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

Postoperative respiratory depression with pregabalin: a case series and a preoperative decision algorithm

Pregabalin is gaining popularity in the perioperative period for its usefulness in treating neuropathic pain and its apparent opioid- sparing effect. The present report describes the perioperative course of three patients who received pregabalin and experienced significant respiratory depression in the postoperative period. All three patients consented to the report and publication of the present case series. The first patient was elderly with borderline renal dysfunction. She experienced respiratory arrest in the immediate postoperative period following a craniotomy for tumour excision. The second patient presented with severe respiratory depression 12 h after receiving a spinal anesthetic for joint replacement, and was later found to have clinically significant obstructive sleep apnea. The third patient, who was an otherwise healthy elderly individual on benzodiazepines for anxiety, experienced respiratory arrest in the postanesthesia care unit after an uneventful anesthesia for lumbar spine decompression. All of these patients were treated successfully with standard resuscitation measures. Although other causes of respiratory depression in these patients were considered, there appears to be an association between pregabalin and this complication. The present article briefly reviews the evidence regarding the perioperative use of pregabalin. Based on the authors' experience and the available evidence, they believe that pregabalin may be useful in the management of acute pain in carefully selected patients undergoing certain surgeries. A clinical algorithm has been developed to guide the perioperative use of pregabalin. This algorithm may be helpful in increasing the safety of perioperative pregabalin use.

The Transition from Acute to Chronic Post Surgical Pain

All chronic pain was once acute, but not all acute pain becomes chronic. The transition of acute postoperative pain to chronic post surgical pain is a complex and poorly understood developmental process. The manuscript describes the various factors associated with the transition from acute to chronic pain. The preoperative, intraoperative and postoperative surgical, psychosocial, socio-environmental and patient-related factors and the mechanisms involved are discussed and preventive (or limitation) strategies are suggested. In future, the increasing understanding of genetic factors and the transitional mechanisms involved may reveal important clues to predict which patients will go on to develop chronic pain. This may assist the development of appropriate interventions affecting not only the individual concerned, but also ultimately the community at large.

Conservative treatment for neck pain: medications, physical therapy, and exercise

This article offers conservative treatment strategies for patients suffering from musculoskeletal causes of neck pain. Basic pharmacology is reviewed, including that of opioids, nonsteroidal anti-inflammatory drugs, adjuvants, and topical analgesics. Moreover, indications for therapeutic exercise, manual therapy, and modalities are reviewed, along with any supporting literature. Treatment considerations with each category of medication and physical therapy are discussed. This article is meant to serve as a resource for physicians to tailor conservative treatment options to their individual patients.

Effects of pregabalin on heart rate variability in patients with painful diabetic neuropathy

Many studies have demonstrated that low heart rate variability (HRV) is a risk for high mortality and morbidity in patients with cardiovascular diseases. The primary purpose of the study was to evaluate whether pregabalin improves HRV in patients with diabetes and painful peripheral neuropathy. Resting heart rates were collected by using the LifeShirt System, developed by VivoMetrics (Ventura, Calif), at baseline and at the end of a 4-week intervention of pregabalin or placebo in patients with painful diabetic peripheral neuropathy. Heart rate variability analysis was performed on the collected R-R intervals using the Vivo- VMLA-036-00 3 Logic of the LifeShirt system. Of the 40 patients enrolled in the study, 70% completed the end of 4-week assessments (n = 15 in pregabalin and n = 14 in placebo). Compared with placebo, pregabalin treatment resulted in significant improvement in HRV measured by frequency domain analysis, that is, a reduction in low frequency-high frequency ratio (-1.30 ± 2.89 vs 0.37 ± 0.33, P = 0.03) and power of normalized low frequency (-0.049 ± 0.092 vs 0.0066 ± 0.023, P = 0.02), as well as an increase in power of normalized high frequency (0.039 ± 0.094 vs -0.038 ± 0.066, P = 0.02). Furthermore, pregabalin resulted in greater reduction of pain and symptoms of anxiety and greater improvement of quality of life. The improvement of HRV measures were not correlated with change of those measures. In conclusion, 4-week pregabalin treatment improved HRV in patients with painful diabetic peripheral neuropathy.

TRIAL REGISTRATION

NCT00573261 (clinicaltrials.gov).

