Clinical pharmacology of neuromuscular blocking agents

Exploring Pharmacological Treatments for Chronic Idiopathic Constipation in Adults: A Look Back to the Future

Despite great progress in pharmaceutical research, the medical treatment of chronic idiopathic constipation is far from ideal. The aim of the present article was to review literature data, focusing on poorly studied or commercially unavailable/unapproved drugs potentially useful for the treatment of chronic idiopathic constipation in adults. An extensive online literature search was conducted using the keywords "chronic constipation", "colon", "constipation", "drugs", "laxatives", and "treatment", in various combinations between January 1960 and December 2022. The literature search showed the presence of some drugs whose efficacy has only recently been demonstrated by modern investigations, and which are likely to be incorporated into future guidelines, of others that are proven effective and potentially effective on constipated patients but limited by small or relatively old studies, or by side effects which could be used in experienced hands, and of others that might be useful but lack a solid scientific background. Looking into the future for patients with chronic constipation might add some more tools to the therapeutic portfolio, especially for certain subgroups of these patients.

Effects of magnesium on the dose of rocuronium for deep neuromuscular blockade: A randomised controlled trial

BACKGROUND

Magnesium is known to enhance the effect of rocuronium, but the extent is not quantified.

OBJECTIVES

We aimed to quantify the effect of magnesium on the dose of rocuronium for deep neuromuscular blockade.

DESIGN

A randomised controlled study.

SETTING

A single tertiary care hospital.

PATIENTS

Seventy males scheduled to undergo robot-assisted laparoscopic prostatectomy, aged between 20 and 80 years with American Society of Anesthesiologists physical status classification 1 or 2, were enrolled.

INTERVENTIONS

Patients were randomised to either the magnesium group or control group. The magnesium group were infused with 50 mg kg-1 of magnesium, followed by a continuous intra-operative infusion at 15 mg kg-1 h-1 while the control group were infused with the same volumes of 0.9% saline. Deep neuromuscular blockade was maintained with a continuous infusion of rocuronium and was reversed using sugammadex.

MAIN OUTCOME MEASURES

The primary outcome was the dose of rocuronium administered to maintain deep neuromuscular blockade. The secondary outcomes were recovery time, defined as the time from the administration of sugammadex to train-of-four ratio 0.9, and the incidence of postoperative nausea and vomiting.

RESULTS

The dose of rocuronium administered to maintain deep neuromuscular blockade was significantly lower in the magnesium group (7.5 vs. 9.4 μg kg-1 min-1, P = 0.01). There was no difference in recovery time or the incidence of nausea and vomiting.

CONCLUSION

Magnesium reduced the dose of rocuronium required for deep neuromuscular blockade by approximately 20% without affecting the recovery time after administration of sugammadex.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04013243.

Drug Safety of Benzodiazepines in Asian Patients With Chronic Obstructive Pulmonary Disease

Purpose: Many comorbidities, including depression, anxiety, and insomnia, occur in patients with chronic obstructive pulmonary disease (COPD). These patients may be prescribed benzodiazepines (BZDs). However, there are some concerns that benzodiazepines increase the risk of drug overdose, hypercapnic respiratory failure, acute exacerbation and increased mortality. The aim of our study was to evaluate the drug safety of BZDs in patients with COPD. Methods: We used the National Health Insurance Research database in Taiwan from 2002 to 2016 to perform a retrospective cohort study. We enrolled patients who were exposed to the first prescription of BZDs, non-BZDs or a combination (mix user) after COPD diagnosis. We performed 1:1:1 propensity score matching in three groups. The outcomes were COPD with acute exacerbation and all-cause mortality. Poisson regression analysis was performed to evaluate the incidence rate ratios for the outcomes in the groups. Results: After propensity score matching, there were 2,856 patients in each group. After adjusting for confounding factors, we found that compared to BZD users, non-BZD and mix users had nonsignificant differences in outpatient management of acute exacerbations, hospitalization management of acute exacerbations, emergency department management of acute exacerbations and all-cause mortality. BZD and mix groups showed significantly increased admission for acute exacerbation of COPD compared with that of the nonuser group, with IRRs of 2.52 (95% CI, 1.52-4.18; p = 0.0004) and 2.63 (95% CI, 1.57-4.40; p = 0.0002), respectively. Conclusion: BZD, non-BZD, and mix users showed increased COPD-related respiratory events compared to nonusers in Asian subjects.

Respiratory events with sugammadex vs. neostigmine following laparoscopic sleeve gastrectomy: a prospective pilot study assessing neuromuscular reversal strategies

Abdominal surgery in obese patients may be associated with pulmonary morbidity, and mortality. Some patients may arrive in the PACU with residual paralysis. The purpose of this study was to find out if there was an association between the type of muscle relaxant reversal agent and the development of postoperative respiratory events in patients undergoing laparoscopic sleeve gastrectomy surgery.

