A Randomised, Placebo-controlled Trial of the Effects of Preoperative Pregabalin on Pain Intensity and Opioid Consumption following Lumbar Discectomy

Different Gabapentin and Pregabalin Dosages for Perioperative Pain Control in Patients Undergoing Spine Surgery: A Systematic Review and Network Meta-Analysis

IMPORTANCE

Patients undergoing spine surgery often experience severe pain. The optimal dosage of pregabalin and gabapentin for pain control and safety in these patients has not been well established.

OBJECTIVE

To evaluate the associations of pain, opioid consumption, and adverse events with different dosages of pregabalin and gabapentin in patients undergoing spine surgery.

DATA SOURCES

PubMed/MEDLINE, Embase, Web of Science, Cochrane library, and Scopus databases were searched for articles until August 7, 2021.

STUDY SELECTION

Randomized clinical trials conducted among patients who received pregabalin or gabapentin while undergoing spine surgery were included.

DATA EXTRACTION AND SYNTHESIS

Two investigators independently performed data extraction following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) reporting guideline. The network meta-analysis was conducted from August 2022 to February 2023 using a random-effects model.

MAIN OUTCOMES AND MEASURES

The primary outcome was pain intensity measured using the Visual Analog Scale (VAS), and secondary outcomes included opioid consumption and adverse events.

RESULTS

Twenty-seven randomized clinical trials with 1861 patients (median age, 45.99 years [range, 20.00-70.00 years]; 759 women [40.8%]) were included in the systematic review and network meta-analysis. Compared with placebo, the VAS pain score was lowest with gabapentin 900 mg per day, followed by gabapentin 1200 mg per day, gabapentin 600 mg per day, gabapentin 300 mg per day, pregabalin 300 mg per day, pregabalin 150 mg per day, and pregabalin 75 mg per day. Additionally, gabapentin 900 mg per day was found to be associated with the lowest opioid consumption among all dosages of gabapentin and pregabalin, with a mean difference of -22.07% (95% CI, -33.22% to -10.92%) for the surface under the cumulative ranking curve compared with placebo. There was no statistically significant difference in adverse events (nausea, vomiting, and dizziness) among all treatments. No substantial inconsistency between direct and indirect evidence was detected for all outcomes.

CONCLUSIONS AND RELEVANCE

These findings suggest that gabapentin 900 mg per day before spine surgery is associated with the lowest VAS pain score among all dosages. In addition, no differences in adverse events were noted among all treatments.

Multimodal analgesia in neurosurgery: a narrative review

Pain following brain surgery can compromise the result of surgery. Several pharmacological interventions have been used to prevent postoperative pain in adults undergoing brain surgery. Pain following craniotomy is considered to be moderate to severe during the first two post-operative days. Opioids have been historically the mainstay and are the current prominent strategy for pain treatment. They produce analgesia but may alter respiratory, cardiovascular, gastrointestinal, and neuroendocrine functions. All these side effects may affect the normal postoperative course of craniotomy by affecting neurological function and increasing intracranial pressure. Therefore, their use in neurosurgery is limited, and opioids are used in case of strict necessity or as rescue medication. In addition to opioids, drugs with differing mechanisms of actions target pain pathways, resulting in additive and/or synergistic effects. Some of these agents include acetaminophen/non-steroidal anti-inflammatory drugs (NSAIDs), alpha-2 agonists, NMDA receptor antagonists, gabapentinoids, and local anesthesia techniques. Multimodal analgesia should be a balance between adequate analgesia and less drug-induced sedation, respiratory depression, hypercapnia, nausea, and vomiting, which may increase intracranial pressure. Non-opioid analgesics can be an useful pharmacological alternative in multimodal regimes to manage post-craniotomy pain. This narrative review aims to outline the current clinical evidence of multimodal analgesia for post craniotomy pain control.

Effect of pregabalin on nociceptive thresholds and immune responses in a mouse model of incisional pain

Background

It is known that some analgesics as well as pain can affect the immune system. The aim of this study was to investigate the analgesic effect and immunomodulation of pregabalin (PGB) in a mouse incisional pain model.

