Liquid chromatography/mass spectrometric bioanalysis of a modified gamma-cyclodextrin (Org 25969) and Rocuronium bromide (Org 9426) in guinea pig plasma and urine: its application to determine the plasma pharmacokinetics of Org 25969

X-ray-Based Techniques to Study the Nano-Bio Interface

X-ray-based analytics are routinely applied in many fields, including physics, chemistry, materials science, and engineering. The full potential of such techniques in the life sciences and medicine, however, has not yet been fully exploited. We highlight current and upcoming advances in this direction. We describe different X-ray-based methodologies (including those performed at synchrotron light sources and X-ray free-electron lasers) and their potentials for application to investigate the nano-bio interface. The discussion is predominantly guided by asking how such methods could better help to understand and to improve nanoparticle-based drug delivery, though the concepts also apply to nano-bio interactions in general. We discuss current limitations and how they might be overcome, particularly for future use in vivo.

Effects of Sugammadex on Time of First Postoperative Bowel Movement: A Retrospective Analysis

Objective

To determine whether time to first postoperative bowel movement after intraperitoneal surgery differs among neuromuscular blockade reversal with either anticholinesterase/anticholinergic combination vs sugammadex.

Patients and Methods

Sugammadex was introduced to our practice in October 2016. Patients were identified who underwent intraperitoneal surgery between January 1, through June 30, 2016, and January 1 through June 30, 2017, and received aminosteroid neuromuscular blockade for paralysis. Reversal was initiated with neostigmine, coadministered with glycopyrrolate (neostigmine/glycopyrrolate) for control participants and sugammadex for patients. Time to first bowel movement was determined from nursing documentation for study cohorts (2016 and 2017). We compared times to first bowel movement between cases and controls using raw and inverse probability of treatment weighting (IPTW) analyses.

Results

In the 2016 cohort, 2583 received neostigmine/glycopyrrolate. Of 2750 patients in 2017, sugammadex reversal technique was administered to 1500 patients and neostigmine/glycopyrrolate to 1250 participants. Without weighting, the groups were relatively balanced for most baseline characteristics, and after IPTW, all standardized differences were <0.035. In comparison with the 2016 and 2017 controls, sugammadex treatment was associated with faster occurrence of first bowel movement. For 2016, unweighted hazard ratio (HR) (95% confidence interval [CI]) was 1.35 (1.21-1.51) (P<.001). After IPTW, HR (95% CI) was 1.27 (1.12-1.43) (P<.001). For 2017, unweighted HR (95% CI) was 1.51 (1.31-1.72) (P<.001); after IPTW, it was 1.25 (1.08-1.45) (P =.003).

Conclusion

Patients undergoing intraperitoneal surgery who had aminosteroid neuromuscular blockade reversal with sugammadex had earlier first postoperative bowel movement than patients with reversal through neostigmine/glycopyrrolate.

Safety and Efficacy of Sugammadex for Neuromuscular Blockade Reversal

Since its first human use in 2005, the γ-cyclodextrin sugammadex (Org 25969) has had the potential to become the reversal agent of choice, for rocuronium- or vecuronium-induced neuromuscular blockade. Sugammadex binds to the aminosteroid neuromuscular blocker, encapsulating it and extracting it from the neuromuscular junction, effectively ceasing activity and allowing neuromuscular transmission to recover rapidly. Phases I–III and subsequent trials have found sugammadex to be safe and effective in a wide range of doses and for the reversal of a range of depth of muscle relaxation in healthy volunteers and a variety of disease states. Sugammadex use may allow refinement of anesthetic practice and improvement in surgical conditions, through the maintenance of deep neuromuscular blockade right to the end of surgery, with subsequent rapid reversal. Debate remains about the use of sugammadex in the treatment of rocuronium anaphylaxis and airway emergencies. The high price of sugammadex currently prohibits its routine use, but if the price falls, after expiry of its patent, it may become cost-effective as a readily available agent in certain specific clinical situations. Serious adverse reactions have occurred in less than 1% of patients and are most commonly because of hypersensitivity. No deaths have been reported, but caution is advised in neonates, pediatrics, and pregnancy where data are lacking.

