Block 9 Pharm Adrenergic W Exp Prt 1

Answer: B
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 alpha-2 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.
E) Chemoreceptors of aortic bodies are stimulated by a decrease, not an increase, in the mean
blood pressure.

Answer: C
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.

Apraclonidine, is a sympathomimetic used in glaucoma therapy. It is an α2-adrenergic agonist and a weak ALPHA-1 ADRENERGIC RECEPTOR AGONIST.
Apraclonidine is administered at a concentration of 1% for the prevention and treatment of postsurgical intraocular pressure elevation and 0.5% for short-term adjunctive therapy in patients on maximally tolerated medical therapy who require additional redirection of intraocular pressure. One drop is usually added one hour prior to laser eye surgery and another drop is given after the procedure is complete.

Answer: D
Phenylephrine is an alpha-1 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.
A) In most exocrine glands of the body (including lacrimal glands) activation of alpha-1 receptors
causes the formation of a concentrated secretion that contains enzymes and mucus. Moreover
the alpha receptor mediated vasoconstriction decreases the blood supply to the gland so the
actual amount of the lacrimal fluid is in fact decreased, not increased.
B) By increasing the blood pressure (both systolic and diastolic) phenylephrine usually triggers a
baroreceptor reflex that causes bradycardia, not tachycardia.
C) Alpha-1 receptor activation has no effect on the ciliary muscle and therefore does not
influence eye accommodation.
E) (see explanation A)

Answer: D
Epinephrine is used quite often together with local anesthetics, in order to prolong the action of
the anesthetic. This increased duration is due to the epinephrine-induced vasoconstriction
(mediated by alpha-1 receptor activation) which localizes the anesthetic at the desired site, so
slowing down its systemic distribution.
A, B, C, E) (see explanation above)

Salmeterol is a long-acting beta-2 selective receptor agonist. This means that it specifically targets and activates beta-2 receptors in the body, leading to relaxation of the smooth muscles in the airways and bronchodilation. It is commonly used as a maintenance treatment for asthma and chronic obstructive pulmonary disease (COPD). By binding to the beta-2 receptors, salmeterol helps to open up the airways and improve breathing. Other drugs listed in the options do not possess the same mechanism of action as salmeterol.

Answer: E
Epinephrine effects on the heart are due to the activation of beta-1 and beta-2 receptors. The
postreceptor mechanism common to all beta receptor activation is the stimulation of adenylyl
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 alpha-1 and M3 receptors
D)This postreceptor mechanism is triggered by the activation of alpha-1 receptors

Answer: A
Isoproterenol is a nonselective beta agonist, that is it activates all beta receptors. Activation of
beta-1 receptors in the juxtaglomerular cells of macula densa stimulates renin secretion.
C) Activation of beta-2 receptors in the vessels causes vasodilation. The decrease in blood
pressure triggers reflex tachycardia, not bradycardia.
D) Activation of beta-2 receptors on the surface of mast cells and basophils actually inhibits
degranulation of those cells.
E) This effects is mediated by the activation of alpha-2 receptors.

Answer: E
Albuterol is a beta-2 selective agonist. Activation of beta-2 receptors in the respiratory tract
increases mucociliary clearance so improving the flow of the coat of mucus toward the pharynx.
A, B, C) Beta-2 receptor agonists actually decrease microvascular permeability, increase
bronchial secretion and prevent the release of histamine from mast cells. All these actions are
useful in case of bronchospastic disorders.
D) Residual respiratory volume is not significantly affected in normal individuals but is actually
decreased in asthmatic patients.

ATUALLY most of these drugs are contraindicated with MAOI's. But Dr B seems to think Tyramine is the most important.

SUPER IMPORTANT CLINICAL NOTE: (not on mini)
Tyramine occurs widely in plants and animals, and is metabolized by the enzyme monoamine oxidase. In foods, it is often produced by the decarboxylation of tyrosine during fermentation or decay. Foods containing considerable amounts of tyramine include meats that are potentially spoiled or pickled, aged, smoked, fermented, or marinated (some fish, poultry, and beef); most pork (except cured ham); chocolate; alcoholic beverages; and fermented foods, such as most cheeses (except ricotta, cottage cheese, cream cheese and neufchatel cheese), sour cream, yogurt, shrimp paste, soy sauce, soy bean condiments, teriyaki sauce, tofu, tempeh, miso soup, sauerkraut, broad (fava) beans, green bean pods, Italian flat (Romano) beans, snow peas, avocados, bananas, pineapple, eggplants, figs, red plums, raspberries, peanuts, Brazil nuts, coconuts, processed meat, yeast, and an array of cacti.

Answer: B
Restlessness and anxiety are common adverse effect of beta-2 receptor agonists. They occur in
10-20% of children receiving inhalatory therapy. This points out that beta agonist are mainly
excitatory drugs for the CNS. In fact toxic doses usually cause convulsions.
A) Beta-2 receptor activation increases AV conduction, so AV block is quite unlikely.
C) Beta-2 receptor activation actually causes insomnia.
D) Hypotension can rarely occur with beta-2 agonists, but postural hypotension is unlikely since
the baroreceptor reflex can function normally.
E) Arrhythmias can occur with beta-2 agonists but ventricular tachycardia is exceedingly rare.

The symptoms and signs of the patient suggest that he had an acute anaphylactic reaction which
sometimes occurs following a blood transfusion. One of the useful actions of epinephrine in this
disorder is the beta-2 receptor mediated inhibition of degranulation of mast cells which prevents
the release of histamine and other inflammatory mediators.
A, B, C, D, F) All these actions of epinephrine contribute little, if any, to the therapeutic efficacy
of the drug in this disorder.

Methyldopa is an indirect acting adrenergic agent that is sometimes used as an antihypertensive. It works by being converted into methylnorepinephrine, which then acts as a false transmitter and reduces sympathetic outflow from the central nervous system. This ultimately leads to a decrease in blood pressure. Methyldopa is commonly used in the management of hypertension during pregnancy.

Answer: E
Dobutamine is a selective beta agonist that activates mainly beta-1 receptors. This would cause
an increase of all the parameters of heart activity but, for unknown reasons, frequency and
automaticity are increased only slightly. Affinity of dobutamine for alpha-1 and beta-2 receptors
is slight (high doses are needed) and, moreover, the consequences of this activation on the
vessel caliber can balance each other. This can explain why there are no major changes or a
decrease in SVR (when the beta-2 mediated vasodilation overrides the alpha-1 mediated
vasoconstriction).
A, B, C, D) All these listed drugs cause substantial changes in heart rate and systemic vascular
resistance..

Answer: A
Clonidine is often used to decrease the symptoms of sympathetic activation which are prominent
during withdrawal from many sedative drugs including alcohol and opioids. Many of those
symptoms are due to an increased firing from locus ceruleus, a brain nucleus with a very high
concentration of alpha receptors. By activation alpha-2 presynaptic receptors clonidine
decreases the central sympathetic outflow so antagonizing the increased firing from locus
ceruleus.
B, D) Clonidine activates peripheral adrenergic receptors only when very high doses are given.
C) Actually clonidine increases central parasympathetic outflow.
E, F) Clonidine activates, not blocks, these receptors.