Pharmacokinetic and pharmacodynamic study of intranasal and intravenous dexmedetomidine

Effectiveness of nebulized dexmedetomidine for treatment of post-dural puncture headache in parturients undergoing elective cesarean section under spinal anesthesia: a randomized controlled study

PURPOSE

The need for effective treatment for post-dural puncture headache (PDPH) is a growing research entity. This study aimed to test the effectiveness of additional dexmedetomidine (DEX) to PDPH conservative management and evaluate its cerebral hemodynamic effects trans-cranial Doppler.

METHODS

This prospective randomized double-blind controlled trial was conducted on 43 post-partum females suffering from PDPH with visual analog score (VAS) ≥ 4 and Lybecker score ≥ 2. The study subjects were allocated into control group [n = 22] received nebulization of 4 mL 0.9% saline and DEX group [n = 21] received nebulization of 1 µg/kg DEX diluted in 4 mL 0.9% saline twice daily that was continued until achieving VAS score ≤ 3 and Lybecker score < 2 and/or for a maximum of 72 h. Both groups received routine conservative management. The primary outcome was the VAS and Lybecker scores and the secondary results were the DEX effects on cerebral vessels and the occurrence of any adverse effects.

RESULTS

VAS and Lybecker scores were significantly lower in DEX group. The middle cerebral artery mean flow velocity was significantly lower, and the pulsatility index was considerably higher after DEX nebulization compared to placebo. Two patients in the control group were indicated for epidural blood patch.

CONCLUSION

The addition of DEX nebulization (1 µg/kg twice daily) to the PDPH conservative care effectively relieved the symptoms and lowered pain scores which could be due to its analgesic and cerebral vasoconstrictive effects.

TRIAL REGISTRATION

This study was approved by the research ethical committee of Faculty of Medicine, Zagazig University with the reference number (ZU-IRB#: 6075/26-4-2020) and it was registered under clinicaltrials.gov (NCT04327726).

Intranasal dexmedetomidine versus oral midazolam premedication to prevent emergence delirium in children undergoing strabismus surgery: A randomised controlled trial

BACKGROUND

Dexmedetomidine is being used increasingly as a premedicant in the paediatric population. However, the effectiveness of pre-operative intranasal dexmedetomidine premedication, compared with oral midazolam, for emergence delirium is not well characterised.

OBJECTIVE

To identify the effectiveness of pre-operative intranasal dexmedetomidine for emergence delirium in the paediatric patient population following general anaesthesia.

DESIGN

A prospective, randomised, double-blind, parallel-group, placebo-controlled trial.

SETTING

Single university teaching hospital, from September 2013 to August 2014.

PATIENTS

One hundred and fifty-six patients undergoing anaesthesia for strabismus surgery were included in the study.

INTERVENTION

Patients were randomised in a 1 : 1 : 1 ratio to receive premedication with intranasal dexmedetomidine 2 μg kg (the dexmedetomidine group), oral midazolam 0.5 mg kg (the midazolam group), or 0.9% saline (the placebo group).

MAIN OUTCOME MEASURES

The primary outcome was the incidence of emergence delirium assessed by the Paediatric Anaesthesia Emergence Delirium scale. Secondary outcomes included the quality of the inhalational induction, emergence time, postoperative pain intensity, length of stay in the postanaesthesia care unit, the incidence of postoperative nausea or vomiting (PONV) and parents' satisfaction.

RESULTS

The incidence of emergence delirium was lower in patients given dexmedetomidine compared with that in patients given midazolam (11.5 versus 44%, relative risk = 0.262, 95% confidence interval 0.116 to 0.592) or 0.9% saline (11.5 versus 49%, relative risk = 0.235, 95% confidence interval 0.105 to 0.525). Likewise, the incidence of PONV was lower in the dexmedetomidine group (3.8%) than that in the midazolam (22%; P = 0.006) or placebo (29.4%; P < 0.001) groups. However, there was no difference among the groups concerning postoperative pain scores and length of postanaesthesia care unit stay.

CONCLUSION

In paediatric patients undergoing strabismus surgery intranasal dexmedetomidine 2 μg kg premedication decreases the incidence of emergence delirium and PONV, and improves parents' satisfaction compared with oral midazolam.

TRIAL REGISTRATION

ClinicalTrials.gov (identifier: NCT01895023).