Analysis of rocuronium in human plasma by liquid chromatography-tandem mass spectrometry with application in clinical pharmacokinetics

Rocuronium (ROC) is a neuromuscular blocking agent used in surgical procedures which is eliminated primarily by biliary excretion. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for analysis of ROC in human plasma. Separation of ROC and IS (verapamil) was performed using an endcapped C-18 column and a mixture of water:acetonitrile:trifluoracetic acid (50:50:0.1, v/v) as mobile phase. Aliquots of 100 μL of human plasma were extracted at pH 3, using dichloromethane. The lower limit of quantification of 5 ng/mL shows the high sensitivity of this method. Intra- and inter-assay precision (as relative standard deviation) was all ≤14.2% and accuracy (as relative standard error) did not exceed 10.1%. The validated method was successfully applied to quantify ROC concentrations in patients under surgical procedures up to 6h after the administration of the 0.4-0.9 mg/kg ROC. The pharmacokinetic parameter estimations of ROC showed AUC/dose of 563 μg min/mL, total clearance of 2.5 mL/min/kg, volume of distribution at steady state of 190 mL/kg and mean residence time of 83 min.

Dialysability of sugammadex and its complex with rocuronium in intensive care patients with severe renal impairment

BACKGROUND

Renal excretion is the primary route for the elimination of sugammadex. We evaluated the dialysability of sugammadex and the sugammadex-rocuronium complex in patients with severe renal impairment in the intensive care unit (ICU).

METHODS

Six patients in the ICU with acute severe renal impairment received general anaesthesia for transoesophageal echocardiography, to replace their tracheal tubes, or for bronchoscopy. Five of the six patients were in the ICU after cardiac/vascular surgery and one for pneumonia-induced respiratory failure. They all received rocuronium 0.6 mg kg(-1), followed 15 min later by sugammadex 4.0 mg kg(-1). Two patients were studied for two dialysis episodes and four patients for four episodes. Rocuronium and sugammadex concentrations were measured in plasma and dialysate at several time points before, during, and after high-flux dialysis. Dialysis clearance in plasma and dialysate, and reduction ratio (RR) (the extent of the plasma concentration reduction at the end of a dialysis episode when compared with before dialysis) were calculated for each dialysis episode.

RESULTS

Dialysis episodes lasted on average 6 h. Observed RRs indicated mean reductions of 69% and 75% in the plasma concentrations of sugammadex and rocuronium, respectively, during the first dialysis episode. Reductions were around 50% during sequential dialysis episodes. On average, dialysis clearance of sugammadex and rocuronium in blood was 78 and 89 ml min(-1), respectively.

CONCLUSIONS

Haemodialysis using a high-flux dialysis method is effective in removing sugammadex and the sugammadex-rocuronium complex in patients with severe renal impairment.

Direct pharmacokinetic analysis of puqietinone by in vivo microdialysis sampling and turbulent-flow chromatography coupled with liquid chromatography-mass spectrometry

Sample pretreatment is a key step in bioanalytical process because of possible interference and matrix effects in mass spectrometry analysis. In this work, a novel strategy towards high speed and sensitivity was developed combining in vivo microdialysis (MD) sampling, turbulent-flow chromatography (TFC), and liquid chromatography-mass spectrometry (LC-MS). The procedures of cleanup, preconcentration, and separation were completed on-line in one step within 10min. During the MD optimization procedure, 1% hydroxypropyl-β-cyclodextrin (HP-β-CD) was used to improve the relative recovery of the analyte. Untreated MD samples were directly injected, and a TFC precolumn was flushed for 1min with aqueous phase of 4mL/min flow rate to desalt and concentrate biosamples. The retained analytes were then back-flushed by a switching valve onto a fast LC column (4.6mm×50mm, 1.8μm) for separation. Another diverter valve was employed to prevent the HP-β-CD that interferes with the ESI process from entering the MS. Puqietinone, a lipophilic alkaloid from Fritillaria puqiensis, was used as a case for validation. Results showed that the limit of quantification for puqietinone was 0.10ng/mL, and good linearity (R(2)=0.9993) was maintained over the range of 1.02-200.02ng/mL. Accuracy and precision were satisfactory within the range of the standard curve. This approach was able to effectively eliminate the influences of matrix effect and carry-over as the injection volume increased up to 20μL. The developed method was successfully applied to pharmacokinetic study of puqietinone after intravenous administration to rat. Results demonstrate the potential of using MD with TFC-LC/MS for in vivo monitoring experiments.

