Gabapentin and pregabalin for chronic neuropathic and early postsurgical pain: current evidence and future directions

PRECISE trial (Pain RElief Combination Intervention StratEgies): protocol for the clinical trial of a pregabalin-melatonin combination for fibromyalgia

INTRODUCTION

Fibromyalgia is associated with chronic widespread pain and disturbed sleep. Multidisciplinary, multimodal management often includes pharmacotherapy; however, current drugs used to treat fibromyalgia provide meaningful benefit to only 30-60% of treated individuals. Combining two or more different drugs is common in clinical practice with the expectation of better efficacy, tolerability or both; however, further research is needed to identify which combinations actually provide added benefit. Thus, we are planning a clinical trial to evaluate melatonin (MLT)-pregabalin (PGB) combination in participants with fibromyalgia.

METHODS AND ANALYSIS

This will be a single-centre, double-blind, randomised, double-dummy, three-period, crossover trial comparing a MLT-PGB combination to each monotherapy in 54 adult participants satisfying the 2016 American College of Rheumatology criteria for fibromyalgia. Participants will receive maximally tolerated doses of MLT, PGB and MLT-PGB combination for 6 weeks. The primary outcome will be daily pain intensity (0-10); secondary outcomes will include the Fibromyalgia Impact Questionnaire, SF-36 survey, Medical Outcomes Study Sleep Scale, Beck Depression Inventory (BDI-II), adverse events and other measures. Analysis of the primary and secondary outcomes will involve a linear mixed model with sequence, period, treatment, the first-order carryover and baseline pain score as fixed effects and participant as a random effect to test whether there are any treatment differences among three treatments and to estimate the least square mean of the mean daily pain intensity for each treatment, adjusting for carryover as well as period effects (ie, stability of pain levels).

ETHICS AND DISSEMINATION

This trial has been registered with the International Standard Randomised Controlled Trial Number Registry, ISRCTN #18278231, has been granted ethical approval by the Queen's University Health Sciences Research Ethics Board (Queen's HSREB Protocol #6040998) and is currently under review for a Clinical Trial Application to Health Canada Natural and Non-prescription Health Products Directorate. All participants will provide written informed consent prior to trial participation. Following trial completion, results will be disseminated in one or more biomedical journal publications and presented at one or more scientific meetings.

TRIAL REGISTRATION NUMBER

This trial has been registered with the International Standard Randomised Controlled Trial Number Registry, ISRCTN18278231.

Analgesic Efficacy of Pre-operative Pregabalin in Dacryocystorhinostomy Surgery: A Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Trials

Dacryocystorhinostomy (DCR) is an effective surgical procedure for addressing lacrimal drainage problems. However, it can be a painful operation that involves incisions both inside and outside the eye, often leading to a high incidence of postoperative nausea and vomiting. Preemptive analgesics can be employed to alleviate this unrelieved pain. Nonetheless, many of the drugs used can induce a wide range of adverse effects. Therefore, the aim of this systematic review and meta-analysis is to assess the current evidence regarding the efficacy of pregabalin in managing postoperative pain following DCR surgery. We conducted a thorough search of five electronic databases, namely, PubMed, Web of Science, Scopus, Cochrane, and Google Scholar, to identify relevant randomized controlled trials (RCTs) published before September 2023. The quality of the included studies was assessed using the Cochrane Risk of Bias tool for RCTs. The outcomes we evaluated included postoperative pain, surgery duration, time to first analgesia, total pethidine consumption, and postoperative nausea and vomiting (PONV). Continues data reported as mean difference (MD), and dichotomous data reported as risk ratio (RR), with 95% confidence interval (CI). A pooled meta-analysis of three RCTs, including 240 patients in both the pregabalin and placebo groups, was conducted. The results revealed that the pooled MD in pain scores was significantly lower in patients treated with pregabalin compared to those receiving a placebo ((MD = -1.35 (95% CI: -1.83 to -0.87, p < 0.00001)). Additionally, the pooled MD of pethidine consumption was significantly lower in patients treated with pregabalin compared to those receiving a placebo (MD = -54.13 (95% CI: -103.77 to -4.50, p = 0.03)). However, there was no statistical significance between both groups in terms of time to first analgesia and duration of surgery (p > 0.05). On the other hand, the pooled RR of PONV was significantly lower in patients treated with pregabalin compared to those receiving a placebo (RR = 0.37 (95% CI: 0.24-0.57, p < 0.001)). This meta-analysis demonstrates that pregabalin is an effective and well-tolerated intervention for reducing postoperative pain and PONV following DCR surgery, without significantly affecting surgery duration or time to first analgesia. These findings support the use of pregabalin in improving patient comfort and outcomes in this surgical context.

E2730, an uncompetitive γ-aminobutyric acid transporter-1 inhibitor, suppresses epileptic seizures in a rat model of chronic mesial temporal lobe epilepsy

OBJECTIVE

More than one third of mesial temporal lobe epilepsy (MTLE) patients are resistant to current antiseizure medications (ASMs), and half experience mild-to-moderate adverse effects of ASMs. There is therefore a strong need to develop and test novel ASMs. The objective of this work is to evaluate the pharmacokinetics and neurological toxicity of E2730, a novel uncompetitive inhibitor of γ-aminobutyric acid transporter-1, and to test its seizure suppression effects in a rat model of chronic MTLE.

METHODS

We first examined plasma levels and adverse neurological effects of E2730 in healthy Wistar rats. Adult male rats were implanted with osmotic pumps delivering either 10, 20, or 100 mg/kg/day of E2730 subcutaneously for 1 week. Blood sampling and behavioral assessments were performed at several timepoints. We next examined whether E2730 suppressed seizures in rats with chronic MTLE. These rats were exposed to kainic acid-induced status epilepticus, and 9 weeks later, when chronic epilepsy was established, were assigned to receive one of the three doses of E2730 or vehicle for 1 week in a randomized crossover design. Continuous video-electroencephalographic monitoring was acquired during the treatment period to evaluate epileptic seizures.

RESULTS

Plasma levels following continuous infusion of E2730 showed a clear dose-related increase in concentration. The drug was well tolerated at all doses, and any sedation or neuromotor impairment was mild and transient, resolving within 48 h of treatment initiation. Remarkably, E2730 treatment in chronically epileptic rats led to seizure suppression in a dose-dependent manner, with 65% of rats becoming seizure-free at the highest dose tested. Mean seizure class did not differ between the treatment groups.

SIGNIFICANCE

This study shows that continuous subcutaneous infusion of E2730 over 7 days results in a marked, dose-dependent suppression of spontaneous recurrent seizures, with minimal adverse neurological effects, in a rat model of chronic MTLE. E2730 shows strong promise as an effective new ASM to be translated into clinical trials.

Multimodal analgesia is superior to opiates alone after tibial fracture in patients with substance abuse history

Objectives: To evaluate the effectiveness of multimodal analgesia in patients with a tibial shaft fracture. Design: Retrospective review. Setting: Large, urban, academic center. Patients: One hundred thirty-eight patients were evaluated before implementation of multimodal analgesia. Thirty-four patients were evaluated after implementation. All patients were treated operatively with internal fixation for their tibial shaft fracture. Patients with polytrauma were excluded. Intervention: Multimodal analgesia. Main Outcome Measures: Pain levels at rest and with movement were assessed. Morphine milligram equivalents (MMEs) dosed per patient were calculated each day. Length of stay was also documented. Results: After implementation of a multimodal analgesic program, there was a statistically significant decrease in pain score at rest (4.7-4.0, P = 0.034) and with movement (5.8-4.8, P = 0.007). MMEs dosed in the multimodal analgesic program correlated with pain score (R² = 0.5), whereas before implementation of the program, MMEs dosed were not dependent on pain score (R² = 0.007). Patients with a history of substance abuse had the most profound effect from this paradigm change. For those with a history of substance abuse, treatment of pain using a multimodal approach reduces MMEs dosed and length of stay (5.7-3.1 days, P = 0.016). Conclusions: Multimodal analgesia improves patient pain scores both at rest and during movement. In patients with a history of substance abuse, multimodal analgesia not only decreases pain but also decreases length of stay and MMEs dosed to levels consistent with someone who does not have a substance abuse history. Level of Evidence: Therapeutic Level III.

