Phase I human safety assessment of intrathecal neostigmine containing methyl- and propylparabens

A comparison of dexamethasone and clonidine as an adjuvant for caudal blocks in pediatric urogenital surgeries

Background:

Caudal block is a reliable regional analgesic technique for pediatric urogenital surgeries. Various adjuvants have been tried to enhance the duration of action of bupivicaine. Though clonidine is extensively used as an adjuvant in caudal anaesthesia, it can have troublesome adverse effects like bradycardia, hypotension and sedation. Lately dexamethasone has become popular as an adjuvant in paediatric caudals due to its safety profile.

Aim:

The aim of this study was to compare dexamethasone and clonidine coadministered with bupivicaine caudally in paediatric patients undergoing urogenital surgeries in terms of analgesia and adverse effects.

Settings and Design:

Prospective, double blinded randomised study.

Subjects and Method:

Sixty American Society of Anesthesiologists physical status I and II children, aged 1-6 years undergoing urogenital surgeries were allocated in 2 groups: Group I: 0.5 mL.kg⁻¹ of 0.25% bupivicaine with dexamethasone 0.1 mg.kg⁻¹ in 1 ml normal saline (NS) Group II: 0.5 mL.kg⁻¹ of 0.25% bupivicaine with clonidine 1 μg.kg⁻¹ diluted in 1 ml normal saline. The parameters studied included duration of analgesia, intraoperative and postoperative hemodynamics, sedation scores and incidence of adverse effects like wound dehiscence, bleeding, vomiting and respiratory depression.

Statistical Analysis Used:

Statistical analysis was carried out using Stata Version 10. After checking for the normality assumption, t-test for comparing means of two independent samples was used for comparing baseline continuous variables. P values <0.05 were considered significant.

Results:

Patients in Group II had longer duration of analgesia postoperatively. Patients in this group also had lower heart rate and more sedation scores.

Conclusion:

Our study shows that caudal dexamethasone is a good alternative to clonidine with more stable hemodynamics and lesser sedation scores in the immediate postoperative period. Both the drugs offer good analgesia postoperatively with the duration of analgesia more in clonidine.

Optimal single-dose epidural neostigmine for postoperative analgesia after partial hepatectomy

Objective:

Neostigmine can produce analgesia by acting on the spinal cord. This study was to determine the optimal single-dose of epidural neostigmine for postoperative analgesia after partial hepatectomy.

Patients and Methods:

Twenty-six patients undergoing elective partial hepatectomy under general anesthesia combined with epidural block were studied. The dose of epidural neostigmine was determined using Dixon's up-and-down method, starting from neostigmine 100 μg with an interval of 25 μg. Thirty minutes after skin incision, a predetermined dose of neostigmine was injected via the epidural catheter. Each patient received 0.125% bupivacaine and fentanyl 2 μg/ml for patient controlled epidural analgesia (PCEA) after the operation. Assessment of analgesia quality was performed at 8 h and 24 h after the operation.

Results:

The ED₅₀ of epidural neostigmine in combination with PCEA for satisfactory analgesia was 226.78 ± 33.20 μg. Probit analysis showed that the ED₅₀ and ED₉₅ of epidural neostigmine were 228.63 μg (95% CI = 197.95–299.77 μg) and 300.12 μg (95% CI = 259.44–741.65 μg), respectively.

Conclusion:

The ED₅₀ and ED₉₅ of epidural neostigmine in combination with PCEA for satisfactory analgesia after partial hepatectomy were 228.63 μg (95% CI = 197.95–299.77 μg) and 300.12 μg (95% CI = 259.44–741.65 μg).

Analgesic efficacy of low-dose intrathecal neostigmine in combination with fentanyl and bupivacaine for total knee replacement surgery

Background and Aim:

Intrathecal (IT) neostigmine has been used as an adjunct to spinal anesthesia. The purpose of this study was to determine whether a combination of low-dose neostigmine IT would enhance analgesia of a fixed dose of fentanyl IT, in patients undergoing unilateral total knee replacement (TKR) surgery with spinal anesthesia.

Settings and Design:

Forty-five patients scheduled for unilateral TKR were randomized to one of the three groups (n = 15) and prospectively studied using placebo-controlled, double-blinded design.

