Chemical Properties
white to almost white crystalline powder
Uses
α-Adrenergic agonist. Mydriatic; decongestant.
Definition
ChEBI: A hydrochloride that is the monohydrochloride salt of phenylephrine.
General Description
Odorless white microcrystalline powder. Bitter taste. pH (1% aqueous solution) about 5.
Reactivity Profile
PHENYLEPHRINE HYDROCHLORIDE(61-76-7) is incompatible with acids, acid chlorides, acid anhydrides and oxidizing agents. PHENYLEPHRINE HYDROCHLORIDE(61-76-7) is also incompatible with butacaine, alkalis and ferric salts.
Air & Water Reactions
May be sensitive to prolonged exposure to air and light. Water soluble.
Biological Activity
α 1 -adrenoceptor agonist; pK i values are 5.86, 4.87 and 4.70 for α 1D , α 1B and α 1A receptors respectively.
Fire Hazard
Flash point data for this chemical are not available; however, PHENYLEPHRINE HYDROCHLORIDE is probably combustible.
Description
R-(-)-Phenylephrine is an adrenergic α
1A receptor agonist (K
i = 1.4 μM) that demonstrates selectivity against the α
1B and α
1C receptor subtypes (K
is = 23.9 and 47.8 μM, respectively).
1 By stimulating adrenergic α
1 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 (Item No.
16673).
2 This compound is frequently used to precontract smooth muscle in preparations designed to study the properties of various vasodilator agents.
3,4
Originator
Neosynephrine, Badrial, France ,1953
Manufacturing Process
4.5 g of the hydrochloride of m-hydroxymethylaminoacetophenone aredissolved in a small amount of water; to the solution a solution of colloidal palladium obtained from palladiumchloride is added, and the mixture is treated with hydrogen.
After diluting the reaction liquid with acetone it is filtered, and the residue obtained after the evaporation of the filtrate in vacuo, and complete drying over pentoxide of phosphorus is then dissolved in absolute alcohol, and to this is added about the same volume of dry ether, until turbidity just commences to occur. After a short time the hydrochloride of the m-hydroxyphenylethanolmethylamine will separate out as a colorless mass of crystals at a melting point of 142°C to 143°C.
Brand name
Afrin 4 Hour Nasal Spray (Schering-Plough
Health Care); Biomydrin (Parke-Davis); Mydfrin (Alcon);
Neo-Synephrine (Sterling Health U.S.A.); Nostril (Boehringer
Ingelheim).
Therapeutic Function
Adrenergic
Veterinary Drugs and Treatments
Phenylephrine is a vasoconstrictor used to differentiate conjunctival
vascular injection (blanches with phenylephrine application)
versus deep episcleral injection (blanches incompletely) associated
with uveitis, glaucoma, or scleritis. It is also used prior to conjunctival
surgery to reduce hemorrhage and in combination with atropine
prior to cataract or other intraocular surgeries that require
maximal pupillary dilation. Phenylephrine can be used to confirm
the diagnosis of Horner’s syndrome. Dilution of 2.5% phenylephrine
solution with saline (1:10) produces a 0.25% solution. Normal
eyes will not demonstrate mydriasis in response to this low concentration
of phenylephrine. Third order Horner’s syndrome of greater
than two weeks duration is associated with receptor up regulation
and therefore a response to 0.25% phenylephrine is noted. In this
way, the diagnosis of Horner’s is confirmed and a suggestion as to
whether or not the condition is 2nd or 3rd order in nature.
In dogs, maximum mydriasis persists for about 2 hours and
effects may last for up to 18 hours. Phenylephrine has significant
alpha adrenergic effects (vasoconstriction and pupillary dilation)
and minimal effects on beta receptors. When used alone, phenylephrine
is reportedly not efficacious in the cat unless used with
other mydriatics.
References
[1] J W LOMASNEY. Molecular cloning and expression of the cDNA for the alpha 1A-adrenergic receptor. The gene for which is located on human chromosome 5.[J]. The Journal of Biological Chemistry, 1991, 266 10: 6365-6369.
[2] J C BESSE R F F. Dissociation constants and relative efficacies of agonists acting on alpha adrenergic receptors in rabbit aorta.[J]. Journal of Pharmacology and Experimental Therapeutics, 1976, 197 1: 66-78.
[3] MUSTAFA DOGAN. Magnesium and diltiazem relaxes phenylephrine-precontracted rat aortic rings.[J]. Interactive cardiovascular and thoracic surgery, 2012: 1-4. DOI:
10.1093/icvts/ivs051[4] A M BRUNSDEN. Mechanisms underlying mechanosensitivity of mesenteric afferent fibers to vascular flow.[J]. American journal of physiology. Gastrointestinal and liver physiology, 2007, 293 2: G422-8. DOI:
10.1152/ajpgi.00083.2007