Feasibility of Intranasal Dexmedetomidine in Treatment of Postoperative Restlessness, Agitation, and Pain in Geriatric Orthopedic Patients

Objective

The aim of this study was to report preliminary data on the use of intranasal dexmedetomidine to treat postoperative restlessness, agitation, and pain in 23 patients aged > 70 years and undergoing orthopedic surgery.

Background

Postoperative agitation and delirium are common among older adult patients undergoing orthopedic surgery. Most preparations used to treat agitation and delirium carry a risk for adverse events such as respiratory failure. Moreover, mere opioid therapy may be insufficient in treatment of pain. Dexmedetomidine, an α2-adrenoreceptor agonist with sedative and analgesic properties, has been shown to reduce opioid requirement and reduce postoperative delirium in older adults.

Methods

We studied the use of post-operative intranasal dexmedetomidine in a retrospective study cohort of geriatric patients undergoing orthopedic surgery. Primary outcomes included alterations in heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral oxygen saturation (SpO2), Modified Richmond Agitation and Sedation Score (mRASS), and opioid consumption following dexmedetomidine administration.

Results

We identified 23 patients with a mean (SD) age of 79.9 (7.5) years who received dexmedetomidine 100 µg intranasally postoperatively. After dexmedetomidine administration, HR decreased by 10.4 (3.7) beats/min (95% CI 2.9–17.8; p = 0.004) and MAP by 16.2 (4.4) mmHg (95% CI 7.3–25.1; p < 0.001). HR decrease was significant at 2 h and MAP decrease at 1, 2, and 3 h following dexmedetomidine administration. Dexmedetomidine administration was associated with significant reductions in opioid consumption (p < 0.001) and mRASS score (p < 0.001). SpO₂ and RR remained unchanged.

Conclusions

These preliminary findings suggest that intranasal dexmedetomidine reduces opioid consumption without causing respiratory depression and may be used to treat postoperative restlessness, agitation, and pain in geriatric patients. However, hemodynamic effects of dexmedetomidine may require close observation for 3 hours following administration in older adult patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40266-021-00846-6.

Intranasal Dexmedetomidine Reduces Postoperative Opioid Requirement in Patients Undergoing Total Knee Arthroplasty Under General Anesthesia

BACKGROUND

Total knee arthroplasty (TKA) causes severe pain, and strong opioids are commonly used in postoperative analgesia. Dexmedetomidine is a novel alpha-2-adrenoceptor-activating drug indicated for procedural sedation, but previous studies have shown clinically relevant analgesic and antiemetic effects. We evaluated retrospectively the effect of intranasal dexmedetomidine on the postoperative opioid requirement in patients undergoing TKA.

METHODS

One hundred and fifty patients with ASA status 1-2, age between 35 and 80 years, and scheduled for unilateral primary TKA under total intravenous anesthesia were included in the study. Half of the patients received 100 μg of intranasal dexmedetomidine after anesthesia induction, while the rest were treated conventionally. The postoperative opioid requirement was calculated as morphine equivalent doses for both groups. The effect of dexmedetomidine on postoperative hemodynamics, length of stay (LOS), and incidence of postoperative nausea and vomiting (PONV), was evaluated.

RESULTS

The cumulative postoperative opioid consumption was significantly reduced in the dexmedetomidine group compared to the control group (-28.5 mg, 95% CI 12-47 mg P < .001). The reduction in cumulative opioid dose was significantly different between the groups already at 2, 12, 24, and 36 h postoperatively (P < .001). LOS was shorter in the dexmedetomidine group (P < .001), and the dexmedetomidine group had lower postoperative mean arterial pressure and heart rates were lower compared to the control group (P < .001). The incidence of PONV did not differ between the groups (P = .64).

CONCLUSION

Intraoperatively administered intranasal dexmedetomidine reduces postoperative opioid consumption and may be associated with a shorter hospital stay in patients undergoing TKA under general anesthesia.

A Pharmacokinetic and Pharmacodynamic Study of Oral Dexmedetomidine

BACKGROUND

Dexmedetomidine is only approved for use in humans as an intravenous medication. An oral formulation may broaden the use and benefits of dexmedetomidine to numerous care settings. The authors hypothesized that oral dexmedetomidine (300 mcg to 700 mcg) would result in plasma concentrations consistent with sedation while maintaining hemodynamic stability.