METHODS

From September 2012 to February 2013, in a prospective randomized pilot study, two different muscle relaxant reversal agents were administered at the end of surgery in 57 patients undergoing laparoscopic sleeve gastrectomy: sugammadex 2 mg/kg (32 patients) vs. neostigmine 2.5 mg (25 patients). We compared the occurrence of early and late respiratory events/complications by the type of reversal agent. Postoperative respiratory rate, oxyhemoglobin saturation (SpO₂), number of patients with SpO₂ lower than 95% in PACU, the minimum value of SpO₂ in PACU, train-of four counts (TOF) before reversal, unexpected ICU admissions, duration of hospitalization and incidence of reintubation were recorded.

RESULTS

SpO₂ in the PACU was significantly lower in the neostigmine group - 95.80 (± 0.014)) vs. in sugammadex group - 96.72 (± 0.011) (p < 0.01), despite a lower TOF count measured in the sugammadex group before reversal, meaning a deeper level of residual relaxation in this group before the administration of the reversal agent (2.53 ± 0.98 vs. 3.48 ± 0.58 p < 0.01). Also, the minimal SpO₂ was significantly lower in the PACU in the neostigmine group: 93% vs. 94% (p = 0.01). Respiratory rates were not different. After the administration of reversal, both groups had TOF counts of 4 with no fade assessed visually. There were no postoperative respiratory events or complications.

CONCLUSIONS

The use of sugammadex (as compared to neostigmine) as a reversal agent following laparoscopic sleeve gastrectomy surgery was associated with higher postoperative SpO₂ despite the lower TOF count before the administration of reversal agent. Despite the statistical difference in SpO₂, its clinical importance seems to be minimal. The lack of difference in the other measured variables may stem from the small number of patients studied (pilot).

Prolonged neuromuscular block in a preeclamptic patient induced by magnesium sulfate

Recent large use of magnesium in the obstetric population should incite anesthesiologists to control its side effects and drugs interactions. We report a case of a 30-year-old woman, with severe preeclampsia and HELLP syndrome, receiving sulfate magnesium and nicardipine, who underwent a cesarean section under general anesthesia. She developed a prolonged and deep neuromuscular blockade, which was antagonized three hours later with neostigmine. In case of therapeutic hypermagnesaemia, non-depolarizing relaxants must be used in reduced doses, and at increased time intervals, with appropriate neuromuscular monitoring.

Comparison of effects of sugammadex and neostigmine on QTc prolongation in rabbits under general anesthesia

PURPOSE

To compare the effects of sugammadex and neostigmine, used to antagonize the effects of rocuronium, on the QTc interval.

METHODS

This study used 10 adult New Zealand white rabbits of 2.5-3.5 kg randomly divided into two groups: sugammadex group (Group S, n:5) and neostigmine group (Group N, n:5). For general anesthesia administering 2 mg/kg iv propofol and 1 mcg/kg iv fentanyl, 0.6 mg/kg iv rocuronium was given. Later to provide reliable airway for all experimental animals V-Gel Rabbit was inserted. The rabbits were manually ventilated by the same anesthetist. After the V-Gel Rabbit was inserted at 2, 5, 10, 20, 25, 27, 30 and 40 minutes measurements were repeated and recorded. At 25 minutes after induction Group N rabbits were given 0.05 mg/kg iv neostigmine + 0.01 mg/kg iv atropine. Group S were administered 2 mg/kg iv sugammadex.

RESULTS

Comparing the QTc interval in the rabbits in Group S and Group N, in the 25th, 27th and 30th minute after muscle relaxant antagonist was administered the QTc interval in the neostigmine group rabbits was significantly increased (p<0.05).

CONCLUSION

While sugammadex, administered to antagonize the effect of rocuronium, did not significantly affect the QTc interval, neostigmine+atropine proloned the QTc interval.

The effect of defasciculating doses of pancuronium and atracurium on succinylcholine neuromuscular blockade

Background:

A defasciculating dose of non-depolarizing muscle relaxant administered prior succinylcholine decrease its side effects including fasciculations and postoperative myalgias; however it is believed that the dosage of succinylcholine should be increased when such a pre-treatment is used.

Objectives:

We hypothesized that a defasciculating dose of pancuronium as a pre-treatment could prolong its duration of effect.

Patients and Methods:

Forty patients scheduled for elective orthopaedic surgery were consecutively assigned into 5 groups, a first group without pre-treatment (succinylcholine 1 mg/kg) and 4 subsequent groups of pretreatment with atracurium 0.05 mg/kg + succinylcholine 1 or 1.5 mg/kg and pancuronium 7.5 µg /kg + succinylcholine 1 and 1.5 mg/kg. The muscle relaxant effect of succinylcholine was assessed with a force transducer using train of four stimulations every 12 seconds. Kruskall Wallis Anova test was used to compare results.

