Clinical use of pregabalin in the management of central neuropathic pain

Chronic Pain: A Complex Condition With a Multi-Tangential Approach

Chronic pain is known as ongoing pain that lasts longer than three months with increasing healing time. It is approximated that 20% of adults of different sexes, races, and socioeconomic backgrounds fall victim to chronic pain. It is a result of several factors and can have lifelong effects. Pain is a complex matter to measure; therefore, the physician needs to understand the patient's health state to create a management plan tending to each issue adequately. There are many complications of such pain, and it can interfere terribly with an individual's quality of life. This article has reviewed the complex pathogenesis of chronic pain and the spectrum of non-pharmacologic modalities and pharmacological treatment options. It has also explored the efficacy of certain drugs and underlined the importance of nonpharmacological options such as physical exercise, cognitive therapy, and physical modalities to treat chronic pain and all the conditions that accompany this disorder.

Pharmacokinetics of a New, Once-Daily, Sustained-Release Pregabalin Tablet in Healthy Male Volunteers

PURPOSE

A new sustained-release (SR) pregabalin formulation (YHD1119) designed for once-daily dosing has recently been developed to improve patient adherence. This study aimed to compare the pharmacokinetics of pregabalin SR and immediate-release (IR) formulations after multiple oral doses and to assess the effect of food on the pharmacokinetic profile of the pregabalin SR formulation after a single dose in healthy individuals.

METHODS

Two clinical trials were conducted: a randomized, open-label, multiple-dose, 2-treatment, 2-period crossover study to evaluate the steady-state pharmacokinetic properties of SR treatment (pregabalin SR 300 mg once daily for 3 days) and IR treatment (pregabalin IR 150 mg twice daily for 3 days) under fed conditions and a randomized, open-label, single-dose, 2-treatment, 2-period, crossover study to evaluate the effect of food intake on the pharmacokinetic properties of the pregabalin SR formulation. Plasma concentrations of pregabalin were measured using LC-MS/MS. The AUC and C_max for pregabalin were calculated using noncompartmental method and compared between treatments in each study.

FINDINGS

Thirty-one individuals in the bioequivalence study and 23 in the food effect study completed the pharmacokinetic sampling. The geometric mean ratios of C_max,ss and AUC_0-τ between the SR and IR formulations were 1.1642 (90% CI, 1.1043-1.2272) and 0.9704 (90% CI, 0.9372-1.0047), respectively. The geometric mean ratios of C_max and AUC_0-last between the SR formulation in the fed state and in the fasted state were 1.6514 (90% CI, 1.3820-1.9732) and 1.7899 (90%CI, 1.4499-2.2097), respectively.

IMPLICATIONS

The bioavailability of the pregabalin SR 300 mg formulation is increased if taken with a high-fat meal. Once-daily pregabalin SR 300 mg is bioequivalent to twice-daily pregabalin IR 150 mg under fed conditions at steady state. The pregabalin SR formulation is expected to improve patient adherence. ClinicalTrials.gov identifiers: NCT02783183 (bioequivalence study) and NCT03191136 (food effect study).

Biomarkers for predicting central neuropathic pain occurrence and severity after spinal cord injury: results of a long-term longitudinal study

Central neuropathic pain (CNP) after spinal cord injury (SCI) is debilitating and immensely impacts the individual. Central neuropathic pain is relatively resistant to treatment administered after it develops, perhaps owing to irreversible pathological processes. Although preemptive treatment may overcome this shortcoming, its administration necessitates screening patients with clinically relevant biomarkers that could predict CNP early post-SCI. The aim was to search for such biomarkers by measuring pronociceptive and for the first time, antinociceptive indices early post-SCI. Participants were 47 patients with acute SCI and 20 healthy controls. Pain adaptation, conditioned pain modulation (CPM), pain temporal summation, wind-up pain, and allodynia were measured above, at, and below the injury level, at 1.5 months after SCI. Healthy control were tested at corresponding regions. Spinal cord injury patients were monitored for CNP emergence and characteristics at 3 to 4, 6 to 7, and 24 months post-SCI. Central neuropathic pain prevalence was 57.4%. Central neuropathic pain severity, quality, and aggravating factors but not location somewhat changed over 24 months. Spinal cord injury patients who eventually developed CNP exhibited early, reduced at-level pain adaptation and CPM magnitudes than those who did not. The best predictor for CNP emergence at 3 to 4 and 7 to 8 months was at-level pain adaptation with odds ratios of 3.17 and 2.83, respectively (∼77% probability) and a cutoff value with 90% sensitivity. Allodynia and at-level CPM predicted CNP severity at 3 to 4 and 24 months, respectively. Reduced pain inhibition capacity precedes, and may lead to CNP. At-level pain adaptation is an early CNP biomarker with which individuals at risk can be identified to initiate preemptive treatment.

