Adrenergic Drugs Practice Questions Flashcards
Which of the following drugs is an α2 selective receptor agonist?
Albuterol Apraclonidine Cocaine Amphetamine Dobutamine Dopamine
Apraclonidine
Apraclonidine is an α2 selective receptor agonist, used locally for glaucoma. By Activating α2 receptors in ciliary epithelium the drug decreases the production of aqueous humor.
Which of the following drugs is a β2 selective receptor agonist? Epinephrine Methyldopa Tyramine Albuterol
Albuterol
Albuterol is a β2 selective receptor agonist used to treat asthma.
Which of the following drugs is an indirect acting adrenergic drug that is sometimes used to treat hypertension, and is the first-choice drug for treating hypertension in pregnant women?
Clonidine Albuterol Methyldopa Phenylephrine Dopamine
Methyldopa
Methyldopa is a false neurotransmitter which is taken up by the adrenergic neurons where it is transformed into methylnorepinephrine, an α2 selective receptor agonist. It is therefore an indirect acting adrenergic drug. The activation of α2 presynaptic receptors in the brain stem causes a decreased firing of adrenergic nerves that results in lowering of blood pressure.
Which of the following may cause a severe hypertensive crisis if ingested together with a MAO inhibitor?
Clonidine Ephedrine Methyldopa Tyramine Phenylephrine
Tyramine
Tyramine which is found in food such as meat, wine and aged cheese is a false transmitter that is taken up by the adrenergic neurons and transformed into octopamine, a very weak adrenergic agonist. Octopamine is stored in the adrenergic vesicles, gradually displacing norepinephrine. Tyramine is inactive if ingested because of a very large first-pass effect (metabolized by hepatic monoamine oxidases). When administered parenterally, (or orally together with a MAO inhibitor), tyramine is not inactivated and it may cause sympathomimetic actions (including a potentially lethal hypertensive crisis), due mainly to norepinephrine release.
A 33-year-old man was brought to the emergency room after a car accident. Upon admission the patient was lucid but completely paralyzed with loss of all sensation and reflex activity below the thorax. Vital signs were: blood pressure 80/40 mm Hg, heart rate 42 bpm, respiration 36 breaths/min. A preliminary diagnosis of spinal shock, due to spinal cord injury, was made and an IV infusion of a drug was started . Which of the following drugs was most likely administered?
Isoproterenol Clonidine Norepinephrine Terbutaline Methyldopa
Norepinephrine
The shock due to the spinal injury is a vasodilatory shock (also called neurogenic or distributive shock) which occurs because the injured sympathetic nervous system fails to maintain the arterial tone. There is hypotension without compensatory tachycardia. Drugs with α-1 adrenergic activity like norepinephrine and phenylephrine are used to restore the arterial tone so counteracting the decreased blood pressure.
A, B, D) These drugs are do not activate α1 receptors.
Methyldopa is used to reduce blood pressure.
The effects of epinephrine on the heart are most likely mediated by which of the following post-receptor signaling mechanisms?
Opening of ligand-gated K+ channels
Opening of ligand-gated Na+ channels
Simulation of phospholipase C
Stimulation of adenylate cyclase
Stimulation of adenylate cyclase
Epinephrine effects on the heart are due to the activation of β1 and β2 receptors. The postreceptor mechanism common to all β receptor activation is the stimulation of adenylate cyclase which in turn increases the amount of cAMP in target tissues.
A) This postreceptor mechanism is triggered by the activation of M2 receptors.
B)This postreceptor mechanism is triggered by the activation of nicotinic receptors
C)This postreceptor mechanism is triggered by the activation α1, M1 and M3 receptors
Which of the following molecular actions best explains the decrease in heart rate observed when and intravenous norepinephrine infusion is administered to a healthy person?
Activation of myocardial α2 receptors
Stimulation of aortic baroreceptors
Activation of Nm receptors
Blockade of myocardial muscarinic receptors
Stimulation of aortic baroreceptors
Norepinephrine causes an increase in systolic and diastolic blood pressure. The mean blood pressure is therefore increased and this causes a stimulation of aortic baroreceptors which activates the baroreceptor reflex. The increased vagal discharge overcomes the direct, tachycardic effect of norepinephrine on the heart rate so the final effects is a decrease in heart rate.
