Pharmacokinetics, safety, and cardiovascular tolerability of phenylephrine HCl 10, 20, and 30 mg after a single oral administration in healthy volunteers

Preparation, quality evaluation and preliminary pharmacokinetic-pharmacodynamic studies of synephrine dry powder inhaler

Acute lung injury (ALI) is a lung disease characterized by pulmonary edema caused by an excessive inflammatory response within the lungs and disruption of the alveolar capillary barrier, with a high morbidity and mortality rate in critically ill patients. Dry powder inhalers (DPI) are an effective way of administering medication to improve efficacy, and inhalation administration not only improves efficacy but also increases the bioavailability of the drug. Synephrine, a natural ingredient derived from the fruit of the citrus plant in the Brassicaceae family, has anti-inflammatory and antioxidant properties. In the present study, we prepared a synephrine dry powder inhaler (SYN-DPI) by anti-solvent precipitation method and evaluated it in vivo and in vitro. The in vitro results show that SYN-DPI has low hygroscopicity and good aerodynamic properties. The in vitro and in vivo efficacy results showed that SYN-DPI not only had low toxicity but also possessed good anti-inflammatory and antioxidant capacity, which could significantly reduce inflammation, oxidative stress, and lung injury. Pharmacokinetic results showed that inhalation administration significantly increased SYN bioavailability. In conclusion, this study provides inhalation administration of synephrine as an inhalable formulation that can be used to improve ALI.

Biopharmaceutics Aspects of Sugar Alcohols: Implementation of Patient-Centricity in Pharmaceutical Development and Clinical Use

Sugar alcohols such as mannitol and sorbitol are frequently used as pharmaceutical excipients in oral dosage forms. Their versatility stems from extensive evidence of use in humans. However, investigations over many years have clearly indicated their osmolarity-derived biopharmaceutics effects on oral drug absorption. Despite this, these accumulated insights have not been fully integrated into pharmaceutical formulation development or clinical use, leading to suboptimal industrial and clinical practices. This review provides a comprehensive summary of the biopharmaceutics of sugar alcohols, detailing their mechanisms of action and the magnitude of their osmotic effects on the oral absorption of various drugs. Additionally, the review discusses the implications for bioequivalence studies, BCS-based biowaiver guidelines, drug-excipient interactions in pediatric polypharmacy, and pharmaceutical compounding. The aim is to guide future successful and patient-centric pharmaceutical formulation development.

MetaPredictor: in silico prediction of drug metabolites based on deep language models with prompt engineering

Metabolic processes can transform a drug into metabolites with different properties that may affect its efficacy and safety. Therefore, investigation of the metabolic fate of a drug candidate is of great significance for drug discovery. Computational methods have been developed to predict drug metabolites, but most of them suffer from two main obstacles: the lack of model generalization due to restrictions on metabolic transformation rules or specific enzyme families, and high rate of false-positive predictions. Here, we presented MetaPredictor, a rule-free, end-to-end and prompt-based method to predict possible human metabolites of small molecules including drugs as a sequence translation problem. We innovatively introduced prompt engineering into deep language models to enrich domain knowledge and guide decision-making. The results showed that using prompts that specify the sites of metabolism (SoMs) can steer the model to propose more accurate metabolite predictions, achieving a 30.4% increase in recall and a 16.8% reduction in false positives over the baseline model. The transfer learning strategy was also utilized to tackle the limited availability of metabolic data. For the adaptation to automatic or non-expert prediction, MetaPredictor was designed as a two-stage schema consisting of automatic identification of SoMs followed by metabolite prediction. Compared to four available drug metabolite prediction tools, our method showed comparable performance on the major enzyme families and better generalization that could additionally identify metabolites catalyzed by less common enzymes. The results indicated that MetaPredictor could provide a more comprehensive and accurate prediction of drug metabolism through the effective combination of transfer learning and prompt-based learning strategies.

Implications of Ocular Confounding Factors for Aqueous Humor Proteomic and Metabolomic Analyses in Retinal Diseases

Purpose

To assess the impact of ocular confounding factors on aqueous humor (AH) proteomic and metabolomic analyses for retinal disease characterization.