METHODS

The authors performed a single-site, open-label, phase I dose-escalation study of a solid oral dosage formulation of dexmedetomidine in healthy volunteers (n = 5, 300 mcg; followed by n = 5, 500 mcg; followed by n = 5, 700 mcg). The primary study outcome was hemodynamic stability defined as lack of hypertension, hypotension, or bradycardia. The authors assessed this outcome by analyzing raw hemodynamic data. Plasma dexmedetomidine concentrations were determined by liquid chromatograph-tandem mass spectrometry. Nonlinear mixed effect models were used for pharmacokinetic and pharmacodynamic analyses.

RESULTS

Oral dexmedetomidine was associated with plasma concentration-dependent decreases in heart rate and mean arterial pressure. All but one subject in the 500-mcg group met our criteria for hemodynamic stability. The plasma concentration profile was adequately described by a 2-compartment, weight allometric, first-order absorption, first-order elimination pharmacokinetic model. The standardized estimated parameters for an individual of 70 kg was V1 = 35.6 [95% CI, 23.8 to 52.8] l; V2 = 54.7 [34.2 to 81.7] l; CL = 0.56 [0.49 to 0.64] l/min; and F = 7.2 [4.7 to 14.4]%. Linear models with effect sites adequately described the decreases in mean arterial pressure and heart rate associated with oral dexmedetomidine administration. However, only the 700-mcg group reached plasma concentrations that have previously been associated with sedation (>0.2 ng/ml).

CONCLUSIONS

Oral administration of dexmedetomidine in doses between 300 and 700 mcg was associated with decreases in heart rate and mean arterial pressure. Despite low oral absorption, the 700-mcg dose scheme reached clinically relevant concentrations for possible use as a sleep-enhancing medication.

EDITOR’S PERSPECTIVE

A Universal Pharmacokinetic Model for Dexmedetomidine in Children and Adults

A universal pharmacokinetic model was developed from pooled paediatric and adult data (40.6 postmenstrual weeks, 70.8 years, 3.1-152 kg). A three-compartment pharmacokinetic model with first-order elimination was superior to a two-compartment model to describe these pooled dexmedetomidine data. Population parameter estimates (population parameter variability%) were clearance (CL) 0.9 L/min/70 kg (36); intercompartmental clearances (Q2) 1.68 L/min/70 kg (63); Q3 0.62 L/min/70 kg (90); volume of distribution in the central compartment (V1) 25.2 L/70 kg (103.9); rapidly equilibrating peripheral compartment (V2) 34.4 L/70 kg (41.8); slow equilibrating peripheral compartment (V3) 65.4 L/70 kg (62). Obesity was best described by fat-free mass for clearances and normal fat mass for volumes with a factor for fat mass (FfatV) of 0.293. Models describing dexmedetomidine pharmacokinetics in adults can be applied to children by accounting for size (allometry) and age (maturation). This universal dexmedetomidine model is applicable to a broad range of ages and weights: neonates through to obese adults. Lean body weight is a better size descriptor for dexmedetomidine clearance than total body weight. This parameter set could be programmed into target-controlled infusion pumps for use in a broad population.

The role of dexmedetomidine in neurosurgery

Dexmedetomidine can be used for sedation and analgesia and has been approved for this use by the European Medicines Agency since 2017. It causes an arousable state of sedation, which is beneficial during neurosurgical procedures that require the patient to cooperate with neurological tests (i.e. tumor surgery or implantation of deep brain stimulators). During procedures where monitoring of somatosensory evoked potentials and/or motor evoked potentials is required, dexmedetomidine can be used as an adjunct to general anesthesia with GABAergic drugs to decrease the dose of the latter when these drugs impair the monitoring signals. The use of dexmedetomidine has also been associated with neuroprotective effects and a decreased incidence of delirium, but studies confirming these effects in the peri-operative (neuro-)surgical setting are lacking. Although dexmedetomidine does not cause respiratory depression, its hemodynamic effects are complex and careful patient selection, choice of dose, and monitoring must be performed.

Systematic review and meta-analysis found that intranasal dexmedetomidine was a safe and effective sedative drug during paediatric procedural sedation

AIM

This systematic review and meta-analysis evaluated the effectiveness of intranasal dexmedetomidine as a sole sedative during paediatric procedural sedation outside the operating room.