Methods

A postoperative pain model was induced by hind paw plantar incision in male BALB/c mice. Mice were randomly divided into four groups (n = 8) a saline-treated incision (incision), PGB-treated incision (PGB-incision), sham controls without incision or drug treatment (control), and a PGB-treated control (PGB-control). In the PGB treated groups, PGB was administered intraperitoneally (IP) 30 minutes before and 1 hour after the plantar incision. Changes of the mechanical nociceptive thresholds following incision were investigated. Mice were euthanized for spleen harvesting 12 hours after the plantar incision, and natural killer (NK) cytotoxicity to YAC 1 cells and lymphocyte proliferation responses to phytohemagglutinin were compared among these four groups.

Results

Mechanical nociceptive thresholds were decreased after plantar incision and IP PGB administration recovered these decreased mechanical nociceptive thresholds (P < 0.001). NK activity was increased by foot incision, but NK activity in the PGB-incision group was significantly lower than that in the Incision group (P < 0.001). Incisional pain increased splenic lymphocyte proliferation, but PGB did not alter this response.

Conclusions

Incisional pain alters cell immunity of the spleen in BALB/c mice. PGB showed antinocieptive effect on mouse incisional pain and attenuates the activation of NK cells in this painful condition. These results suggest that PGB treatment prevents increases in pain induced NK cell activity.

A Single Preoperative Administration of Dexamethasone, Low-dose Pregabalin, or a Combination of the 2, in Spinal Surgery, Does Not Provide a Better Analgesia Than a Multimodal Analgesic Protocol Alone

OBJECTIVES

A single perioperative dose of glucocorticoid or gabapentinoid, or a combination of the 2, may improve postoperative analgesia, but data are still insufficient to be conclusive. In this single-center, randomized, double-blind, and double-dummy trial, we aimed to test whether the analgesic effect of adding preoperative pregabalin, at a dose unlikely to induce side effects, to preoperative dexamethasone improves early mobilization after spinal surgery.

MATERIALS AND METHODS

A total of 160 patients undergoing scheduled lumbar disk surgery (145 analyzed) comprised the study cohort. The patients received either 0.2 mg/kg intravenous dexamethasone before incision, or 150 mg oral pregabalin 1 hour before surgery, or a combination of the 2, or none of the above (control). Analgesia was supplemented by acetaminophen and ketoprofen, plus oxycodone ad libitum. The primary outcome was pain intensity during the first attempt to sit up, assessed the morning of the first postoperative day on an 11-point Numerical Rating Scale. Pain at rest and when standing up, opioid consumption, and tolerance were also assessed.

RESULTS

None of the treatments tested differed from the control group in terms of efficacy or tolerance, even 6 months after surgery. The overall quality of analgesia was good, with only 10% and 30% of pain scores exceeding 3/10 for pain at rest and during movement, respectively.

DISCUSSION

In this surgical model with the given anesthetic and analgesic environment, there was no advantage gained by adding low-dose pregabalin or dexamethasone. The multimodal analgesic protocol applied to all patients may have reduced the size of the effect.

Perioperative Use of Gabapentinoids for the Management of Postoperative Acute Pain

Background

Widely used for acute pain management, the clinical benefit from perioperative use of gabapentinoids is uncertain. The aim of this systematic review was to assess the analgesic effect and adverse events with the perioperative use of gabapentinoids in adult patients.

Methods

Randomized controlled trials studying the use of gabapentinoids in adult patients undergoing surgery were included. The primary outcome was the intensity of postoperative acute pain. Secondary outcomes included the intensity of postoperative subacute pain, incidence of postoperative chronic pain, cumulative opioid use, persistent opioid use, lengths of stay, and adverse events. The clinical significance of the summary estimates was assessed based on established thresholds for minimally important differences.

Results

In total, 281 trials (N = 24,682 participants) were included in this meta-analysis. Compared with controls, gabapentinoids were associated with a lower postoperative pain intensity (100-point scale) at 6 h (mean difference, −10; 95% CI, −12 to −9), 12 h (mean difference, −9; 95% CI, −10 to −7), 24 h (mean difference, −7; 95% CI, −8 to −6), and 48 h (mean difference, −3; 95% CI, −5 to −1). This effect was not clinically significant ranging below the minimally important difference (10 points out of 100) for each time point. These results were consistent regardless of the type of drug (gabapentin or pregabalin). No effect was observed on pain intensity at 72 h, subacute and chronic pain. The use of gabapentinoids was associated with a lower risk of postoperative nausea and vomiting but with more dizziness and visual disturbance.