Efficacy of Electrical Spinal Cord Stimulation with Neuromodulating Medications: A Systematic Review

BACKGROUND

Chronic pain is a prevalent and debilitating problem for millions of people and spinal cord stimulation (SCS) is one option for treatment. It has been shown to have membrane stabilizing properties and is often used in conjunction with medications that are also believed to offer pain control through membrane stabilization.

OBJECTIVE

The goal of this review is to analyze the effects of SCS combined with medications to evaluate for augmentative therapeutic effect.

SETTING

Systematic review.

METHODS

A systematic computerized search of the literature was conducted using PubMed, the Cochrane Library, and EMBASE for articles published in English.

RESULTS

We report three articles that discuss the potential for augmentative effects of medication in combination with SCS. Located articles related primarily to SCS combined with Gabapentin, TCA, or SNRI.

LIMITATIONS

The limited number of articles reflects a need for more investigation in this area.

CONCLUSION

Based on the suspected mechanisms for SCS and neuromodulating medications, there is reason to believe adding these medical therapies may enhance the effects of SCS.

Pregabalin-induced sexual disinhibition

INTRODUCTION

Sexual side effects have rarely been reported secondary to treatment with Pregabalin, a structural analogue of the inhibitory neurotransmitter gamma amino butyric acid (GABA).

METHOD

We present the case of AB, a 27-year-old single man with a diagnosis of recurrent depressive disorder who was prescribed pregabalin to alleviate the significant anxiety symptoms he was experiencing.

RESULTS

A significant amelioration in anxiety symptoms was attained; however, he developed the adverse effects of acute sexual disinhibition and increased libido. These adverse effects were temporally related to treatment with pregabalin and reduced with dose reduction of this agent.

CONCLUSIONS

To date, limited published data are available relating such a reaction to pregabalin. A greater clinical recognition of this association between pregabalin and sexual disinhibition, would allow clinicians to intervene at an earlier stage of this adverse effect and potentially as in this case, management may only require dose reduction rather than treatment discontinuation.

Response to pregabalin and progesterone differs in male and female rat models of neuropathic and cancer pain

Background: Cancer pain involves nervous system damage and pathological neurogenesis. Neuropathic pain arises from damage to the nervous system and is driven by ectopic signaling. Both progesterone and pregabalin are neuroprotective in animal models, and there is evidence that both drugs bind to and inhibit voltage-gated calcium channels. Aims: This study was designed to characterize the effects of progesterone and pregabalin in preclinical models of cancer and neuropathic pain in both sexes. Methods: We measured peripheral sensory signaling by intracellular in vivo electrophysiology and behavioral indicators of pain in rat models of cancer-induced bone pain and neuropathic pain. Results: Female but not male models of cancer pain showed a behavioral response to treatment and pregabalin reduced excitability in C and A high-threshold but not low-threshold sensory neurons of both sexes. Male models of neuropathic pain treated with pregabalin demonstrated higher signaling thresholds only in A high-threshold neurons, and behavioral data indicated a clear recovery to baseline mechanical withdrawal thresholds in all treatment groups. Female rat treatment groups did not show excitability changes in sensory neurons, but all demonstrated higher mechanical withdrawal thresholds than vehicle-treated females, although not to baseline levels. Athymic female rat models of neuropathic pain showed no behavioral or electrophysiological responses to treatment. Conclusions: Both pregabalin and progesterone showed evidence of efficacy in male models of neuropathic pain. These results add to the evidence demonstrating differential effects of treatments for pain in male and female animals and widely differing responses in models of cancer and neuropathic pain.