A) Activation of α2 receptors decreases the release of norepinephrine from adrenergic terminal, but this has nothing to do with the actions of norepinephrine given by IV infusion.
C, D) Norepinephrine does not activate Nm receptors and does not block muscarinic receptors.
22-year-old man complained to his physician that his nasal stuffiness was getting worse. The man started two days ago an over-the-counter topical preparation containing phenylephrine because of an annoying common cold. Initially the preparation was effective but later the patient noticed that when the drug effect subsided, nasal stuffiness was worse than it originally had been. Which of the following statements best explains this adverse drug effect?
Poor patient compliance Insufficient dosing Drug induced increased blood pressure Drug induced reflex bradycardia Drug induced allergic reaction Rebound congestion
Rebound congestion
Phenylephrine is an α-1 agonist frequently used locally as nasal decongestant because of the vasoconstricting effects on nasal mucosa. The most common adverse effect of topical nasal decongestants is rebound nasal congestion that mainly occurs after 2-3 days of use. The is a result of receptor down-regulation/desensitization.
Which of the following is the most common adverse effect of phenylephrine given locally into the eye for diagnostic purposes?
Lacrimation
Tachycardia
Difficulty with far vision
Photophobia
Photophobia
Phenylephrine is an α1 selective receptor agonist. When given locally in the conjunctival sac it contracts the radial muscle of iris so causing mydriasis. The most common consequence of mydriasis is photophobia since the pupil cannot constrict in response to bright light.
B) By increasing the blood pressure (both systolic and diastolic) phenylephrine usually triggers a baroreceptor reflex that causes bradycardia, not tachycardia.
C) α1 receptor activation has no effect on the ciliary muscle and therefore does not influence eye accommodation.
Which of the following is a pharmacological effect of isoproterenol?
Stimulation of renin secretion
Reflex bradycardia
Release of inflammatory mediators from mast cells
Stimulation of platelet aggregation
Stimulation of renin secretion
Isoproterenol is a nonselective β-agonist, that activates all β-receptors. Activation of β1 receptors in the juxtaglomerular cells stimulates renin secretion.
B) Activation of β2 receptors in the vessels causes vasodilation. The decrease in blood pressure triggers reflex tachycardia, not bradycardia.
C) Activation of β2 receptors on the surface of mast cells and basophils actually inhibits degranulation of those cells.
D) This effects is mediated by the activation of α2 receptors.
A new autonomic drug that does not enter the brain was administered intravenously to healthy volunteers in a phase 1 clinical trial. The cardiovascular effects are tabulated below. The new drug has effects that are similar to which of the following drugs?
Parameter Control Peak Drug Effect Systolic BP (mmHg) 126 130 Diastolic BP (mmHg) 80 78 Heart rate (bpm) 70 80 Cardiac output (L/min) 5 7 Ejection fraction 60% 80%
Dobutamine Terbutaline Isoproterenol Norepinephrine Phenylephrine
Dobutamine
The drug causes a negligible change in both systolic and diastolic pressure, a small increase in heart rate and a substantial increase in cardiac output. This suggest that the increase in cardiac output is mainly due to the increase in stroke volume. In fact: stroke volume (SV) = cardiac output/heart rate ; therefore: SV control = 5L/70 = 71 mL ; SV drug = 7L/80 = 87 mL. The ejection fraction is also substantially increased, indicating that the drug must have β-adrenergic activity (remember that the only way to increase the ejection fraction is to increase the contractility of the heart). Among the listed drugs only dobutamine has negligible effect on diastolic blood pressure and (for unknown reasons), little effect on the heart rate.
Which of the following statements best explains the main mechanism of adrenergic actions of cocaine?