Conclusions

No clinically significant analgesic effect for the perioperative use of gabapentinoids was observed. There was also no effect on the prevention of postoperative chronic pain and a greater risk of adverse events. These results do not support the routine use of pregabalin or gabapentin for the management of postoperative pain in adult patients.

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Risk factors of postoperative low back pain for low-grade isthmic spondylolisthesis: a retrospective study

Objective

To investigate the risk factors of postoperative low back pain (LBP) following posterior lumbar interbody fusion (PLIF) surgery for low-grade isthmic spondylolisthesis (IS).

Methods

This retrospective study enrolled patients with IS that underwent PLIF between January 2011 and January 2016. Demographic, clinical, surgical and radiological characteristics were analysed to determine associations between these characteristics and LBP as measured using a visual analogue scale (VAS) pain score.

Results

A total of 192 patients were enrolled in the study. The mean VAS pain score of LBP decreased significantly after surgery. The mean preoperative VAS pain score was significantly greater in patients with symptoms of ≤3 years duration compared with those with symptoms lasting >3 years. The postoperative VAS pain score was significantly lower in patients with grade 1 slippage compared with those with grade 2 slippage. There was a significant correlation between preoperative to postoperative change of VAS pain score and postoperative disc height (r = 0.99).

Conclusion

PLIF significantly improved LBP in patients with low-grade IS, although patients still reported some postoperative LBP. The grade of slippage was a risk factor for postoperative LBP. Restoring the disc height appeared to improve LBP.

Effects of a single dose of preoperative pregabalin and gabapentin for acute postoperative pain: a network meta-analysis of randomized controlled trials

Background

Pregabalin (PGB) and gabapentin (GBP) are current and emerging drugs in the field of pre-emptive preoperative analgesia. However, the role of PGB or GBP in acute postoperative pain management still remains elusive.

Materials and methods

We conducted a comprehensive literature search of articles published by December 3, 2017. A total of 79 randomized controlled trials with 6,201 patients receiving single-dose premedication were included. Through a network meta-analysis (NMA), we validated the analgesic effect and incidence of adverse events by using various doses of PGB or GBP administration.

Results

NMA results suggested that the analgesic effect may be dose related. For 24-hour opioid consumption, a consistent decrease was found with the increase in the dose of PGB or GBP. For 24-hour pain score at rest, a high dose (≥150 mg) of PGB was more effective in decreasing pain score than a dose of 75 mg, and a high dose (≥900 mg) of GBP reduced pain intensity than doses of 300 or 600 mg. Moreover, the incidence of adverse reactions varied with varying doses of PGB or GBP.

Conclusion

A dose-response relationship was detected in opioid consumption and postoperative pain for a single-dose preoperative administration of PGB and GBP. Making reasonable choice of drugs and dosage may prevent the occurrence of adverse reactions.

A meta-analysis of the preoperative use of gabapentinoids for the treatment of acute postoperative pain following spinal surgery

BACKGROUND

Gabapentinoid drugs, which include gabapentin and pregabalin, play an established role in the management of neuropathic pain. However, whether preoperative administration of gabapentinoids has a beneficial role in controlling acute pain after spinal surgery is unknown. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to determine the efficacy and safety of the preoperative use of gabapentinoids (gabapentin and pregabalin) for the treatment of acute postoperative pain following spinal surgery.

METHODS

In March 2017, a systematic computer-based search was conducted in PubMed, EMBASE, Web of Science, Cochrane Library, and Google databases. RCTs comparing gabapentinoids (gabapentin and pregabalin) with placebo in patients undergoing spine surgery were retrieved. The primary endpoint was the visual analogue scale (VAS) score with rest or mobilization at 6, 12, 24, and 48 hours and cumulative morphine consumption at 24 and 48 hours. The secondary outcomes were complications of nausea, vomiting, sedation, dizziness, headache, urine retention, pruritus, and visual disturbances. After tests for publication bias and heterogeneity among studies were performed, data were aggregated for random-effects models when necessary.

RESULTS

Sixteen clinical studies (gabapentin group n = 8 and pregabalin group n = 8) were ultimately included in the meta-analysis. Gabapentinoids were associated with reduced pain scores at 6, 12, 24, and 48 hours. Similarly, gabapentinoids were associated with a reduction in cumulative morphine consumption at 24 and 48 hours. Furthermore, gabapentinoids can significantly reduce the occurrence of nausea, vomiting, and pruritus. There were no significant differences in the occurrence of sedation, dizziness, headache, visual disturbances, somnolence, or urine retention.

