Pharmacokinetics and pharmacodynamics of a new reformulated microemulsion and the long-chain triglyceride emulsion of propofol in beagle dogs

Comparison of remifentanil consumption in pupillometry-guided versus conventional administration in children: a randomized controlled trial

BACKGROUND

Remifentanil is a commonly used opioid analgesic during anesthesia in children. Objective measurement of pain is required for adequate dosing of remifentanil. We investigated whether pupillometry-guided remifentanil administration can reduce intraoperative consumption of remifentanil in children.

METHODS

We performed a single-blinded, prospective, randomized controlled trial from December 2018 through June 2019. Children who were 3-12 years of age and classified as having an American Society of Anesthesiologists physical status I-II and undergoing elective surgery under general anesthesia were included. Fifty-six fulfilled the inclusion criteria, and fifty-four completed the study. Participants were randomly assigned to either a pupillometry or conventional group. Patients in both groups received target-controlled infusion of remifentanil. In the pupillometry group, the adjustment of the remifentanil effect site concentration was determined by the pupillary diameter, whereas in the conventional group, the adjustment was based on the anesthesiologist's experience. Primary outcome was intraoperative remifentanil consumption, divided by patient weight and infusion time (ng kg^-1 min^-1).

RESULTS

Remifentanil consumption was reduced by 25% in the pupillometry group compared to the conventional group (116.7±56.0 ng kg^-1 min^-1 vs. 155.8±64.9 ng kg^-1 min^-1, respectively; P=0.02). There were no differences in intra- and postoperative blood pressure and heart rate. The incidences of postoperative desaturation or nausea/vomiting were not significantly different.

CONCLUSIONS

Pupillometry-guided remifentanil administration in children undergoing general anesthesia can reduce the intraoperative remifentanil consumption.

Novel Approach for Characterizing Propofol Binding Affinities to Serum Albumins from Different Species

The interaction between the main carrier (serum albumin, SA) of endogenous and exogenous compounds in the bloodstream of different species (human, bovine, canine, rat, rabbit, and sheep) and a general anesthetic agent (propofol, PR) was investigated using an experimental technique (high-performance liquid chromatography) and computational methods (molecular docking, molecular dynamics, sequence, and phylogenetic analyses). The obtained results revealed the differences in the PR binding affinity to various homologous forms of this protein with reliable statistics (R ² = 0.9 and p-value < 0.005), correlating with the evolutionary relationships among SAs from different species. Additionally, the protein conformational changes (root-mean-square deviation ≈ 1.0 Å) and amino acid conservation of binding sites in protein domains were detected, contributing to the SA-PR binding modes. Overall, the outcomes from this study might provide a novel methodology to assess protein-ligand interactions and to gain some interesting insights into drug pharmacokinetics and pharmacodynamics to explain its variations among different species.

Pain on propofol injection: Causes and remedies

Pain on propofol injection (POPI) is a minor problem that all anesthetists face every day. Introduction of several new formulations and hundreds of clinical trials have failed to find its remedy with just one intervention in all patients. This article highlights the causes of POPI and interventions that are used to eliminate this pain in current practice. Relevant articles from Medline and Embase databases were searched and included in this descriptive review with the following conclusions: (1) POPI is due to irritation of venous adventitia leading to release of mediators such as kininogen from kinin cascade. (2) When two or more drugs or measures are used, the incidence of POPI decreases considerably. Hence, the approach to eliminating POPI should be multimodal. (3) Any regimen that includes a drug having local anesthetic effect combined with central sedative/analgesic and rapid injection into a large vein should definitely reduce the risk of POPI to negligible levels.

An Open-label Comparison of a New Generic Sevoflurane Formulation With Original Sevoflurane in Patients Scheduled for Elective Surgery Under General Anesthesia

PURPOSE

To compare the stability, effectiveness, and safety profiles of a new generic sevoflurane with those of the original sevoflurane formulation in patients undergoing elective surgery.

METHODS

An accelerated 3-month storage test was performed to evaluate the compositional changes in generic sevoflurane stored in glass bottles. In addition, 182 patients were randomly allocated to receive generic (n = 89 [54 men and 35 women]; mean [SD] age, 49.9 [11.6] years) or original (n = 93 [61 men and 32 women]; mean [SD] age, 49.6 [11.1] years) sevoflurane at a gas flow of 3 L/min for approximately 3 hours. The mean minimum alveolar concentration (MAC) during sevoflurane anesthesia was evaluated, and gas samples for measuring compound A were collected from the inspiratory limb of the circuit at preset intervals. Blood samples for measuring serum inorganic fluoride were obtained at preset intervals (pharmacokinetic group: generic/original sevoflurane = 45/46). Renal biomarkers, such as N-acetyl-β-glucosaminidase, α- and π-glutathione-S-transferase, albumin, urine protein and osmolality, serum creatinine and osmolality, creatinine clearance, and blood urea nitrogen, were measured at preset intervals (renal biomarker group: generic/original sevoflurane = 44/47). Adverse reactions were monitored for 72 hours after discontinuation of sevoflurane use.