The preemptive effects of oral pregabalin on perioperative pain management in lower limb orthopedic surgery: a systematic review and meta-analysis

BACKGROUND

To systematically review the literature and provide a comprehensive understanding of the preemptive effects of oral pregabalin on perioperative pain management in lower limb orthopedic surgery.

METHOD

We searched three electronic databases for randomized controlled trials comparing the results of preoperative pregabalin and placebo in patients undergoing lower limb orthopedic surgery. Data analyses were conducted using RevMan 5.4.

RESULTS

Twenty-one randomized controlled trials met our inclusion criteria. The cumulative opioid consumption within 24 and 48 h postoperatively in the pregabalin group was significantly less than that in the placebo group. The pooled static pain intensity at all time points within the first day was significantly lower in the pregabalin group than in the placebo group. Lower dynamic pain intensity at 48 h was detected in the pregabalin group than in the placebo group. Meanwhile, pregabalin led to a lower incidence of nausea but appeared to be associated with a higher incidence of dizziness and sedation. Subgroup analyses showed that no difference was detected between subgroups stratified by dosing regimen or pregabalin dose in the results of opioid consumption, pain intensity and incidence of complications.

CONCLUSION

This meta-analysis supports the use of pregabalin preoperatively in patients undergoing lower limb orthopedic surgery. However, it was wary of the resulting increase in dizziness and sedation. There is no evidence to support the continued use of pregabalin postoperatively or using more than 150 mg of pregabalin per day.

TRIAL REGISTRATION

This study was registered on 09 November 2021 with INPLASY (registration number: INPLASY2021110031).

Considerations for Better Management of Postoperative Pain in Light of Chronic Postoperative Pain: A Narrative Review

Chronic postoperative pain (CPOP) is prevalent, with particularly high rates in breast surgery, thoracotomy, and amputation. As the world emerges from the coronavirus disease 2019 (COVID-19) lockdowns, it is expected that there will be an increase in surgical procedures, elevating the importance of preventing CPOP in the coming years. Risk factors are emerging to better stratify patients at high risk for CPOP. Perioperative analgesia plays an important role in managing acute postoperative pain and in some cases may limit its transition to CPOP. Acute postoperative pain is adaptive, normal, expected, and has a well-defined trajectory, while CPOP is maladaptive and, as a form of chronic pain, is challenging to treat. Good analgesia, early ambulation, and rehabilitation efforts may be helpful in preventing CPOP following certain surgeries. Enhanced Recovery After Surgery (ERAS) protocols present guidance to help promote recovery and prevent CPOP.

Examination of the Novel Sigma-1 Receptor Antagonist, SI 1/28, for Antinociceptive and Anti-allodynic Efficacy against Multiple Types of Nociception with Fewer Liabilities of Use

Neuropathic pain is a significant problem with few effective treatments lacking adverse effects. The sigma-1 receptor (S1R) is a potential therapeutic target for neuropathic pain, as antagonists for this receptor effectively ameliorate pain in both preclinical and clinical studies. The current research examines the antinociceptive and anti-allodynic efficacy of SI 1/28, a recently reported benzylpiperazine derivative and analog of the S1R antagonist SI 1/13, that was 423-fold more selective for S1R over the sigma-2 receptor (S2R). In addition, possible liabilities of respiration, sedation, and drug reinforcement caused by SI 1/28 have been evaluated. Inflammatory and chemical nociception, chronic nerve constriction injury (CCI) induced mechanical allodynia, and adverse effects of sedation in a rotarod assay, conditioned place preference (CPP), and changes in breath rate and locomotor activity were assessed after i.p. administration of SI 1/28. Pretreatment with SI 1/28 produced dose-dependent antinociception in the formalin test, with an ED50 (and 95% C.I.) value of 13.2 (7.42-28.3) mg/kg, i.p. Likewise, SI 1/28 produced dose-dependent antinociception against visceral nociception and anti-allodynia against CCI-induced neuropathic pain. SI 1/28 demonstrated no impairment of locomotor activity, conditioned place preference, or respiratory depression. In summary, SI 1/28 proved efficacious in the treatment of acute inflammatory pain and chronic neuropathy without liabilities at therapeutic doses, supporting the development of S1R antagonists as therapeutics for chronic pain.

Perioperative Oral Pregabalin Results in Postoperative Pain Scores Equivalent to Those of Interscalene Brachial Plexus Block After Arthroscopic Rotator Cuff Repair: A Randomized Clinical Trial

PURPOSE

To compare the analgesic effects of pregabalin to those of single-shot interscalene brachial plexus block (ISBPB) in adults having arthroscopic rotator cuff (RC) repair, as well as ISBPB's effect on postoperative opioid consumption, patient satisfaction, and opioid-related adverse effects.

METHODS

In this randomized trial, 79 adults having arthroscopic RC repair were randomized to receive perioperative oral pregabalin (Lyrica, twice daily starting the evening before surgery, for a total of 4 doses) or single-shot ISBPB (20 ml of bupivacaine 0.25%). Intra- and postoperative management was standardized. The primary outcome was median self-reported pain score (on a visual analog scale of 0 to 100) at rest during the initial 10 postoperative days. Other outcomes included pain during activity, postoperative opioid consumption, opioid-related adverse effects, quality of recovery, and pain satisfaction score.

RESULTS

Of 71 eligible patients, 59 were analyzed, of whom 29 received pregabalin and 30 received ISBPB. Groups were similar regarding demographic, baseline, and intraoperative variables. Median pain score at rest over the 10 postoperative days was 51 (interquartile range 26, 76) in the pregabalin group and 52 (22, 74) in the ISBPB group (difference 0.5 points; 95% confidence interval [CI] -3.2 to 6.3; P = .53). Opioid consumption during the initial 10 postoperative days was also similar (difference in median 90 mg of morphine equivalents; 95% CI -32 to 177.5; P = .12). No differences were found in any other outcome.

CONCLUSIONS

Perioperative use of pregabalin in adults undergoing arthroscopic RC repair provided analgesia comparable to that of ISBPB for 10 days after surgery.

LEVEL OF EVIDENCE

II, randomized controlled trial (high dropout rate).

An Update on Assessment, Therapeutic Management, and Patents on Insomnia

Insomnia is an ordinary situation related to noticeable disability in function and quality of life, mental and actual sickness, and mishappenings. It represents more than 5.5 million appointments to family doctors every year. Nonetheless, the ratio of insomniacs who are treated keeps on being low, demonstrating the requirement for proceeding with advancement and dispersal of effective treatments. Accordingly, it becomes significant to provide a compelling treatment for clinical practice. It indicates a need for the determination of various critical viewpoints for the evaluation of insomnia along with various accessible alternatives for treatment. These alternatives incorporate both nonpharmacological therapy, specifically cognitive behavioural therapy for insomnia, and a number of pharmacological treatments like orexin antagonists, "z-drugs," benzodiazepines, selective histamine H1 antagonists, nonselective antihistamines, melatonin receptor agonists, antipsychotics, antidepressants, and anticonvulsants. Besides in individuals whose insomnia is due to restless leg syndrome, depression/mood disorder, or/and circadian disturbance, there is insignificant proof favouring the effectiveness of different prescriptions for the treatment of insomnia though they are widely used. Other pharmacological agents producing sedation should be prescribed with care for insomnia therapy because of greater risk of next-day sleepiness along with known adverse effects and toxicities. This review is also aimed at providing an update on various patents on dosage forms containing drugs for insomnia therapy.