Painful sequelae following limb salvage: etiology and management

Inadequately controlled pain is a significant problem during limb salvage and is associated with poor outcomes. This pain has several causes, and many management options exist. Chronic pain associated with limb salvage causes unnecessary suffering and negatively affects long-term function. Chronic pain and disability in this population may be prevented with early, aggressive, comprehensive treatment. Ongoing research into the cause and clinical course of limb salvage pain likely will lead to advances in pain management and functional improvement.

A cost-consequences analysis of the effect of pregabalin in the treatment of peripheral neuropathic pain in routine medical practice in primary care settings

Background

Neuropathic pain (NeP) is a common symptom of a group of a variety of conditions, including diabetic neuropathy, trigeminal neuralgia, or postherpetic neuralgia. Prevalence of NeP has been estimated to range between 5-7.5%, and produces up to 25% of pain clinics consultations. Due to its severity, chronic evolution, and associated co-morbidities, NeP has an important individual and social impact. The objective was to analyze the effect of pregabalin (PGB) on pain alleviation and longitudinal health and non-health resources utilization and derived costs in peripheral refractory NeP in routine medical practice in primary care settings (PCS) in Spain.

Methods

Subjects from PCS were older than 18 years, with peripheral NeP (diabetic neuropathy, post-herpetic neuralgia or trigeminal neuralgia), refractory to at least one previous analgesic, and included in a prospective, real world, and 12-week two-visit cost-of-illness study. Measurement of resources utilization included both direct healthcare and indirect expenditures. Pain severity was measured by the Short Form-McGill Pain Questionnaire (SF-MPQ).

Results

One-thousand-three-hundred-fifty-four PGB-naive patients [58.8% women, 59.5 (12.7) years old] were found eligible for this secondary analysis: 598 (44%) switched from previous therapy to PGB given in monotherapy (PGBm), 589 (44%) received PGB as add-on therapy (PGB add-on), and 167 (12%) patients changed previous treatments to others different than PGB (non-PGB). Reductions of pain severity were higher in both PGBm and PGB add-on groups (54% and 51%, respectively) than in non-PGB group (34%), p < 0.001. Incremental drug costs, particularly in PGB subgroups [€34.6 (80.3), €160.7 (123.9) and €154.5 (133.0), for non-PGB, PGBm and PGBadd-on, respectively (p < 0.001)], were off-set by higher significant reductions in all other components of health costs yielding to a greater total cost reductions: -€1,045.3 (1,989.6),-€1,312.9 (1,543.0), and -€1,565.5 (2,004.1), for the three groups respectively (p = 0.03).

Conclusion

In Spanish primary care settings, PGB given either add-on or in monotherapy in routine medical practice was associated with pain alleviation leading to significant longitudinal reductions in resource use and total costs during the 12-week period of the study compared with non-PGB-therapy of patients with chronic NeP of peripheral origin. The use of non-appropriate analgesic therapies for neuropathic pain in a portion of subjects in non-PGB group could explain partially such findings.

Preoperative and postoperative anesthetic and analgesic techniques for minimally invasive surgery of the spine

STUDY DESIGN

A review of methods to optimize anesthesia and analgesia for minimally invasive spine procedures.

OBJECTIVE

To provide information to surgeons and anesthesiologists of methods to provide optimal anesthesia and pain control for minimally invasive spine surgery with an emphasis on preoperative planning.

SUMMARY OF BACKGROUND DATA

Postoperative pain management in patients undergoing minimally invasive spine surgery is a challenge for the perioperative anesthesiologist. In addition to the incisional pain, trauma to deeper tissues, such as ligaments, muscles, intervertebral discs, and periosteum are reasons for significant pain. The increasing number of minimally invasive surgeries and the need for improved and rapid return of the patient of functionality have brought the perioperative anesthesiologist and the surgeon closer.

METHODS

We undertook a review of the literature currently available on anesthesia and analgesia for minimally invasive spine surgery with an emphasis on preoperative planning. A large number of reports of randomized controlled clinical trials with respect to perioperative anesthetic and postoperative pain management for minimally invasive spine surgery are reviewed and the applicability of some of the principles and protocols used for other types of minimally invasive surgical procedures are placed in the context of spine surgery.

