropine for bradycardia |
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What will the EKG show if a patient overdoses on a beta-blocker?
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Increased PR interval
Wide QRS |
