Podcast
Questions and Answers
What is the phenomenon called when prolonged exposure to catecholamines reduces receptor responsiveness?
What is the phenomenon called when prolonged exposure to catecholamines reduces receptor responsiveness?
Which mechanism is NOT suggested to explain receptor desensitization?
Which mechanism is NOT suggested to explain receptor desensitization?
Which of the following compounds is classified as a catecholamine?
Which of the following compounds is classified as a catecholamine?
What is the effect of catecholamines on the central nervous system (CNS)?
What is the effect of catecholamines on the central nervous system (CNS)?
Signup and view all the answers
What structural feature significantly influences the ability of adrenergic drugs to target α and β receptors?
What structural feature significantly influences the ability of adrenergic drugs to target α and β receptors?
Signup and view all the answers
Which enzyme is responsible for the rapid inactivation of catecholamines in the gut wall?
Which enzyme is responsible for the rapid inactivation of catecholamines in the gut wall?
Signup and view all the answers
Which characteristics are common for catecholamines?
Which characteristics are common for catecholamines?
Signup and view all the answers
Which of the following is NOT a catecholamine?
Which of the following is NOT a catecholamine?
Signup and view all the answers
What is the primary result of norepinephrine's rapid metabolism?
What is the primary result of norepinephrine's rapid metabolism?
Signup and view all the answers
What adverse effect might result from extravasation of norepinephrine?
What adverse effect might result from extravasation of norepinephrine?
Signup and view all the answers
Which receptor does dopamine activate at lower doses?
Which receptor does dopamine activate at lower doses?
Signup and view all the answers
What action does dopamine exert on renal blood flow?
What action does dopamine exert on renal blood flow?
Signup and view all the answers
How can impaired circulation from norepinephrine be treated?
How can impaired circulation from norepinephrine be treated?
Signup and view all the answers
Which of the following describes the relationship between dopamine and norepinephrine?
Which of the following describes the relationship between dopamine and norepinephrine?
Signup and view all the answers
What is a notable effect of dopamine at very high doses?
What is a notable effect of dopamine at very high doses?
Signup and view all the answers
Which alternative treatment can be used for tissue necrosis caused by norepinephrine extravasation?
Which alternative treatment can be used for tissue necrosis caused by norepinephrine extravasation?
Signup and view all the answers
What is the primary effect of stimulating β1 receptors in the heart?
What is the primary effect of stimulating β1 receptors in the heart?
Signup and view all the answers
Which receptor type predominates in the vasculature of skeletal muscle?
Which receptor type predominates in the vasculature of skeletal muscle?
Signup and view all the answers
Which process explains the reduced responsiveness of adrenergic receptors after prolonged exposure to catecholamines?
Which process explains the reduced responsiveness of adrenergic receptors after prolonged exposure to catecholamines?
Signup and view all the answers
What occurs as a result of stimulating α1 receptors?
What occurs as a result of stimulating α1 receptors?
Signup and view all the answers
Which receptor is primarily involved in lipolysis?
Which receptor is primarily involved in lipolysis?
Signup and view all the answers
What is one potential mechanism behind the desensitization of adrenergic receptors?
What is one potential mechanism behind the desensitization of adrenergic receptors?
Signup and view all the answers
What physiological response is associated with stimulation of β2 receptors?
What physiological response is associated with stimulation of β2 receptors?
Signup and view all the answers
Which of the following describes the primary action of adrenergically innervated tissues that have a predominant type of receptor?
Which of the following describes the primary action of adrenergically innervated tissues that have a predominant type of receptor?
Signup and view all the answers
What is the primary mechanism by which propranolol lowers blood pressure in hypertension?
What is the primary mechanism by which propranolol lowers blood pressure in hypertension?
Signup and view all the answers
What effect does β-blockade have on glucose metabolism?
What effect does β-blockade have on glucose metabolism?
Signup and view all the answers
How does propranolol assist in the management of angina pectoris?
How does propranolol assist in the management of angina pectoris?
Signup and view all the answers
What is one of the therapeutic uses of propranolol in patients who have had a myocardial infarction?
What is one of the therapeutic uses of propranolol in patients who have had a myocardial infarction?