Pharmacokinetics of oral and compounded intravenous gabapentin in Duroc swine (Sus Scrofa)

The objective of this study was to determine the pharmacokinetics (PK) of oral (OS; 20 mg/kg) and compounded intravenous (IV; 5.5 mg/kg) gabapentin in 6 healthy, adult, Duroc pigs. Subjects were randomized to receive IV and OS gabapentin in a cross-over design, with at least 14 days of wash-out period between the two rounds of drug administrations. Blood samples were obtained before gabapentin administration and at various times up to 24 h, and harvested plasma was stored at -80°C until analysis. Concentration of gabapentin was quantified using a previously validated liquid chromatography/tandem mass spectrometry method, and compartment models were fitted to time-concentration data using non-linear mixed effect (population) analysis. A two-compartment model best fitted the data following IV administration. Typical values for volume of the central compartment and clearance and calculated volume of distribution at steady-state and terminal half-life were 170 ml/kg, 1.2 ml/(kg*min), and 594 ml/kg and 360 min, respectively. For the oral route, absorption half-life, estimated maximal plasma concentration and time to reach maximal plasma concentration were 58 min, 9155 ng/ml, and 194 min, respectively. Estimated oral bioavailability was 47%. Short-lived sedation (approximately 15 min) with sternal or lateral recumbency after IV administration was observed in all subjects without adverse clinical effects. Simulation based on the results of this study suggests that a first oral gabapentin dose of 15 mg/kg and subsequent doses of 8.5 mg/kg every 8 h would achieve and maintain plasma concentrations between 5 and 8 μg/ml in pigs.

Association of gabapentinoid utilization with postoperative pulmonary complications in gynecologic surgery: a retrospective cohort study

OBJECTIVE

To investigate gabapentinoid utilization and association with postoperative pulmonary complications after gynecologic surgery.

METHODS

After Institutional Review Board approval, we performed this retrospective cohort study using the Premier Healthcare Database. We used ICD-10 and charge codes to identify adults who underwent elective gynecologic surgery from 2015 to 2018 and received either gabapentin or pregabalin on the day of surgery. Our primary outcome was a composite of pulmonary complications: respiratory failure, pneumonia, reintubation, pulmonary edema, and non-invasive or invasive ventilation. Secondary outcomes included mortality, intensive care unit admission, mechanical or non-invasive ventilation, hospital length of stay, re-admission within 30 days, opioid consumption and antiemetic use. Multivariable generalized linear mixed models were utilized to examine the associations between gabapentinoids and our outcome measures, adjusted for all covariates.

RESULTS

Data from 253,013 patients were analyzed, with 19,121 (7.6%) receiving gabapentinoids. Gabapentinoid utilization increased from 3.9% in 2015 to 12.3% in 2018, and was associated with increased pulmonary complications (OR 1.19; 95% CI 1.03-1.38), non-invasive ventilation (odds ratio [OR] 1.53; 95% CI 1.29-1.81), duration of hospital stay (% change 1.75; 95% CI 0.92-2.59), daily antiemetic doses on day of surgery (mean difference [MD] 1.37; 95% CI 1.26-1.49) and subsequently (MD 1.61; 95% CI 1.30-1.99), and higher daily average (MD 4.59 mg; 95% CI 3.55-5.63) and total (MD 8.74 mg; 95% CI 6.83-10.62) parenteral morphine equivalents.

CONCLUSIONS

Gabapentinoid utilization in gynecologic surgery is increasing and is associated with postoperative pulmonary complications.

A novel gabapentin analogue assuages neuropathic pain response in chronic sciatic nerve constriction model in rats

Gabapentin (GBP) is an established drug that has been used in the management of symptoms of neuropathy but it is associated with unwanted side effects such as sedation and motor incoordination. The goal of the study was to find out a drug with greater efficacy and safety for the treatment of neuropathic pain. Our previously synthesized GABA analogue (Gabapentsal, GPS) was tested (25-100 mg/kg, i.p) in chronic constriction injury (CCI) induced nociceptive model of static allodynia, dynamic allodynia, thermal hyperalgesia, mechanical hyperalgesia and cold allodynia in rats (Sprague Dawley). Open field and rotarod tests were performed to assess the impact of GPS on the motor performance of the animals. GBP (100 mg/kg, i.p) was used as a standard for comparison. GPS dose dependently reduced static (P <0.001) and dynamic allodynia (P <0.001), thermal hyperalgesia (P <0.001), mechanical hyperalgesia (P < 0.001) and cold allodynia (P < 0.001). In comparison to GBP, GPS failed to alter any significantly the motor performance of rats in both the open field and rotarod assays. These results suggest that GPS is effective in alleviating nociception in CCI neuropathic pain model but free from the side effect of motor discoordination seen in the treatment with GBP. In conclusion, GPS may prove to be a prospectively more effective and safer option in the management of neuropathic syndromes.

Non-medical use of benzodiazepines and GABA analogues in Europe

AIMS

We investigated the prevalence of non-medical use (NMU) of benzodiazepines and GABA analogues in Europe.

METHODS

Data were collected using the online Non-Medical Use of Prescription Drugs (NMURx) survey from France, Germany, Italy, Spain and the UK.

RESULTS

The study included 55 223 eligible surveys which, after post-stratification weights were applied, represented approximately 260 million European adults. Lifetime NMU of benzodiazepines was highest in Spain (6.5%, 95% CI: 6.0-7.0) and lowest in Germany (1.7%, 1.5-2.0). Lifetime NMU of GABA analogues was highest in Germany (5.4%, 5.0-5.7) and lowest in France (2.2%, 1.9-2.5) and the UK (2.2%, 1.9-2.6) While no notable difference was observed for France or the UK, there was a higher prevalence of last 12-month NMU of benzodiazepines compared to GABA analogues in Italy (2.4 times higher) and Spain (3.0 times higher) and a higher prevalence of NMU of GABA analogues compared to benzodiazepines in Germany (2.6 times higher).

CONCLUSION

This study shows that there is variation in NMU of benzodiazepines and GABA analogues among countries. Of particular interest is the high incidence of GABA analogue NMU in Germany and benzodiazepine NMU in Spain. Further research to identify factors and motivations responsible for the higher prevalence observed are essential to inform public health policies in those countries.

Consensus statements on the clinical uses of pregabalin for Hong Kong

To facilitate the understanding of pregabalin and optimize its clinical usage in Hong Kong, an expert panel (11 psychiatrists, one family physician and one anesthesiologist) experienced in treating anxiety and somatic symptoms was invited to establish a set of consensus statements based on several discussion areas. A non-systematic literature search for relevant articles was conducted. The panelists addressed the discussion areas by sharing their clinical experience and available literature in a couple of meetings. At the last meeting, consensus statements derived from the proceedings were discussed and finalized. A total of 11 statements were ultimately accepted by panel voting based on their practicability of recommendation in Hong Kong. These statements are aimed to act as a practical reference for local clinicians when they consider prescribing pregabalin in different clinical situations.

The analgesic efficiency of pregabalin for the treatment of postoperative pain in total hip arthroplasty: A randomized controlled study protocol

BACKGROUND

Only few studies have yet investigated whether perioperative administration of pregabalin can reduce the incidence of postoperative chronic neuropathic pain after total hip arthroplasty (THA). This prospective, randomized study compared placebo with pregabalin in the hope that a lower pregabalin dose would improve analgesia without increasing side-effects after THA.

METHODS

This study was a prospective randomized blinded study, with a parallel design and an allocation ratio of 1:1 for the treatment groups. The study was approved by the Institutional Review Board in Weifang People's Hospital and written informed consent was obtained from all subjects before enrolment. A total of 120 patients who meet inclusion criteria are randomized to either pregabalin or placebo group. The primary objective of the study was visual analog scale score. As secondary outcomes, opioid consumption measurement, Harris Hip Score, hip range of motion, patient satisfaction, and complications were made at different time points throughout the study for comparison.

RESULTS

The null hypothesis of this study was that pregabalin would reduce pain after THA.

TRIAL REGISTRATION

This study protocol was registered in Research Registry (researchregistry5669).