METHODS

Relevant literature identified by PubMed, Scopus, ClinicalTrials.gov, ScienceDirect and Cochrane Library up to 31 December 2019 was systematically reviewed. Randomised controlled trials that compared intranasal dexmedetomidine with another sedative or placebo during paediatric procedural sedation were included. Trials that studied intranasal dexmedetomidine as a premedication before anaesthesia were excluded. The primary outcome was the success of the planned procedure.

RESULTS

We analysed seven randomised controlled trials of 730 patients: four trials with 570 patients compared dexmedetomidine with chloral hydrate and three trials with 160 patients compared dexmedetomidine with midazolam. The incidence of successfully completing the procedure did not differ between dexmedetomidine and chloral hydrate, but dexmedetomidine had a higher success rate than midazolam. The incidence of hypotension, bradycardia or respiratory complications did not differ between the sedatives used. Nausea and vomiting were more common in children treated with chloral hydrate than in those treated with other sedatives.

CONCLUSION

Intranasal dexmedetomidine was a safe and effective sedative for minor paediatric procedures.

Comparison of Intranasal Dexmedetomidine Versus Intranasal Ketamine as Premedication for Level of Sedation in Children Undergoing Radiation Therapy: A Prospective, Randomised, Double-Blind Study

OBJECTIVE

Radiation therapy is indicated in many solid tumours in children. Absolute immobility is required to precisely position children for optimal delivery of radiation energy to the target tissues, improve success rate and reduce the damage to nearby normal tissues. Intranasal (IN) administration of drugs is well tolerated, effective and fast acting. The primary aim of the present study was to evaluate the effectiveness of IN ketamine and dexmedetomidine for providing sedation in children before shifting to the radiotherapy suite. The secondary objective was to assess the requirement of propofol dosage in these patients.

METHODS

A total of 243 children aged between 1 and 5 years scheduled to undergo external beam radiotherapy were randomised to receive 5 mg kg^-1 ketamine (group K, n=80), 2.5 μg kg^-1 dexmedetomidine (group D, n=85) or 0.5 ml of saline (group S, n=78) in each nostril. After 45 min, sedation score was measured according to the modified Ramsay score (MRS) at the time of shifting for radiation. Time to awakening and time to discharge after the procedure were also noted.

RESULTS

A significantly higher proportion of children in group D (84.7%) achieved an MRS score ≥3 as compared to group K (36.2%) and group S (3.84%). The total propofol dose (mg kg^-1) required was significantly less in group D (p<0.01). The patients in group D required more time to awakening, but this difference was not clinically significant.

CONCLUSION

The present study demonstrated that IN dexmedetomidine is superior to IN ketamine to provide procedural sedation for radiotherapy in children.

Pharmacokinetics and Sedative Effects of Intranasal Dexmedetomidine in Ambulatory Pediatric Patients

BACKGROUND

Our aim was to characterize the pharmacokinetics and sedative effects of intranasally (IN) administered dexmedetomidine used as an adjuvant in pediatric patients scheduled for magnetic resonance imaging (MRI) requiring sedation.

METHODS

This was an open-label, single-period study without randomization. Pediatric patients from 5 months to 11 years of age scheduled for MRI and receiving IN dexmedetomidine for premedication as part of their care were included in this clinical trial. Single doses of 2-3 µg·kg of dexmedetomidine were applied IN approximately 1 hour before MRI. Five or 6 venous blood samples were collected over 4 hours for dexmedetomidine concentration analysis. Sedation was monitored with Comfort-B scores, and vital signs were recorded. Pharmacokinetic variables were calculated with noncompartmental methods and compared between 3 age groups (between 1 and 24 months, from 24 months to 6 years, and over 6-11 years).

RESULTS

We evaluated 187 consecutive patients for suitability, of which 132 were excluded. Remaining 55 patients were recruited, of which 5 were excluded before the analysis. Data from 50 patients were analyzed. The average (standard deviation [SD]) dose-corrected peak plasma concentration (Cmax) was 0.011 liter (0.0051), and the median (interquartile range [IQR]) time to reach peak concentration (tmax) was 37 minutes (30-45 minutes). There was negative correlation with Cmax versus age (r = -0.58; 95% confidence interval [CI], -0.74 to -0.37; P < .001), but not with tmax (r = -0.14; 95% CI, 0.14-0.39; P = .35). Dose-corrected areas under the concentration-time curve were negatively correlated with age (r = -0.53; 95% CI, 0.70 to -0.29; P < .001). Median (IQR) maximal reduction in Comfort-B sedation scores was 8 (6-9), which was achieved 45 minutes (40-48 minutes) after dosing. Median (IQR) decrease in heart rate was 15% (9%-23%) from the baseline.

