Pharmacokinetics of esmolol in children

Safety and Efficacy of Landiolol Hydrochloride in Children with Tachyarrhythmia of Various Etiologies

The safety and efficacy of landiolol have not been fully elucidated in pediatric patients. This study aimed to clarify the safety and efficacy of landiolol in a pediatric cohort. We retrospectively assessed the clinical features of 21 pediatric patients who were administered landiolol at our hospital. We also investigated the rates of sinus rhythm conversion and heart rate response. The median patient age was 7 months (interquartile range 1-13 months). The etiology of tachyarrhythmia was junctional ectopic tachycardia in 10 patients (47.6%), atrial tachycardia in 10 patients (47.6%), and ventricular tachycardia in 1 patient (4.8%). Of the 21 children, 18 (85.7%) had congenital heart defects, including 14 (77.8%) in whom a landiolol infusion was performed perioperatively. The landiolol infusion was effective in 18 pediatric patients (85.7%), as measured by the conversion to sinus rhythm or a reduced heart rate. Atrial tachycardia in the perioperative period was terminated in all patients. Of 7 patients with tachyarrhythmias unrelated to the perioperative period, landiolol was effective in 5. No adverse effects were reported in any patient. Landiolol infusion is effective and safe in pediatric patients with tachyarrhythmia of various etiologies, especially those with atrial tachyarrhythmia during the perioperative period.

Pharmacologic Control of Blood Pressure in Infants and Children

Alterations in blood pressure are common during the perioperative period in infants and children. Perioperative hypertension may be the result of renal failure, volume overload, or activation of the sympathetic nervous system. Concerns regarding end-organ effects or postoperative bleeding may mandate regulation of blood pressure. During the perioperative period, various pharmacologic agents have been used for blood pressure control including sodium nitroprusside, nitroglycerin, β-adrenergic antagonists, fenoldopam, and calcium channel antagonists. The following manuscript outlines the commonly used pharmacologic agents for perioperative BP including dosing regimens and adverse effect profiles. Previously published clinical trials are discussed and efficacy in the perioperative period reviewed.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antihypertensives

OBJECTIVE

Hypertension remains a common condition in pediatric cardiac intensive care. The physiologic effects of hypertension in this population are complex and are impacted by patient age, comorbidities, and primary cardiac disease. The objective of this study is to review current pharmacotherapies for the management of systemic hypertension in the pediatric cardiac ICU.

DATA SOURCES

Relevant literature to the treatment of systemic hypertension in children was included. Specific focus was given to literature studying the use of therapies in critically ill children and those with heart disease. Reference textbooks and drug packaging inserts were used for drug-specific pediatric guidelines.

STUDY SELECTION

A search of MEDLINE, PubMed, and the Cochrane Database was performed to find literature about the management of hypertension in children. Metaanalyses and pediatric-specific studies were primarily considered and cross-referenced. Pertinent adult studies were included.

DATA EXTRACTION

Once the studies for inclusion were finalized, priority for data extraction was given to pediatric-specific studies that focused on children with heart disease and critical illness.

CONCLUSIONS

Systemic hypertension is common, and there is significant heterogeneity in the patient population with critical heart disease. There are limited large, prospective analyses of safety and efficacy for pediatric drug antihypertensive agents. Despite patient heterogeneity, most pharmacotherapies are safe and efficacious.

Drug treatment of hypertensive crisis in children

Hypertensive crisis is a relatively rare event and is associated with significant morbidity and mortality in adults and pediatric patients alike. Rapid, safe, and effective treatment is imperative to alleviate immediate presenting clinical symptoms, prevent devastating morbidity, preserve long-term quality of life, and prevent mortality. Many medications in the hypertensive crisis arsenal have been used for nearly half a century. Nearly all treatment options have been utilized in children for decades, yet reliable data and sound clinical literature remain elusive. Every agent considered to be a first-line, second-line, or adjunctive option has yet to be evaluated in a randomized controlled trial in pediatric patients. With a paucity of clinical data to form evidence-based decisions, the clinician must rely entirely on the extrapolation from adult data and small retrospective studies, case series, and case reports of medication use in pediatric patients. Although more research in the treatment of pediatric hypertensive crisis is desperately needed, current practice demands a sharp knowledge of the pediatric clinical literature and pharmacology in this area as an essential tool to consistently improve patient outcomes with respect to morbidity and mortality.