RESULTS

It is important to understand and implement a multimodal analgesic therapy during a patient's preoperative visits. Perioperative multimodal analgesia with a fast-track anesthetic protocol is also important and provided in the manuscript. This protocol poses a challenge to the anesthesiologist with respect to neurophysiologic monitoring, which requires further study. The postoperative analgesic management should be a continuance of the multimodal analgesia provided before surgery. Some drugs are not appropriate for patients undergoing fusion surgery because of their effect on bone healing.

CONCLUSION

An optimal preoperative, perioperative, and postoperative anesthesia and analgesia protocol is important to best possible pain relief and rapid return to normal function. Communication between the anesthesiologist and spine surgeon is important to achieve a protocol with the best short- and long-term outcomes for the benefit of the patient.

Gabapentin and pregabalin inhibit the itch-associated response induced by the repeated application of oxazolone in mice

We investigated the effects of gabapentin and pregabalin on the itch-associated response in a mouse model of chronic dermatitis induced by the repeated application of 4-ethoxymethylene-2-phenyl-2-oxazolin-5-one (oxazolone). Challenging the mice with oxazolone-induced chronic dermatitis with the oxazolone evoked severe and transient scratching behavior until 1 h after the application of oxazolone. Thereafter, a more mild and continuous scratching behavior was also observed for at least 8 h. Both severe and continuous scratching behaviors were suppressed by systemic injection of gabapentin and pregabalin. This effect of these compounds was correlated with its affinity for the α₂δ subunit of voltage-gated Ca²(+) channels. Intrathecal injection, but not peripheral treatment, with gabapentin inhibited the scratching behavior in this model. Gabapentin failed to suppress the scratching behavior induced by the intradermal injection of compound 48/80 in normal mice. The expression of the α₂δ-1 subunit in dorsal root ganglion (DRG) from mice following repeated application of oxazolone was significantly higher than that from normal mice. These results suggest that gabapentin and pregabalin show an anti-pruritic activity through α₂δ-subunit binding, and the up-regulation of the α₂δ-1 subunit in DRG may therefore play an important role in its anti-pruritic activity.

[Sedation and analgesia in intensive care: physiology and application]

Many therapeutic and diagnostic procedures in intensive care medicine are perceived as painful by most patients. As a consequence analgesia and sedation represent two of the main pillars in the treatment of the critically ill. Adaptation to the individual needs of the patients poses one of the biggest challenges that we are confronted with. Both morbidity and mortality can be positively influenced by adequate treatment. In the first part of this review we will discuss the physiology of sleep patterns and pain. Furthermore modes of action and side effects of the most common anesthetics and analgetics will be presented. Finally, the last part of the manuscript deals with the practical application of these therapeutics and their monitoring in intensive care medicine.

Neuropathic pain management in chronic laminitis

Managing pain in horses afflicted by chronic laminitis is one of the greatest challenges in equine clinical practice because it is the dreadful suffering of the animals that most often forces the veterinarian to end the battle with this disease. The purpose of this review is to summarize our current understanding of the complex mechanisms involved in generating and amplifying pain in animals with laminitis and, based on this information, to propose a modified approach to pain therapy. Furthermore, a recently developed pain scoring technique is presented that may help better quantify pain and the monitoring of responses to analgesic treatment in horses with laminitis.

Gabapentin improves cold-pressor pain responses in methadone-maintained patients

Individuals on methadone maintenance for the treatment of addiction (MM) are demonstrated to be hyperalgesic to cold-pressor pain in comparison to matched controls and ex-opioid addicts, a finding described as clinical evidence of opioid-induced hyperalgesia (OIH). Interestingly, opioids induce hyperalgesia via many of the same neuro-inflammatory and central sensitization processes that occur with the development of neuropathic pain. Evaluated in this study was the efficacy of a key pharmacotherapy for neuropathic pain, gabapentin (GPN), to reverse OIH in MM patients. Utilizing a clinical trial design and double blind conditions, changes in cold-pressor pain threshold and tolerance following a 5-week trial of GPN (titrated to 2400mg/day) were evaluated at peak and trough methadone plasma levels in a well-characterized MM sample. Drug abstinence was encouraged via an escalating payment schedule, and compliance monitored via pill counts and GPN plasma levels; entered into the analyses were only those subjects compliant and abstinent throughout the study (approximately 45%). Utilizing change scores from baseline, significant improvements in cold-pressor pain threshold and pain tolerance were observed at both peak and trough methadone levels (p<0.05). Notably, drop-out rates due to medication side effects were low (2%) and the medication was well-tolerated. These results support that GPN, as prescribed for the treatment of neuropathic pain, is effective in decreasing OIH in patients who are abstinent and stable in methadone treatment.