CONCLUSIONS

Dexmedetomidine is relatively rapidly absorbed after IN administration and provides clinically meaningful but short-lasting sedation in pediatric patients.

Comparison of Intranasal Dexmedetomidine and Oral Midazolam for Premedication in Pediatric Dental Patients under General Anesthesia: A Randomised Clinical Trial

The aim of this study was to compare the effects of preoperative intranasal dexmedetomidine and oral midazolam on preoperative sedation and postoperative agitation in pediatric dentistry. A total of 60 children (ASA grade I, aged 3-6 years) scheduled for elective pediatric dental treatment were randomly divided into the dexmedetomidine (DEX) and midazolam (MID) groups. Ramsay sedation score, parental separation anxiety scale, mask acceptance scale, pediatric anesthesia emergence delirium scale, and hemodynamic parameters were recorded. The Ramsay sedation scale and hemodynamic parameters of the children were observed and recorded immediately before administration and 10, 20, and 30 min after administration. A satisfactory mask acceptance scale rate was 93.33% in both MID and DEX groups, and there was no significant difference between the two groups (p > 0.05). The proportions of children that "successfully separated from their parents" were 93.33% (MID) and 96.67% (DEX). No significant difference was found between the two groups (p > 0.05). The incidence of agitation was 20% in the MID group and 0% in the DEX group, and the difference was statistically significant (p < 0.05). Intranasal dexmedetomidine and oral midazolam provided satisfactory sedation. No significant difference between the two groups was found in terms of parental separation anxiety and mask acceptance (p > 0.05). The incidence of postoperative pediatrics emergence delirium was significantly lower in the DEX group (p < 0.05).

Neuroregenerative and protective functions of Leukemia Inhibitory Factor in perinatal hypoxic-ischemic brain injury

Neonatal hypoxic-ischemic encephalopathy remains the most important neurological problem of the newborn. Delays in diagnosing perinatal brain injuries are common, preventing access to acute therapies. Therefore, there is a critical need for therapeutic strategies that are beneficial when delivered beyond 24 h after birth. Here we show that Leukemia Inhibitory Factor (LIF) functions as an essential injury-induced neurotrophic cytokine in the CNS and that non-invasively administering LIF as late as 3 days after a hypoxic-ischemic insult improves neurological function. Using a mouse model of late preterm brain injury we show that astroglial and microglial/macrophage reactivity to hypoxia-ischemia was diminished at 3 days of recovery, but then exacerbated at 2 weeks of recovery in LIF haplodeficient mice. There also were significantly more CD68+/Iba-1+ cells in the ipsilateral striatum in LIF-Het mice compared to WT mice at 2 weeks of recovery. This desynchronized glial response was accompanied by increased neuronal cell death in the striatum and neocortex (Fluorojade C), hypomyelination (reduced MBP staining and thinner external capsule), increased extent of brain damage (Nissl) and diminished neurological function on sensorimotor tests. To our surprise, injured LIF-Het mice had ~7-fold higher IGF-1 levels than injured WT mice at 3 days after HI injury. Intranasally administered LIF activated the Jak-Stat-3 pathway both within the subventricular zone and the neocortex at 30 min after administration. When delivered with a delay of 3 days after the insult, intranasal LIF reduced the extent of brain injury by ~60%, attenuated astrogliosis and microgliosis in striatum, improved subcortical white matter thickness, increased numbers of Olig2+ cells in corpus callosum and improved performance on sensorimotor tests at 2 weeks of recovery. These studies provide key pre-clinical data recommending LIF administration as a neuroprotectant and regenerative cytokine and they highlight the feasibility of pursuing new therapeutics targeting the tertiary phase of neurodegeneration for hypoxic-ischemic encephalopathies.

Intranasal dexmedetomidine in elderly subjects with or without beta blockade: a randomised double-blind single-ascending-dose cohort study

BACKGROUND

The aim of this double-blind, placebo-controlled, single-ascending-dose study was to determine the safety and tolerability of intranasal dexmedetomidine in the elderly.