Materials and Methods:

A 19-G epidural catheter was introduced through the L3–L4 interspace with patient in the sitting position, followed by spinal anesthesia administration through the L3–L4 interspace. Fifteen milligrams of hyperbaric bupivacaine (3 ml) plus the test drug (0.5 ml) was administered IT. The test drug was normal saline (0.5 ml) in group I; fentanyl 20 mcg (0.4 ml) and normal saline (0.1 ml) in group II; and fentanyl 20 mcg (0.4 ml) and neostigmine 1 mcg (0.1 ml) in group III. Characteristics of sensory and motor block, heart rate, and blood pressure were recorded intraoperatively. Postoperatively, pain scores, postoperative nausea and vomiting (PONV) scores, and sedation scores, and postoperative analgesic dose were recorded.

Results:

Forty-five patients were enrolled in this study and 43 patients were subjected to statistical analysis. Overall 24-h visual analog score in group III was significantly less than in those who received fentanyl alone (P = 0.00). The durations of complete analgesia and effective analgesia were longer for all patients in group III compared with group II (P < 0.05) and group I (P < 0.005) patients. The total number of epidural top ups (rescue analgesia) required was less in group II (P < 0.05) and group III (P < 0.005) patients, compared with the control group. The incidence of nausea and vomiting was not increased in group III patients.

Conclusions:

The addition of 1 mcg neostigmine IT increased the duration of analgesia and decreased the analgesic consumption in 24 h in TKR. There was no increase in the incidence of adverse effects.

Neuraxial analgesia in neonates and infants: a review of clinical and preclinical strategies for the development of safety and efficacy data

Neuraxial drugs provide robust pain control, have the potential to improve outcomes, and are an important component of the perioperative care of children. Opioids or clonidine improves analgesia when added to perioperative epidural infusions; analgesia is significantly prolonged by the addition of clonidine, ketamine, neostigmine, or tramadol to single-shot caudal injections of local anesthetic; and neonatal intrathecal anesthesia/analgesia is increasing in some centers. However, it is difficult to determine the relative risk-benefit of different techniques and drugs without detailed and sensitive data related to analgesia requirements, side effects, and follow-up. Current data related to benefits and complications in neonates and infants are summarized, but variability in current neuraxial drug use reflects the relative lack of high-quality evidence. Recent preclinical reports of adverse effects of general anesthetics on the developing brain have increased awareness of the potential benefit of neuraxial anesthesia/analgesia to avoid or reduce general anesthetic dose requirements. However, the developing spinal cord is also vulnerable to drug-related toxicity, and although there are well-established preclinical models and criteria for assessing spinal cord toxicity in adult animals, until recently there had been no systematic evaluation during early life. Therefore, in the second half of this review, we present preclinical data evaluating age-dependent changes in the pharmacodynamic response to different spinal analgesics, and recent studies evaluating spinal toxicity in specific developmental models. Finally, we advocate use of neuraxial drugs with the widest demonstrable safety margin and suggest minimum standards for preclinical evaluation before adoption of new analgesics or preparations into routine clinical practice.

Two different doses of caudal neostigmine co-administered with levobupivacaine produces analgesia in children

SUMMARY BACKGROUND

This study was aimed to evaluate the analgesic efficacy duration of analgesia, and side effects of two different doses of caudal neostigmine used with levobupivacaine in children.

METHODS

Sixty boys, between 5 months and 5 years, undergoing genitourinary surgery were allocated randomly to one of three groups (n =20 each). Group I patients received caudal 0.25% levobupivacaine (1 ml.kg(-1)) alone. Groups II and III patients received neostigmine (2 and 4 microg.kg(-1) respectively) together with levobupivacaine used in the same does as Group I. Pain scores were assessed using Children's and Infant's Postoperative Pain Scale (CHIPPS) at 15th (t(1)) min after arrival to postanesthetic care unit, and 1st (t(2)), 2nd (t(3)), 3rd (t(4)), 4th (t(5)), 8th (t(6)), 16th (t(7)), and 24th (t(8)) hour postoperatively. Duration of analgesia, amount of additional analgesic (paracetamol), score of motor blockade and complications were recorded for 24 h postoperatively, and compared between groups.

RESULTS

CHIPPS scores were higher during t(2), t(3), t(6), t(7), and t(8) periods, duration of analgesia was shorter, and total analgesic consumption was higher in Group I compare to neostigmine groups (P < 0.05). Duration of postoperative analgesia and total analgesic consumption were similar in Groups II and III (P > 0.05). Adverse effects were not different between three groups.