Results:

The duration of succinylcholine induced paralysis (1 and 1.5 mg/kg) was significantly prolonged with pre-treatment with pancuronium but succinylcholine 1mg/kg did not reached maximum blockade after pre-treatment with atracurium. After pancuronium, full recovery after succinylcholine 1.5 and 1 mg/kg occurred respectively after 18 and 15 minutes. P < 0.05 vs. 12 minutes for succinylcholine 1mg/kg alone.

Conclusions:

This study highlights potentiation effect of a defasciculating dose of pancuronium on succinylcholine paralysis suggesting the lack of justification to increase succinylcholine dosage.

Rocuronium blockade reversal with sugammadex vs. neostigmine: randomized study in Chinese and Caucasian subjects

Background

This study compared efficacy and safety of the selective relaxant binding agent sugammadex (2 mg/kg) with neostigmine (50 μg/kg) for neuromuscular blockade (NMB) reversal in Chinese and Caucasian subjects.

Methods

This was a randomized, active-controlled, multicenter, safety-assessor-blinded study (NCT00825812) in American Society of Anesthesiologists Class 1-3 subjects undergoing surgery with propofol anesthesia. Rocuronium 0.6 mg/kg was administered for endotracheal intubation, with 0.1–0.2 mg/kg maintenance doses given as required. NMB was monitored using TOF-Watch^® SX. At second twitch reappearance, after last rocuronium dose, subjects received sugammadex 2 mg/kg or neostigmine 50 μg/kg plus atropine 10–20 μg/kg, according to randomization. Primary efficacy variable was time from sugammadex/neostigmine to recovery of the train-of-four (TOF) ratio to 0.9.

Results

Overall, 230 Chinese subjects (sugammadex, n = 119, neostigmine, n = 111); and 59 Caucasian subjects (sugammadex, n = 29, neostigmine, n = 30) had evaluable data. Geometric mean (95% CI) time to recovery to TOF ratio 0.9 was 1.6 (1.5–1.7) min with sugammadex vs 9.1 (8.0–10.3) min with neostigmine in Chinese subjects. Corresponding times for Caucasian subjects were 1.4 (1.3–1.5) min and 6.7 (5.5–8.0) min, respectively. Sugammadex 2 mg/kg was generally well tolerated, with no serious adverse events reported. There was no residual NMB or recurrence of NMB.

Conclusion

Both Chinese and Caucasian subjects recovered from NMB significantly faster after sugammadex 2 mg/kg vs neostigmine 50 μg/kg, with a ~5.7 times (p < 0.0001) faster recovery with sugammadex vs neostigmine in Chinese subjects. Sugammadex was generally well tolerated.

Trial registration

ClinicalTrials.gov Identifier: NCT00825812.

Inhibitors of acetylcholinesterase and butyrylcholinesterase meet immunity

Acetylcholinesterase (AChE) inhibitors are widely used for the symptomatic treatment of Alzheimer’s disease and other dementias. More recent use is for myasthenia gravis. Many of these inhibitors interact with the second known cholinesterase, butyrylcholinesterase (BChE). Further, evidence shows that acetylcholine plays a role in suppression of cytokine release through a “cholinergic anti-inflammatory pathway” which raises questions about the role of these inhibitors in the immune system. This review covers research and discussion of the role of the inhibitors in modulating the immune response using as examples the commonly available drugs, donepezil, galantamine, huperzine, neostigmine and pyridostigmine. Major attention is given to the cholinergic anti-inflammatory pathway, a well-described link between the central nervous system and terminal effector cells in the immune system.

Magnesium: a versatile drug for anesthesiologists

Magnesium sulfate has been used in preeclampsia patients in order to prevent seizure. It is also used for the treatment of arrhythmia and asthma and as an anesthetic adjunct in patients undergoing surgery for pheochromocytoma. However, its potentiating effects on perioperative analgesia and muscle relaxation have drawn attention recently. These characteristics of magnesium (anesthetic- and analgesic-sparing effect) enable anesthesiologists to reduce the use of anesthetics during surgery and the use of analgesics after surgery. Magnesium sulfate has a high therapeutic index and cost-effectiveness. Considering these diverse characteristics useful for anesthesia, appropriate use of magnesium sulfate would improve surgical outcome and patients' satisfaction.

Reversed Ipsilateral Acoustic Reflex: A Study on Subjects Treated With Muscle Relaxants

OBJECTIVES

To rule out any possible involvement of the middle ear muscles in the genesis of the reversed ipsilateral acoustic reflex (RIAR).