METHODS

We randomly assigned 48 surgical patients ≥65 yr of age to receive single intranasal doses of dexmedetomidine or placebo (5:1 ratio) in four sequential dose cohorts: 0.5, 1.0, 1.5, and 2.0 μg kg-1. Each dose cohort comprised two groups of six subjects: a group of subjects using β-blockers and a group not taking β-blockers. Vital signs and sedation depth (Modified Observer's Assessment of Alertness and Sedation [MOAA/S] and bispectral index) were measured for 2 h after administration. Blood samples were taken to determine dexmedetomidine plasma concentrations.

RESULTS

One subject (1.0 μg kg-1) had acute hypotension requiring ephedrine. Systolic arterial BP decreased >30% in 15 of 40 subjects (37.5%) receiving dexmedetomidine, lasting longer than 5 min in 11 subjects (27.5%). The MAP decreased >30% (>5 min) in 10%, 20%, 50%, and 30% of subjects receiving dexmedetomidine 0.5, 1.0, 1.5, and 2.0 μg kg-1, respectively, irrespective of β-blocker use. HR decreased 10-26%. MOAA/S score ≤3 occurred in 18 (45%) subjects; eight (20%) subjects receiving dexmedetomidine showed no signs of sedation. Tmax was 70 min. Cmax was between 0.15 ng ml-1 (0.5 μg kg-1) and 0.46 ng ml-1 (2.0 μg kg-1).

CONCLUSIONS

Intranasal dexmedetomidine in elderly subjects had a sedative effect, but caused a high incidence of profound and sustained hypotension irrespective of β-blocker use. The technique is unsuitable for routine clinical use.

CLINICAL TRIAL REGISTRATION

NTR5513 (The Netherlands Trial Registry 5513).

Intranasal dexmedetomidine versus oral chloral hydrate for diagnostic procedures sedation in infants and toddlers: A systematic review and meta-analysis

BACKGROUND

Intranasal dexmedetomidine is a relatively new way to sedate young children undergoing nonpainful diagnostic procedures. We performed a meta-analysis to compare the efficacy and safety of intranasal dexmedetomidine in young children with those of oral chloral hydrate, which has been a commonly used method for decades.

METHODS

We searched PubMed, Embase, and the Cochrane Library for all randomized controlled trials that compared intranasal dexmedetomidine with oral chloral hydrate in children undergoing diagnostic procedures. Data on success rate of sedation, onset time, recovery time, and adverse effects were extracted and respectively analyzed.

RESULTS

Five studies with a total of 720 patients met the inclusion criteria. Intranasal dexmedetomidine provided significant higher success rate of sedation (relative risk [RR], 1.12; 95% confidence interval [CI], 1.02 to 1.24; P = .02; I = 74%) than oral chloral hydrate. Furthermore, it experienced significantly shorter onset time (weight mean difference [WMD], -1.79; 95% CI, -3.23 to -0.34; P = .02; I = 69%). Nevertheless, there were no statistically differences in recovery time (WMD, -10.53; 95% CI, -24.17 to 3.11; P = .13; I = 92%) and the proportion of patients back to normal activities (RR, 1.11; 95% CI, 0.77-1.60; P = .57; I = 0%). Intranasal dexmedetomidine was associated with a significantly lower incidence of nausea and vomiting (RR, 0.05; 95% CI, 0.01-0.22; P < .0001; I = 0%) than oral chloral hydrate. Although adverse events such as bradycardia, hypotension and hypoxia were not synthetized due to lack of data, no clinical interventions except oxygen supplementation were required in any patients.

CONCLUSION

Our meta-analysis revealed that intranasal dexmedetomidine is possibly a more effective and acceptable sedation method for infants and toddlers undergoing diagnostic procedures than oral chloral hydrate. Additionally, it shows similar safety profile and could be a potential alternative to oral chloral hydrate.

Dexmedetomidine infusion overdose during anesthesia: A case report

A 12-kg infant was given intravenous dexmedetomidine 0.2 µg kg^-1  min^-1 as an adjunct for general anesthesia. The 60-fold increase in dexmedetomidine infusion rate caused a biphasic response with initial hypertension followed by bradycardia and hypotension requiring inotropic support. No postoperative or long-term sequelae were noted. Dexmedetomidine infusion is usually delivered as µg kg^-1  h^-1 .