Pregabalin Abuse in Combination With Other Drugs: Monitoring Among Methadone Patients

INTRODUCTION

In recent years, there has been an increase in the non-medical use of psychoactive prescription drugs including pregabalin (PGB). Studies have shown that multiple drug users and patients in methadone treatment programs administered PGB at high dosages in order to achieve euphoria, reduce withdrawal symptoms, or potentiate the effects of methadone. For these reasons, accurate toxicological monitoring is required for these high-risk individuals.

MATERIALS AND METHODS

The present study investigated whether PGB could be detected in the hair samples of 250 patients with a history of opiate dependency, and under toxicological surveillance assess their compliance with methadone maintenance therapy.

RESULTS

Opiates were found in 54/250 of all hair samples, while cannabis was present in 74/250 patients, cocaine was detected in 21/250 patients, and benzodiazepines without prescription were identified in 49/250 patients. As expected, methadone was present in all 250 patients (100%). PGB without prescription was found in the hair samples of 35/250 patients (14%). Of these, 91.43% were male, 48.57% were <30 y old, and 45.71% were between ages 30 and 50 y. There were no apparent associations among PGB use, daily methadone dosage, and duration of methadone maintenance therapy. Psychiatric comorbidities were present in 25.71% of the patients abusing PGB. Anxiety (55.56%) and depression (33.33%) were the most prevalent psychiatric disorders.

DISCUSSION

Most of the patients taking PGB (57.14%) used other drugs (especially opiates) concurrently. The utility of hair analysis is explained by easy and rapid sample collection and the ability of the hair to reflect long-term drug use and incorporate drug metabolites. The findings of this study suggested that PGB has significant potential for abuse by high-risk populations such as opioid users and patients with dual diagnosis. These risks are particularly high in cases of poly-drug use and drug intake that are not in compliance with prescription guidelines.

Pregabalin in the reduction of pain and opioid consumption after burn injuries: A preliminary, randomized, double-blind, placebo-controlled study

BACKGROUND

The primary objective of the study was to evaluate the efficacy of 300 milligrams (mg) and 600 mg of pregabalin compared to placebo in the reduction of pain in patients with noncritical partial and full thickness burn injuries.

METHODS

A prospective, randomized, double-blinded, single center, placebo-controlled trial was conducted. Simple randomization method was used in this trial. After subjects met all the inclusion and none of the exclusion criteria, they were randomized and assigned to 1 of the 3 18-day treatments groups: Pregabalin 300 group, Pregabalin 600 group, or Placebo group. Demographics and clinical characteristics were recorded. The severity of pain was assessed by using the visual analog scale for pain intensity at baseline on day 3, day 9 ± 3, day 25 ± 7, day 90 ± 6, and day 180 ± 12.

RESULTS

A total of 54 subjects were randomly assigned, and 51 were included in the data analysis. Demographics and clinical characteristics did not differ significantly between the 3 groups. There was a statistically significant difference in pain between the Pregabalin 300 and Pregabalin 600 groups (P-value = .0260). The Pregabalin 300 group had 17.93 units (95% confidence interval: 1.83-34.04) higher pain scores on average than the Pregabalin 600 group, regardless of time. The adjusted P-value comparing 0 to 300 was .1618, while the adjusted P-value for 0 versus 600 was .5304. There was an overall difference in pain across time regardless of study group (P-value = <.0001). An overall difference in opioid consumption (P-value = .0003) and BSHS (P-value = .0013) across time regardless of study group was noted.

CONCLUSIONS

Pregabalin could be part of a promising multimodal analgesic regimen in noncritical burn population. Future placebo-controlled studies assessing the use of pregabalin in burn victim patients may further endorse our findings.

A combination pharmacotherapy of tapentadol and pregabalin to tackle centrally driven osteoarthritis pain

BACKGROUND

Many Osteoarthritis (OA) patients report with clinical features to their pain that cannot be explained by purely peripheral mechanisms. Yet, the analgesic agents available that tackle centrally driven chronic pain often provide only partial pain relief, or have dose-limiting side effects. We explored a combination therapy of the centrally acting analgesic agents tapentadol and pregabalin, to investigate if they could be used in combination to provide superior analgesia.