Methoxycarbonyl-etomidate: a novel rapidly metabolized and ultra-short-acting etomidate analogue that does not produce prolonged adrenocortical suppression

BACKGROUND

Etomidate is a rapidly acting sedative-hypnotic that provides hemodynamic stability. It causes prolonged suppression of adrenocortical steroid synthesis; therefore, its clinical utility and safety are limited. The authors describe the results of studies to define the pharmacology of (R)-3-methoxy-3-oxopropyl1-(1-phenylethyl)-1H-imidazole-5-carboxylate (MOC-etomidate), the first etomidate analogue designed to be susceptible to ultra-rapid metabolism.

METHODS

The gamma-aminobutyric acid type A receptor activities of MOC-etomidate and etomidate were compared by using electrophysiological techniques in human alpha1beta2gamma2l receptors. MOC-etomidate's hypnotic concentration was determined in tadpoles by using a loss of righting reflex assay. Its in vitro metabolic half-life was measured in human liver S9 fraction, and the resulting metabolite was provisionally identified by using high-performance liquid chromatography/mass spectrometry techniques. The hypnotic and hemodynamic actions of MOC-etomidate, etomidate, and propofol were defined in rats. The abilities of MOC-etomidate and etomidate to inhibit corticosterone production were assessed in rats.

RESULTS

MOC-etomidate potently enhanced gamma-aminobutyric acid type A receptor function and produced loss of righting reflex in tadpoles. Metabolism in human liver S9 fraction was first-order, with an in vitro half-life of 4.4 min versus more than 40 min for etomidate. MOC-etomidate's only detectable metabolite was a carboxylic acid. In rats, MOC-etomidate produced rapid loss of righting reflex that was extremely brief and caused minimal hemodynamic changes. Unlike etomidate, MOC-etomidate produced no adrenocortical suppression 30 min after administration.

CONCLUSIONS

MOC-etomidate is an etomidate analogue that retains etomidate's important favorable pharmacological properties. However, it is rapidly metabolized, ultra-short-acting, and does not produce prolonged adrenocortical suppression after bolus administration.

The safety, efficacy, and pharmacokinetics of esmolol for blood pressure control immediately after repair of coarctation of the aorta in infants and children: a multicenter, double-blind, randomized trial

OBJECTIVES

Blood pressure control is important after repair of coarctation of the aorta. We report the first prospective multi-institutional trial addressing the safety and efficacy of esmolol after repair of coarctation of the aorta in infants and children.

METHODS

The primary objective of this phase IIIb, multicenter, double-blind, randomized, dose-ranging trial was the efficacy of esmolol to control hypertension. Candidates included subjects younger than 6 years and weighing 2.5 kg or more who underwent surgical intervention for coarctation of the aorta and required therapy for systemic hypertension. One hundred sixteen subjects received esmolol: 36 received a low dose (125 microg/kg), 43 received a medium dose (250 microg/kg), and 37 received a high dose (500 microg/kg). The primary outcomes were the change in systolic blood pressure and the need for additional antihypertensive rescue medication 5 minutes after the initiation of esmolol.

RESULTS

All dose groups showed a significant decrease from baseline in systolic blood pressure (-9.6 +/- 16.3 mm Hg, P < .001). There were no differences in systolic blood pressure response at 5 minutes between dose groups (high, medium, or low) or age groups. The need for rescue medication at 5 minutes was not different between dose groups. All dose groups showed similar incidences of adverse events. There were no serious adverse events.