Acute pain after total hip arthroplasty does not predict the development of chronic postsurgical pain 6 months later

PURPOSE

Much remains unknown about the relationship between acute postoperative pain and the development of pathologic chronic postsurgical pain (CPSP). The purpose of this project was to identify the extent to which maximum pain scores on movement over the first two days after total hip arthroplasty predicted the presence of chronic pain 6 months later after controlling for potentially important covariates.

METHODS

The sample comprised 82 of 114 patients who participated in a double-blinded randomized controlled trial in which all patients received acetaminophen 1 g p.o., celecoxib 400 mg p.o., and dexamethasone 8 mg i.v., 1-2 h preoperatively. In addition, patients received gabapentin (GBP) 600 mg (G2) or placebo (G1 and G3) 2 h prior to surgery [G1: placebo/placebo (n = 38); G2: GBP/placebo (n = 38); G3: placebo/GBP (n = 38)]. In the PACU, patients received gabapentin 600 mg (G3) or placebo (G1 and G2). Follow-up data from the 82 patients who were contacted by telephone 6 months postsurgery were used for the current study.

RESULTS

Maximal movement-evoked pain intensity over the first two postoperative days (P = 0.38) failed to predict the presence of CPSP 6 months later after controlling for age (P = 0.09), treatment group (P = 0.91), and cumulative morphine consumption (P = 0.8) (multivariate logistic regression likelihood ratio test against the intercept only model P = 0.59).

CONCLUSION

Neither maximum movement-evoked acute pain, nor any other factor measured, predicted the presence of CPSP at 6 months. Further research is needed to identify risk factors for CPSP after total hip arthroplasty.

Co-administered gabapentin and venlafaxine in nerve injured rats: Effect on mechanical hypersensitivity, motor function and pharmacokinetics

A high proportion of patients suffering from neuropathic pain do not receive satisfactory pain relief from their current treatment, due to incomplete efficacy and dose-limiting adverse effects. Hence, one strategy to improve treatment outcome is the use of a combination of analgesic drugs. The potential benefits of such approach include improved and prolonged duration of analgesic effect and fewer or milder adverse effects with lower doses of each drug. Gabapentin is recommended as a first-line drug in the treatment of neuropathic pain, and has recently been demonstrated to act on supraspinal structures to stimulate the descending noradrenergic pain inhibitory system. Hypothetically, the analgesic effect of gabapentin may be potentiated if combined with a drug that prolongs the action of noradrenaline.

In this study, gabapentin was co-administered with the serotonin and noradrenaline reuptake inhibitor venlafaxine, and subsequently evaluated for its effect on mechanical hypersensitivity in the rat spared nerve injury model of neuropathic pain. In this model, two branches of the sciatic nerve (the tibial and common peroneal nerves) are ligated and cut, leaving the third branch (the sural nerve) intact to innervate the hind paw of the animal. Treatment-induced ataxia was tested in order to exclude biased effect measurements. Finally, the pharmacokinetics of gabapentin was investigated alone and in combination with venlafaxine to elucidate any alterations which may have consequences for the pharmacological effect and safety.

The overall effect on nerve injury-induced hypersensitivity of co-administered gabapentin (60 mg/kg s.c.) and venlafaxine (60 mg/kg s.c.), measured as the area under the effect-time curve during the three hour time course of testing, was similar to the highest dose of gabapentin (200 mg/kg s.c.) tested in the study. However, this dose of gabapentin was associated with ataxia and severe somnolence, while the combination was not. Furthermore, when administered alone, an effect delay of approximately one hour was observed for gabapentin (60 mg/kg s.c.) with maximum effect occurring 1.5 to 2.5 h after dosing, while venlafaxine (60 mg/kg s.c.) was characterised by a rapid onset of action (within 30 min) which declined to baseline levels before the end of the three hour time of testing. The effect of co-administered drugs (both 60 mg/kg s.c.), in the doses used here, can be interpreted as additive with prolonged duration in comparison to each drug administered alone. An isobolographic study design, enable to accurately classify the combination effect into additive, antagonistic or synergistic, was not applied. The pharmacokinetics of gabapentin was not altered by co-administered venlafaxine, implying that a pharmacokinetic interaction does not occur. The effect of gabapentin on the pharmacokinetics of venlafaxine was not studied, since any alterations are unlikely to occur on the basis of the pharmacokinetic properties of gabapentin.