Attenuation of haemodynamic responses to laryngoscopy and endotracheal intubation with dexmedetomidine: A comparison between intravenous and intranasal route

Background and Aims:

Haemodynamic changes during endotracheal intubation are major concerns in general anaesthesia This study compared the efficacy of intranasal and intravenous dexmedetomidine (DEX) to attenuate the stress response of laryngoscopy and endotracheal intubation.

Methods:

In this prospective, randomised, double-blinded study, 70 adults were divided into two groups [Group D_IV(n=35) and Group D_IN(n=35)]. D_IV group received intravenous dexmedetomidine (DEX) infusion (0.5 μg/kg) over 40 min and D_IN group received intranasal dexmedetomidine (1 μg/kg) 40 min before induction. The primary objective was the comparison the mean arterial pressure (MAP) between two groups from 40 min before induction at every 10 min intervals till induction of anaesthesia, at the time of intubation, thereafter every 1 min interval till 5 min, at 7 min and 10 min after intubation. The secondary outcomes were comparison of heart rate, systolic and diastolic blood pressure along with sedation and other adverse effects. Statistical analysis was with Statistica 6.0 and Graph Pad prism version 5.

Results:

In both the groups, all the haemodynamic parameters were maintained within (20% of baseline values) throughout the study period. There was no statistically significant difference in MAP between two groups (P>0.05). Preoperative sedation score was significantly higher in the D_IV group than the D_IN group (P = 0.014).

Conclusion:

Like IV DEX, intranasal DEX can also attenuate the haemodynamic stress responses of laryngoscopy and endotracheal intubation without significant differences in MAP between two groups.

Dose rationale and pharmacokinetics of dexmedetomidine in mechanically ventilated new-borns: impact of design optimisation

PURPOSE

There is a need for alternative analgosedatives such as dexmedetomidine in neonates. Given the ethical and practical difficulties, protocol design for clinical trials in neonates should be carefully considered before implementation. Our objective was to identify a protocol design suitable for subsequent evaluation of the dosing requirements for dexmedetomidine in mechanically ventilated neonates.

METHODS

A published paediatric pharmacokinetic model was used to derive the dosing regimen for dexmedetomidine in a first-in-neonate study. Optimality criteria were applied to optimise the blood sampling schedule. The impact of sampling schedule optimisation on model parameter estimation was assessed by simulation and re-estimation procedures for different simulation scenarios. The optimised schedule was then implemented in a neonatal pilot study.

RESULTS

Parameter estimates were more precise and similarly accurate in the optimised scenarios, as compared to empirical sampling (normalised root mean square error: 1673.1% vs. 13,229.4% and relative error: 46.4% vs. 9.1%). Most importantly, protocol deviations from the optimal design still allowed reasonable parameter estimation. Data analysis from the pilot group (n = 6) confirmed the adequacy of the optimised trial protocol. Dexmedetomidine pharmacokinetics in term neonates was scaled using allometry and maturation, but results showed a 20% higher clearance in this population compared to initial estimates obtained by extrapolation from a slightly older paediatric population. Clearance for a typical neonate, with a post-menstrual age (PMA) of 40 weeks and weight 3.4 kg, was 2.92 L/h. Extension of the study with 11 additional subjects showed a further increased clearance in pre-term subjects with lower PMA.

CONCLUSIONS

The use of optimal design in conjunction with simulation scenarios improved the accuracy and precision of the estimates of the parameters of interest, taking into account protocol deviations, which are often unavoidable in this event-prone population.

Pharmacokinetics of Intranasally Administered Dexmedetomidine in Chinese Children

Background: Intranasal application is a comfortable, effective, nearly non-invasive, and easy route of administration in children. To date, there is, however, only one pharmacokinetic study on intranasal dexmedetomidine in pediatric populations and none in Chinese children available. Therefore, this study aimed to characterize the pharmacokinetics of intranasally administered dexmedetomidine in Chinese children.

Methods: Thirteen children aged 4 to 10 years undergoing surgery received 1 µg/kg dexmedetomidine intranasally. Arterial blood samples were drawn at various time points until 180 min after dose. Dexmedetomidine plasma concentrations were measured with high performance liquid chromatography (HPLC) and mass spectrometry. Pharmacokinetic modeling was performed by population analysis using linear compartment models with first-order absorption.