Methods

This study recruited 138 subjects (eyes): 102 with neovascular age-related macular degeneration (nAMD), 18 with diabetic macular edema (DME), and 18 with cataract (control group). AH samples underwent analysis using Olink Target 96 proteomics and Metabolon's metabolomics platform Data analysis included correlation, differential abundance, and gene-set analysis.

Results

In total, 756 proteins and 408 metabolites were quantified in AH. Total AH protein concentration was notably higher in nAMD (3.2-fold) and DME (4.1-fold) compared to controls. Pseudophakic eyes showed higher total AH protein concentrations than phakic eyes (e.g., 1.6-fold in nAMD) and a specific protein signature indicative of matrix remodeling. Unexpectedly, pupil-dilating drugs containing phenylephrine/tropicamide increased several AH proteins, notably interleukin-6 (5.4-fold in nAMD). Correcting for these factors revealed functionally relevant protein correlation clusters and disease-relevant, differentially abundant proteins across the groups. Metabolomics analysis, for which the relevance of confounder adjustment was less apparent, suggested insufficiently controlled diabetes and chronic hyperglycemia in the DME group.

Conclusions

AH protein concentration, pseudophakia, and pupil dilation with phenylephrine/tropicamide are important confounding factors for AH protein analyses. When these factors are considered, AH analyses can more clearly reveal disease-relevant factors.

Translational Relevance

Considering AH protein concentration, lens status, and phenylephrine/tropicamide administration as confounders is crucial for accurate interpretation of AH protein data.

Safety evaluation of 8 drug degradants present in over-the-counter cough and cold medications

Although the United States Food & Drug Administration (FDA) has provided guidance on the control of drug degradants for prescription drugs, there is less guidance on how to set degradant specifications for FDA OTC monograph drugs. Given that extensive impurity testing was not part of the safety paradigm in original OTC monographs, a weight of evidence (WOE) approach to qualify OTC degradants is proposed. This approach relies on in silico tools and read-across approaches alongside standard toxicity testing to determine safety. Using several drugs marketed under 21 CFR 341 as case studies, this research demonstrates the utility of a WOE approach across data-rich and data-poor degradants. Based on degradant levels ranging from 1 to 4% of the maximum daily doses of each case study drug and 10th percentile body weight data for each patient group, children were recognized as having the highest potential exposure relative to adults per body mass. Depending on data availability and relationship to the parent API, margins of safety (MOS) or exposure margins were calculated for each degradant. The findings supported safe use, and indicated that this contemporary WOE approach could be utilized to assess OTC degradants. This approach is valuable to establish specifications for degradants in OTCs.

Topical Hemostatic Agents in Burn Surgery: A Systematic Review

Acute burn surgery has long been associated with significant intra-operative bleeding. Several techniques were introduced to limit hemorrhage, including tourniquets, tumescent infiltration, and topical agents. To date, no study has comprehensively investigated the available data regarding topical hemostatic agents in burn surgery. A systematic review was performed by two independent reviewers using electronic databases (PubMed, Scopus, Web of Science) from first available to September 10, 2021. Articles were included if they were published in English and described or evaluated topical hemostatic agents used in burn excision and/or grafting. Data were extracted on the agent(s) used, their dosage, mode of delivery, hemostasis outcomes, and complications. The search identified 1982 nonduplicate citations, of which 134 underwent full-text review, and 49 met inclusion criteria. In total, 32 studies incorporated a vasoconstrictor agent, and 28 studies incorporated a procoagulant agent. Four studies incorporated other agents (hydrogen peroxide, tranexamic acid, collagen sheets, and TT-173). The most common vasoconstrictor used was epinephrine, with doses ranging from 1:1000 to 1:1,000,000. The most common procoagulant used was thrombin, with doses ranging from 10 to 1000 IU/ml. Among the comparative studies, outcomes of blood loss were not reported in a consistent manner, therefore meta-analysis could not be performed. The majority of studies (94%) were level of evidence III-V. Determining the optimal topical hemostatic agent is limited by low-quality data and challenges with consistent reporting of intra-operative blood loss. Given the routine use of topical hemostatic agents in burn surgery, high-quality research is essential to determine the optimal agent, dosage, and mode of delivery.