In conclusion, the results from this preclinical study support the rationale for improved effect and less adverse effects through combination therapy with gabapentin and venlafaxine in the management of neuropathic pain.

Surgical incision induces anxiety-like behavior and amygdala sensitization: effects of morphine and gabapentin

The role of affective dimension in the postoperative pain is still poorly understood. The present study investigated the development of anxiety-like behavior and amygdala sensitization in incisional pain. Using hind-paw incision model in rats, we showed that surgical incision induced the anxiety-like behavior as determined by elevated plus-maze and open-field tests. Intraperitoneal (IP) morphine administration reversed mechanical allodynia and anxiety-like behavior in a dose-dependent manner. Gabapentin also partially reduced incision-evoked mechanical allodynia and anxiety-like behavior in a dose-dependent manner. After incision, the expression of phosphorylated cAMP response elements (CRE-) binding protein (p-CREB) was transiently upregulated in the central and basolateral nuclei in the bilateral amygdala. The upregulation of p-CREB was inhibited by morphine and gabapentin. The present study suggested that surgical incision could induce anxiety and amygdala sensitization that can be inhibited by morphine and gabapentin. Thus treatment of surgery-induced affective disturbances by morphine and gabapentin may be a potential important adjunct therapy in the postoperative pain management.

Perioperative oral pregabalin reduces chronic pain after total knee arthroplasty: a prospective, randomized, controlled trial

BACKGROUND

Despite the enormous success of total knee arthroplasty (TKA), chronic neuropathic pain can develop postoperatively and is both distressing and difficult to treat once established. We hypothesized that perioperative treatment with pregabalin, a chronic pain medication, would reduce the incidence of postsurgical neuropathic pain.

METHODS

We performed a randomized, placebo-controlled, double-blind trial of pregabalin (300 mg) administered before TKA and for 14 days after TKA (150-50 mg twice daily). Patients were screened for the presence of neuropathic pain at 3 and 6 mo postoperatively using the Leeds Assessment of Neuropathic Symptoms and Signs scale. Secondary outcomes included postsurgical recovery and rehabilitation measures, including knee range of motion, opioid consumption, postoperative pain scores, sleep disturbance, and time to discharge as well as the occurrence of postoperative systemic complications.

RESULTS

Of the 240 patients randomly assigned to the 2 treatment groups (120 in each), data for the primary outcome were obtained from 113 pregabalin patients and 115 placebo patients. At both 3 and 6 mo postoperatively, the incidence of neuropathic pain was less frequent in the pregabalin group (0%) compared with the placebo group (8.7% and 5.2% at 3 and 6 mo, respectively; P = 0.001 and P = 0.014). Patients receiving pregabalin also consumed less epidural opioids (P = 0.003), required less oral opioid pain medication while hospitalized (P = 0.005), and had greater active flexion over the first 30 postoperative days (P = 0.013). There were no differences in the actual recorded duration of hospitalization between the 2 groups, although time to achieve hospital discharge criteria was longer for placebo patients, 69.0 +/- 16.0 h (mean +/- SD), than that of pregabalin patients, 60.2 +/- 15.8 h (P = 0.001). Sedation (P = 0.005) and confusion (P = 0.013) were more frequent on the day of surgery and postoperative day 1 in patients receiving pregabalin.

CONCLUSION

Perioperative pregabalin administration reduces the incidence of chronic neuropathic pain after TKA, with less opioid consumption and better range of motion during the first 30 days of rehabilitation. However, in the doses tested, it is associated with a higher risk of early postoperative sedation and confusion.

Strategies to enhance the therapeutic efficacy of antidepressants: targeting residual symptoms

Major depressive disorder (MDD) is an illness of great morbidity that affects many people across the world. The current goal for treatment of MDD is to achieve remission (i.e., no depressive symptoms). However, despite scientific advances in the treatment for MDD, antidepressants as first-line agents yield only modest remission rates. In fact, a recent study indicated that only one out of three subjects who received a standard, first-line antidepressant attained remission. Not achieving remission from depressive symptoms increases the risk of a more chronic and debilitating course of illness with frequent recurrences. Although a number of reasons contribute to these modest outcomes, the presence of residual symptoms is a major problem. Residual symptoms are defined as symptoms that linger despite an adequate dose and duration of an antidepressant medication. This article reviews the prevalence and clinical impact of common residual symptoms and discusses the utility of aggressively addressing residual symptoms to enhance the efficacy of antidepressant medications.