DISCUSSION

Esmolol can be administered safely to patients younger than 6 years after repair of coarctation of the aorta. In the dose range of 125 to 500 microg/kg, esmolol significantly decreased systolic blood pressure.

The pharmacokinetics of esmolol in pediatric subjects with supraventricular arrhythmias

Esmolol is often used in the acute management of children with arrhythmias and/or hypertension; however, pharmacokinetic studies of the drug in children have been limited. The objective of this study was to determine the pharmacokinetics of esmolol in children with a history of supraventricular arrhythmias (SVT) who were scheduled for diagnostic electrophysiology study or a catheter ablation procedure. Subjects were stratified into two age groups: 2-11 and 12-16 years. After an episode of stimulated or spontaneous SVT, esmolol was administered intravenously as a 1,000 microg/kg bolus followed by continuous infusion at 300 microg/kg/min. Blood samples were collected before, at 5, 10 and 15 min after the loading dose, and 3, 6, 9, 12, 15 and 20 min after the end of the infusion. Plasma concentration of esmolol was quantitated by a specific LC/MS assay. Pharmacokinetic data were available for 25 subjects. Arterial esmolol concentrations were approximately five times greater than venous concentrations. Esmolol had an extremely short distribution half-life (0.6 min), a rapid terminal elimination half-life (6.9 min), and a rapid clearance (119 +/- 51 mL/min/kg) which was not related to subject age or weight. Seventeen of the subjects (63%) converted to normal sinus rhythm in an average of 2 min (range 0-5 min). The pharmacokinetics of esmolol and its efficacy in terminating SVT in children is similar to that observed in adults.

Liquid chromatography-electrospray mass spectrometry (LC-MS) method for determination of esmolol concentration in human plasma

Esmolol is a very short-acting beta-blocker commonly used in critically ill patients. To study the pharmacokinetics of esmolol in pediatric patients, a liquid chromatography-electrospray mass spectrometry (LC-MS) method to quantitate esmolol concentration in plasma was developed. Following methylene chloride extraction from 200 microl aliquots of plasma containing internal standard and reconstitution in 0.05% formic acid, 10 microl are injected onto column, eluted using a methanol/formic acid gradient over 15 min, and monitored with selected ion recording at 296.2 and 282.2. The assay is linear between 2 and 1000 ng/ml. The intra-day and inter-day coefficients of variation are less than 8 and 10%, respectively.

Successful treatment of long QT syndrome-induced ventricular tachycardia with esmolol

Esmolol is a cardioselective beta-blocker with very rapid onset of action and short half-life due to its metabolism by blood-borne esterases. This unique profile among currently available beta-blockers renders esmolol highly useful in critical care situations. However, published experience with the use of esmolol in critically ill children is scant. The case of a 4-year-old boy with secondary long QT syndrome and ventricular tachycardia successfully treated with esmolol is presented.

Human variability for metabolic pathways with limited data (CYP2A6, CYP2C9, CYP2E1, ADH, esterases, glycine and sulphate conjugation)

Human variability in the kinetics of a number of phase I (CYP2A6, CYP2C9, CYP2E1, alcohol dehydrogenase and hydrolysis) and phase II enzymes (glycine and sulphate conjugation) was analysed using probe substrates metabolised extensively (>60%) by these routes. Published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and available data on subgroups of the population (effects of ethnicity, age and disease) were abstracted using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration time-curve (AUC)] and acute exposure (C(max)). Interindividual differences in kinetics for all these pathways were low in healthy adults ranging from 21 to 34%. Pathway-related uncertainty factors to cover the 95th, 97.5th and 99th centiles of healthy adults were derived for each metabolic route and were all below the 3.16 kinetic default uncertainty factor in healthy adults, with the possible exception of CYP2C9*3/*3 poor metabolisers (based on a very limited number of subjects). Previous analyses of other pathways have shown that neonates represent the most susceptible subgroup and this was true also for glycine conjugation for which an uncertainty factor of 29 would be required to cover 99% of this subgroup. Neonatal data were not available for any other pathway analysed.

