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

A Routine over the Counter Phenylephrine Causing Rarer Drug Eruption as Adverse Drug Reaction - A Case Report

BACKGROUND

Phenylephrine is a sympathomimetic, which means it acts analogous to adrenaline. Phenylephrine can be taken orally to treat nasal congestion symptoms. It is also frequently mixed with other medicines in products meant to relieve cough and cold symptoms. Given the widespread usage of phenylephrine, related drug eruptions appear to be uncommon.

CASE PRESENTATION

Here we discuss a case of a 19-year-old female patient who reported to our hospital with blebs on the skin throughout her legs and torso. The drug eruption or adverse drug response was linked with itching, had a slow beginning, and progressed. Her medical history indicated that she had been taking phenylephrine 10 mg orally twice a day. On the sixth day, she experienced an adverse medication response caused by the medicine phenylephrine. Phenylephrine was stopped immediately and the other medications, such as levocetirizine, montelukast, and nasal spray, were continued. The patient was told not to use phenylephrine, either alone or in combination with FDCs. There are no other complaints. As a result, the patient was diagnosed with phenylephrine- induced eruption.

CONCLUSION

We present this case to highlight the importance of inspiring a pharmacovigilance mindset among all clinicians providing care as a routine alert drug, phenylephrine-induced drug eruption.

Safety of topical administration of nasal decongestants and vasoconstrictors in paediatric nasal surgery - A systematic review

OBJECTIVES

Topical intranasal decongestants are essential in nasal surgery to improve operative field. There are concerns regarding safety in paediatric population. Data on safety and safe dosage are limited. This systematic review evaluated the literature on safety and dosage of intranasal decongestant in paediatric population.

METHODS

We performed a systematic search of PubMed, EMBASE, Cochrane library for relevant articles. Quality assessment was done on included articles.

RESULTS

A total of 10 articles were included: five case reports; three observational studies; and two randomised control trials. Decongestants evaluated were phenylephrine, oxymetazoline, epinephrine, xylometazoline, and cocaine. In total, 209 patients were included. Side effects reported included bradycardia, tachycardia and hypertension. These were mostly self-limiting and of no clinical compromise to the patients. A total of 4/209 (1.9%) of patients required treatment for these reported effects. No mortality was reported in the included studies.

CONCLUSION

In the paediatric population, the literature suggests that when delivered in a pre-specified, controlled dosage, the haemodynamic effects of phenylephrine, oxymetazoline, xylometazoline are minimal and of no clinical significance. There is scope for further studies to establish safe dosage in the paediatric population given the paucity of current literature.

In-silico analysis of closed-loop vasopressor control of phenylephrine versus norepinephrine

We have previously demonstrated in in-silico, pre-clinical animal models, and finally human clinical studies the ability of a novel closed-loop vasopressor titration system to manage norepinephrine infusion rates to keep mean arterial blood pressure in a very tight range, reduce hypotension time and severity, and reduce overtreatment. We hypothesized that the same controller could, with modification for pharmacologic differences, suitably titrate a lower-potency longer duration of action agent like phenylephrine. Using the same physiologic simulation model as was used previously for in-silico testing of our controller for norepinephrine, we first updated the model to include a new vasopressor agent modeled after phenylephrine. A series of simulation tests patterned after our previous norepinephrine study was then conducted, this time using phenylephrine for management, in order to both test the system with the new agent and allow for comparisons between the two. Hundreds of simulation trials were conducted across a range of patient and environmental variances. The controller performance was characterized based on time in target, time above and below target, coefficient of variation, and using Varvel's criteria. The controller kept the simulated patients' MAP in target for 94% of management time in the simple scenarios and more than 85% of time in the most challenging scenarios. Varvel criteria were all under 1% error for expected pharmacologic responses and were consistent with those established for norepinephrine in our previous studies. The controller was able to acceptably titrate phenylephrine in this simulated patient model consistent with performance previously seen for norepinephrine after adjusting for the anticipated differences between the two agents.