Single-Dose Pharmacokinetics and Metabolism of the Oral Decongestant Phenylephrine HCl in Children and Adolescents

INTRODUCTION

Pediatric data for phenylephrine, a decongestant used in cold medicines, are limited. This study characterized the pharmacokinetics and metabolism of phenylephrine HCl in children aged 2-17 years.

METHODS

Forty-one children experiencing nasal congestion were dosed orally with phenylephrine HCl from 2.5 to 10 mg using a modified weight-age schedule. Plasma from blood samples collected up to 4.5 h after dosing was analyzed for phenylephrine. Urine collected over 24 h was analyzed for phenylephrine and metabolites. Blood pressure and pulse were measured after each blood sampling, and electrocardiograms were recorded before and after dosing. Pharmacokinetic parameters were estimated using noncompartmental methods.

RESULTS

Mean phenylephrine total exposure (AUC_∞) for children aged 2-5, 6-11, and 12-17 years was 672, 830, and 1020 pg∙h/mL, and mean maximum concentration (C_max) was 477, 589, and 673 pg/mL, respectively. Times to peak concentration (T_max) ranged from 0.17 to 1.5 h, and elimination half-life (t_½,β) was short from 1.2 to 1.6 h. Oral clearance (CL/F) increased with age, but with allometric scaling for body size, this trend reversed as scaled clearance (CL/F,_scaled) was modestly higher in youngest children. No clinically relevant changes in vital signs or electrocardiograms were observed.

CONCLUSION

A dosing schedule with additional weight-age increments would provide more consistent systemic concentrations as children age and receive the next higher dose. No developmental delays in clearance mechanisms were apparent when oral clearance was scaled for body size. Phenylephrine pharmacokinetics and metabolism were consistent with adult data, although AUC∞ for the youngest group and C_max for all pediatric groups were lower. Single doses of phenylephrine HCl were well tolerated. TRIAL REGISTRATION: Clintrials.gov NCT00762567, registered 30 September 2008.

Why Is Oral Phenylephrine on the Market After Compelling Evidence of Its Ineffectiveness as a Decongestant?

Ineffective over-the-counter (OTC) drugs should be removed from the US market. Despite solid research showing that oral phenylephrine is ineffective as a decongestant, the US Food and Drug Administration has failed to respond to a 2015 citizen's petition to remove it from the OTC nasal decongestant monograph. Other examples of scientifically proven ineffective OTC medications include guaifenesin as an expectorant, dextromethorphan as a cough suppressant, and chlorpheniramine for cold symptoms.

Safety, Pharmacokinetic, and Pharmacodynamic Study of a Sublingual Formula for the Treatment of Vasovagal Syncope

Background

Vasovagal syncope is a common cause of syncope which, if recurrent, can have multiple negative consequences such as injury and occupational disability. Various medications can be used to decrease the recurrence of vasovagal syncope but there are no drugs that can be used by patients to interrupt a perceived vasovagal episode.

Methods

A phase I study was performed to evaluate the tolerability and safety of a gel formulation containing capsaicin (1 mg), phenylephrine HCL (PE) and caffeine citrate (200 mg) (CPC) in normal adult volunteers. Secondary objectives were to characterize the pharmacokinetics (PK) of the CPC formulation and the highest dose of PE needed to achieve a target increase in systolic BP of at least 40 mmHg. After receiving the first dose, a second dose of the CPC mixture was administered at 2 h. Suboptimal changes in systolic blood pressure (SBP) were noted at PE doses of 0.6, 1.2, and 1.8 mg, therefore a second cohort was studied at PE doses of 10, 20, and 30 mg. Blood samples were collected in rapid sequence and were assayed for all three drugs.

Results

A total of 17 subjects received the drug with no serious adverse effects reported. All doses were well tolerated, although the capsaicin content usually caused expected temporary oral and gastric discomfort. One subject did not complete the study because of a vasovagal reaction that was associated with the frequent blood sampling. There was a 5–25 min lag in the appearance of measurable blood concentrations of capsaicin and phenylephrine. Most subjects had baseline caffeine concentrations from dietary use, with a gradual increase noted after 15 min consistent with GI absorption. Although the intended criterion of a 40 mmHg increase in SBP was not reached, a clinically significant increase in BP for at least 15 min was noted in the six subjects who received the highest dose of PE (30 mg), with a gradual decline over the next 2 h.