Patient-reported outcomes in subjects with painful trigeminal neuralgia receiving pregabalin: evidence from medical practice in primary care settings

Effects of pregabalin (PGB) on patient-reported health outcomes were assessed in 65 PGB-naive subjects with trigeminal neuralgia refractory to previous analgesic therapy in a prospective, multicentre observational study carried out in primary care. Twelve weeks' monotherapy with PGB (n = 36) or add-on (n = 29), reduced baseline intensity of pain by a mean +/- S.D. of -40.0 +/- 22.1 mm [-55.4%, effect size (ES) 2.32; P < 0.0001] with 59.4% of responders (pain reduction >or= 50%), and produced 34.6 +/- 29.3 additional days with no/mild pain. Anxiety/depression symptoms decreased by -3.8 +/- 3.5 and -4.5 +/- 4.2 points (ES 0.95 and 1.02; P < 0.0001), respectively. PGB improved sleep by -17.9 +/- 19.6 points (ES 1.18; P < 0.0001) and improved patient functioning (Sheehan Disability Index) by decreasing overall scoring by -8.6 +/- 5.9 points (ES 1.59; P < 0.0001). Health state (EQ-5D) increased by 31.6 +/- 22.2 mm (ES 1.67; P < 0.0001), with 0.0388 +/- 0.0374 gained quality-adjusted life-years. In spite of the small sample size, results support the effectiveness of PGB for the improvement in pain and related health symptoms.

Transition from acute to chronic postsurgical pain: risk factors and protective factors

Most patients who undergo surgery recover uneventfully and resume their normal daily activities within weeks. Nevertheless, chronic postsurgical pain develops in an alarming proportion of patients. The prevailing approach of focusing on established chronic pain implicitly assumes that information generated during the acute injury phase is not important to the subsequent development of chronic pain. However, a rarely appreciated fact is that every chronic pain was once acute. Here, we argue that a focus on the transition from acute to chronic pain may reveal important cues that will help us to predict who will go on to develop chronic pain and who will not. Unlike other injuries, surgery presents a unique set of circumstances in which the precise timing of the physical insult and ensuing pain are known in advance. This provides an opportunity, before surgery, to identify the risk factors and protective factors that predict the course of recovery. In this paper, the epidemiology of chronic postsurgical pain is reviewed. The surgical, psychosocial, socio-environmental and patient-related factors that appear to confer a greater risk of developing chronic postsurgical pain are described. The genetics of chronic postsurgical pain are discussed with emphasis on known polymorphisms in human genes associated with chronic pain, genetic studies of rodent models of pain involving surgical approaches, the importance of developing accurate human chronic postsurgical pain phenotypes and the expected gains for chronic postsurgical pain medicine in the post-genomic era. Evidence is then reviewed for a preventive multimodal analgesic approach to surgery. While there is some evidence that chronic postsurgical pain can be minimized or prevented by an analgesic approach involving aggressive perioperative multimodal treatment, other studies fail to show this benefit. The transition of acute postoperative pain to chronic postsurgical pain is a complex and poorly understood developmental process, involving biological, psychological and social-environmental factors.

Multimodal analgesia for hip arthroplasty

Multimodal analgesia incorporates the use of analgesic adjuncts with different mechanisms of action to enhance postoperative pain management. Acetaminophen, anti-inflammatories, and gabapentinoids provide effective analgesia while reducing opioid requirements and opioid-related side effects. Intrathecal morphine and periarticular local anesthetic infiltration further enhance dynamic analgesia and improve postoperative mobilization. Epidural analgesia, peripheral nerve blocks, tramadol, ketamine, and/or clonidine can be added for improved benefit in opioid-tolerant individuals.

