Simple and rapid high-performance liquid chromatographic assay for esmolol

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.

Determination of esmolol in serum by capillary zone electrophoresis and its monitoring in course of heart surgery

A new Capillary Zone Electrophoresis (CZE) procedure for determination of esmolol, an ultra-short-acting beta-blocker, in serum was developed. Dichloromethane was applied as a deproteination agent and it was used also for the inactivation of erythrocytal esterase and in the same time for the extraction of esmolol from blood. The re-extraction of esmolol from organic phase to water phase was performed by 0.01 M HCl. An aliquot of 200 ml of acid aqueous phase was used for the injection and analysis. CZE determination was done in 50 mM phosphate buffer (pH=8.0) with detection at 222 nm. The concentration detection limit of esmolol in serum was 0.051 microg/ml. This method was applied in an extensive heart surgery experiment on pigs (Sus scrofa).

Evaluating a possible pharmacokinetic interaction between remifentanil and esmolol in the rat

Remifentanil (Ultiva) is a novel, ultra-short-acting opioid which has recently been approved for use as an analgesic during induction and maintenance of general anesthesia. Esmolol is a short-acting beta-blocker used during surgical procedures to reduce heart rate and blood pressure. Both drugs are metabolized by nonspecific esterases in the blood and other tissues and may be administered concomitantly during surgery. The goal of this study was to determine if coadministration of esmolol significantly alters the pharmacokinetics of remifentanil in the rat. Two groups of rats were dosed with remifentanil [25 micrograms/kg/min (n = 8)] and remifentanil plus esmolol [25 and 200 mg/kg/min (n = 7)] for 20 min. Cardiovascular measurements were collected continuously over the course of the study. Serial blood samples (12) were collected over 25 min into test tubes containing 0.5 mL of acetonitrile. Blood samples were extracted (liquid-liquid) with methylene chloride and then analyzed by a validated GC-MS assay. Compartmental data analysis was performed using PCNONLIN. The mean(+/- SD) for Cl and t1/2 observed in treatment I were 390(+/- 98) mL/min/kg and 0.69(+/- 0.27) min and in treatment II were 421(+/- 164) mL/min/kg and 0.56(+/- 0.22) min, respectively. Comparison of clearance, volume of distribution, and terminal half-life between the two groups showed that coadministration of esmolol had no significant (p < 0.05) effect on the pharmacokinetics of remifentanil in the rat.

Antifibrillatory effect of esmolol alone and in combination with lidocaine

The primary objective of this study was to determine the effect of esmolol, administered alone and in combination with lidocaine, on ventricular fibrillation threshold (VFT) in pigs. A secondary objective was to determine the relationship between blood esmolol concentrations and VFT. We determined VFT using a train of electrical stimuli delivered to the right ventricle after eight paced beats at a basic cycle length of 285 ms. Current was increased in 2-mA increments until VF occurred. VFT determinations were performed during administration of esmolol 1,000 mu g/kg/min, during a continuous infusion of lidocaine, and during infusion of esmolol and lidocaine in combination. Mean increases in VFT from baseline during infusion of esmolol and lidocaine alone were 32.3 +/- 12.9 and 8.5 +/- 7.2 mA, respectively (p < 0.05, each drug compared with baseline; p < 0.05, esmolol vs. lidocaine). Mean increase in VFT from baseline during infusion of the combination was 52.0 +/- 22.0 mA (p < 0.05 as compared with baseline and with esmolol or lidocaine alone). The relationship between blood esmolol concentrations and VFT was described by a counterclockwise hysteresis curve, suggesting delay in equilibration of esmolol between blood and site of effect. The antifibrillatory efficacy of esmolol is significantly greater than that of lidocaine in this model. Administration of the two agents in combination resulted in significantly greater antifibrillatory efficacy than that associated with either drug administered alone.

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.

Screening of beta-blockers in human serum by ion-pair chromatography and their identification as methyl or acetyl derivatives by gas chromatography-mass spectrometry

A simultaneous screening method for atenolol, acebutolol, metoprolol, oxprenolol, alprenolol and propranolol by ion-pair chromatography with a column-switching technique was developed. The serum samples were purified using either liquid-liquid extraction or solid-phase extraction methods. The pretreatment of the samples consisted of hydrolysis and protein precipitation. The drug separation was on either octadecylsilica or polymer-based alkyl column material. Binary eluent mixtures containing methanol and a buffer solution with a quaternary ammonium salt as an ion-pair former were used. Detection of the compounds in liquid chromatographic analysis was based on ultraviolet spectra. The effects of methanol, two buffers and the ion-pair former on the retention of the compounds were studied. The determination limits ranged from nanograms to micrograms in the ion-pair chromatographic method, depending on the drug studied. Identification was based on the mass spectra or, if necessary, on selected-ion monitoring spectra of either the methylated or the acetylated compounds obtained by means of gas chromatography-electron impact or negative chemical ionization mass spectrometry. The detection limits for the identified compounds were in the picogram range. The matrix effect was strong, and this resulted in determination limits in the nanogram range with the scan method.