METHODS

Using electrophysiological single-unit recordings taken from spinal wide dynamic range neurons, Diffuse Noxious Inhibitory Controls (DNIC) were assessed as a marker of potential changes in descending controls in a monoiodoacetate (MIA) model of OA. We investigated if a subcutaneous injection of tapentadol or pregabalin, both alone and in combination, inhibited neuronal responses and restored the expression of DNIC, quantified as a reduction in neuronal firing in the presence of a conditioning noxious stimulus.

RESULTS

Tapentadol restored DNIC-induced neuronal inhibition in MIA animals, while pregabalin inhibited pre-conditioned mechanically evoked neuronal responses but did not restore DNIC. Given in combination, tapentadol and pregabalin restored DNIC expression and also inhibited spinal neuronal responses.

CONCLUSIONS

We propose that there is both central sensitization and an imbalance in inhibitory and facilitatory descending controls in MIA animals. The combination therapy of tapentadol and pregabalin restored descending noradrenergic inhibitory tone and also inhibited nociceptive transmission at the level of the spinal cord.

SIGNIFICANCE

This study shows that pregabalin and tapentadol target different mechanisms of centrally driven chronic pain associated with osteoarthritis, and that when administered together can restore descending inhibitory tone whilst also tackling spinal neuronal hyperexcitability and may therefore provide superior analgesia.

Dose-proportional pharmacokinetic properties of GLA5PR GLARS-NF1 controlled-release pregabalin in healthy Korean volunteers: a randomized, open, single-dose, parallel study

Purpose

The aim of this study was to evaluate the dose-proportional pharmacokinetic characteristics of pregabalin following the administration of GLA5PR GLARS-NF1 tablets (150, 300, 450, and 600 mg) in the fed state.

Subjects and methods

An open-label, randomized, single-dose, parallel study was conducted in 40 eligible subjects who were randomly assigned to receive a single 150, 300, 450, or 600 mg dose of GLA5PR GLARS-NF1. Serial blood samples were collected before and after dosing for 36 hours, and plasma concentrations were determined using liquid chromatography-tandem mass spectrometry. Safety profiles were evaluated throughout the study (trial registration number: NCT02327000).

Results

Thirty-seven subjects completed the studies. The area under the plasma concentration-time curve up to the last measurable concentration of pregabalin exhibited dose proportionality following administration of GLA5PR GLARS-NF1 tablets from 150 to 600 mg while its maximum plasma concentration showed dose proportionality at a dose range of 150–450 mg. The safety evaluations showed no clinically significant finding after administration of GLA5PR GLARS-NF1 tablets (150, 300, 450, and 600 mg) in the fed state.

Conclusions

The dose-proportional properties of GLA5PR GLARS-NF1 150–450 mg tablets were determined.

Is there a role for combined use of gabapentin and pregabalin in pain control? Too good to be true?

Gabapentin (Neurontin ¹ ) and pregabalin (Lyrica ² ) are first- and second-generation α2δ ligands, respectively, and are both approved for use as adjunctive therapy in pain control. Although they do not bind to gamma-aminobutyric acid (GABA) receptors they have been successfully used to treat neuropathic pain conditions. Their mechanism of action is not yet fully understood, but research has demonstrated promising results. Despite their similarities, they have been used in combination in both clinical and research situations, and have been noted to have a synergistic effect in pain control without concern for clinically significant pharmacokinetic interactions. This combined approach can be made use of to reduce the dose of an individual agent, its side effects, and to enhance therapeutic response compared to a single agent. Pharmacokinetics, drug interactions, and adverse reaction to combinations have to be taken into consideration before combination therapy with gabapentin and pregabalin is proposed as first-line treatment in refractory pain situations and in patients with low levels of tolerance for an individual agent.

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.

Crying spells triggered by thumb-index rubbing after thalamic stroke: a case report

Background

Pathologic crying, devoid of any emotional counterpart, is known to occur as a consequence of various brain stem, cortical hemispheric and cerebellar lesions or, quite exceptionally, of “dacrystic” epilepsy. The case reported here suggests that thalamic lesions may also cause crying spells, under the special circumstances described below.