CONCLUSIONS

Caudal neostigmine in doses of 2 and 4 microg.kg(-1) with levobupivacaine extends the duration of analgesia without increasing the incidence of adverse effects, and 2 microg.kg(-1) seems to be the optimal dose, as higher dose has no further advantages.

Neostigmine decreases bupivacaine use by patient-controlled epidural analgesia during labor: a randomized controlled study

BACKGROUND

Intrathecal neostigmine not only produces analgesia but also severe nausea. In contrast, epidural neostigmine enhances opioid and local anesthetic analgesia without causing nausea. Previous studies examined only single epidural neostigmine bolus administration and did not assess the efficacy of continuous epidural infusion or several aspects of maternal and fetal safety. We therefore tested the hypothesis that epidural neostigmine in combination with bupivacaine by continuous infusion during labor would reduce the amount of bupivacaine required.

METHODS

Twelve healthy women scheduled for elective cesarean delivery were assigned to receive epidural neostigmine, 40 microg (first six subjects) or 80 microg (second six subjects) as a single bolus, with fetal heart rate (FHR) and uterine contractions monitored for 20 min. In a subsequent experiment, 40 healthy laboring women were randomized to receive bupivacaine 1.25 mg/mL alone or with neostigmine 4 microg/mL by patient-controlled epidural analgesia. The primary outcome measure was hourly bupivacaine use.

RESULTS

Epidural neostigmine bolus did not alter baseline FHR, induce contractions, or produce nausea. Epidural neostigmine infusion reduced bupivacaine requirement by 19% in all patients and 25% in those with >4 h of treatment (P < 0.05 for both) but might have contributed to the incidence of mild sedation. Mode of delivery, incidence of maternal nausea, and FHR abnormality were similar between groups.

CONCLUSIONS

These data show that adding epidural neostigmine 4 microg/mL reduces the hourly bupivacaine requirement by 19%-25% with patient-controlled epidural analgesia during labor. Administered as a bolus and by continuous infusion at the studied doses, epidural neostigmine does not cause nausea and does not induce uterine contractions or FHR abnormalities, but mild sedation can occur.

The neurotoxic effects of intrathecal midazolam and neostigmine in rabbits

In parallel with improvements in understanding pain neurophysiology, many chemicals have recently been investigated for spinal anaesthesia and analgesia. However, studies discussing the effects of these drugs on neural tissue indicate that knowledge about some aspects of neurotoxicity is limited. Forty-nine New Zealand albino rabbits, weighing 2.2 +/- 0.2 kg, were randomly assigned to seven groups of seven animals each. Single dose groups received intrathecally through the atlantooccipital membrane 0.9% saline 1.5 ml; midazolam 100 microg/kg (low dose midazolam group) or 500 microg/kg (high dose midazolam group); neostigmine 10 microg/kg (low dose neostigmine group) or 50 microg/kg (high dose neostigmine group). Two groups had seven days of repeated dosing with either midazolam 100 microg/kg/day (repeat midazolam group) or 10 microg/kg/day neostigmine (repeat neostigmine group). The animals were sacrificed on day 8, and two spinal cord sections from the fourth cervical level and fourth lumbar level were removed and prepared for histopathological study. Transmission electron microscopic evaluations were performed on transverse spinal cord sections by a neuropathologist blinded to the group allocation. Twenty myelinated axons and neurones in the cervical and lumbar sections were investigated for the histopathological study. This study indicates that midazolam and neostigmine have different neurotoxic effects that depend on the dose and the repetition of dosing when these drugs are administered intrathecally.

Anaesthetists as pain management consultants

Anaesthetists who manage acute and chronic pain need to be familiar with current research and practice guidelines in these areas. New local anaesthetics and new routes of administration for opioids and adjuvants may further improve our management of acute pain. The safety of epidural analgesia in combination with low molecular weight heparins and the role of the anaesthetist on the acute pain service are reviewed. Chronic pain disability is increasing, necessitating a re-evaluation of our approach to chronic pain. The limitations of nerve blocks are acknowledged and guidelines for managing chronic pain and opioids are available. Anaesthetists must recognize psychological difficulties as a significant perpetuating factor in chronic pain.