An Insight into Gabapentin and Pregabalin in Scottish Prisoners

The aim of this study was to evaluate the prevalence and abuse potential of antiepileptic drugs (AEDs) among prison populations in Scotland, UK. Participants consisted of all admitted and released prisoners over a 1 month period who consented to provide samples. Urine samples were collected and analyzed by liquid chromatography coupled with triple quadrupole tandem mass spectrometry using a method validated for the simultaneous quantification of 21 AEDs in urine. A total of 904 samples were collected. The samples were also screened for drugs of abuse by using point-of-care testing kits. A total of 18% of the samples were positive for AEDs. Gabapentin (GBP) was identified in 118 samples (13%) and pregabalin (PRG) in 32 samples (3.5%). Interestingly, 12 samples contained both drugs (1.3%). The concentrations ranged from 0.5 to 1,100 mg/L (median, 15 mg/L) for GBP and from 0.5 to 440 mg/L (median, 7.3 mg/L) for PRG. Four samples were found to have concentrations &gt;400 mg/L, two samples for GBP and two samples for PRG. These concentrations are at least 20 times above the median concentrations. Other AEDs detected were levetiracetam (four samples), vigabatrin (four samples), lamotrigine (three samples), valproic acid (three samples), carbamazepine (two samples) and topiramate (one sample). Illicit or non-prescribed drugs were detected in 81% of urine samples of which 80% were from admitted prisoners and 20% from released prisoners. Benzodiazepines, opiates and cannabis were the most frequently detected drugs. Other drugs found in positive AED samples were methadone (26%), cocaine (18%), buprenorphine (17%), amphetamines (4%), methamphetamines (4%) and barbiturates (4%). This study shows a high prevalence of AEDs within the Scottish prison system, primarily due to GBP and PRG; however, due to the anonymity of the sample collection, it is unknown if these are prescribed or illicit drug ingestions.

Comparing the prophylactic effects of oral gabapentin, pregabalin, and celecoxib on postoperative pain management in orthopedic surgery of the lower extremity: A double-blind randomized controlled trial

Background:

Lower extremity pain after orthopedic surgery is so frequent that has led to many treatment modalities. This study aims to compare the prophylactic effects of oral gabapentin, pregabalin, and celecoxib on reducing postsurgical pain of the lower extremity orthopedic surgery.

Materials and Methods:

In a double-blind randomized controlled trial, 120 patients were randomly divided into four groups using block design randomization. 1 h before spinal anesthesia, the studied groups received 300 mg oral gabapentin; 75 mg oral pregabalin; 200 mg oral celecoxib; and starch as placebo. The severity of postoperative pain (using visual analog scale), mean arterial pressure, heart rate, opioid consumption dose, and drug side effects were recorded for six times (each 60 min up to two times and then every 6 h for the next four times). Chi-square, one-way analysis of variance (ANOVA), and ANOVA repeated measure tests were used for statistical analysis.

Results:

Significant reduction of pain severity was observed only at the first time measurement between pregabalin and placebo groups (P: 0.014). Patients in the pregabalin group required lower dose of opioid compared to placebo group during admission in surgical ward. There were no significant differences concerning pain reduction, opioid administration, and side effects between pregabalin, gabapentin, and celecoxib groups.

Conclusion:

Taking 75 mg oral pregabalin before lower extremity orthopedic surgery can attenuate postoperative pain, especially during the 1^st h postoperation as well as less opioid consumption and much more patients' satisfaction.

Sleep deprivation of rats increases postsurgical expression and activity of L-type calcium channel in the dorsal root ganglion and slows recovery from postsurgical pain

Perioperative sleep disturbance is a risk factor for persistent pain after surgery. Clinical studies have shown that patients with insufficient sleep before and after surgery experience more intense and long-lasting postoperative pain. We hypothesize that sleep deprivation alters L-type calcium channels in the dorsal root ganglia (DRG), thus delaying the recovery from post-surgical pain. To verify this hypothesis, and to identify new predictors and therapeutic targets for persistent postoperative pain, we first established a model of postsurgical pain with perioperative sleep deprivation (SD) by administering hind paw plantar incision to sleep deprivation rats. Then we conducted behavioral tests, including tests with von Frey filaments and a laser heat test, to verify sensory pain, measured the expression of L-type calcium channels using western blotting and immunofluorescence of dorsal root ganglia (an important neural target for peripheral nociception), and examined the activity of L-type calcium channels and neuron excitability using electrophysiological measurements. We validated the findings by performing intraperitoneal injections of calcium channel blockers and microinjections of dorsal root ganglion cells with adeno-associated virus. We found that short-term sleep deprivation before and after surgery increased expression and activity of L-type calcium channels in the lumbar dorsal root ganglia, and delayed recovery from postsurgical pain. Blocking these channels reduced impact of sleep deprivation. We conclude that the increased expression and activity of L-type calcium channels is associated with the sleep deprivation-mediated prolongation of postoperative pain. L-type calcium channels are thus a potential target for management of postoperative pain.

Patterns and predictors of outpatient opioid use after cytoreductive surgery with hyperthermic intraperitoneal chemotherapy

Background: Long-term opioid use is a well-known complication after surgery. In this retrospective study of adults who had undergone cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRS-HIPEC), we sought to determine the rates and factors associated with outpatient opioid use within the sixth and twelfth postoperative months. Methods: Records of 288 opioid-naïve patients were included. Logistic regression models were used to determine factors prognostic of outpatient opioid use. Results: The median patient age was 54 years, and 63% were female. Rates of outpatient opioid use within the sixth and twelfth postoperative months were 21 and 13%, respectively. In the multivariate analysis, every doubling in the amount of in-hospital postoperative opioid consumption was associated with a 44% increase in odds of opioid use within the sixth postoperative month (OR 1.44, 95% CI 1.11-1.87, p = .006) and a 70% increase within the twelfth postoperative month (OR 1.70, 95% CI 1.70-2.37, p = .001). Other factors associated with opioid use within the sixth postoperative month included physical status (OR 5.26, 95% CI 1.08-25.55, p = .039) and recent additional surgery (OR 23.02, 95% CI 2.03-261.30, p = .011). Age (OR 4.39, 95% CI 1.77-10.89, p = .001) and tumor grade (OR 3.31, 95% CI 1.31-8.41, p = .012) were associated with opioid use within the twelfth postoperative month. Conclusion: In this study, the amount of in-hospital postoperative opioid consumption was an important contributory factor to outpatient opioid use in the sixth and twelfth postoperative months. Synopsis In this study of adults who had undergone CRS-HIPEC, higher postoperative opioid consumption during hospitalization was associated with higher odds of opioid use within the sixth and twelfth postoperative months.

The assessment and management of insomnia: an update

Insomnia poses significant challenges to public health. It is a common condition associated with marked impairment in function and quality of life, psychiatric and physical morbidity, and accidents. As such, it is important that effective treatment is provided in clinical practice. To this end, this paper reviews critical aspects of the assessment of insomnia and the available treatment options. These options include both non-medication treatments, most notably cognitive behavioral therapy for insomnia, and a variety of pharmacologic therapies such as benzodiazepines, "z-drugs", melatonin receptor agonists, selective histamine H1 antagonists, orexin antagonists, antidepressants, antipsychotics, anticonvulsants, and non-selective antihistamines. A review of the available research indicates that rigorous double-blind, randomized, controlled trials are lacking for some of the most commonly administered insomnia therapies. However, there are an array of interventions which have been demonstrated to have therapeutic effects in insomnia in trials with the above features, and whose risk/benefit profiles have been well characterized. These interventions can form the basis for systematic, evidence-based treatment of insomnia in clinical practice. We review this evidence base and highlight areas where more studies are needed, with the aim of providing a resource for improving the clinical management of the many patients with insomnia.

Increased postoperative dexamethasone and gabapentin reduces opioid consumption after total knee arthroplasty

PURPOSE

Dexamethasone and gabapentin are used in multimodal pain management protocols to reduce postoperative pain after total knee arthroplasty. For both analgesic adjuvants, the optimal dose regimen to reduce opioid usage is still unclear.

METHODS

The opioid consumption of patients undergoing primary TKA before and after a change of the analgesic adjuvant medication in our protocol (old protocol: 4 mg of dexamethasone daily for 2 days, 600 mg gabapentin daily for 1 week; new protocol: 10 mg dexamethasone daily for 2 days, 300 mg gabapentin every 8 h for 1 week) were retrospectively compared. All surgeries were performed under spinal anesthesia. Peri- and postoperative pain medication remained unchanged.