Development and potential clinical impairment of ultra-short-acting neuromuscular blocking agents

Developing a non-depolarizing neuromuscular blocking agent that, like succinylcholine, has a rapid onset and a short duration of effect remains a goal of ongoing research. While rocuronium fills a portion of this need, the large doses required for rapid intubation render it a much longer-acting neuromuscular blocking agent. Postoperative residual neuromuscular block (NMB) is an increasingly recognized complication of non-depolarizing neuromuscular blocking agents. This occurs because of dosing choices for neuromuscular blocking agents and anticholinesterases as well as insensitivity of typically used monitors of depth of NMB. While antagonism of NMB is necessary with partial recovery, it is unnecessary with more complete recovery. Even when monitoring with an accelerograph, reversal of NMB is complicated. In addition to the pharmacodynamics of the individual neuromuscular blocking agents, factors such as timing of anticholinesterase administration, dose of anticholinesterase, concomitant medications, electrolyte abnormalities, and hepatic or renal disease can influence the degree of reversal. Sugammadex works differently than anticholinesterases and, when administered in appropriate doses, can reverse even profound block induced with vecuronium or rocuronium. Two new fumarate neuromuscular blocking agents have a rapid onset of effect and can be reversed at any time by administration of cysteine, which could significantly reduce the risk of postoperative residual NMB.

Sugammadex rapidly reverses moderate rocuronium- or vecuronium-induced neuromuscular block during sevoflurane anaesthesia: a dose-response relationship

BACKGROUND

Sugammadex shows a dose-response relationship for reversal of neuromuscular block (NMB) during propofol anaesthesia. Sevoflurane, unlike propofol, can prolong the effect of neuromuscular blocking agents (NMBAs), increasing recovery time. This open-label, randomized, dose-finding trial explored sugammadex dose-response relationships, safety, and pharmacokinetics when administered for reversal of moderate rocuronium- or vecuronium-induced NMB during sevoflurane maintenance anaesthesia.

METHODS

After anaesthesia induction with propofol, adult patients were randomized to receive single-dose rocuronium 0.9 mg kg⁻¹ or vecuronium 0.1 mg kg⁻¹, with maintenance doses as needed. Anaesthesia was maintained with sevoflurane. NMB was monitored using acceleromyography. After the last dose of NMBA, at reappearance of T(2), single-dose sugammadex 0.5, 1.0, 2.0, or 4.0 mg kg⁻¹ or placebo was administered. The primary efficacy variable was time from the start of sugammadex administration to recovery of T₄/T₁ ratio to 0.9. Safety assessments were performed throughout.

RESULTS

The per-protocol population comprised 93 patients (rocuronium, n=46; vecuronium, n=47). A statistically significant dose-response relationship was demonstrated for mean recovery times of T₄/T₁ ratio to 0.9 with increasing sugammadex dose with both NMBAs: rocuronium, 96.3 min (placebo) to 1.5 min (sugammadex 4.0 mg kg⁻¹); vecuronium, 79.0 min (placebo) to 3.0 min (sugammadex 4.0 mg kg⁻¹). Plasma sugammadex concentrations indicated linear pharmacokinetics, independent of NMBA administered. No study drug-related serious adverse events occurred. Evidence of reoccurrence of block was reported in seven patients [sugammadex 0.5 mg kg⁻¹ (suboptimal dose), n=6; 2.0 mg kg⁻¹, n=1].

CONCLUSIONS

During sevoflurane maintenance anaesthesia, sugammadex provides well-tolerated, effective, dose-dependent reversal of moderate rocuronium- and vecuronium-induced NMB.

[Sugammadex, a novel drug for neuromuscular blockade reversal]

Significant progress in the management of aminosteroid nondepolarizing neuromuscular blockers will follow the introduction of sugammadex (Org 25969). Safety and rapid recovery of muscle force will improve and the adverse effects of acetylcholinesterase inhibitors will be avoided. Sugammadex is a modified gamma-cyclodextrin agent developed for the specific reversal of rocuronium and, to a lesser extent, vecuronium. This novel drug functions by means of encapsulation (chelation). Sugammadex was recently approved by the European Medicines Evaluation Agency and became available in Spain in 2009, leading to a series of changes related to patient safety and surgical conditions. We review the literature on sugammadex published to date.