CONCLUSIONS

Preoperative use of gabapentinoids was able to reduce postoperative pain, total morphine consumption, and morphine-related complications following spine surgery. Further studies should determine the optimal dose and whether pregabalin is superior to gabapentin in controlling acute pain after spine surgery.

The Effect of Preoperative Pregabalin on Postoperative Nausea and Vomiting: A Meta-analysis

BACKGROUND

Nonopioid adjuvant medications are increasingly included among perioperative Enhanced Recovery After Surgery protocols. Preoperative pregabalin has been shown to improve postoperative pain and limit reliance on opioid analgesia. Our group investigated the ability of preoperative pregabalin to also prevent postoperative nausea and vomiting (PONV).

METHODS

Our group performed a meta-analysis of randomized trials that report outcomes on the effect of preoperative pregabalin on PONV endpoints in patients undergoing general anesthesia.

RESULTS

Among all included trials (23 trials; n = 1693), preoperative pregabalin was associated with a significant reduction in PONV (risk ratio [RR] = 0.53; 95% confidence interval [CI], 0.39-0.73; P = 0.0001), nausea (RR = 0.62; 95% CI, 0.46-0.83; P = 0.002), and vomiting (RR = 0.68; 95% CI, 0.52-0.88; P = 0.003) at 24 hours. Subgroup analysis designed to account for major PONV confounders, including the exclusion trials with repeat dosing, thiopental induction, nitrous oxide maintenance, and prophylactic antiemetics and including high-risk surgery, resulted in similar antiemetic efficacy. Preoperative pregabalin is also associated with significantly increased rates of postoperative visual disturbance (RR = 3.11; 95% CI, 1.34-7.21; P = 0.008) compared with a control.

CONCLUSIONS

Preoperative pregabalin is associated with significant reduction of PONV and should not only be considered as part of a multimodal approach to postoperative analgesia but also for prevention of PONV.

Is pregabalin effective and safe in total knee arthroplasty? A PRISMA-compliant meta-analysis of randomized-controlled trials

BACKGROUND

Pain management after total knee arthroplasty (TKA) varies and has been investigated for years. Pregabalin as an anticonvulsant agent that selectively affects the nociceptive process has been used for pain relief after operation. This meta-analysis was conducted to examine the evidence of pregabalin in TKA.

METHODS

Systematic searches of all related literatures were conducted using the following databases: MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials. Only randomized-controlled trials (RCTs) for TKA were included. The postoperative narcotic requirements, visual analog scale scores, knee flexion range, and relative risk of incidence rate of adverse effects in the pregabalin group versus placebo group were extracted throughout the study.

RESULTS

Seven placebo-controlled RCTs met the inclusion criteria. The use of pregabalin significantly decrease the postoperative total morphine consumption (P < .05) and increase the passive knee flexion range (P < .05). Compared with the control group, the incidence of some side effects (nausea, vomiting, pruritus, and constipation) was less in the pregabalin group (P < .05).

CONCLUSIONS

The administration of pregabalin is not only efficacious in the reduction of narcotic requirements and incidence of some adverse effect, but also workable for the improvement of passive knee flexion range after TKA.

Preoperative use of pregabalin for acute pain in spine surgery: A meta-analysis of randomized controlled trials

BACKGROUND

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy and safety of pregabalin for pain management following spine surgery.

METHODS

In September 2016, a systematic computer-based search was conducted in PubMed, EMBASE, Web of Science, and Cochrane Database of Systematic Reviews. RCTs of patients prepared for spine surgery that compared pregabalin with placebo were retrieved. The primary endpoint was the VAS score with rest or mobilization at 12 hours, 24 hours, and 48 hours and cumulative morphine consumption at 24 hours and 48 hours. The secondary outcomes were complications of nausea, sedation, dizziness, headache, and visual disturbances. After testing for publication bias and heterogeneity between studies, data were aggregated for random-effects models when necessary.