RESULTS

A total of 186 patients who received TKA between 11/29/2016 and 06/09/2017 were screened. Six patients who received general anesthesia, 4 patients who underwent simultaneous bilateral TKA, and 16 patients with ongoing opioid consumption at the time of surgery were excluded, leaving 80 patients in each group. Opioid consumption within 24 h [morphine equivalents in mg: mean 50.5, standard deviation (SD) 30.0 (old) vs. 39.8, SD 24.2 (new); P = 0.0470], cumulative consumption over 48 h (97.3, SD 64.4 vs. 70.4, SD 51.2; P = 0.0040) and cumulative consumption over 72 h (108.1, SD 79.5 vs. 82.5, SD 72.6; P = 0.0080), were all significantly lower in the new protocol.

CONCLUSION

Increased postoperative administration of dexamethasone and gabapentin after TKA is associated with lower opioid consumption. Within the first 48 h, up to about 25% of opioids can be spared, comparing high-dose to low-dose protocols.

LEVEL OF EVIDENCE

Therapeutic Level III.

Prolonged Perioperative Use of Pregabalin and Ketamine to Prevent Persistent Pain after Cardiac Surgery

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Background

Persistent postsurgical pain is common and affects quality of life. The hypothesis was that use of pregabalin and ketamine would prevent persistent pain after cardiac surgery.

Methods

This randomized, double-blind, placebo-controlled trial was undertaken at two cardiac surgery centers in the United Kingdom. Adults without chronic pain and undergoing any elective cardiac surgery patients via sternotomy were randomly assigned to receive either usual care, pregabalin (150 mg preoperatively and twice daily for 14 postoperative days) alone, or pregabalin in combination with a 48-h postoperative infusion of intravenous ketamine at 0.1 mg · kg−1 · h−1. The primary endpoints were prevalence of clinically significant pain at 3 and 6 months after surgery, defined as a pain score on the numeric rating scale of 4 or higher (out of 10) after a functional assessment of three maximal coughs. The secondary outcomes included acute pain, opioid use, and safety measures, as well as long-term neuropathic pain, analgesic requirement, and quality of life.

Results

In total, 150 patients were randomized, with 17 withdrawals from treatment and 2 losses to follow-up but with data analyzed for all participants on an intention-to-treat basis. The prevalence of pain was lower at 3 postoperative months for pregabalin alone (6% [3 of 50]) and in combination with ketamine (2% [1 of 50]) compared to the control group (34% [17 of 50]; odds ratio = 0.126 [0.022 to 0.5], P = 0.0008; and 0.041 [0.0009 to 0.28], P &lt; 0.0001, respectively) and at 6 months for pregabalin alone (6% [3 of 50]) and in combination with ketamine 0% (0 of 5) compared to the control group (28% [14 of 50]; odds ratio = 0.167 [0.029 to 0.7], P = 0.006; and 0.000 [0 to 0.24], P &lt; 0.0001). Diplopia was more common in both active arms.

Conclusions

Preoperative administration of 150 mg of pregabalin and postoperative continuation twice daily for 14 days significantly lowered the prevalence of persistent pain after cardiac surgery.

Crossing the Chloride Channel: The Current and Potential Therapeutic Value of the Neuronal K+-Cl- Cotransporter KCC2

Chloride (Cl-) homeostasis is an essential process involved in neuronal signalling and cell survival. Inadequate regulation of intracellular Cl- interferes with synaptic signalling and is implicated in several neurological diseases. The main inhibitory neurotransmitter of the central nervous system is γ-aminobutyric acid (GABA). GABA hyperpolarises the membrane potential by activating Cl- permeable GABAA receptor channels (GABAAR). This process is reliant on Cl- extruder K+-Cl- cotransporter 2 (KCC2), which generates the neuron's inward, hyperpolarising Cl- gradient. KCC2 is encoded by the fifth member of the solute carrier 12 family (SLC12A5) and has remained a poorly understood component in the development and severity of many neurological diseases for many years. Recent advancements in next-generation sequencing and specific gene targeting, however, have indicated that loss of KCC2 activity is involved in a number of diseases including epilepsy and schizophrenia. It has also been implicated in neuropathic pain following spinal cord injury. Any variant of SLC12A5 that negatively regulates the transporter's expression may, therefore, be implicated in neurological disease. A recent whole exome study has discovered several causative mutations in patients with epilepsy. Here, we discuss the implications of KCC2 in neurological disease and consider the evolving evidence for KCC2's potential as a therapeutic target.

Mesenchymal stem cells therapy enhances the efficacy of pregabalin and prevents its motor impairment in paclitaxel-induced neuropathy in rats: Role of Notch1 receptor and JAK/STAT signaling pathway

Peripheral neuropathy is a common adverse effect observed during the use of paclitaxel (PTX) as chemotherapy. The present investigation was directed to estimate the modulatory effect of bone marrow derived mesenchymal stem cells (BM-MSCs) on pregabalin (PGB) treatment in PTX-induced peripheral neuropathy. Neuropathic pain was induced in rats by injecting PTX (2 mg/kg, i.p) 4 times every other day. Rats were then treated with PGB (30 mg/kg/day, p.o.) for 21 days with or without a single intravenous administration of BM-MSCs. At the end of experiment, behavioral and motor abnormalities were assessed. Animals were then sacrificed for measurement of total antioxidant capacity (TAC), nerve growth factor (NGF), nuclear factor kappa B p65 (NF-κB p65), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and active caspase-3 in the sciatic nerve. Moreover, protein expressions of Notch1 receptor, phosphorylated Janus kinase 2 (p-JAK2), phosphorylated signal transducer and activator of transcription 3 (p-STAT3), and phosphorylated p38 mitogen-activated protein kinase (p-p38-MAPK) were estimated. Finally, histological examinations were performed to assess severity of sciatic nerve damage and for estimation of BM-MSCs homing. Combined PGB/BM-MSCs therapy provided an additional improvement toward reducing PTX-induced oxidative stress, neuro-inflammation, and apoptotic markers. Interestingly, BM-MSCs therapy effectively prevented motor impairment observed by PGB treatment. Combined therapy also induced a significant increase in cell homing and prevented PTX-induced sciatic nerve damage in histological examination. The present study highlights a significant role for BM-MSCs in enhancing treatment potential of PGB and reducing its motor side effects when used as therapy in the management of peripheral neuropathy.

Pregabalin and lacosamide ameliorate paclitaxel-induced peripheral neuropathy via inhibition of JAK/STAT signaling pathway and Notch-1 receptor

Anticonvulsant drugs such as pregabalin (PGB) and lacosamide (LCM), exhibit potent analgesic effects in diabetic neuropathy; however, their possible role/mechanisms in paclitaxel (PTX)-induced peripheral neuropathy have not been elucidated, which is the aim of the present study. Neuropathic pain was induced in rats by injecting PTX (2 mg/kg, i. p) on days 0, 2, 4 and 6. Forty eight hours after the last dose of PTX, rats were treated orally with 30 mg/kg/day of either PGB or LCM for 21 days. Both therapies improved thermal hyperalgesia and cold allodynia induced by PTX. Interestingly, LCM therapy showed no motor impairment that was observed upon using PGB, as demonstrated using rotarod test. Treatment with PGB or LCM restored the sciatic nerve content of the depleted total antioxidant capacity (TAC) and nerve growth factor (NGF), and lessened the elevated contents of nuclear factor kappa B p65 (NF-kB p65), tumor necrosis factor-α (TNF-α), and active caspase-3. On the molecular level, the drugs reduced the protein expression of Notch1 receptor, phosphorylated p38 mitogen-activated protein kinase (p-p38-MAPK), and the trajectory interleukin-6/phosphorylated janus kinase 2/phosphorylated signal transducer and activator of transcription 3 (IL-6/p-JAK2/p-STAT3). Therefore, the current study demonstrated a pivotal role for LCM in the management of PTX-induced peripheral neuropathy similar to PGB, but without motor adverse effects via the inhibition of oxidative stress, inflammation and apoptosis, as well as IL-6/JAK/STAT pathway and Notch1 receptor over-expression.

Comprehensive Acute Pain Management in the Perioperative Surgical Home

The careful coordination of care throughout the perioperative continuum offered by the perioperative surgical home (PSH) is important in the treatment of postoperative pain. Physician anesthesiologists have expertise in acute pain management, pharmacology, and regional and neuraxial anesthetic techniques, making them ideal leaders for managing perioperative analgesia within the PSH. Severe postoperative pain is one of many patient- and surgery-specific factors in the development of chronic postsurgical pain. Delivering adequate perioperative analgesia is important to avoid this development, to decrease perioperative morbidity, and to improve patient satisfaction.