Results: An average peak plasma concentration of 748 ± 30 pg/ml was achieved after 49.6 ± 7.2 min. The pharmacokinetics of dexmedetomidine was best described by a two-compartment model with first-order absorption and an allometric scaling with estimates standardized to 70-kg body weight. The population estimates (SE) per 70 kg bodyweight of the apparent pharmacokinetic parameters were clearance CL/F = 0.32 (0.02) L/min, central volume of distribution V1/F = 34.2 (4.9) L, intercompartmental clearance Q2/F = 10.0 (2.2) L/min, and peripheral volume of distribution V2/F = 34.9 (2.3) L. The estimated absorption rate constant was Ka = 0.038 (0.004) min⁻¹.

Conclusions: When compared with studies in Caucasians, Chinese children showed a similar time to peak plasma concentration after intranasal administration, but the achieved plasma concentrations were about three times higher. Possible reasons are differences in age, ethnicity, and mode of administration.

Safety and sedative effect of intranasal dexmedetomidine in mandibular third molar surgery: a systematic review and meta-analysis

Objective

The focus of this meta-analysis was to assess the sedative effect and safety of intranasal dexmedetomidine (Dex) in mandibular third molar surgery.

Methods

The PubMed/Medline, Web of Science, Cochrane Library, and China National Knowledge Infrastructure databases were searched for studies published until May 1, 2018. Eligible studies were restricted to randomized controlled trials (RCTs) and controlled clinical trials. The evaluation indicators mainly included the bispectral index, observer assessment of alertness/sedation scale, systolic blood pressure, and heart rate. Data for each period in the Dex and control groups were pooled to evaluate its sedative effect and safety.

Results

Five RCTs met the inclusion criteria. This study included 363 patients: 158 patients received intranasal inhalation of Dex before surgery, and 158 patients were negative controls. The pooled results showed a good sedative effect during tooth extraction when intranasal inhalation of Dex was performed 30 minutes before third molar extraction (assessment of alertness/sedation, Dex vs control SMD −1.20, 95% CI −1.73 to −0.67, I²=0, P=0.95; bispectral index, Dex vs control SMD −11.68, 95% CI −19.49 to −3.87, I²=89%; P=0.0001), and parameters returned to normal within 90 minutes after inhalation. During the operation, blood pressure and heart rate decreased to some extent, but the decreases did not exceed 20% of the baseline, and all patients returned to normal conditions within 90 minutes after inhalation.

Conclusion

Intranasal inhalation of Dex 30 minutes before third molar extraction can provide a good sedative effect, and large-sample multicenter RCTs are needed to evaluate the analgesic effect of Dex.

Impact of CYP2A6 gene polymorphism on the pharmacokinetics of dexmedetomidine for premedication

BACKGROUND

Dexmedetomidine is a widely used sedative in clinic, which is mainly metabolized by cytochrome P450 2A6 (CYP2A6). Dexmedetomidine was rarely reported for off-label usage of premedication, but lacking relevant pharmacokinetic investigations. Therefore, our study determined the dexmedetomidine pharmacokinetics of CYP2A6*4 allele in Chinese patients pretreated with dexmedetomidine whose mutation frequency of CYP2A6*4 are high, in order to provide clinical references.

METHODS

Thirty-one elective surgery patients received premedication with 0.5 μg/kg dexmedetomidine via intravenous pump. Their plasma concentrations at multiple time-points and polymorphism of CYP2A6*4 were determined and statistically analyzed.

RESULTS

9 patients were *1/*4 or *4/*4, and 22 patients were *1/*1. The main pharmacokinetic parameters were area under curve (AUC) 1396.19 ± 332.47h· ng· l^-1, peak blood concentration (C_max) 495.50 ± 104.90ng· l^-1, distribution volume (V) 0.68 ± 0.20 L/kg, clearance (CL) 0.38 ± 0.11 L/h/kg, distribution half-life (t_1/2α) 0.05 ± 0.01h, elimination half-life (t_1/2β) 2.53 ± 0.04h. No significant pharmacokinetic differences were found among CYP2A6*1/*1, *1/*4, and *4/*4 patients.

CONCLUSIONS

In Chinese patients pretreated with dexmedetomidine, T_1/2β was consistent with that published, but T_1/2α, V and Cl were lower. It was unnecessary to consider the mutation when developing the precision regimen of dexmedetomidine.