Signup and view all the answers
What additional monitoring is necessary when propranolol is given to diabetic patients receiving insulin?
What additional monitoring is necessary when propranolol is given to diabetic patients receiving insulin?
Signup and view all the answers
What happens to the normal physiological response to hypoglycemia when β-blockers are administered?
What happens to the normal physiological response to hypoglycemia when β-blockers are administered?
Signup and view all the answers
Which β-blocker is more potent than propranolol in reducing intraocular pressure?
Which β-blocker is more potent than propranolol in reducing intraocular pressure?
Signup and view all the answers
What is a common side effect of propranolol associated with hypoglycemia?
What is a common side effect of propranolol associated with hypoglycemia?
Signup and view all the answers
What is the primary effect of propranolol on cardiac output?
What is the primary effect of propranolol on cardiac output?
Signup and view all the answers
How does propranolol affect heart rate during exercise or stress?
How does propranolol affect heart rate during exercise or stress?
Signup and view all the answers
What is the result of blocking β2 receptors in the lungs by propranolol?
What is the result of blocking β2 receptors in the lungs by propranolol?
Signup and view all the answers
What effect does propranolol have on peripheral vasoconstriction?
What effect does propranolol have on peripheral vasoconstriction?
Signup and view all the answers
In hypertensive patients, what change occurs in blood pressure due to propranolol?
In hypertensive patients, what change occurs in blood pressure due to propranolol?
Signup and view all the answers
Why are nonselective β-blockers contraindicated in patients with asthma?
Why are nonselective β-blockers contraindicated in patients with asthma?
Signup and view all the answers
What specific action does propranolol have on the SA and AV nodes?
What specific action does propranolol have on the SA and AV nodes?
Signup and view all the answers
What happens to epinephrine's action in the presence of a nonselective β-blocker like propranolol?
What happens to epinephrine's action in the presence of a nonselective β-blocker like propranolol?
Signup and view all the answers
Which β-blocker is specifically indicated for the treatment of chronic open-angle glaucoma?
Which β-blocker is specifically indicated for the treatment of chronic open-angle glaucoma?
Signup and view all the answers
What is the primary mechanism by which β-blockers lower intraocular pressure in glaucoma?
What is the primary mechanism by which β-blockers lower intraocular pressure in glaucoma?
Signup and view all the answers
Which of the following β-blockers is classified as a selective β1 antagonist?
Which of the following β-blockers is classified as a selective β1 antagonist?
Signup and view all the answers
In patients with portal hypertension, which of the following β-blockers can significantly reduce the risk of variceal hemorrhage?
In patients with portal hypertension, which of the following β-blockers can significantly reduce the risk of variceal hemorrhage?
Signup and view all the answers
Which patient population should consider cardioselective β-blockers due to their reduced risk of bronchoconstriction?
Which patient population should consider cardioselective β-blockers due to their reduced risk of bronchoconstriction?
Signup and view all the answers
What effect do β-blockers have when administered at high doses regarding their receptor selectivity?
What effect do β-blockers have when administered at high doses regarding their receptor selectivity?
Signup and view all the answers
What is the typical onset time and duration of effect for intraocularly administered β-blockers in glaucoma?
What is the typical onset time and duration of effect for intraocularly administered β-blockers in glaucoma?
Signup and view all the answers
Which of the following is true regarding the use of β-blockers in acute attacks of glaucoma?
Which of the following is true regarding the use of β-blockers in acute attacks of glaucoma?
Signup and view all the answers
Study Notes
Adrenergic Agonists & Antagonists
- Adrenergic drugs affect receptors stimulated by norepinephrine (noradrenaline) or epinephrine (adrenaline).
- These receptors are known as adrenergic receptors or adrenoceptors.
- Drugs that activate adrenergic receptors are sympathomimetics.
- Drugs that block adrenergic receptor activation are sympatholytics.
- Some sympathomimetics directly activate adrenergic receptors (direct-acting agonists).
- Others act indirectly by enhancing norepinephrine release or blocking its reuptake (indirect-acting agonists).