Case presentation

After a mild left thalamic stroke a caucasian 77 years old man presented with crying spells with no emotional counterpart, triggered by thumb-index rubbing of his right hand. Only a modest sensation loss on right infra-orbital and nose-labial areas and the first three right fingers could be detected at clinical examination. The circumstances and processes leading to the crying spells were investigated, together with their neural substrate. Brain computerized tomography (CT), magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) were conducted. Neurophysiologic studies included Video-Electroencephalography, Electromyography, motor and sensory Evoked potentials. Active thumb-index rubbing, passive fingertips stimulation and interaction of sensory-motor stimulation with cognitive/speech activities were tested under different paradigms. A treatment with pregabalin (75 mg twice a day) was attempted. CT and MRI showed a small ischemic infarct in the left ventral postero-lateral thalamus, while fMRI led to the expected findings, i.e. a bilateral activation of the hand motor representation during the crying-triggering right-hand finger rubbing activity. Sensory potentials evoked from stimulation of the right upper limb were the only abnormal neurophysiologic test. Crying spells could be invariably evoked by both real and imagined active finger rubbing, in either the left of right hemi-space. Rubbing by an examiner was ineffective. Immersion in water (18 °C) but not oiling of the fingertips prevented the symptom. Administration and discontinuation of pregabalin 75 mg daily could be associated with suppression and reappearance of the symptom, respectively.

Conclusions

In this patient loss of sensation seemed to generate crying spells rather than the more common allodynia. As a matter of speculation, both symptoms might represent responses to a sensory loss, but in this case the pathway might have been selectively affected providing inhibition from the lateral to the medial segment of the VPLT, which is linked to the anterior cingulate (limbic) cortex engaged in emotional behaviour.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-017-2425-z) contains supplementary material, which is available to authorized users.

Comparative study between 2 different doses of pregabalin and lidocaine on pain following propofol injection: A double-blind, randomized clinical consort study

BACKGROUND

Propofol, an intravenous anesthetic, often causes pain on injection, which can be very distressful to patients. We investigated the analgesic effect of pregabalin on pain following propofol injection, compared with lidocaine.

METHODS

In a randomized, double-blind, prospective trial, 120 patients were randomized into 3 groups of 40 each; who received oral placebo and intravenous lidocaine 40 mg with venous occlusion for 1 minute (group L, n = 40), oral pregabalin 75 mg and intravenous normal saline with venous occlusion for 1 minute (group LP, n = 40), and oral pregabalin 150 mg and intravenous normal saline with venous occlusion for 1 minute (group HP, n = 40) as pretreatment, followed by administration of 1% propofol 0.5 mg/kg. Pain intensity was measured on a 4-point scale (0 = no, 1 = mild, 2 = moderate, and 3 = severe pain). Any side effects associated with pretreatment substances were recorded during the first 24 hours after surgery.

RESULTS

A total of 120 patients completed this trial. Demographic data were similar between groups. The incidence of pain following propofol injection was significantly reduced in group HP (50%) and group L (55%) compared with group LP (92.5%) (P < 0.05, respectively). The incidences of moderate pain in group HP (12.5%) and group L (15%) were significantly decreased compared with group LP (37.5%; both, P < 0.05). There were no significant differences in the incidence of side effects such as headache and dizziness between groups.

CONCLUSION

Pretreatment with oral pregabalin 150 mg and intravenous lidocaine 40 mg with venous occlusion equally reduced pain from propofol injection.

An Exploratory Human Laboratory Experiment Evaluating Vaporized Cannabis in the Treatment of Neuropathic Pain From Spinal Cord Injury and Disease

