Phenylephrine HCl

Phenylephrine HCl is a phenylephrine (PE) and an α1-adrenoceptor agonist.

Simultaneous high-performance liquid chromatographic determination of paracetamol, phenylephrine HCl, and chlorpheniramine maleate in pharmaceutical dosage forms.[Pubmed:11881712]

J Chromatogr Sci. 2002 Feb;40(2):97-100.

A rapid, precise, and specific high-performance liquid chromatographic method is described for the simultaneous determination of paracetamol, phenylephrine HCI, and chlorpheniramine maleate in combined pharmaceutical dosage forms. The method involves the use of a microBondapak CN RP analytical column (125 A, 10 microm, 3.9 x 150 mm) at 22 degrees C as the stationary phase with the mixture of acetonitrile and phosphate buffer (pH 6.22, 78:22) as the mobile phase. Derivatization of the drugs is not required. The method is applied to commercial pediatric cough-cold syrups, tablets, and capsules marketed in Turkey. The relative standard deviation for 10 replicate measurements of each drug in the medicaments is always less than 2%.

Pharmacokinetics, safety, and cardiovascular tolerability of phenylephrine HCl 10, 20, and 30 mg after a single oral administration in healthy volunteers.[Pubmed:26267590]

Clin Drug Investig. 2015 Sep;35(9):547-58.

BACKGROUND AND OBJECTIVES: Phenylephrine HCl 10 mg has been used as a nasal decongestant for over 50 years, yet only limited pharmacokinetic and metabolic data are available. The purpose of this study was to evaluate single-dose pharmacokinetics and safety of Phenylephrine HCl 10, 20, and 30 mg and to assess cardiovascular tolerability compared with baseline and placebo in healthy volunteers. METHODS: Twenty-eight adults were enrolled in this randomized, double-blind, placebo-controlled, single-dose, four-treatment crossover study. Subjects remained housed for 6 days to permit time-matched, serial measurements of pulse, blood pressure, and electrocardiograms (ECGs) for baseline and complete treatments on consecutive days. After fasting overnight, subjects were dosed with oral Phenylephrine HCl 10, 20, or 30 mg or placebo. Pharmacokinetic blood samples were collected over 7 h, whereas pulse, blood pressure, and ECGs were measured over 12 h. Urine was collected over each 24-h period to quantify phenylephrine and metabolites. RESULTS: After oral administration, phenylephrine was rapidly absorbed with median times to maximum plasma concentrations (t max) from 0.33 to 0.5 h. For Phenylephrine HCl 10, 20, and 30 mg, the mean (standard deviation) maximum concentration (C max) was 1354 (954), 2959 (2122), and 4492 (1978) pg/mL, and total systemic exposure [area under the plasma concentration-time curve from time zero to infinity (AUCinfinity)] was 955.8 (278.5), 2346 (983.8), and 3900 (1764) pg.h/mL, respectively. Both parameters increased disproportionally with increasing dose, as beta >1 in the power model. Negligible amounts of phenylephrine and phenylephrine glucuronide were excreted in urine. With increasing dose, percentages by dose of phenylephrine sulfate decreased, whereas percentages of 3-hydroxymandelic acid increased. Eight subjects reported nine mild adverse events; one (somnolence) was deemed to be treatment related. Means of time-matched differences in pulse and blood pressure from baseline showed similar fluctuations over 12 h among Phenylephrine HCl doses and placebo, although small differences in systolic pressure were observed during the initial 2 h. No apparent dose-related effects were observed for Fridericia-corrected QT interval (QTcF) values, and individual changes from time-matched baseline (DQTcF). CONCLUSIONS: Maximum and total systemic exposures following singe doses of Phenylephrine HCl 10, 20, and 30 mg increased disproportionally with increasing dose. Safety and cardiovascular tolerability were comparable among doses and placebo.

Oral Phenylephrine HCl for Nasal Congestion in Seasonal Allergic Rhinitis: A Randomized, Open-label, Placebo-controlled Study.[Pubmed:26143019]

J Allergy Clin Immunol Pract. 2015 Sep-Oct;3(5):702-8.