Pregabalin in the treatment of chronic pain: an overview

Chronic 'pathological' pain is sustained by mechanisms of peripheral and central sensitization, which are being increasingly investigated at the molecular and cellular levels. The molecular determinants of nociceptive sensitization are natural targets for potential analgesic drugs used in the treatment of different forms of pain. Most of these determinants are common to all forms of chronic pain, and it is therefore not surprising that drugs specifically targeted for the treatment of neuropathic pain are effective in relieving nociceptive inflammatory pain and vice versa. The molecular mechanisms of sensitization that occur in peripheral nociceptors and the dorsal horns of the spinal cord are putative targets for context-dependent drugs, i.e. drugs that are able to discriminate between 'normal' and 'pathological' pain transmission. Among these, pregabalin and gabapentin bind to the alpha(2)delta subunit of voltage-sensitive Ca2+ channels, which sustain the enhanced release of pain transmitters at the synapses between primary afferent fibres and second-order sensory neurons under conditions of chronic pain. Pregabalin in particular represents a remarkable example of a context-dependent analgesic drug that acts at a critical step of nociceptive sensitization. Preclinical and clinical data suggest that pregabalin is more than a structural and functional analogue of gabapentin and may be effective in the treatment of nociceptive inflammatory pain that is resistant to gabapentin.

Trigeminal neuralgia treated with pregabalin in family medicine settings: its effect on pain alleviation and cost reduction

The purpose of this study is to analyze the effect of pregabalin (PGB) on pain alleviation, use of health care and non-health care resources, and associated costs in patients with trigeminal neuralgia under usual clinical practice in primary care settings. Sixty-five PGB-naïve patients receiving PGB as monotherapy (n = 36, 55%) or combined with other drugs (n = 29, 45%) fulfill criteria for inclusion in a secondary analysis from a 12-week, multicenter, observational prospective study aimed to ascertain the cost of illness in subjects with neuropathic pain. Pain is evaluated using the Short Form McGill Pain Questionnaire. Use of health care and non-health care resources and lost workdays equivalents (LWDEs) are also recorded. PGB significantly reduces pain scores, use of health care resources (ancillary tests and unscheduled medical visits), and number of LWDEs. Additional cost of PGB treatment (+euro 174 +/- 106) is broadly compensated for by a reduction in both health care costs (-euro 621 +/-1211, P < .001) and indirect costs (-euro 1210 +/- 1141, P < .001). It is concluded that PGB as monotherapy or combined with other drugs is effective in pain management in patients with trigeminal neuralgia and reduces the cost of illness.

The perioperative management of pain from intracranial surgery

Analgesic therapy following intracranial procedures remains a source of concern and controversy. Although opioids are the mainstay of the "balanced" general anesthetic techniques frequently used during intracranial procedures, neurosurgeons and others have been reluctant to administer opioid analgesics to patients following such procedures. This practice is supported by the concern that the sedation and miosis associated with opioid administration could mask the early signs of intracranial catastrophe, or even exacerbate it through decreased ventilatory drive, elevated arterial carbon dioxide levels, and increased cerebral blood flow. This reluctance to use opioids following intracranial surgery is enabled by decades of training and anecdote emphasizing that pain is minimal following these procedures. However, recent data suggests otherwise, and raises the question of how to provide safe and effective analgesia for these patients. Here, this data is reviewed along with the relevant pain pathways, analgesic drugs and techniques, and the available data on their use following intracranial surgery. Although pain following intracranial surgery appears to be more intense than initially believed, it is readily treated safely and effectively with techniques that have proven useful following other types of surgery, including patient-controlled administration of opioids. The use of multimodal analgesic therapy is emphasized not only for its effectiveness, but to reduce dosages and, therefore, side effects, primarily of the opioids, that could be of legitimate concern to physicians and affect the comfort of their patients.

Antinociceptive action of GLYX-13: an N-methyl-D-aspartate receptor glycine site partial agonist

Inhibition of N-methyl-D-aspartate (NMDA)-mediated neurotransmission has been demonstrated to provide antinociceptive actions in a number of animal models of tonic and neuropathic pain. However, both competitive and noncompetitive NMDA receptor antagonists are ataxic at analgesic doses. Partial agonists and antagonists of the NMDA-associated glycine site have demonstrated antinociceptive actions at doses that are not ataxic. In this study, we present data showing that GLYX-13, an NMDA receptor, glycine-site, partial agonist, also is antinociceptive in the rat formalin model of tonic pain and in the rat constriction nerve injury model of neuropathic pain at doses not inducing ataxia.