Esmolol for the management of pediatric hypertension after cardiac operations

OBJECTIVE

Hypertension frequently occurs during the immediate postoperative period in children after repair of aortic coarctation but may also occur after repair of other congenital heart defects. Nitroprusside has often been used to control blood pressure in this setting. Because hypertension after coarctation repair is frequently associated with elevations in catecholamines, esmolol, a short-acting beta-blocking agent, may be an effective alternative. Therefore we undertook the first systematic investigation to determine the efficacy and disposition of esmolol in pediatric patients with acute hypertension after cardiac operations.

METHODS

Twenty patients aged 1 month to 12 years (median 25.6 months) with acute hypertension after cardiac operations received esmolol in an opened-labeled trial. Esmolol was titrated to a blood pressure less than or equal to the 90th percentile for age.

RESULTS

Ten patients had coarctation repair and the remaining patients underwent repair of other congenital heart defects. On final esmolol dose (mean +/- standard deviation dosage 700 +/- 232 microg/kg/min) there was a significant percent decrease in heart rate and systolic and diastolic blood pressures from postoperative values. Esmolol dose was significantly associated with percent reduction in systolic blood pressure. Final esmolol dose and total body clearance were significantly higher in patients after coarctation repair. There were significant associations between esmolol dose and esmolol blood concentrations at steady state.

CONCLUSIONS

The dosage required to control hypertension in patients after repair of aortic coarctation was higher than patients who underwent repair of other congenital heart defects. Esmolol was effective in controlling blood pressure in 19 of 20 patients without adverse effects.

Esmolol. A review of its therapeutic efficacy and pharmacokinetic characteristics

Esmolol is an ultra short-acting intravenous cardioselective beta-antagonist. It has an extremely short elimination half-life (mean: 9 minutes; range: 4 to 16 minutes) and a total body clearance [285 ml/min/kg (17.1 L/h/kg)] approaching 3 times cardiac output and 14 times hepatic blood flow. The alpha-distribution half-life is approximately 2 minutes. When esmolol is administered as a bolus followed by a continuous infusion, onset of activity occurs within 2 minutes, with 90% of steady-state beta-blockade occurring within 5 minutes. Full recovery from beta-blockade is observed 18 to 30 minutes after terminating the infusion. Esmolol blood concentrations are undetectable 20 to 30 minutes postinfusion. The elimination of esmolol is independent of renal or hepatic function as it is metabolised by red blood cell cytosol esterases to an acid metabolite and methanol. The acid metabolite, which is renally eliminated, has 1500-fold less activity than esmolol. Methanol concentrations remain within the range of normal endogenous levels. Clinically, esmolol is used for the following: (i) situations where a brief duration of adrenergic blockade is required, such as tracheal intubation and stressful surgical stimuli; and (ii) critically ill or unstable patients in whom the dosage of esmolol is easily titrated to response and adverse effects are rapidly managed by termination of the infusion. In adults, bolus doses of 100 to 200mg are effective in attenuating the adrenergic responses associated with tracheal intubation and surgical stimuli. For the control of supraventricular arrhythmias, acute postoperative hypertension and acute ischaemic heart disease, doses of < 300 micrograms/kg/min, administered by continuous intravenous infusion, are used. The principal adverse effect of esmolol is hypotension (incidence of 0 to 50%), which is frequently accompanied with diaphoresis. The incidence of hypotension appears to increase with doses exceeding 150 micrograms/kg/min and in patients with low baseline blood pressure. Hypotension infrequently requires any intervention other than decreasing the dose or discontinuing the infusion. Symptoms generally resolve within 30 minutes after discontinuing the drug. In surgical and critical care settings where clinical conditions are rapidly changing, the pharmacokinetic profile of esmolol allows the drug to provide rapid pharmacological control and minimises the potential for serious adverse effects.

