Фенилэфрин

Описание

This synthetic drug has both chemical and pharmacological similarities to norepinephrine. A characteristic quality of phenylephrine is the distinctly expressed selectivity to α- adrenoreceptors, especially α1-adrenoreceptors. Although phenylephrine increases the contractibility of blood vessels, in practical terms it is not considered a cardiostimulant.

Химические свойства

White or almost white, crystalline powder.

Использование

L-Phenylephrine is an adrenergic α1A receptor agonist (Ki = 1.4 μM) that demonstrates selectivity against the α1B and α1C receptor subtypes (Kis = 23.9 and 47.8 μM, respectively). By stimulating adrenergic α1 receptors, L-phenylephrine can induce aortic smooth muscle contractions, although reported relative affinity and potency values in rabbit are 5-fold weaker compared to that of L-norepinephrine. This compound is frequently used to precontract smooth muscle in preparations designed to study the properties of various vasodilator agents. Because L-phenylephrine acts on adrenergic α1 receptors in the arterioles of the nasal mucosa to produce constriction, it has been examined clinically as an oral decongestant.

Определение

ChEBI: A member of the class of the class of phenylethanolamines that is (1R)-2-(methylamino)-1-phenylethan-1-ol carrying an additional hydroxy substituent at position 3 on the phenyl ring.

Общее описание

(Neo-Synephrine, a prototypical selectivedirect-acting 1-agonist) differs from E only inlacking a p-OH group. It is orally active, and its DOA isabout twice that of E because it lacks the catechol moietyand thus is not metabolized by COMT. However, its oralbioavailability is less than 10% because of its hydrophilicproperties (log P＝0.3), intestinal 3 -O-glucuronidation/sulfation and metabolism by MAO. Lacking the p-OHgroup, it is less potent than E and NE but it is a selectiveα1-agonist and thus a potent vasoconstrictor. It is usedsimilarly to metaraminol and methoxamine for hypotension.Another use is in the treatment of severe hypotensionresulting from either shock or drug administration. It alsohas widespread use as a nonprescription nasal decongestantin both oral and topical preparations. When applied tomucous membranes, it reduces congestion and swelling byconstricting the blood vessels of the membranes. In theeye, it is used to dilate the pupil and to treat open-angleglaucoma. In addition, it is used in spinal anesthesia toprolong the anesthesia and to prevent a drop in blood pressureduring the procedure. It is relatively nontoxic and produceslittle CNS stimulation. Metaraminol is just anotherexample.

Клиническое использование

Phenylephrine is a potent direct-acting α1-agonist with clinical effects similar to those of noradrenaline. It causes widespread vasoconstriction with an increase in arterial pressure, reflex bradycardia and decrease in cardiac output. It may be administered by i.v. bolus (50–100μg boluses) and i.v. infusion (50–150μgmin –1) to maintain arterial pressure during general anaesthesia or other causes of low SVR. It may also be used topically as a nasal decongestant or mydriatic. There is some evidence suggesting a paradoxical reduction in cerebral oxygen delivery.

Профиль безопасности

Poison by ingestion, subcutaneous, intravenous, intraperitoneal, and intraduodenal routes. Human systemic effects by ocular route: blood pressure increase. An experimental teratogen. Other experimental reproductive effects. A nasal decongestant. When heated to decomposition it emits toxic fumes of NOx.