Inhibition of monoamine oxidase A
Blockade of α2 receptors in sympathetic terminals
Inhibition of norepinephrine reuptake into sympathetic nerve terminals
Stimulation of epinephrine release from adrenal medulla
Stimulation of norepinephrine release from sympathetic nerve terminals
Inhibition of norepinephrine reuptake into sympathetic nerve terminals
Cocaine is an indirect-acting adrenergic drug that block catecholamine uptake in both the central and peripheral nervous system. Therefore the adrenergic actions of cocaine are due to the increased availability of norepinephrine in the synaptic cleft.
A, B, D, E) All these listed mechanisms can increase the availability of norepinephrine or epinephrine, but these are not mechanisms of action of cocaine.
Which of the following correctly pairs the adrenergic agonist with its appropriate therapeutic use? Ephedrine - insomnia Dopamine - oliguria Dobutamine - anaphylactic shock Norepinephrine - migraine Albuterol -intrauterine fetal death
Dopamine - oliguria
Dopamine can be used to treat oliguria due to insufficient blood flow. This kind of oliguria occurs most often in case of acute cardiac failure when the low cardiac output cannot maintain a sufficient blood flow. Therapeutic doses of dopamine can increase cardiac output by activating β1 receptors and, at the same time, dopamine can dilate the renal vessels by activating D1 receptors. Therefore renal blood flow can be significantly increased.
A) Ephedrine is a mixed acting sympathomimetic drug that can center the brain and can have actions similar to those of amphetamine. Therefore insomnia is a contraindication, not an indication, for the use of this drug.
C) Dobutamine used to treat cardiogenic shock, but epinephrine remains the most appropriate drug for anaphylactic shock.
D) There is no rationale for the use of norepinephrine for migraine.
E) Albuterol is contraindicated, not indicated, since it can decrease uterine contractions. Instead labor must be induced in case of intrauterine fetal death.
A 12-year-old boy was stung by a wasp while walking in the woods. A few minutes later he developed pruritus and erythema, dyspnea, wheezing and dizziness. Swelling of the face, eyes, lips and tongue was prominent. Paramedics were called and they administered a drug intramuscularly upon arrival. Which of the following drugs was most likely administered to this patient? Norepinephrine Isoproterenol Epinephrine Ephedrine Phenylephrine
Epinephrine
The signs and symptoms strongly suggest that this boy had an acute anaphylactic reaction to the wasp venom. Epinephrine is the drug of choice for the pharmacologic management of anaphylaxis for the following reasons:
- Its action is almost immediate. Other drugs used for the same purpose (antihistamines, corticosteroids) have a slower onset of action.
- The α adrenergic effects maintain blood pressure to overcome the hypotensive effects of histamine and the other mediators of anaphylaxis. These effects also prevent the edema of the glottis that can threaten the patency of the airways an lead to death in few minutes. .
- The β adrenergic effects promote bronchodilation, increase cardiac contractility and inhibit further release of mediator from basophils and mast cells.
A, B, D, E) These drugs lack some of epinephrine effects and therefore are not used for the pharmacologic management of anaphylaxis.
A 52-year-old man suffering from hypertension was admitted to the hospital because of 24 hours anuria. Pertinent plasma levels on admission are shown in the table below. An appropriate therapy was initiated which included intravenous albuterol. Which of the following statements best explains why this drug was administered to the patient? Parameter Patient Normal K+ (mEq/L) 7.9 3.5 - 5 Ca2+ (mmol/L) 1.5 1.03 - 1.23 Creatinine (mg/dL) 7 0.8 - 1.3 BUN (mg/dL) 52 8 - 21
To counteract high creatinine values To counteract hyperkalemia To counteract hypocalcemia To increase kidney blood flow To activate diuresis
To counteract hyperkalemia
The lab values of this patient indicate that he is suffering from acute renal failure, a condition that can be caused by prolonged renal ischemia (due to the patient’s hypertension). K+ values higher than 6.5 mEql/L require emergency treatment. The therapy includes:
- Agents that antagonize the cardiac effects of hyperkalemia (like calcium which counteract the depolarizing effect of hyperkalemia).
- Drugs that shift K+ from the extracellular to the intracellular space (like insulin and β2 agonists)
- Drugs that enhance K+ elimination (like ion exchange resins that bind K+ in the bowel lumen). Dialysis may be necessary for patients with severe renal impairment.