Using 8-hour human laboratory experiments, we evaluated the analgesic efficacy of vaporized cannabis in patients with neuropathic pain related to injury or disease of the spinal cord, most of whom were experiencing pain despite traditional treatment. After obtaining baseline data, 42 participants underwent a standardized procedure for inhaling 4 puffs of vaporized cannabis containing either placebo, 2.9%, or 6.7% delta 9-THC on 3 separate occasions. A second dosing occurred 3 hours later; participants chose to inhale 4 to 8 puffs. This flexible dosing was used to attempt to reduce the placebo effect. Using an 11-point numerical pain intensity rating scale as the primary outcome, a mixed effects linear regression model showed a significant analgesic response for vaporized cannabis. When subjective and psychoactive side effects (eg, good drug effect, feeling high, etc) were added as covariates to the model, the reduction in pain intensity remained significant above and beyond any effect of these measures (all P < .0004). Psychoactive and subjective effects were dose-dependent. Measurement of neuropsychological performance proved challenging because of various disabilities in the population studied. Because the 2 active doses did not significantly differ from each other in terms of analgesic potency, the lower dose appears to offer the best risk-benefit ratio in patients with neuropathic pain associated with injury or disease of the spinal cord.

PERSPECTIVE

A crossover, randomized, placebo-controlled human laboratory experiment involving administration of vaporized cannabis was performed in patients with neuropathic pain related to spinal cord injury and disease. This study supports consideration of future research that would include longer duration studies over weeks to months to evaluate the efficacy of medicinal cannabis in patients with central neuropathic pain.

Pharmacokinetic equivalence study of two formulations of the anticonvulsant pregabalin

Purpose

The present study was conducted to evaluate whether the bioavailability of pregabalin capsules 150 mg manufactured by PT Dexa Medica was equivalent to the reference formulation.

Methods

This was a randomized, open-label, two-period, two-sequence, and crossover study under fasting condition, with a 1-week washout period. Plasma concentrations of pregabalin from 20 subjects were determined by using a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) detection method. Pharmacokinetic parameters assessed in this study were: area under the plasma concentration–time curve from time zero to last observed quantifiable concentration (AUC_0–t), area under the plasma concentration–time curve from time zero to infinity (AUC_0–∞), maximum plasma concentration (C_max), time to maximum plasma concentration (t_max), and terminal half-life (t_1/2). The 90% confidence intervals (CIs) for the geometric mean ratios of test formulation/reference formulation were calculated for the AUC and C_max parameters; while t_max difference was analyzed nonparametrically on the original data using the Wilcoxon matched-pairs test, and t_1/2 difference was analyzed using Student’s paired t-test.

Results

The mean (standard deviation [SD]) AUC_0–t, AUC_0–∞, C_max, and t_1/2 of pregabalin from the test formulation were 27,845.86 (4,508.27) ng · h/mL, 28,311.70 (4,790.55) ng · h/mL, 3,999.71 (801.52) ng/mL, and 5.66 (1.20) hours, respectively; while the mean (SD) AUC_0–t, AUC_0–∞,C_max, and t_1/2 of pregabalin from the reference formulation were 27,398.12 (4,266.28) ng · h/mL, 27,904.24 (4,507.31) ng · h/mL, 3,849.50 (814.50) ng/mL, and 5.87 (1.25) hours, respectively. The median (range) t_max of pregabalin from the test formulation and reference formulation was 1.00 (0.67–2.00) hours and 1.00 (0.67–3.00) hours, respectively. The 90% CIs for the geometric mean ratios of test formulation/reference formulation for pregabalin were 101.54% (98.75%–104.41%) for AUC_0–t, 101.35% (98.66%–104.11%) for AUC_0–∞, and 104.19% (98.75%–109.93%) for C_max.

Conclusion

The study concluded that the two formulations of pregabalin capsules studied were bioequivalent.

Efficacy and safety of pregabalin in patients with neuropathic cancer pain undergoing morphine therapy

AIM

To evaluate the efficacy and the safety of pregabalin (PGB)-morphine combination for the treatment of neuropathic cancer pain (NCP).

METHODS

In this double-blind, randomized, placebo (PL)-controlled crossover study, 40 cancer patients with severe NCP were randomized into two groups (20 per group): PGB-PL and PL-PGB. Patients in the PGB-PL group received PGB plus oral morphine in phase I, and PL plus oral morphine in phase II. The treatment sequence for the PL-PGB group was PL plus oral morphine in phase I, and PGB plus oral morphine in phase II. These 2-week treatment periods were separated by a 1-week washout period. The primary outcome measure was the decrements in morphine dose; secondary outcomes included quantitative assessments of sleep (rated according to the Medical Outcomes Study Sleep Scale), the Constipation Assessment Scale and adverse effects.