Safety and tolerability of single intravenous doses of sugammadex administered simultaneously with rocuronium or vecuronium in healthy volunteers

BACKGROUND

Sugammadex rapidly reverses rocuronium- and vecuronium-induced neuromuscular block. To investigate the effect of combination of sugammadex and rocuronium or vecuronium on QT interval, it would be preferable to avoid the interference of anaesthesia. Therefore, this pilot study was performed to investigate the safety, tolerability, and plasma pharmacokinetics of single i.v. doses of sugammadex administered simultaneously with rocuronium or vecuronium to anaesthetized and non-anaesthetized healthy volunteers.

METHODS

In this phase I study, 12 subjects were anaesthetized with propofol/remifentanil and received sugammadex 16, 20, or 32 mg kg(-1) combined with rocuronium 1.2 mg kg(-1) or vecuronium 0.1 mg kg(-1); four subjects were not anaesthetized and received sugammadex 32 mg kg(-1) with rocuronium 1.2 mg kg(-1) or vecuronium 0.1 mg kg(-1) (n=2 per treatment). Neuromuscular function was assessed by TOF-Watch SX monitoring in anaesthetized subjects and by clinical tests in non-anaesthetized volunteers. Sugammadex, rocuronium, and vecuronium plasma concentrations were measured at several time points.

RESULTS

No serious adverse events (AEs) were reported. Fourteen subjects reported 23 AEs after study drug administration. Episodes of mild headache, tiredness, cold feeling (application site), dry mouth, oral discomfort, nausea, increased aspartate aminotransferase and gamma-glutamyltransferase levels, and moderate injection site irritation were considered as possibly related to the study drug. The ECG and vital signs showed no clinically relevant changes. Rocuronium/vecuronium plasma concentrations declined faster than those of sugammadex.

CONCLUSIONS

Single-dose administration of sugammadex 16, 20, or 32 mg kg(-1) in combination with rocuronium 1.2 mg kg(-1) or vecuronium 0.1 mg kg(-1) was well tolerated with no clinical evidence of residual neuromuscular block, confirming that these combinations can safely be administered simultaneously to non-anaesthetized subjects. Rocuronium and vecuronium plasma concentrations decreased faster than those of sugammadex, reducing the theoretical risk of neuromuscular block developing over time.

Sugammadex: a novel agent for the reversal of neuromuscular blockade

To achieve spontaneous ventilation after completion of surgery, the nondepolarizing effects on skeletal muscle relaxation are often reversed by administration of an acetylcholinesterase inhibitor. However, these agents increase acetylcholine at both the neuromuscular junction and the muscarinic receptors. Therefore, coadministration of an anticholinergic agent is required to prevent parasympathetic adverse effects. In addition, a relative pharmacologic ceiling effect is seen with inhibition of acetylcholinesterase, necessitating some recovery of neuromuscular function before an acetylcholinesterase inhibitor is administered. Sugammadex is a new modified gamma-cyclodextrin compound under clinical investigation in the United States. It does not interact with cholinergic mechanisms to elicit reversal. Instead, it is a selective relaxant binding agent and acts by forming a 1:1 complex with steroidal nondepolarizing neuromuscular blockers in the plasma, lowering the effective concentration available at the receptor. Due to its selectivity, sugammadex does not inhibit the effects of nondepolarizing agents of the benzylisoquinolinium class. In contrast to acetylcholinesterase inhibition, sugammadex is effective even when administered during profound blockade, and it does not require coadministration of an anticholinergic agent. It provides a novel mechanism of action for reversal of the neuromuscular block induced by nondepolarizing aminosteroidal agents.

Sugammadex: a novel neuromuscular blocker binding agent

PURPOSE OF REVIEW

Sugammadex is a novel drug that binds selected neuromuscular blocking drugs and prevents them from acting at the neuromuscular junction. Due to its rapid onset and relative lack of side effects, this drug promises to change the method of anesthesia delivery. This review summarizes the literature on the drug and addresses some of the potential changes that it may bring.

RECENT FINDINGS

Currently in phase III clinical trials, sugammadex has been shown to be safe and efficacious in small animal and human study groups and is now undergoing wider clinical testing to secure FDA approval for general use.

SUMMARY

Sugammadex binds neuromuscular blocking drugs and encapsulates them, making cholinesterase inhibitors unnecessary. Its rapid reversal of blockade makes it possible to keep patients profoundly muscle relaxed until drapes come down and it can enable a rapid return to spontaneous ventilation in a 'cannot intubate, cannot ventilate' situation. Costs and date of availability have yet to be determined.