Electroencephalographic signatures of pain and analgesia in rats

Pain modulates rhythmic neuronal activity recorded by Electroencephalography (EEG) in humans. Our laboratory previously showed that rat models of acute and neuropathic pain manifest increased power in primary somatosensory cortex (S1) recorded by electrocorticography (ECoG). In this study, we hypothesized that pain increases EEG power and corticocortical coherence in different rat models of pain, whereas treatments with clinically effective analgesics reverse these changes. Our results show increased cortical power over S1 and prefrontal cortex (PFC) in awake, freely behaving rat models of acute, inflammatory and neuropathic pain. Coherence between PFC and S1 is increased at a late, but not early, time point during the development of neuropathic pain. Electroencephalography power is not affected by ibuprofen in the acute pain model. However, pregabalin and mexiletine reverse the changes in power and S1-PFC coherence in the inflammatory and neuropathic pain models. These data suggest that quantitative EEG might be a valuable predictor of pain and analgesia in rodents.

Oral pregabalin for acute pain relief after cervicofacial surgery: a systematic review

OBJECTIVE

The objectives of this systematic review were to unify criteria on the effectiveness of oral pregabalin to treat acute post-operative pain after cervicofacial surgery, to establish the most effective dose regimens, and to determine its effect on rescue medicine consumption and its association with adverse effects.

MATERIALS AND METHODS

PubMed/Medline (National Library of Medicine, Washington, DC), Scopus, Web of Science, and Cochrane databases were searched for studies in any language published between January 2000 and September 2016. The following question was posed, in accordance with PRISMA guidelines: Is oral pregabalin effective and safe for the relief of acute pain after cervicofacial surgery? The critical reading of the literature utilized a list of questions prepared by the CASPe Network, applying the Jadad scale for evaluation of the methodological quality of trials.

RESULTS

Eleven randomized controlled clinical trials were selected. The 11 trials obtained a score ≥ 3, considered as Ib evidence level and high quality. A single oral dose of 75-mg pregabalin before or after cervicofacial surgery alleviates pain and lessens the need for rescue analgesia consumption, while the statistical significance of these effects is higher with a single dose of 150-mg pregabalin, either before or after the surgery.

CONCLUSION

Oral pregabalin appears to significantly alleviate post-operative pain and reduce rescue analgesia consumption, with no severe adverse effects. However, the ideal dose and most effective administration regimen remain controversial issues that need to be addressed in further high-quality clinical trials.

CLINICAL RELEVANCE

These findings suggest that pregabalin may be useful for acute pain relief after cervicofacial surgery.

Exploring Opioid-Sparing Multimodal Analgesia Options in Trauma: A Nursing Perspective

Challenges with opioids (e.g., adverse events, misuse and abuse with long-term administration) have led to a renewed emphasis on opioid-sparing multimodal management of trauma pain. To assess the extent to which currently available evidence supports the efficacy and safety of various nonopioid analgesics and techniques to manage trauma pain, a literature search of recently published references was performed. Additional citations were included on the basis of authors' knowledge of the literature. Effective options for opioid-sparing analgesics include oral and intravenous (IV) acetaminophen; nonsteroidal anti-inflammatory drugs available via multiple routes; and anticonvulsants, which are especially effective for neuropathic pain associated with trauma. Intravenous routes (e.g., IV acetaminophen, IV ketorolac) may be associated with a faster onset of action than oral routes. Additional adjuvants for the treatment of trauma pain are muscle relaxants and alpha-2 adrenergic agonists. Ketamine and regional techniques play an important role in multimodal therapy but require medical and nursing support. Nonpharmacologic treatments (e.g., cryotherapy, distraction techniques, breathing and relaxation, acupuncture) supplement pharmacologic analgesics and can be safe and easy to implement. In conclusion, opioid-sparing multimodal analgesia addresses concerns associated with high doses of opioids, and many pharmacologic and nonpharmacologic options are available to implement this strategy. Nurses play key roles in comprehensive patient assessment; administration of patient-focused, opioid-sparing, multimodal analgesia in trauma; and monitoring for safety concerns.

Effect of gastroretentive gabapentin (Gralise) on postmastectomy pain syndrome: a proof-of-principle open-label study

Introduction

Chronic pain is a common and debilitating complication following breast surgery. One of the most challenging for treatment is the neuropathic pain condition, postmastectomy pain syndrome (PMPS). Gabapentin is a pharmacotherapy for neuropathic pain disorders; however, its once-daily, gastroretentive formulation, Gralise, has not been evaluated in PMPS.

Objective

To evaluate the safety and effectiveness of Gralise in patients with moderate-to-severe PMPS.

Methods

The primary effectiveness endpoint was a change in the worst pain intensity score from baseline to completion of 8 weeks of Gralise therapy. The secondary endpoints included the change in mood, coping behavior, sleep, and function. Sensitivity to experimental stimuli was tested before and after treatment via quantitative sensory testing. The incidence and type of adverse event were used to evaluate the safety and tolerability of Gralise.

Results

Twenty-one patients with confirmed moderate-to-severe PMPS were enrolled. Nineteen of 21 (90.5%) patients completed the 8-week treatment with Gralise. A significant positive change was found in pain intensity, pain impact, and sleep. There was no change in sensory testing scores. Of total, 63.16% of patients reported reduction in present pain, 78.95% in average pain, 89.47% in worst pain, and 84.21% in overall pain severity at posttreatment visit. No significant adverse effects were noted in the study.

Limitations

Variation in type of breast surgery, small sample size, lack of placebo control.

Conclusion

There was a significant improvement in pain and sleep, and Gralise was well tolerated in patients with PMPS. Further investigation is warranted.

Pharmacodynamic response profiles of anxiolytic and sedative drugs

AIM

Centrally-acting acutely anxiolytic drugs, such as benzodiazepines, barbiturates and gabapentinoids, affect various central nervous system (CNS) functions, which reflects not only their anxiolytic effects but also neuropsychological side-effects. To validate the pharmacodynamic biomarkers for GABA-ergic anxiolytics, this study determined the pharmacodynamics of two anxiolytics and a nonanxiolytic control, and linked them to their anxiolytic and sedative effects, during an anxiety-challenge study day.

METHODS

Twenty healthy volunteers were randomized in this placebo-controlled, double-blind, four-way cross-over study with single-dose alprazolam (1 mg), diphenhydramine (50 mg), pregabalin (200 mg) or placebo. The Neurocart was used between repeated fear-potentiated startle assessments. Thus, the potential influence of anxiety on CNS pharmacodynamic markers could be examined.

RESULTS

Compared to placebo, VAS_calmness increased with alprazolam (2.0 mm) and pregabalin (2.5 mm) but not with diphenhydramine. Saccadic peak velocity (SPV) declined after alprazolam (-57 ° s^-1 ) and pregabalin (-28 ° s^-1 ), more than with diphenhydramine (-14 ° s^-1 ); so did smooth pursuit. The average responses of SPV and smooth pursuit were significantly correlated with the drug-induced increases in VAS_calmness . The SPV-relative responses of VAS_alertness , body-sway and adaptive-tracking also differed among alprazolam, pregabalin and diphenhydramine.

CONCLUSIONS

Compared with the antihistaminergic sedative diphenhydramine, alprazolam and pregabalin caused larger SPV reduction, which was correlated with simultaneous improvement of subjective calmness, during a study day in which anxiety was stimulated repeatedly. The different effect profiles of the three drugs are in line with their pharmacological distinctions. These findings corroborate the profiling of CNS effects to demonstrate pharmacological selectivity, and further support SPV as biomarker for anxiolysis involving GABA-ergic neurons. The study also supports the use of prolonged mild threat to demonstrate anxiolytic effects in healthy volunteers.