RESULTS

Ten clinical studies with 535 patients (pregabalin group = 294, control group = 241) were included in the meta-analysis. Pregabalin was associated with reduced pain scores at 12 hours, 24 hours, and 48 hours, corresponding to a reduction of 1.91 points (95% CI, -4.07 to 0.24 point) at 12 hours, 2.66 points (95% CI, -4.51 to -0.81 point) at 24 hours, and 4.33 points (95% confidence interval, -6.38 to -2.99 point) at 48 hours on a 100-point numeric rating scale. There was no significant difference between VAS scores with mobilization at 12 hours, 24 hours, or 48 hours. Similarly, pregabalin was associated with a reduction in cumulative morphine consumption at 24 hours (-7.07, 95% CI -9.84, -4.30) and 48 hours (-6.52, 95% CI -7.78, -5.25, P = 0.000). Furthermore, pregabalin can reduce the occurrence of nausea (RR 0.57, 95% CI 0.41, 0.79, P = 0.001, number needed to treat = 8.4). There were no significant differences in the occurrence of sedation, dizziness, headache, or visual disturbances.

CONCLUSIONS

Preoperative use of pregabalin was efficacious in reduction of postoperative pain, total morphine consumption, and the occurrence of nausea following spine surgery. Because the sample size and the number of included studies were limited, a multicenter RCT is needed to identify the effects and optimal dose of pregabalin for reducing acute pain after spine surgery.

Perioperative use of pregabalin for acute pain-a systematic review and meta-analysis

Evidence supporting postoperative pain management using pregabalin as an adjunct intervention across various surgical pain models is lacking. The objective of this systematic review was to evaluate "model-specific" comparative effectiveness and harms of pregabalin following a previously published systematic review protocol. MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials were searched from inception through August 2013. Data were screened and single extraction with independent verification and dual risk of bias assessment was performed. Quality of evidence (QoE) was rated using the GRADE approach. Primary outcomes were pain relief at rest and on movement and reduction in postoperative analgesic consumption. A total of 1423 records were screened, and 43 studies were included. Perioperative pregabalin resulted in: 16% (95% confidence interval [CI], 9%-21%) reduction in analgesic consumption (moderate QoE, 24 trials) and a small reduction in the magnitude of pain in surgeries associated with pronociceptive pain. Per 1000 patients, 10 more will experience blurred vision (95% CI, 5-20 more; moderate QoE, 17 trials) and 41 more sedation (95% CI, 13-77 more, 17 trials). To prevent 1 case of perioperative nausea and vomiting, the number needed to treat is 11 (95% CI: 7-28, 25 trials). Inadequate evidence addressed outcomes of enhanced recovery and serious harms. Pregabalin analgesic effectiveness is largely restricted to surgical procedures associated with pronociceptive mechanisms. The clinical significance of observed pregabalin benefits must be weighed against the uncertainties about serious harms and enhanced recovery to inform the careful selection of surgical patients. Recommendations for future research are proposed.

Effects of methylene blue on postoperative low-back pain and functional outcomes after lumbar open discectomy: a triple-blind, randomized placebo-controlled trial

OBJECT

Despite advances in surgical and anesthesiology techniques, many patients continue to experience postoperative pain after lumbar disc operations. This study aims to investigate the effects of methylene blue (MB) on preventing postoperative low-back pain (LBP) with or without radicular pain and improving the quality of life (QOL) in patients undergoing lumbar open discectomy.

METHODS

This is a prospective, randomized, triple-blind, placebo-controlled clinical trial, which was conducted at Shiraz University of Medical Sciences between July 2011 to January 2012. Of a total of 130 patients, 115 were eligible for participation; 56 received 1 ml of MB solution at a concentration of 0.5% (MB group) and 59 received an equivalent volume of normal saline (control group). Primary outcomes were the control of LBP with or without radicular pain, which was evaluated preoperatively and at 24 hours and 3 months after surgery with the use of a visual analog scale (VAS), and the improvement of QOL, which was assessed preoperatively and 3 months postoperatively by means of the Persian translation of the Oswestry Disability Index questionnaire.

RESULTS

The mean VAS scores for LBP were significantly lower in the MB group compared with the control group at 24 hours (1.25 ± 0.97 vs 2.80 ± 0.69, p < 0.001) and 3 months (1.02 ± 1.29 vs 2.07 ± 1.10, p = 0.019) after treatment. The mean radicular pain scores decreased significantly in the 2 groups at 24 hours after surgery, but the mean radicular pain score was significantly lower in the MB-treated patients than the control group. However, the difference between radicular pain scores in the MB group (1 ± 1.1) and the control group (1.2 ± 1) was not statistically significant (p = 0.64). The reduction in LBP was greater in the MB group than the control group (8.11 ± 1.74 vs 6.07 ± 1.52, p = 0.023, CI 95% −1.37 to −0.10). The functional QOL improved significantly 3 months after the operation in both groups (p < 0.001). Moderate disability occurred more frequently in the control group than in the MB group (14.5% vs 7.7%, p = 0.004). No toxicity, adverse effects, or complications were found in the group of patients treated with MB injection.