FINDINGS

Generic sevoflurane contained in glass bottles was stable for 3 months. The mean MAC was similar for generic and original sevoflurane (median [range], 0.93 [0.67-1.29] vs 0.94 [0.63-1.5] vol%). Adverse event rates were similar (90.3% vs 84.3%), as were the AUClast of inorganic fluoride (333.7 [112.7-1264.7] vs 311.9 [81.5-1266.5] hours·μmol/L) and compound A (51.8 [6.3-204.5] vs 55.3 [10.8-270.6] hours·ppm). Biomarkers associated with renal injury were not significantly different between the 2 formulations.

IMPLICATIONS

No significant difference was found in the mean MAC between generic and original sevoflurane. ClinicalTrials.gov identifier: NCT01096212.

A population pharmacokinetic approach to describe cephalexin disposition in adult and aged dogs

This study was conducted in order to characterize the pharmacokinetics of orally administered cephalexin to healthy adult and aged dogs, using a population pharmacokinetic approach. Two hundred and eighty-six cephalexin plasma concentrations obtained from previous pharmacokinetic studies were used. Sex, age, pharmaceutical formulation, and breed were evaluated as covariates. A one-compartment model with an absorption lag-time (Tlag) best described the data. The final model included age (adult; aged) on apparent volume of distribution (Vd/F), apparent elimination rate (ke/F), and Tlag; sex (female; male) on ke/F, and breed (Beagle; mixed-breed) on Vd/F. Addition of the covariates to the model explained 78% of the interindividal variability (IIV) in Vd/F, 36% in ke/F, and 24% in Tlag, respectively. Formulation did not affect the variability of any of the pharmacokinetic parameters. Tlag was longer, whereas Vd/F and ke/F were lower in aged compared to adult animals; in female aged dogs ke/F was lower than in male aged dogs; however, the differences were of low magnitude. Different disposition of cephalexin may be expected in aged dogs.

Impact of aminophylline on the pharmacodynamics of propofol in beagle dogs

This study aimed to characterize pharmacodynamic interaction between propofol and aminophylline. Nine beagle dogs were randomly allocated at the propofol rates of 0.75 (group A), 1.00 (group B), and 1.25 (group C) mg/kg/min. During period 1, propofol only was infused, while during period 2, aminophylline only, at the rate of 0.69 (group A), 1.37 (group B), and 2.62 (group C) mg/kg/h. During periods 3-5, the two drugs were co-administered. The aminophylline infusion rate was 0.69 (period 3), 1.37 (period 4), and 2.62 (period 5) mg/kg/h. The aminophylline was infused from 0 to 30 h, and the propofol was infused at 24 h for 20 min. Blood samples and electroencephalograms were obtained at preset intervals. In the linear regression between log-transformed doses of aminophylline and AUC inf, the slope was 0.6976 (95% CI 0.5242-0.8710). Pharmacokinetics of aminophylline was best described by a one-compartment, with enzyme auto-induction, model. Pharmacokinetics and pharmacodynamics of propofol were best described by a three-compartment model and a sigmoid Emax model, respectively. Pharmacodynamic parameter estimates of propofol were: k(e0) = 0.805/min, E0 = 0.76, Emax = 0.398, Ce(50 na) = 2.38 μg/mL (without aminophylline-exposure), C(e50 wa) = 4.49 μg/mL (with aminophylline-exposure), and γ = 2.21. Propofol becomes less potent when exposed to aminophylline. Pharmacodynamic antagonistic interaction of aminophylline with propofol sedation, may occur, not in a dose-dependent manner, but in an all-or-none response.

Intravenous lidocaine pretreatment with venous occlusion for reducing microemulsion propofol induced pain: Comparison of three doses of lidocaine

Objective

Pretreatment with intravenous 40 mg or 0.5 mg/kg lidocaine with venous occlusion is recommended to prevent pain following injection of lipid emulsion propofol. This approach is not sufficient to prevent pain from the injection of microemulsion propofol. The present study investigated whether a higher dose of lidocaine pretreatment with venous occlusion would be more effective for reducing pain following injection of microemulsion propofol compared with 40 mg lidocaine.

Methods

Patients undergoing elective surgery were randomly assigned to one of three groups: pretreatment with 40 mg (group L40), 60 mg (group L60) or 80 mg (group L80) lidocaine intravenously with venous occlusion, followed by injection with microemulsion propofol 1 min later. Pain was assessed on a four-point scale (severe, moderate, mild, none) based on physical responses to the injection.

Results

A total of 68 patients were included in the final analysis. Pain severity and incidence were significantly lower in patients in group L60 and L80 compared with patients in group L40. There were no statistically significant differences in pain incidence or severity between group L60 and group L80.

Conclusions

Pretreatment with 60 mg lidocaine intravenously with venous occlusion may be the most effective minimum dose for reducing injection pain following microemulsion propofol administration for induction of anaesthesia.

