L-フェニレフリン

外観

白色～ほとんど白色粉末～結晶

解説

フェニレフリンは，交感神経興奮薬の一つ。ネオシネフリンともいう。メタヒドロキシ-ω-クロロアセトフェノンとメチルアミンとを希釈アルコール中で反応させて合成する。交感神経興奮作用をもつので，部分的血管収縮，瞳孔散大，鼻孔充血除去などに用いられる。アドレナリンとよく似た化学構造をもち，とくにα‐アドレナリン作動性受容体に対する選択性が高い薬物として知られる。末梢血管の収縮による血圧上昇作用が強く，持続的である。フェニレフリンの塩酸塩とその溶液は，日本薬局方，アメリカ薬局方などに収載されており，急性低血圧の昇圧薬，鼻づまりの点鼻液，瞳孔散大のための点眼薬などとして使われる。【粕谷 豊】
株式会社平凡社 世界大百科事典 第２版について　情報

効能

血管収縮薬, α1アドレナリン受容体作動薬

説明

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.

化学的特性

White or almost white, crystalline powder.

使用

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.

定義

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.

一般的な説明

(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.

臨床応用

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.

安全性プロファイル

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.