CONCLUSIONS

A single dose of MB (1 ml 0.5%) for coating the dura and surrounding tissues (facet and muscle) shows promising results in terms of safety, reduction of postoperative pain, and functional outcome compared with placebo.

Efficacy of Pregabalin in Acute Postoperative Pain Under Different Surgical Categories: A Meta-Analysis

The efficacy of pregabalin in acute postsurgical pain has been demonstrated in numerous studies; however, the analgesic efficacy and adverse effects of using pregabalin in various surgical procedures remain uncertain. We aim to assess the postsurgical analgesic efficacy and adverse events after pregabalin administration under different surgical categories using a systematic review and meta-analysis of randomized controlled trials.A search of the literature was performed between August 2014 to April 2015, using PubMed, Ovid via EMBASE, Google Scholar, and ClinicalTrials.gov with no limitation on publication year or language. Studies considered for inclusion were randomized controlled trials, reporting on relevant outcomes (2-, 24-hour pain scores, or 24 hour morphine-equivalent consumption) with treatment with perioperative pregabalin.Seventy-four studies were included. Pregabalin reduced pain scores at 2 hours in all categories: cardiothoracic (Hedge's g and 95%CI, -0.442 [-0.752 to -0.132], P = 0.005), ENT (Hedge g and 95%CI, -0.684 [-1.051 to -0.316], P < 0.0001), gynecologic (Hedge g, 95%CI, -0.792 [-1.235 to -0.350], P < 0.0001), laparoscopic cholecystectomy (Hedge g, 95%CI, -0.600 [-0.989 to -0.210], P = 0.003), orthopedic (Hedge g, 95%CI, -0.507 [-0.812 to -0.202], P = 0.001), spine (Hedge g, 95%CI, -0.972 [-1.537 to -0.407], P = 0.001), and miscellaneous procedures (Hedge g, 95%CI, -1.976 [-2.654 to -1.297], P < 0.0001). Pregabalin reduced 24-hour morphine consumption in gynecologic (Hedge g, 95%CI, -1.085 [-1.582 to -0.441], P = 0.001), laparoscopic cholecystectomy (Hedge g, 95%CI, -0.886 [-1.652 to -0.120], P = 0.023), orthopedic (Hedge g, 95%CI, -0.720 [-1.118 to -0.323], P < 0.0001), spine (Hedge g, 95%CI, -1.016 [-1.732 to -0.300], P = 0.005), and miscellaneous procedures (Hedge g, 95%CI, -1.329 [-2.286 to -0.372], P = 0.006). Pregabalin resulted in significant sedation in all surgical categories except ENT, laparoscopic cholecystectomy, and gynecologic procedures. Postoperative nausea and vomiting was only significant after pregabalin in miscellaneous procedures.Analgesic effects and incidence of adverse effects of using pregabalin are not equal in different surgical categories.

Pregabalin in neuropathic pain: evidences and possible mechanisms

Pregabalin is an antagonist of voltage gated Ca2+ channels and specifically binds to alpha-2-delta subunit to produce antiepileptic and analgesic actions. It successfully alleviates the symptoms of various types of neuropathic pain and presents itself as a first line therapeutic agent with remarkable safety and efficacy. Preclinical studies in various animal models of neuropathic pain have shown its effectiveness in treating the symptoms like allodynia and hyperalgesia. Clinical studies in different age groups and in different types of neuropathic pain (peripheral diabetic neuropathy, fibromyalgia, post-herpetic neuralgia, cancer chemotherapy-induced neuropathic pain) have projected it as the most effective agent either as monotherapy or in combined regimens in terms of cost effectiveness, tolerability and overall improvement in neuropathic pain states. Preclinical studies employing pregabalin in different neuropathic pain models have explored various molecular targets and the signaling systems including Ca2+ channel-mediated neurotransmitter release, activation of excitatory amino acid transporters (EAATs), potassium channels and inhibition of pathways involving inflammatory mediators. The present review summarizes the important aspects of pregabalin as analgesic in preclinical and clinical studies as well as focuses on the possible mechanisms.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).