Gabapentinoids as a Part of Multi-modal Drug Regime for Pain Relief following Laproscopic Cholecystectomy: A Randomized Study

Background:

Gabapentinoids have been used as preemptive analgesics for pain management following laparoscopic cholecystectomy. Recently, multimodal analgesic techniques have been found superior to preemptive analgesia alone.

Aim:

The aim of this study is to evaluate and compare a single preoperative dose of pregabalin 150 mg and gabapentin 300 mg for pain relief following laparoscopic cholecystectomy as a part of multimodal drug regime.

Settings and Design:

This randomized, single-blind study was conducted after Ethical Committee approval and written informed consent from the patients.

Materials and Methods:

Fifty patients undergoing laparoscopic cholecystectomy under general anesthesia were randomly allocated to receive either 150 mg pregabalin (Group PG), or 300 mg gabapentin (Group GB) orally, 2 h before surgery. Standard anesthesia induction and maintenance were done. For intraoperative pain management, injection fentanyl 2 μg.kg^-1 intravenous (IV) along with injection voveran 75 mg IV and port site infiltration was used. Postoperatively, injection diclofenac 75 mg intramuscular TDS was continued. Severity of postoperative pain (visual analog scale [VAS]), postoperative fentanyl requirement and incidence, and severity of side effects were assessed. When VAS >40 mm or on patient's request, a Fentanyl bolus at an increment of 25–50 μg IV was given as rescue analgesia.

Results:

Intraoperative fentanyl requirement was 135 ± 14 μg in Group PG and 140 ± 14 μg in Group GB (P = 0.21). Postoperative, fentanyl requirement was 123 ± 18 μg in Group PG and 131 ± 23 μg in Group GB (P = 0.17) There was no statistically significant difference in the VAS score for static and dynamic pain. Time to the first requirement of analgesic was 5.4 ± 1.1 h in Group PG and 4.6 ± 1.6 h in Group GB (P = 0.015). No side effects were observed.

Conclusion:

We conclude that a single preoperative dose of pregabalin (150 mg) or gabapentin (300 mg) are equally efficacious in providing pain relief following laparoscopic cholecystectomy as a part of multimodal regime without any side effects.

Comparison of the effects of gabapentin and pregabalin on wound healing in rats

Gabapentinoids are effective adjunct drugs for reducing postoperative pain. However, the effects of gabapentinoids on wound healing have not been evaluated yet. In this study we evaluated their effects on wound healing. A total of 17 male Wistar-Albino rats, 250-350 g, were divided into three groups randomly: control group (n = 5, 2 ml saline), gabapentin group (n = 6, 20 mg/kg gabapentin) and pregabalin group (n = 6, 20 mg/kg pregabalin). Until day 13 inflammation scores were significantly lower (P < 0·05) and wound healing was significantly better in the control group when compared with gabapentin and pregabalin groups (P < 0·001). Inflammation scores were significantly lower in pregabalin group when compared with gabapentin group until day 13. But wound healing was significantly better in gabapentin group than in pregabalin group between days 13 and 21. In conclusion when gabapentin and pregabalin were compared, although pregabalin decreases inflammation scores, gabapentin has better results in wound healing.

Adverse event assessment and reporting in trials of newer treatments for post-operative pain

BACKGROUND

Assessment and reporting of adverse events (AEs) in studies of perioperative interventions is critical given the potential for unintended and preventable iatrogenic morbidity and mortality. This focused review evaluated the quality of AE assessment and reporting in acute post-operative pain treatment trials. Since older analgesics (e.g., opioids, NSAIDs) already have a well-characterized safety profile, we concentrated on trials of pregabalin and gabapentin as a representative sample of studies where the perioperative safety profile was relatively unknown.

METHODS

We reviewed primary reports of trials of pregabalin and gabapentin for treatment of acute post-operative pain for: (1) adherence to the 10 recommendations from the 'CONSORT Extension for Harms,' (2) AE assessment method, (3) timing of AE assessment and reporting, and (4) assessment and reporting of AE severity.

RESULTS

We identified 31 trials of pregabalin and 59 of gabapentin. The median number of CONSORT harms recommendations that were satisfied was 7 of 10. The most common (41%) method of AE assessment was direct questioning about specific AEs by investigators. However, AE assessment method was not described in 18% of trials. AE assessments were reported for specified perioperative time points in only 24% of trials. Of greatest concern, no AE data were reported whatsoever in 8 of the included publications.

CONCLUSIONS

Considerable widespread improvements are needed in AE reporting for post-operative pain treatment trials. In addition to heightened awareness among clinical investigators, mandatory journal editorial policies may further facilitate improvements in safety assessment and reporting.

Population Pharmacokinetic Modelling of Morphine, Gabapentin and their Combination in the Rat

PURPOSE

The combination of morphine and gabapentin seems promising for the treatment of postoperative and neuropathic pain. Despite the well characterised pharmacodynamic interaction, little is known about possible pharmacokinetic interactions. The aim of this study was to evaluate whether co-administration of the two drugs leads to modifications of their pharmacokinetic profiles.

METHODS

The pharmacokinetics of morphine, morphine-3-glucuronide and gabapentin were characterised in rats following subcutaneous injections of morphine, gabapentin or their combination. Non-linear mixed effects modelling was applied to describe the pharmacokinetics of the compounds and possible interactions.

RESULTS

The plasma-concentration-time profiles of morphine and gabapentin were best described using a three- and a one-compartment disposition model respectively. Dose dependencies were found for morphine absorption rate and gabapentin bioavailability. Enterohepatic circulation of morphine-3-glucuronide was modelled using an oscillatory model. The combination did not lead to pharmacokinetic interactions for morphine or gabapentin but resulted in an estimated ~33% diminished morphine-3-glucuronide formation.

CONCLUSIONS

The finding of a lack of pharmacokinetic interaction strengthens the notion that the combination of the two drugs leads to better efficacy in pain treatment due to interaction at the pharmacodynamic level. The interaction found between gabapentin and morphine-3-glucuronide, the latter being inactive, might not have any clinical relevance.

Analgesic efficacy of pregabalin in acute postmastectomy pain: placebo controlled dose ranging study

STUDY OBJECTIVE

We hypothesized that oral administration of a single dose of pregabalin 2 hours before modified radical mastectomy (MRM) would produce dose-related reduction in postoperative opioid consumption.

DESIGN

Prospective randomized controlled clinical trial.

SETTING

Postanesthesia care unit.

PATIENTS

One hundred twenty adult women scheduled for unilateral (MRM) with axillary evacuation.

INTERVENTIONS

Patients were randomized to receive either, placebo capsule, pregabalin 75 mg, pregabalin 150 mg, or pregabalin 300 mg.

MEASUREMENTS

The assessment parameters were the postoperative analgesic effect using visual analog scale (VAS) pain scores, the subsequent 24-hour morphine consumption, and the systemic adverse effects of pregabalin doses.

MAIN RESULTS

The VAS score at rest and movement was significantly decreased only in group P300 and group P150 in comparison to group P0 and group P75 at 0 hour (P<.01). The median (interquartile range) consumption of morphine in the first postoperative 24 hours was significantly decreased in group P300 in comparison to group P0 and group P75 (P300 vs P0: 6.5 [5-6.5] vs 20.5 [15.8-20.5] [P<.001]; P300 vs P75: 6.5 [5-6.5] vs 20 [14-20] [P<.001]), but there was no significant difference between group P300 and group P150. In addition, there was a significant decrease in consumption of morphine in group P150 in comparison to group P0 and group P75 (P150 vs P0: 7 [5-7] vs 20.5 [15.8-20.5] [P<.001]; P150 vs P75: 7 [5-7] vs 20 [14-20] [P<.001]). There were statistical significant increase in dizziness and blurred vision in group P300 in comparison to other groups (P<.05).

CONCLUSIONS

A single preoperative oral dose of pregabalin 150 mg is an optimal dose for reducing postoperative pain and morphine consumption in patients undergoing MRM.