Conclusion

The ternary mixture of capsaicin, phenylephrine, and caffeine was well tolerated when administered as two sublingual/oral doses over a 2-h period.

The Adrenergic System in Plastic and Reconstructive Surgery: Physiology and Clinical Considerations

ABSTRACT

The primary organ systems and tissues concerning plastic and reconstructive surgery include the integument, vasculature, subcutis, and peripheral nerves, because these may individually or collectively be injured requiring reconstruction, or indeed be used in reconstruction themselves through grafts, flaps, or anastomoses. Adrenergic receptors are present throughout these anatomic components on the vasculature, adipose, platelets, immune cells, keratinocytes, melanocytes, fibroblasts, peripheral nerves, and tendons. Herein, the influence of adrenergic signaling on the physiology of anatomic components related to plastic surgery is discussed, along with clinical considerations of this systems involvement in procedures, such as free flap reconstruction, skin grafting, fat grafting, and other areas relevant to plastic and reconstructive surgery. Current evidence as well as potential for further investigation is discussed.

Enzyme Models-From Catalysis to Prodrugs

Enzymes are highly specific biological catalysts that accelerate the rate of chemical reactions within the cell. Our knowledge of how enzymes work remains incomplete. Computational methodologies such as molecular mechanics (MM) and quantum mechanical (QM) methods play an important role in elucidating the detailed mechanisms of enzymatic reactions where experimental research measurements are not possible. Theories invoked by a variety of scientists indicate that enzymes work as structural scaffolds that serve to bring together and orient the reactants so that the reaction can proceed with minimum energy. Enzyme models can be utilized for mimicking enzyme catalysis and the development of novel prodrugs. Prodrugs are used to enhance the pharmacokinetics of drugs; classical prodrug approaches focus on alternating the physicochemical properties, while chemical modern approaches are based on the knowledge gained from the chemistry of enzyme models and correlations between experimental and calculated rate values of intramolecular processes (enzyme models). A large number of prodrugs have been designed and developed to improve the effectiveness and pharmacokinetics of commonly used drugs, such as anti-Parkinson (dopamine), antiviral (acyclovir), antimalarial (atovaquone), anticancer (azanucleosides), antifibrinolytic (tranexamic acid), antihyperlipidemia (statins), vasoconstrictors (phenylephrine), antihypertension (atenolol), antibacterial agents (amoxicillin, cephalexin, and cefuroxime axetil), paracetamol, and guaifenesin. This article describes the works done on enzyme models and the computational methods used to understand enzyme catalysis and to help in the development of efficient prodrugs.

Studying the effect of vasopressors on therapeutic drug monitoring of two local anesthetics using hybrid micelle liquid chromatography as an analysis tool

A hybrid micelle based mobile phase was used to develop and validate a liquid chromatographic method for the separation and quantification of two local anesthetics namely; lidocaine hydrochloride (LID), and bupivacaine hydrochloride (BPV) in presence of the frequently co administered vasopressors phenyl ephrine (PHR) and ephedrine (EPH). Optimization of chromatographic separation conditions was performed applying experimental one factor at a time tool, and design of experiment, where the retention behavior of all analytes using both optimization protocols was in accordance. Chromatographic separation was carried on a C8 column operating at 40 °C at a flow rate of 1.5 mL/min. using a mobile phase consisting of 0.18 M sodium dodecyl sulphate, 10% acetonitrile, containing 0.3% triethyl amine and adjusted to pH 7 using 2 M ortho phosphoric acid, adopting UV detection at 230 nm. The proposed method was fully validated and applied to both in vitro and in vivo analysis of rat blood samples. The pharmacokinetics of both LID and BPV was followed when they were solitary injected or when co administered with either PHR or EPH. Moreover, the in vitro spiked experiment was also subjected to documented bio-analytical validation procedures.