DESIGN

Prospective study to evaluate the effects of muscle relaxants on the RIAR of otosclerotic ears as well as on the acoustic reflex of individuals with normal middle ear function. Admittance recording during ipsilateral acoustic stimulation was performed in patients undergoing pharmacological treatment for surgical procedures. Fentanyl, propofol, and a muscle relaxant were sequentially administered intravenously. Ipsilateral acoustic reflexes were recorded before and after each drug injection. Three patients were affected from otosclerosis, whereas 14 individuals had normal middle ear function. Moreover, the ipsilateral acoustic reflex obtained in normal subjects after their treatment with muscle relaxants was compared with that of 10 otosclerotic patients who were not treated pharmacologically.

RESULTS

The RIAR of three otosclerotic ears was not inhibited by muscle relaxants as well as by fentanyl and propofol. Moreover, muscle relaxants, when administered in normal subjects, always induced the block of the stapedial reflex that was replaced by a reversed reflex strictly similar to the RIAR of the 10 otosclerotic patients not treated pharmacologically. Propofol could also induce, in most of the cases, the reduction and in some occasion even the reversal of the stapedial reflex, whereas fentanyl did not affect it significantly.

CONCLUSION

The RIAR does not appear to be related to the contraction of the middle ear muscles.

Acute toxicity of gymnodimine to mice

The acute toxicity of the phycotoxin gymnodimine to female Swiss mice by intraperitoneal injection and by oral administration has been determined. Gymnodimine was highly toxic by injection, the LD50 being only 96 microg/kg. Animals either died within 10 min of injection or made a full recovery with no perceptible long-term effects. Gymnodimine was also toxic after oral administration by gavage (LD50 755 microg/kg), but was much less toxic when administered with food. No signs of toxicity were seen in mice voluntarily ingesting food containing gymnodimine at a level sufficient to give a dose of approximately 7500 microg/kg. Pre-treatment with physostigmine or neostigmine protected against injected gymnodimine, suggesting that the latter exerts its toxic effects via blockade of nicotinic receptors at the neuromuscular junction. The low toxicity of gymnodimine when ingested with food suggests that this compound is of low risk to humans, a conclusion that is consonant with anecdotal evidence for the absence of harmful effects in individuals consuming shellfish contaminated with gymnodimine.

Bradycardia and medications: identify the dangerous pace

Review bradycardia and medications that can cause the condition.

Tensilon and the diagnosis of myasthenia gravis: are we using the Tensilon test too much?

BACKGROUND

Tensilon (edrophonium chloride) is a reversible acetylcholinesterase inhibitor used in the diagnosis of myasthenia gravis, diagnosis and treatment of arrhythmias, detection of early digitalis toxicity, reversal of neuromuscular blockade, and other medical conditions. Toxicity associated with Tensilon use has appeared in the literature for decades.

REVIEW SUMMARY

This review discusses the risks of Tensilon and the information practitioners should know before administering the drug. We review the literature regarding serious toxicity of this drug and offer recommendations for its safe use.

CONCLUSIONS

A careful medication history should be taken before the administration of Tensilon. Additionally, physicians should be aware of appropriate alternative methods of diagnosis before choosing to administer Tensilon. Physicians should be aware of the clinical situations where the Tensilon test no longer is indicated.

Pediatric trauma. Anesthesia management

Prevention of childhood injury remains the cornerstone of reducing the number of children who present for post-traumatic surgical intervention. Beyond prevention, the next best step is the accurate diagnosis and treatment of traumatic injury. Anesthesiologists contribute to this step by providing timely resuscitation and optimal care to avoid secondary injury. This article classifies trauma in children into different categories depending on the location of the injury. Trauma, of course, is rarely focal, and is often a multisystem entity. With knowledge in management for each subset of trauma, one may be efficient in prioritizing injury and have a good understanding of the appropriate management of the pediatric patient with multiple traumatic injuries.

Quantitative determination of rocuronium in human plasma by liquid chromatography-electrospray ionization mass spectrometry

Liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) was used for the quantification of the neuromuscular blocking agent rocuronium in human plasma. Verapamil was used as internal standard. The samples were subjected to a dichloromethane liquid-liquid extraction after ion pairing of the positively charged ammonium compound with iodide prior to LC-MS. Optimized conditions involved separation on a Symmetry Shield RP-18 column (50 x 2.1 mm, 3.5 microm) using a 15-min gradient from 10 to 90% acetonitrile in water containing 0.1% trifluoroacetic acid at 250 microl/min. Linear detector responses for standards were observed from 25 to 2,000 ng/ml. The extraction recovery averaged 59% for rocuronium and 83% for the internal standard. The limit of quantification (LOQ), using 500 microl of plasma, was 25 ng/ml. Precision ranged from 1.3 to 19% (LOQ), and accuracy was between 92 and 112%. In plasma samples, at 20 and 4 degrees C, rocuronium was stable at physiological pH for 4 h; frozen at -30 degrees C it was stable for at least 75 days. The method was found suitable for the analysis of samples collected during pharmacokinetic investigations in humans.