Pharmacodynamics and pharmacokinetics of esmolol, a short-acting beta-blocking agent, in children

Esmolol, a short-acting intravenous cardioselective beta-blocking agent, was evaluated for age-dependent pharmacodynamic and pharmacokinetic features in 17 young patients (6 months to 14 years). A loading dose (500 micrograms/kg/min) alternating with a maintenance dose (25-200 micrograms/kg/min, titrating by 25 micrograms/kg/min every 4 min) was infused until the heart rate or mean arterial pressure decreased 10%. Cardiac index, left ventricular shortening fraction, and systemic vascular resistance were measured at baseline, peak esmolol effect, and recovery. Serum esmolol concentrations were obtained to determine the half-life and the elimination rate constant. Esmolol reduced the heart rate, blood pressure, shortening fraction, and cardiac index in all patients, but it did not change systemic vascular resistance. Maintenance esmolol dose was 118 +/- 49 micrograms/kg/min, and the half-life was 2.88 +/- 2.67 min. Blood pressure and heart rate returned to normal within 2-16 min, but cardiac index and shortening fraction took longer to recover. There were no statistically significant age-dependent pharmacodynamic effects, but blood pressure decreased prior to heart rate and cardiac index took longer to recovery in patients who weighed < or = 15 kg. The pharmacokinetic profile in young patients was similar to that of older patients, but the half-life was shorter. The only side effect was transient nausea and vomiting in one patient. Esmolol is a safe and efficacious beta-blocking agent in young patients.

Esmolol tilt testing with esmolol withdrawal for the evaluation of syncope in the young

BACKGROUND

Head-upright tilt (HUT) testing is valuable in evaluating syncope. Isoproterenol is used to increase sensitivity. However, isoproterenol is contraindicated or dangerous in undiagnosed heart disease and produces false-positives. We introduced esmolol withdrawal during esmolol HUT, hypothesizing that (1) acute withdrawal of the ultrashort-acting beta-blocker induces beta-adrenergic effects by unmasking endogenous catecholamines and may provoke syncope with fewer risks, and (2) response to esmolol/esmolol withdrawal may predict effective therapy.

METHODS AND RESULTS

Thirty-six patients with unexplained recurrent syncope/presyncope (7 to 35 years old, known heart disease or arrhythmia in 14) underwent 2 to 4 HUT tests (60 degrees, 49 minutes): (1) baseline, (2) esmolol (500 micrograms/kg plus 50 micrograms.kg-1.min-1), (3) esmolol withdrawal (HUT continued after esmolol stopped), and (4) isoproterenol if tests 1 through 3 were negative and isoproterenol was not contraindicated. A positive test reproduced symptoms with hypotension or bradycardia, requiring recumbency for recovery. Twenty-five had positive tests, and 11 had negative tests. In 5, only the baseline test was positive; in 15, esmolol/esmolol withdrawal tests were also positive, with 3 in whom esmolol withdrawal was positive although negative at baseline. Two isoproterenol tilts were positive. Esmolol withdrawal and isoproterenol tilts had the highest initial heart rate and similar maximal heart rate increment. Only isoproterenol caused hypertension. One isoproterenol test was false-positive, with hypertension-induced arterial baroreflex. Treatment was beta-blockers (8), Na/fludrocortisone (9), both (6), and DDD pacemakers (2). Esmolol/esmolol withdrawal accurately predicted therapeutic response in 15; isoproterenol predicted therapeutic response in none.

CONCLUSIONS

Esmolol withdrawal tilt testing is preferable to isoproterenol for provocative testing of syncope in the young, and it appears to be safer. Esmolol withdrawal testing has clinical utility before invasive testing as a first-line investigation for syncope in patients with or without heart disease.