Oláh A, Fésüs L, Mádi A. Transglutaminase 2 Has Metabolic and Vascular Regulatory Functions Revealed by In Vivo Activation of Alpha1-Adrenergic Receptor

The multifunctional tissue transglutaminase has been demonstrated to act as α1-adrenergic receptor-coupled G protein with GTPase activity in several cell types. To explore further the pathophysiological significance of this function we investigated the in vivo effects of the α1-adrenergic receptor agonist phenylephrine comparing responses in wild type and TG2-/- mice. Injection of phenylephrine, but not a beta3-adrenergic agonist (CL-316,243), resulted in the long-term decline of the respiratory exchange ratio and lower lactate concentration in TG2-/- mice indicating they preferred to utilize fatty acids instead of glucose as fuels. Measurement of tail blood pressure revealed that the vasoconstrictive effect of phenylephrine was milder in TG2-/- mice leading to lower levels of lactate dehydrogenase (LDH) isoenzymes in blood. LDH isoenzyme patterns indicated more damage in lung, liver, kidney, skeletal, and cardiac muscle of wild type mice; the latter was confirmed by a higher level of heart-specific CK-MB. Our data suggest that TG2 as an α1-adrenergic receptor-coupled G protein has important regulatory functions in alpha1-adrenergic receptor-mediated metabolic processes and vascular functions.

p-Synephrine, ephedrine, p-octopamine and m-synephrine: Comparative mechanistic, physiological and pharmacological properties

Confusion and misunderstanding exist regarding the lack of cardiovascular and other adverse health effects of p-synephrine and p-octopamine relative to ephedrine and m-synephrine (phenylephrine) which are known for their effects on the cardiovascular system. These four molecules have some structural similarities. However, the structural and stereochemical differences of p-synephrine and p-octopamine as related to ephedrine and m-synephrine result in markedly different adrenergic receptor binding characteristics as well as other mechanistic differences which are reviewed. p-Synephrine and p-octopamine exhibit little binding to α-1, α-2, β-1 and β-2 adrenergic receptors, nor are they known to exhibit indirect actions leading to an increase in available levels of endogenous norepinephrine and epinephrine at commonly used doses. The relative absence of these mechanistic actions provides an explanation for their lack of production of cardiovascular effects at commonly used oral doses as compared to ephedrine and m-synephrine. As a consequence, the effects of ephedrine and m-synephrine cannot be directly extrapolated to p-synephrine and p-octopamine which exhibit significantly different pharmacokinetic, and physiological/pharmacological properties. These conclusions are supported by human, animal and in vitro studies that are discussed.

Sustained Release Bilayer Tablet of Ibuprofen and Phenylephrine Hydrochloride: Preparation and Pharmacokinetics in Beagle Dogs

Cold is a global common infectious disease accompanied by symptoms such as headache and stuffy nose. Ibuprofen (IBU) and phenylephrine hydrochloride (PE) were commonly used for common cold due to their different effects in relieving fever and the main symptoms such as nasal congestion and high sinus pressure. However, the commercial tablets of IBU and PE have to be administered 2 to 3 times per day due to their short half-life, with inconvenience for patient and fluctuations of plasma concentration. Bilayer tablet technology was utilized to design the IBU-PE sustained release tablets because of the significantly different solubility of IBU and PE in release media. The formulations of IBU layer and PE layer contain different viscosity grades of hydroxypropyl methylcellulose (HPMC) as sustained-release matrix, hydrophilic diluent, and traditional glidant and lubricant. The sustained release bilayer tablet exhibited satisfying sustained release performance with the mechanisms of diffusion and matrix erosion. Compared with the conventional tablets, the IBU-PE sustained release bilayer tablet expressed significantly sustained-release behavior with decreased C_max and prolonged T_max in fasted conditions for IBU and PE. Though IBU of IBU-PE sustained release bilayer tablet was bioequivalent to the commercial IBU tablet, the relative bioavailability of PE from the bilayer tablets was 87.49 ± 20.00% (90% confidence interval was 72.3 to 102.5%), indicating bioinequivalence probably due to the "first pass" effect.

Increased Sympathetic Outflow Induces Adaptation to Acute Experimental Pain

BACKGROUND

There are interrelationships between the autonomic nervous system and pain. This study aims to explore the effect of different autonomic manipulations on pain perception and modulation.