The antiallodynic action of pregabalin in neuropathic pain is independent from the opioid system

BACKGROUND

Clinical management of neuropathic pain, which is pain arising as a consequence of a lesion or a disease affecting the somatosensory system, partly relies on the use of anticonvulsant drugs such as gabapentinoids. Therapeutic action of gabapentinoids such as gabapentin and pregabalin, which act by the inhibition of calcium currents through interaction with the α2δ-1 subunit of voltage-dependent calcium channels, is well documented. However, some aspects of the downstream mechanisms are still to be uncovered. Using behavioral, genetic, and pharmacological approaches, we tested whether opioid receptors are necessary for the antiallodynic action of acute and/or long-term pregabalin treatment in the specific context of neuropathic pain.

RESULTS

Using the cuff model of neuropathic pain in mice, we show that acute pregabalin administration at high dose has a transitory antiallodynic action, while prolonged oral pregabalin treatment leads to sustained antiallodynic action, consistent with clinical observations. We show that pregabalin remains fully effective in μ-opioid receptor, in δ-opioid receptor and in κ-opioid receptor deficient mice, either female or male, and its antiallodynic action is not affected by acute naloxone. Our work also shows that long-term pregabalin treatment suppresses tumor necrosis factor-α overproduction induced by sciatic nerve constriction in the lumbar dorsal root ganglia.

CONCLUSIONS

We demonstrate that neither acute nor long-term antiallodynic effect of pregabalin in a context of neuropathic pain is mediated by the endogenous opioid system, which differs from opioid treatment of pain and antidepressant treatment of neuropathic pain. Our data are also supportive of an impact of gabapentinoid treatment on the neuroimmune aspect of neuropathic pain.

Opioid-induced redistribution of 6TM and 7TM μ opioid receptors: A hypothesized mechanistic facilitator model of opioid-induced hyperalgesia

Opioids are still the most popular form of pain treatment, but many unavoidable side effects make opioids a big challenge in effective pain management. Opioid-induced hyperalgesia (OIH), a paradoxical phenomenon, portrays an increased sensitivity to harmful stimuli caused by opioid exposure. Changes in the neural modulation are considered a major contributor to the development of OIH. Activation of opioid receptors (ORs) and corresponding downstream molecules are the vital composition of functional performance of opioids. Increasing interests were proposed of the interaction between ORs and other neural transmitter systems such as glutamatergic, GABAergic and adrenergic ones to the genesis of OIH. G protein coupled μ-opioid receptor (MOR) was studied comprehensively on its role in the development of OIH. In addition to the relationship between MOR and other neurotransmitter receptors, a new intracellular MOR that has six transmembrane (6TM) domains was identified, and found to perform a pro-nociceptive task in contrast to the counterpart 7TM isoform. A mechanistic model of OIH in which both 6TM and 7TM MORs undergoing membrane redistribution upon opioid exposure is proposed which eventually facilitates the neurons more sensitive to nociceptive stimulation than that of the preceding opioid exposure.

The Acute to Chronic Pain Transition: Can Chronic Pain Be Prevented?

Chronic postsurgical pain (CPSP) is a distressing disease process that can lead to long-term disability, reduced quality of life, and increased health care spending. Although the exact mechanism of development of CPSP is unknown, nerve injury and inflammation may lead to peripheral and central sensitization. Given the complexity of the disease process, no novel treatment has been identified. The preoperative use of multimodal analgesia has been shown to decrease acute postoperative pain, but it has no proven efficacy in preventing development of CPSP.

Pregabalin Has Analgesic, Ventilatory, and Cognitive Effects in Combination with Remifentanil

Background

Pregabalin is widely used perioperatively. The authors explored the effects of pregabalin, remifentanil, and their combination on experimental pain, ventilatory, and cognitive function.

Methods

In a randomized, double-blinded crossover study, 12 volunteers received (1) pregabalin + placebo, (2) placebo + remifentanil, (3) pregabalin + remifentanil, and (4) placebo + placebo. Pregabalin 150 mg/placebo was administered twice orally. After baseline, remifentanil/placebo was given as effect-site target-controlled infusion (TCI): 0.6, 1.2, and 2.4 ng/ml. Pain during cold pressor test was scored on visual analog scale (0 to 100 mm). Ventilation was measured by spirometry and cognition tested with Color-Word Interference and Rapid Information Processing tests.

Results

Pain intensity after placebo was (mean) 72 mm (95% CI, 62 to 83). Pregabalin reduced pain score by −10 mm (−14 to −7, P &lt; 0.001). Remifentanil had dose-dependent analgesic effect, reducing pain score by −47 mm (−54 to −39, P &lt; 0.001) on highest TCI level, whereas pregabalin + remifentanil exerted additive effect, reducing pain score by −57 mm (−64 to −50, P &lt; 0.001). Respiratory depression was potentiated by adding pregabalin to remifentanil; end-tidal carbon dioxide was 39.3 mmHg (37.2 to 41.3) with placebo, increased 1.8 mmHg (−0.9 to 4.6, P = 0.4) with pregabalin, 10.1 mmHg (4.9 to 15.4, P &lt; 0.001) with remifentanil, and 16.4 mmHg (11.3 to 21.5, P &lt; 0.001) with pregabalin + remifentanil on highest TCI level. The combination pregabalin + remifentanil, but not either drug alone, adversely affected all cognitive tests.

Conclusions

The combination of pregabalin and remifentanil had additive analgesic effects, pregabalin potentiated remifentanil ventilatory depression, and the combination adversely affected cognition. These results question the clinical benefit of the combination compared with higher doses of opioids.

Co-administration of morphine and gabapentin leads to dose dependent synergistic effects in a rat model of postoperative pain

Despite much evidence that combination of morphine and gabapentin can be beneficial for managing postoperative pain, the nature of the pharmacological interaction of the two drugs remains unclear. The aim of this study was to assess the interaction of morphine and gabapentin in range of different dose combinations and investigate whether co-administration leads to synergistic effects in a preclinical model of postoperative pain. The pharmacodynamic effects of morphine (1, 3 and 7mg/kg), gabapentin (10, 30 and 100mg/kg) or their combination (9 combinations in total) were evaluated in the rat plantar incision model using an electronic von Frey device. The percentage of maximum possible effect (%MPE) and the area under the response curve (AUC) were used for evaluation of the antihyperalgesic effects of the drugs. Identification of synergistic interactions was based on Loewe additivity response surface analyses. The combination of morphine and gabapentin resulted in synergistic antihyperalgesic effects in a preclinical model of postoperative pain. The synergistic interactions were found to be dose dependent and the increase in observed response compared to the theoretical additive response ranged between 26 and 58% for the synergistic doses. The finding of dose-dependent synergistic effects highlights that choosing the right dose-dose combination is of importance in postoperative pain therapy. Our results indicate benefit of high doses of gabapentin as adjuvant to morphine. If these findings translate to humans, they might have important implications for the treatment of pain in postoperative patients.

A streptozotocin-induced diabetic neuropathic pain model for static or dynamic mechanical allodynia and vulvodynia: validation using topical and systemic gabapentin

Neuropathic vulvodynia is a state of vulval discomfort characterized by a burning sensation, diffuse pain, pruritus or rawness with an acute or chronic onset. Diabetes mellitus may cause this type of vulvar pain in several ways, so this study was conducted to evaluate streptozotocin-induced diabetes as a neuropathic pain model for vulvodynia in female rats. The presence of streptozotocin (50 mg/kg i.p.)-induced diabetes was initially verified by disclosure of pancreatic tissue degeneration, blood glucose elevation and body weight loss 5-29 days after a single treatment. Dynamic (shortened paw withdrawal latency to light brushing) and static (diminished von Frey filament threshold pressure) mechanical allodynia was then confirmed on the plantar foot surface. Subsequently, both static and dynamic vulvodynia was detected by application of the paradigm to the vulval region. Systemic gabapentin (75 mg/kg, i.p.) and topical gabapentin (10 % gel) were finally tested against allodynia and vulvodynia. Topical gabapentin and the control gel vehicle significantly increased paw withdrawal threshold in the case of the static allodynia model and also paw withdrawal latency in the model for dynamic allodynia when compared with the streptozotocin-pretreated group. Likewise, in the case of static and dynamic vulvodynia, there was a significant antivulvodynia effect of systemic and topical gabapentin treatment. These outcomes substantiate the value of this model not only for allodynia but also for vulvodynia, and this was corroborated by the findings not only with systemic but also with topical gabapentin.