BACKGROUND: Phenylephrine hydrochloride (PE HCl) is widely used for the treatment of nasal congestion, but efficacy at the 10-mg dose is not known for certain. The Food and Drug Administration has requested that sufficiently powered, multicenter, dose-ranging studies be conducted to assess the efficacy and safety of PE HCl. OBJECTIVE: To evaluate subjective nasal congestion symptom relief and safety of 4 different doses of PE HCl immediate-release 10-mg tablets and placebo in adults with seasonal allergic rhinitis (SAR). METHODS: This multicenter, phase 2, parallel, open-label trial randomized 539 adults with SAR (but otherwise healthy) to 7 days of treatment with either PE HCl 10-mg tablets at fixed doses of 10, 20, 30, or 40 mg or placebo. The primary efficacy end point was the mean change from baseline over the entire treatment period in daily reflective nasal congestion score. Other efficacy end points and safety were also evaluated. RESULTS: None of the PE HCl treatment groups had a statistically significant change from baseline in instantaneous or reflective nasal congestion scores compared with the placebo group. PE HCl was well tolerated at doses of up to 30 mg. At least 1 treatment-emergent adverse event was experienced by 18.4% of the participants, the most common being headache (3.0%). CONCLUSIONS: PE HCl, at doses of up to 40 mg every 4 hours, is not significantly better than placebo at relieving nasal congestion in adults with SAR. The phenylephrine section of the Food and Drug Administration monograph on over-the-counter cold, cough, allergy, bronchodilator, and antiasthmatic products should be revised accordingly.

Spectrophotometric determination of phenylephrine HCl and orphenadrine citrate in pure and in dosage forms.[Pubmed:12408930]

J Pharm Biomed Anal. 2002 Nov 7;30(4):1385-92.

A simple and rapid spectrophotometric methods have been estimated for the microdetermination of Phenylephrine HCl (I) and orphenadrine citrate (II). The proposed methods are based on the formation of ion-pair complexes between the examined drugs with alizarine (Aliz), alizarine red S (ARS), alizarine yellow G (AYG) or quinalizarine (Qaliz), which can be measured at the optimum lambda(max). The optimization of the reaction conditions is investigated. Beer's law is obeyed in the concentration ranges 2-36 microgram ml(-1), whereas optimum concentration as adopted from Ringbom plots was 3.5-33 microgram ml(-1). The molar absorptivity, Sandell sensitivity, and detection limit are also calculated. The correlation coefficient was >/=0.9988 (n=6) with a relative standard deviation of

Alpha(1A)-adrenoceptors mediate contractions to phenylephrine in rabbit penile arteries.[Pubmed:17115072]

Br J Pharmacol. 2007 Jan;150(1):112-20.

BACKGROUND AND PURPOSE: Maintained penile erection depends on the absence of alpha-adrenoceptor (alpha-AR) activation and so can be facilitated by alpha-blockers. This study seeks the alpha(1)-AR subtypes involved in order to inform the pro-erectile consequences of subtype selective blockade. EXPERIMENTAL APPROACH: Wire myography was used with dorsal (nutritional supply) and cavernous (erectile inflow) penile arteries; standard alpha-AR-selective agonists and antagonists were employed to classify responses. KEY RESULTS: In both penile arteries noradrenaline (NA) and phenylephrine (PE, alpha(1)-AR agonist) caused concentration-dependent contractions. Sensitivity to NA was increased by NA uptake blockers, cocaine (3 microM) and corticosterone (30 microM). PE responses were antagonised by phentolamine (non-selective alpha-AR: dorsal pK(B) 8.00, cavernous 8.33), prazosin (non-subtype-selective alpha(1)-AR: dorsal 8.60, cavernous 8.41) and RS100329 (alpha(1A)-AR selective: dorsal 9.03, cavernous 8.80) but not by BMY7378 (alpha(1D)-AR selective: no effect at 1-100 nM) or Rec15/2615 (alpha(1B)-AR selective: no effect at 1-100 nM). Schild analysis was straightforward in cavernous artery, indicating that PE activates only alpha(1A)-AR. In dorsal artery Schild slopes were low, though alpha(1A)-AR was still indicated. Analysis using UK 14,304 and rauwolscine indicated an alpha(2)-AR component in dorsal artery that may account for low slopes to alpha(1)-AR antagonists. CONCLUSIONS AND IMPLICATIONS: Penile arteries have a predominant, functional alpha(1A)-AR population with little evidence of other alpha(1)-AR subtypes. Dorsal arteries (nutritional supply) also have alpha(2)-ARs. Thus, alpha-AR blockers with affinity for alpha(1A)-AR or alpha(2)-AR would potentially have pro-erectile properties; the combination of these perhaps being most effective. This should inform the design of drugs to assist/avoid penile erection.

Pharmacological pleiotropism of the human recombinant alpha1A-adrenoceptor: implications for alpha1-adrenoceptor classification.[Pubmed:9249248]

Br J Pharmacol. 1997 Jul;121(6):1127-35.

