Adrenergic agonists

A 22-year-old male is brought to the emergency room with suspected cocaine overdose. Which of the following symptoms is most likely in this patient? A. Hypertension B. Bronchoconstriction C. Bradycardia D. Miosis (constriction of pupil)

A. Hypertension (Cocaine is an indirect adrenergic agonist that prevents the reuptake of norepinephrine into the nerve terminals, thus increasing the levels of NE in the synaptic cleft. The increase in NE leads to an increase in blood pressure (hypertension), tachycardia (not bradycardia), mydriasis (not miosis), and other symptoms of sympathetic overactivity.)

Which of the following is correct regarding adrenergic neurotransmission? A. Norepinephrine is the major neurotransmitter released from sympathetic nerve terminals. B. Norepinephrine is mainly released from the adrenal glands. C. Tricyclic antidepressants and cocaine prevent the release of norepinephrine from the nerve terminals. D. Monoamine oxidase (MAO) converts dopamine to norepinephrine in the nerve terminal.

A. Norepinephrine is the major neurotransmitter released from sympathetic nerve terminals. (Norepinephrine (NE) is the major neurotransmitter released from sympathetic nerve terminals. Epinephrine, not norepinephrine, is mainly released from the adrenal glands. Tricyclic antidepressants (TCAs) and cocaine inhibit the reuptake of norepinephrine into the sympathetic nerve terminals, but they do not prevent the release of NE. Dopamine is converted to norepinephrine by dopamine β-hydroxylase, not by MAO.)

Which of the following is correct regarding responses mediated by adrenergic receptors? A. Stimulation of α1 receptors increases blood pressure. B. Stimulation of sympathetic presynaptic α2 receptors increases norepinephrine release. C. Stimulation of β2 receptors increases heart rate (tachycardia). D. Stimulation of β2 receptors causes bronchoconstriction.

A. Stimulation of α1 receptors increases blood pressure. (Stimulation of α1 receptors, mostly found in the blood vessels, causes vasoconstriction and an increase in blood pressure. Stimulation of α2 receptors on the sympathetic presynaptic terminal reduces the release of norepinephrine. β2 receptors are not found in the heart, so activation of β2 receptors does not affect heart rate. Stimulation of β2 receptors found in the bronchial tissues causes bronchodilation, not bronchoconstriction.)

An asthma patient was given a nonselective β agonist to relieve bronchoconstriction. Which adverse effect would you expect in this patient? A. Bradycardia B. Tachycardia C. Hypotension (reduction in blood pressure) D. Worsening bronchoconstriction

B. Tachycardia (A nonselective β agonist activates both β1 and β2 receptors. β1 Activation causes an increase in heart rate (tachycardia), contractility, and subsequent increase in blood pressure. It relieves bronchoconstriction because of the β2 receptor activation.)

Which of the following classes of adrenergic agents has utility in the management of hypertension? A. α1 Agonist B. α2 Agonist C. β1 Agonist D. β3 Agonist

B. α2 Agonist (α2 Agonists activate α2 receptors located in the presynaptic terminal of sympathetic neurons and cause a reduction in the release of norepinephrine from sympathetic nerve terminals. This leads to a reduction in blood pressure. α2 Agonists such as clonidine and methyldopa are therefore used as antihypertensive agents. α1 Agonists cause vasoconstriction, and β1 agonists cause increased cardiac output and renin release, so these agents may increase blood pressure. β3 Agonists are not used in the management of hypertension.)

An elderly patient is brought to the emergency room with a blood pressure of 76/60 mm Hg, tachycardia, and low cardiac output. He is diagnosed with acute heart failure. Which of the following drugs is most appropriate to improve his cardiac function? A. Epinephrine B. Fenoldopam C. Dobutamine D. Isoproterenol

C. Dobutamine (Among the choices, the ideal drug to increase contractility in acute heart failure is dobutamine, since it is a selective β1-adrenergic agonist. Fenoldopam is a dopamine agonist used to treat severe hypertension. The other drugs are nonselective adrenergic agonists that could cause unwanted side effects.)

A patient who has hypertension and mild asthma attacks bought a herbal remedy for asthma online. He does not take any prescription medications for asthma, but takes a β1-selective blocker for hypertension. The herbal remedy relieves the asthma attacks, but his blood pressure seems to increase despite the β-blocker therapy. Which of the following drugs is most likely present in the herbal remedy? A. Phenylephrine B. Norepinephrine C. Ephedrine D. Salmeterol

C. Ephedrine (Both ephedrine and salmeterol can relieve asthma symptoms, as they activate β2 receptors in the bronchioles and cause bronchodilation. However, salmeterol is a selective β2 agonist and should not increase blood pressure. By contrast, ephedrine stimulates the release of norepinephrine and acts as a direct agonist at α- and β-adrenergic receptors, thus causing an increase in blood pressure. Phenylephrine (a nonselective α agonist) does not cause bronchodilation, so it would not relieve asthma symptoms. Norepinephrine is a nonselective adrenergic agonist that does not have any stimulatory effects on β2 receptors. In addition, norepinephrine is not active when given orally.)

Which of the following adrenergic agonists is commonly present in nasal sprays available over-the-counter (OTC) to treat nasal congestion? A. Clonidine B. Albuterol C. Oxymetazoline D. Formoterol

C. Oxymetazoline (Drugs with selective α1 agonistic activity are commonly used as nasal decongestants because of their ability to cause vasoconstriction in the nasal vessels. Oxymetazoline is an α1 agonist and therefore the preferred drug among the choices as a nasal decongestant. Clonidine is an α2 agonist, albuterol is a β2 agonist, and formoterol is a long-acting β2 agonist.)

A 12-year-old boy with a peanut allergy is brought to the emergency room after accidental consumption of peanuts. He is in anaphylactic shock. Which of the following drugs is most appropriate to treat this patient? A. Norepinephrine B. Phenylephrine C. Dobutamine D. Epinephrine

D. Epinephrine (Norepinephrine has more α agonistic effects and activates mainly α1, α2, and β1 receptors. Epinephrine has more β agonistic effects and activates mainly α1, α2, β1, and β2 receptors. Phenylephrine has predominantly α effects and activates mainly α1 receptors. Dobutamine mainly activates β1 receptors and has no significant effects on β2 receptors. Thus, epinephrine is the drug of choice in anaphylactic shock that can both stimulate the heart (β1 activation) and dilate bronchioles (β2 activation).)

Which of the following adrenergic drugs is used in the treatment of overactive bladder? A. Epinephrine B. Dobutamine C. Phenylephrine D. Mirabegron

D. Mirabegron (Detrusor muscles in the urinary bladder wall have β3 receptors. Stimulation of these receptors relaxes the urinary bladder wall and relieves overactive bladder. Mirabegron is a β3 agonist and therefore used in treating overactive bladder. None of the other drugs listed have β3 agonist activity.)