The effect of beta-cyclodextrin on liquid chromatography/electrospray-mass spectrometry analysis of hydrophobic drug molecules

Cyclodextrins (CDs) are widely used in the pharmaceutical industry for their capability of improving bioavailability, solubility, or stability of drugs via the formation of soluble inclusion complexes. CDs have also been widely used in various chemical analysis methods. In this work, liquid chromatography/electrospray mass spectrometry (LC/ESI-MS) analysis for four different drugs (imipramine, desipramine, propranolol, and naproxen) that form inclusion complexes with CDs was performed in the presence and absence of beta-CD. These drugs are subject to nonspecific adsorption when brought into contact with plastics, such as HPLC tubing, sample collection and preparation apparatus, etc. Inclusion of the CD in the samples reduces this nonspecific adsorption due to competitive complex formation between the CD and the analyte. ESI-MS ion intensities increased when beta-CD was included in the sample with concentrations up to 1% (w:v), with a diverter valve installed post LC column. The degree of increased ion signal correlated with the beta-cyclodextrin:analyte binding constant. beta-CD appeared to elute within the void volume time and was observed in a full spectrum scan among the different analyte samples with up to 0.01% beta-CD injected directly to the LC/MS system with the diverter valve switched inline with the mass spectrometer. The use of the diverter valve allowed for direct injection of samples containing up to 1% beta-CD to the LC/MS without any deterioration of analyte ion signal.

Time course of action of sugammadex (Org 25969) on rocuronium-induced block in the Rhesus monkey, using a simple model of equilibration of complex formation

BACKGROUND

Reversal of neuromuscular block can be accomplished by chemical encapsulation of rocuronium by sugammadex (Org 25969), a synthetic gamma-cyclodextrin derivative. The present study determined the time course of the reversal action of sugammadex on rocuronium-induced block in the anaesthetized Rhesus monkey using train-of-four stimulation.

METHODS

A bolus injection of rocuronium 100 microg kg(-1) (about 1xED(90)) was given to determine the degree of neuromuscular block reached by this dose. After complete spontaneous recovery, a rapid bolus injection of sugammadex, 1 mg kg(-1), was given and at different time intervals (15, 30 or 60 min, in three different experiments) the effect of another rocuronium bolus injection of 100 microg kg(-1) was determined.

RESULTS

Injection of the first dose of rocuronium resulted in a mean neuromuscular block (depression of first twitch) of 93 (SEM=1.6)%. Fifteen minutes after injection of sugammadex the same rocuronium dose resulted in 17% (SEM=5.6) block. After 30 and 60 min these maximum blocks amounted to 49% (SEM=7.6) and 79% (SEM=4.2), respectively. The estimated half-life of sugammadex in Rhesus monkey is 30 (SEM=4.9) min.

CONCLUSIONS

The half-life of sugammadex (Org 25969), a new fast and efficient reversal agent for rocuronium-induced block, is relatively short in the Rhesus monkey, implying the possibility to perform neuromuscular block by rocuronium shortly after reversal of a prior block. In translation to the human situation differences in rocuronium sensitivity and kinetics should be taken into account.

An analytical strategy for quaternary ammonium neuromuscular blocking agents in a forensic setting using LC-MS/MS on a tandem quadrupole/time-of-flight instrument

An analytical strategy is described for analyzing quaternary ammonium neuromuscular blocking agents in a wide variety of biological specimens in a forensic setting. Neuromuscular blocking agents such as succinylcholine, pancuronium, and tubocurarine, often used as paralytic agents during surgery, are occasionally suspected as paralytic poisoning agents involved in suspected homicide and suicide cases. Because suspicion in such cases can develop slowly, the age, nature, and quality of available specimens varies greatly. The compounds are challenging analytically because of their simultaneous precharged yet lipophilic character. An analytical strategy has been devised for extracting these compounds from complex matrices using a combination of a modified Bligh and Dyer liquid-liquid extraction (used in reverse) followed by reverse-phase ion pairing solid-phase extraction using heptafluorobutyric acid as an ion pairing reagent. Final analysis is by LC-MS/MS using a tandem quadrupole orthogonal acceleration time of flight instrument (Q-TOF) with repetitive product ion scanning at high resolution. Native and spiked specimens are compared for both quantitative and especially qualitative purposes. The method has been applied to a wide variety of fluid and tissue specimen types, including numerous specimens from exhumation autopsies. For most specimens, detection limits are in the 2 to 10 ng/g range. Succinylmonocholine has been demonstrated to be present at low levels in normal posthumous kidney and liver. The Q-TOF is an excellent platform for forensic analytical investigations. This analytical strategy should also be applicable to other problematic analytes and sample matrices.