1. Three fully-defined alpha1-adrenoceptors (alpha1A, alpha1B and alpha1D) have been established in pharmacological and molecular studies. A fourth alpha1-adrenoceptor, the putative alpha1L-adrenoceptor, has been defined in functional but not molecular studies, and has been proposed to mediate contraction of human lower urinary tract tissues; its relationship to the three fully characterized alpha1-adrenoceptors is not known. 2. In the present study, binding affinities were estimated by displacement of [3H]-prazosin in membrane homogenates of Chinese hamster ovary (CHO-K1) cells stably expressing the human alpha1A-, alpha1B- and alpha1D-adrenoceptors and were compared with affinity estimates obtained functionally in identical cells by measuring inhibition of noradrenaline (NA)-stimulated accumulation of [3H]-inositol phosphates. 3. For the alpha1A-adrenoceptor, binding studies revealed a pharmacological profile typical for the classically defined alpha1A-adrenoceptor, such that prazosin, RS-17053, WB 4101, 5-methylurapidil, Rec 15/2739 and S-niguldipine all displayed subnanomolar affinity. A different profile of affinity estimates was obtained in inositol phosphates accumulation studies: prazosin, WB 4101, 5-methylurapidil, RS-17053 and S-niguldipine showed 10 to 40 fold lower affinity than in membrane binding. However, affinity estimates were not 'frameshifted', as tamsulosin, indoramin and Rec 15/2739 yielded similar, high affinity estimates in binding and functional assays. 4. In contrast, results from human alpha1B- and alpha1D-adrenoceptors expressed in CHO-K1 cells gave antagonist affinity profiles in binding and functional assays that were essentially identical. 5. A concordance of affinity estimates from the functional (inositol phosphates accumulation) studies of the alpha1A-adrenoceptor in CHO-K1 cells was found with estimates published recently from contractile studies in human lower urinary tract tissues (putative alpha1L-adrenoceptor). These data show that upon functional pharmacological analysis, the cloned alpha1A-adrenoceptor displays pharmacological recognition properties consistent with those of the putative alpha1L-adrenoceptor. Why this profile differs from that obtained in membrane binding, and whether it explains the alpha1L-adrenoceptor pharmacology observed in many native tissues, requires further investigation.

Selectivity of agonists for cloned alpha 1-adrenergic receptor subtypes.[Pubmed:7969082]

Mol Pharmacol. 1994 Nov;46(5):929-36.

The potencies and intrinsic activities of agonists in activating cloned alpha 1-adrenergic receptor (AR) subtypes were compared. The hamster alpha 1B-, bovine alpha 1C-, or rat alpha 1A/D-ARs were expressed at high levels in human embryonic kidney 293 cells. Catecholamines and phenylethylamines, but not lower efficacy agonists, were more potent in inhibiting radioligand binding to the expressed alpha 1A/D subtype than to the alpha 1B or alpha 1C subtypes; this selectivity remained in the presence of different buffers, nucleotides, and cations. Activation of all three subtypes caused substantial increases in [3H]inositol phosphate formation in cells grown in 96-well plates. Pretreatment with phenoxybenzamine decreased maximal responses to norepinephrine (NE) with only small decreases in apparent potency, suggesting similar small receptor reserves for all three subtypes. The catecholamines NE, epinephrine, and 6-fluoro-NE were full agonists with similar potencies at the three subtypes; alpha-methyl-NE was also a full agonist but was about 20-fold less potent at alpha 1B-ARs than at alpha 1C- or alpha 1A/D-ARs. Phenylephrine had similar potencies at all three subtypes but gave a submaximal response at alpha 1B-ARs. Methoxamine was a full agonist at alpha 1C- and alpha 1A/D-ARs, with about 20-fold greater potency at the alpha 1C subtype, but showed lower intrinsic activity at alpha 1B-ARs. A number of imidazolines, amidephrine, and SKF 89748 had substantial intrinsic activity at alpha 1C-ARs but little or no intrinsic activity at the other two subtypes. We conclude that the potencies of many agonists in competing for radioligand binding sites are related to their potencies in activating functional responses but that this relationship is not the same for all subtypes. NE and epinephrine activate all three cloned alpha 1-AR subtypes with similar potencies and intrinsic activities, but many widely used agonists show significant selectivity for different alpha 1-AR subtypes.

(R)-(-)-Phenylephrine hydrochloride is a selective α1-adrenoceptor agonist with pKis of 5.86, 4.87 and 4.70 for α1D, α1B and α1A receptors respectively.

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