Adrenergic Agonists
- Overview
- Most adrenergic drugs are derivatives of β-phenylethylamine
- Substitutions on the benzene or ethylamine side change compound properties
- Important features of these drugs: number and location of OH substitutions on benzene ring; nature of the substituent on the amino nitrogen.
- Agonists can be catecholamines or noncatecholamines
- Catecholamines
- Contain 3,4-dihydroxybenzene (catechol) group attached to an amine group
- Dopamine, epinephrine, norepinephrine, isoproterenol
- Noncatecholamines
- Lack catechol hydroxyl groups
- Phenylephrine, ephedrine, amphetamine
- Longer half-lives, greater access to the CNS, generally less rapid metabolism.
- Substitutions on the amine nitrogen
- Substituents on the amine nitrogen influence $\beta$ selectivity
- Example: epinephrine with -CH3 substituent is more potent at β receptors than norepinephrine.
- Mechanism of action
- Direct-acting: bind directly to a or $\beta$ receptors
- Indirect-acting: block norepinephrine reuptake or cause release
- Mixed-action agonists:
- Ephedrine and its stereoisomer pseudoephedrine stimulate adrenoceptors directly and enhancing norepinephrine release.
Indications and Contraindications
- Used for short-term treatment, usually in cases of:
- Refractory heart failure, cardiogenic shock, hypotension caused by hemorrhage or sepsis.
- Long-term use may produce deleterious adverse effects, typically extending the physiological effects of the sympathetic system
- Overdose with epinephrine can lead to hypertension, cardiac arrhythmias, possible cerebral hemorrhage and pulmonary edema.
- Avoid long-term use in patients with heart failure or coronary artery disease due to potential myocardial ischemia.
Direct-Acting Agonists
- Bind directly to $\alpha$ or $\beta$ receptors, mimicking effects of sympathetic nerve stimulation or natural adrenaline secretion.
- Examples include epinephrine, norepinephrine, dopamine, isoproterenol, and phenylephrine.
Indirect-Acting Agonists
- Release endogenous norepinephrine or block its reuptake to increase stimulation of the receptors. This action amplifies the effects of natural catecholamines
- Examples include amphetamine, tyramine, and cocaine.
Mixed-Action Agonists
- Both directly activate receptors and enhance the release of endogenous norepinephrine
- Examples include ephedrine and pseudoephedrine.
Adrenergic Antagonists
- overview
- Bind to $α$ and/or $β$ adrenoceptors, but do not trigger intracellular effects.
- They prevent activation by exogenous or endogenous agonists.
- The drugs are classified by their selectivity for $\alpha$ or $\beta$ receptors.
- Non-selective
- Selective ($\alpha$1, $\alpha$2,$\beta$1, $\beta$2 subtypes)
$\alpha$-Adrenergic Blocking Agents
- Block the effects of norepinephrine in the sympathetic nervous system
- Examples include phenoxybenzamine (nonselective and irreversible) and phentolamine (competitive and reversible).
- Reduced peripheral resistance and reflex tachycardia
- Used in pheochromocytoma treatment; less frequently for Raynaud's disease
$\beta$-Adrenergic Blocking Agents
- Block the effects of norepinephrine or epinephrine at $\beta$ receptors
- Examples include propranolol (non-selective), atenolol and metoprolol (selective $\beta$1 antagonists); and labetalol, carvedilol (both$\alpha$ and $\beta$ antagonists)
- Decrease cardiac output, workload and oxygen consumption
- Used in hypertension, angina, cardiac arrhythmias, myocardial infarction, hyperthyroidism, prophylaxis of migraine headaches, glaucoma, and portal hypertension.
Specific Adrenergic Antagonists
- Prazosin, terazosin, doxazosin, tamsulosin, alfuzosin
- Selective a1 antagonists: used in hypertension and benign prostatic hyperplasia (BPH)
- Beta blockers: used in a variety of cardiovascular and pulmonary conditions.
Other Important Considerations
- The classification of these drugs depends on the receptor they primarily target ($α$1, $\alpha$2, $\beta$1, $\beta$2), how they influence the body, and the type of action they produce (direct, indirect or mixed).
- Some of these drugs can cause side effects like dizziness, orthostatic hypotension, or impairment of sexual function.
- Be aware of drug interactions when using these agents
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