Sugammadex, a new reversal agent for neuromuscular block induced by rocuronium in the anaesthetized Rhesus monkey †

BACKGROUND

Binding of the steroidal molecule of rocuronium by a cyclodextrin is a new concept for reversal of neuromuscular block. The present study evaluated the ability of Sugammadex Org 25969, a synthetic gamma-cyclodextrin derivative, to reverse constant neuromuscular block of about 90% induced by rocuronium or the non-steroidal neuromuscular blocking drugs, mivacurium or atracurium, in the anaesthetized Rhesus monkey.

METHODS

After a bolus injection of rocuronium, mivacurium or atracurium, a continuous infusion of these drugs was started to maintain the first twitch contraction of the train-of-four at approximately 10% of its baseline value. After a steady state block of at least 10 min the infusion was stopped and the preparation was allowed to recover spontaneously. This process was repeated, but at the time the infusion was stopped, either sugammadex 0.5 or 1.0 mg kg(-1) was given in the rocuronium-induced blockade and sugammadex 1.0 mg kg(-1) was given in the mivacurium- and atracurium-induced blockade.

RESULTS

Sugammadex caused a rapid and complete reversal of rocuronium-induced neuromuscular block. The recovery time to train of four ratio=0.9 after spontaneous recovery was 14.4 min (sd=3.4 min; n=14). This was reduced significantly (P<0.001) to 3.7 min (sd=3.3 min; n=4) with sugammadex 0.5 mg kg(-1) and to 1.9 min (sd=1.0 min; n=4) with sugammadex 1.0 mg kg(-1). Signs of residual blockade or re-curarization were not observed. Reversal of mivacurium- or atracurium-induced neuromuscular block (n=2 in each experiment) by sugammadex (1.0 mg kg(-1)) was not effective. In all experiments, injection of sugammadex had no effects on blood pressure or heart rate.

CONCLUSIONS

Sugammadex is effective in reversing rocuronium, but not mivacurium- or atracurium-induced neuromuscular block.

Chemical encapsulation of rocuronium by synthetic cyclodextrin derivatives: reversal of neuromuscular block in anaesthetized Rhesus monkeys †

BACKGROUND

At present, reversal of neuromuscular block induced by steroidal neuromuscular blocking agents (NMBAs) is achieved by administration of cholinesterase inhibitors. Chemical encapsulation of steroidal NMBAs, such as rocuronium, by a cyclodextrin is a new concept in neuromuscular block reversal. The present study evaluates the capacity of nine synthetic cyclodextrin derivatives (Org 25288, Org 25289, Org 25467, Org 25168, Org 25169, Org 25555, Org 25166, Org 26142, and Org 25969) to reverse constant neuromuscular block of approximately 90%, induced by rocuronium infusion in the Rhesus monkey, using single twitch stimulation. The ability of these cyclodextrin derivatives to reverse neuromuscular block was compared with the reversal of the same neuromuscular block by the commonly used combination of neostigmine and atropine.

METHODS

After a bolus injection of rocuronium, continuous infusion was started to reduce twitch contractions to approximately 10% of baseline values. After a steady state block of at least 10 min the infusion was stopped and the preparation was allowed to recover spontaneously. This process was repeated, but at the time the infusion was stopped, either one of the nine cyclodextrin derivatives or a combination of neostigmine and atropine was given.

RESULTS

Recovery with cyclodextrin derivatives Org 26142 and Org 25969 was faster than after a combination of neostigmine and atropine (P<0.05). Injection of these cyclodextrin derivatives did not affect blood pressure or heart rate. Signs of residual block or recurarization were not observed in any of these experiments. In the experiments in which a combination of neostigmine and atropine was given, two animals showed signs of abdominal discomfort as frequently seen after the administration of neostigmine and significant changes in circulatory variables.

CONCLUSIONS

Chemical encapsulation or chelation of rocuronium is a new concept in reversing neuromuscular block induced by rocuronium.