METHODS

Twenty healthy subjects (10 men and 10 women, mean age 25 ± 3 years) participated in this single-blinded, semi-randomized, controlled study, which included 2 study visits. Warm detection thresholds, heat pain thresholds, conditioned pain modulation (CPM), and pain adaptation were tested before and after administration of phenylephrine, clonidine, yohimbine, and saline.

RESULTS

Changes in heart rate and blood pressure were found after all the pharmacological interventions. The only effect on pain measures was that yohimbine enhanced pain adaptation capacity while phenylephrine reduced it (P = 0.032). Several significant correlations were found between autonomic and pain parameters; greater decreases in heart rate after phenylephrine were associated with reduced pain ratings (r² = 0.288, P = 0.018). In addition, enhanced pain adaptation was associated with higher total vascular resistance (r² = 0.442, P = 0.01).

CONCLUSIONS

Different effects of acute autonomic manipulations on experimental pain were found: an increase in sympathetic tone induced by yohimbine led to reduced pain sensitivity; a decrease in sympathetic tone with no effect on vagal-parasympathetic tone induced by phenylephrine led to reduction in pain adaptation capacity; and a decrease in sympathetic tone and increase in vagal parasympathetic tone by clonidine led to no change in pain adaptation capacity. While increased sympathetic outflow does facilitate pain adaptation, activation of either the sympathetic or parasympathetic limbs of the autonomic nervous system does not affect pain thresholds or CPM. Finally, a correlation exists between nociception and cardiovascular parameters only due to baroreflex activation.

Hemodynamic responses and plasma phenylephrine concentrations associated with intranasal phenylephrine in children

INTRODUCTION

Intranasal phenylephrine, an alpha-1 adrenergic agonist, causes vasoconstriction of the nasal mucosa and is used to reduce bleeding associated with nasotracheal intubation or endoscopic sinus surgery. The purpose of this study was to describe the hemodynamic effects associated with plasma phenylephrine concentrations following topical intranasal administration of 0.25% and 0.5% phenylephrine in children.

METHODS

After Institutional Review Board and parental approval, 77 children between the ages of 2 and 12 years were studied in a prospective, double-blind manner and randomized into three groups. Group 1 received intranasal saline, while groups 2 and 3 received 0.1 mL/kg of 0.25% or 0.5% phenylephrine, respectively. All received the same anesthetic of halothane, N₂ O, O₂ , and vecuronium. After inhalation induction, endtidal halothane and PaCO₂ were maintained at 1.5% and 35 mm Hg, respectively. Heart rate and rhythm, systolic, diastolic, and mean, noninvasive arterial blood pressures were recorded and venous blood was obtained for measurement of plasma phenylephrine concentration by high-performance liquid chromatography at baseline and at 2, 5, 10, and 20 minutes following intranasal spray application of the study drug. Nasotracheal intubation was performed immediately following the 5-minute measurements, and the presence of bleeding was assessed. Hemodynamic data were compared by analysis of variance for repeated measures. Bleeding and arrhythmia incidence among groups were analyzed using chi-squared tests. Phenylephrine levels were correlated with hemodynamic values via regression analysis.

RESULTS

Fifty-two patients received intranasal phenylephrine. Increases in blood pressure correlated with increasing plasma phenylephrine concentration. Systolic blood pressure increased 8%, and mean blood pressure increased 14%, which were statistically significant but clinically insignificant. Heart rate did not change, and the incidence of arrhythmia was low and similar among groups. Bleeding following nasotracheal intubation was less frequent in Group 3 (11/27 subjects) than in Group 1 (17/25). Peak plasma phenylephrine concentrations were observed by 14±7 minutes following intranasal administration, and were highly variable among individuals (37.8±39.7 and 49.6±93.9 ng/mL [mean±SD] in Groups 2 and 3).

DISCUSSION

Administration of intranasal phenylephrine, 0.25% and 0.50%, results in rapid but highly variable systemic absorption that is associated with mild increases of blood pressure that are clinically insignificant. Bleeding associated with nasotracheal intubation was less following administration of 0.5% intranasal phenylephrine than following intranasal saline.