Phenylephrine, a common cold remedy active ingredient, suppresses uterine contractions through cAMP signalling

Regulation of uterine contractility is an important aspect of women’s health. Phenylephrine, a selective agonist of the α₁-adrenoceptor and a potent smooth muscle constrictor, is widely used in women even during pregnancy to relieve cold-related symptoms, to treat postpartum haemorrhoid, and during routine eye exams. We performed isometric tension recordings to investigate the effect of phenylephrine on mouse uterine contractility. Phenylephrine decreased spontaneous and oxytocin-induced contractions in non-pregnant mouse uterine rings and strips with an IC₅₀ of ~1 μM. Prazosin, an inhibitor of α₁-adrenoceptor, did not prevent phenylephrine-mediated relaxations. Conversely, ICI118551, an antagonist of β2-adrenoceptors, inhibited phenylephrine relaxation. In the presence of ICI118551, high concentrations (>30 μM) of phenylephrine caused mouse uterine contractions, suggesting that β-adrenoceptor-mediated inhibition interferes with the phenylephrine contractile potential. Phenylephrine-dependent relaxation was reduced in the uterus of pregnant mice. We used primary mouse and human uterine smooth muscle cells (M/HUSMC) to establish the underlying mechanisms. Phenylephrine stimulated large increases in intracellular cAMP in M/HUSMCs. These cAMP transients were decreased when HUSMCs were cultured in the presence of oestrogen and progesterone to mimic the pregnancy milieu. Thus, phenylephrine is a strong relaxant in the non-pregnant mouse uterus, but exhibits diminished effect in the pregnant uterus.

The phenylephrine concentration-response relationship for blood pressure after nasal delivery in children

BACKGROUND

Intranasal phenylephrine is commonly used to vasoconstrict the nasal mucosa, reducing bleeding associated with nasotracheal intubation or endoscopic sinus surgery. There are few data quantifying either absorption pharmacokinetics or phenylephrine concentration effect on blood pressure in children.

METHODS

Published observations of plasma concentration and blood pressure changes after phenylephrine nasal administration (0.1 mL kg^-1 , 0.25% or 0.5%) in children (n = 52, 2-12 years, 10-40 kg) were pooled with those in adults (23-81 years) given phenylephrine 2.5% (n = 10) and 10% (n = 10) eyedrops. Further pharmacokinetic (PK) data were available from healthy volunteers given oral phenylephrine 10 mg alone, with blood for concentration assay taken at 5, 15, 30, 45 minutes and 1, 2, 3, 6 hours (n = 28). Intravenous time-concentration data were available from four healthy volunteers given phenylephrine 1 mg and who had blood taken for assay on 17 occasions over the subsequent 4 hours. Data were analyzed using an integrated pharmacokinetic-pharmacodynamic (PK-PD) model using nonlinear mixed-effects models. Allometry, scaled to a 70-kg person, was used for PK size standardization. Effect was described using an E_MAX model.

RESULTS

A two-compartment model was used to fit PK data while an additional compartment, linked by an equilibration half-time (T_1/2 keo), was used to describe effect. PK parameter estimates for the nasal formulation were clearance (CL) 160 L h^-1 , central volume of distribution (V1) 13.3 L, intercompartment clearance (Q) 25.3 L h^-1 , peripheral volume of distribution (V2) 225 L, absorption half-time (Tabs) 6.2 minutes, absorption lag time (Tlag) 1.5 minutes, and bioavailability (F) 0.183. Bioavailability and absorption of the ophthalmic solution were concentration dependent (F 0.13, Tabs 5.5 minutes for 2.5% solution; F 0.15, Tabs 9.6 minutes for 10% solution). Absorption of the oral formulation was slow (Tabs 48 minutes) with poor bioavailability (F 0.0128). The pediatric PD interrogation revealed a baseline mean arterial pressure of 60 mm Hg, a maximum effect (E_MAX ) of 25 mm Hg, and an EC₅₀ of 10.3 μg L^-1 . The effect on vasculature was immediate and T_1/2 keo was not estimable.

CONCLUSION

Absorption of phenylephrine through the nasal mucosa was rapid and similar to the ophthalmic formulation. Bioavailability was also similar to the ophthalmic formulation. The maximum effect (E_MAX ) in children was half that in adults (E_MAX 50 mm Hg).