Phenylephrine Propranolol

Alprenolol, bendroflumethiazide, furosemide, nadolol, phenylephrine, propranolol and triamterene... 

FIG. 17 Chemical structures of (a) epinephrine hydrochloride, (b) dopamine hydrochloride, (c) isoproterenol hydrochloride, (d) phenylephrine hydrochloride, (e) tolazoline hydrochloride, (f) oxyprenolol hydrochloride, (g) alprenolol hydrochloride, and (h) propranolol hydrochloride. 

The answer is a. (Katzung, p 240.) Older therapies—all designed to favor parasympathetic control of rhythm—include digoxin, propranolol, edrophonium, and vasoconstrictors. The vasoconstrictor phenylephrine (given by intravenous bolus) causes stimulation of the carotid sinus and reflex vagal stimulation of the atria. More recently, adenosine has been favored over verapamil, which is also very effective but slower acting... 

The release of stored Ca2+ is often triggered by a adrenergic receptors.269 Like (3 adrenergic receptors, the a receptors are activated by adrenaline. Specific inhibitors distinguish them. For example, the (3 receptors are inhibited by propranolol, while the a receptors are blocked by phenoxybenzamine. The synthetic agonist phenylephrine activates only a receptors and no increases in cAMP or in protein kinase activity are observed. 

Patients taking monoamine oxidase inhibitors, anticholinergic drugs (such as tricyclic antidepressants), propranolol, reserpine, guanethidine, and methyldopa should be monitored closely if phenylephrine is used (SEDA-16, 542) (16). 

Clinically important, potentially hazardous interactions with albuterol, alpha-blockers, amitriptyline, amoxapine, atenolol, beta-blockers, carteolol, chlorpromazine, clomipramine, cocaine, desipramine, doxepin, ephedra, ergotamine, furazolidone, halothane, imipramine, insulin detemir, MAO inhibitors, metoprolol, nadolol, nortriptyline, oxprenolol, penbutolol, phenelzine, phenoxybenzamine, phenylephrine, pindolol, prazosin, propranolol, protriptyline, sympathomimetics, terbutaline, thioridazine, timolol, tranylcypromine, tricyclic antidepressants, trimipramine, vasopressors... 

Treatment with berbamine was found to relax K+-precontracted rat aortal rings, with an ICJ0 of about 20 pmol/liter. This relaxation was not inhibited by denudation of the endothelium or by premedication of the aortas with indomethacin, methylene blue or propranolol. In addition, the alkaloid inhibited contractions induced by norepinephrine, phenylephrine, and serotonin in a non-competitive manner, as well as competitively blocking calcium-induced contraction in a Ca+2-free depolarizing PSS. The blockade of calcium entry appears to be the major mechanism of the dilatory effect of this alkaloid, but its interaction with a-adrenoceptors was not excluded [188]. 

Answer A. Although used primarily via inhalation for asthma, systemic effects of albuterol include vasodilation due to its p2 receptor activation. This can result in a decrease in PVR and mean BP, which elicits a reflex tachycardia. Methoxamine and phenylephrine are Ct-receptor activators causing vasoconstriction, which would result in reflex bradycardia. Ganglion blockers (mecamylamine) prevent autonomic reflexes, and a reflex increase in heart rate could not occur in the presence of a beta blocker (propranolol). 

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