Feline drug metabolism and disposition: pharmacokinetic evidence for species differences and molecular mechanisms

Although it is widely appreciated that cats respond differently to certain drugs compared with other companion animal species, the causes of these differences are poorly understood. This article evaluates published evidence for altered drug effects in cats, focusing on pharmacokinetic differences between cats, dogs, and humans, and the molecular mechanisms underlying these differences. More work is needed to better understand drug metabolism and disposition differences in cats, thereby enabling more rational prescribing of existing medications, and the development of safer drugs for this species.

Reducing the pain of microemulsion propofol injections: a double-blind, randomized study of three methods of tourniquet and lidocaine

BACKGROUND

Although the new formulation of lipid-free microemulsion propofol (MP) has some advantages over the lipid emulsion, it reportedly produces more injection pain than lipid-based propofol. Intravenous lidocaine with application of a rubber tourniquet before administration of propofol is considered to be the best method for reducing injection pain; however, this technique is not perfect.

OBJECTIVE

The goal of this study was to evaluate the effect of different methods of tourniquet application and lidocaine administration on MP injection pain.

METHODS

This single-center, randomized controlled clinical trial was conducted in 140 patients aged 18 to 65 years. Patients were randomly divided into 4 groups (n = 35 each). Group A received MP (2 mg/kg) after lidocaine (0.6 mg/kg) with a tourniquet with arm down (venous engorgement); group B received MP after lidocaine with a tourniquet with arm up (venous gravity drainage); group C received MP with a tourniquet with arm down; and group D (control group) received MP only (with no tourniquet). In groups A and C, the tourniquet was released after MP; in group B, the tourniquet was released before MP. Injection pain was evaluated by using a verbal pain score (VPS). The bispectral index, the time from the beginning of drug injection to the loss of eyelash reflex, and time to the lowest bispectral index value were recorded.

RESULTS

Group A showed significantly less incidence of pain than the control group when MP was injected. The mean VPS was significantly lower in groups A, B, and C than in group D (the control group). The VPS of group A was significantly lower than that in group B. Other observed values were not significantly different.

CONCLUSIONS

We concluded that intravenous retention of lidocaine with the application of a rubber tourniquet under venous engorgement of the arm reduces the incidence and intensity of MP injection pain.

CLINICAL TRIAL REGISTRY

UMIN000010725.

Reduction of microemulsion propofol-induced injection pain via target-controlled remifentanil infusion

The intravenous injection of microemulsion propofol to induce anaesthesia causes more intense and frequent pain than lipid emulsion propofol. This study investigated whether different target effect-site concentrations of remifentanil could prevent pain due to microemulsion propofol injection. In total, 96 patients were randomly assigned to one of three groups receiving target effect-site concentrations of remifentanil 0 (control group), 4 or 6 ng/ml, followed by injection with microemulsion propofol. Remifentanil pretreatment significantly reduced the incidence and severity of injection pain compared with the control group. Although no difference in pain reduction between the two remifentanil-treated groups was observed, those receiving a target effect-site concentration of 6 ng/ml exhibited an increased rate of complications, compared with those receiving 4 ng/ml. In conclusion, prior administration of remifentanil at a target effect-site concentration of 4 ng/ml is a useful strategy to decrease the injection pain of microemulsion propofol.

The effect and optimal dose of sufentanil in reducing injection pain of microemulsion propofol

Background

Propofol is used as an induction and maintenance agent for general anesthesia but it can cause adverse reactions like hyperlipidemia, growth of microorganisms, and pulmonary embolisms. Microemulsion propofol was developed to avoid these side effects but incidence and severity of pain on injection is higher than with lipid emulsion propofol. We aimed to compare the effects of sufentanil in analgesic doses for reducing the injection pain of microemulsion propofol.

Methods

The candidates included eighty patients, 19-60 years old and ASA I-II. They were randomly classified into four groups and pretreated with normal saline, sufentanil 0.1 µg/kg, 0.2 µg/kg or 0.3 µg/kg before injection of microemulsion propofol. Five minutes after receiving pretreatment drug, 2 mg/kg of microemulsion propofol was injected and VAS was recorded.

Results

There were no significant differences in the incidence of injection pain among the groups. Severity of injection pain was significantly lower in the sufentanil 0.3 µg/kg group than normal saline and sufentanil 0.1 µg/kg group. Significant differences in blood pressure and heart rate were observed in sufentanil groups only after endotracheal intubation. One patient each in sufentanil 0.1 µg/kg and 0.3 µg/kg group experienced mild cough, one from sufentanil 0.3 µg/kg group experienced dizziness and another showed signs of hypoxia. One patient each in normal saline and sufentanil 0.1 µg/kg group showed clinical symptoms of phlebitis in the injection area.

Conclusions

Pretreatment with sufentanil 0.3 µg/kg reduced the severity of microemulsion propofol injection pain without increasing arterial blood pressure and heart rate after endotracheal intubation.