RESULTS

The mean minimal effective dose of morphine was 184.4 ± 69.9 mg/day in the period of PGB treatments, which was significantly lower than that of PL-controls (228.7 ± 66.9 mg/day; P < 0.001) and baseline (247.5 ± 80.0 mg/day; P < 0.001). Compared with PL, PGB resulted in a significant sleep improvement as measured by sleep disturbance, sleep quantity, and sleep problems index (P < 0.001), as well as a Constipation Assessment Scale reduction (P < 0.001). PGB resulted in a higher frequency of dry mouth and somnolence than PL (P < 0.05).

CONCLUSION

PGB enhances the efficacy of oral morphine and reduces dose-related adverse reactions. The PGB-morphine combination is an effective approach to controlling NCP.

Broad spectrum and prolonged efficacy of dimiracetam in models of neuropathic pain

Dimiracetam, a bicyclic 2-pyrrolidinone derivative originally developed as cognition enhancer, is a member of the nootropic family for which anecdotal efficacy in models of neuropathic pain has been reported. Its antineuropathic activity was evaluated in established models of neuropathic pain induced by nerve injury, chemotherapy or MIA-induced osteoarthritis. Acutely, dimiracetam was very effective in models of antiretroviral drug induced painful neuropathy, oxaliplatin-induced hyperalgesia and in the MIA-osteoarthritis. Chronic dimiracetam dosing in the MIA and ART- induced models completely reverted hyperalgesia back to the level of healthy controls. Once reached, the maximal effect was maintained despite dose diminution and increased inter-dose interval. The effect of the last dose outlasted dimiracetam half-life longer than 12 times. In synaptosomal preparations, dimiracetam counteracted the NMDA-induced release of glutamate with highest potency in the spinal cord, possibly via NMDA receptor isoforms containing pH-sensitive GluN1 and GluN2A subunits. Dimiracetam appears to be a promising and safe treatment for neuropathic pain conditions for which there are very limited therapeutic options.

Myoclonus in renal failure: Two cases of gabapentin toxicity

Gabapentin, an AED approved for the adjunctive treatment of partial seizures with/without secondary generalization and for the treatment of postherpetic neuralgia, is frequently used off-label for the treatment of both psychiatric and pain disorders. Since gabapentin is cleared solely by renal excretion, dosing requires consideration of the patient's renal function. Myoclonic activity may occur as a complication of gabapentin toxicity, especially with acute kidney injury or end-stage renal disease. We report 2 cases of myoclonic activity associated with gabapentin toxicity in the setting of renal disease which resolved with discontinuation of gabapentin and treatment with hemodialysis and peritoneal dialysis. As gabapentin has multiple indications and off-label uses, an understanding of myoclonus, neurotoxicity, and renal dosing is important to clinicians in multiple specialties.

Pregabalin for the management of neuropathic pain in spinal cord injury

SUMMARY Pregabalin is the only US FDA-approved drug to date for neuropathic pain in spinal cord injured patients. Pregabalin is a novel GABA analog whose primary mechanism of action involves binding at the α2-δ subunit of voltage-sensitive calcium channels. Efficacy is noted within the first several days of administration. Dosing is typically initiated at 150 mg/day in divided doses, but may be started at even lower doses. Dosing can be increased gradually to a recommended maximum of 600 mg per day in divided dosing. Adverse events include somnolence, dizziness and dry mouth, and typically manifest within the first 2 weeks of treatment. Pregabalin is generally safe to use in combination with other pain medications or antidepressants, but safety in pregnant patients has not been established.

Post hoc analysis of pregabalin vs. non-pregabalin treatment in patients with cancer-related neuropathic pain: better pain relief, sleep and physical health

BACKGROUND AND PURPOSE

A previous study of cancer-related neuropathic pain (NP) found that a 10-fold increase in pregabalin (PGB) use increased patients' satisfaction with treatment. Further research of PGB vs. non-pregabalin (non-PGB) treatment was carried out to assess if the use of more specific NP-targeting drugs, such as PGB, in combined therapy, in patients with cancer-related NP, provides better health outcomes.

PATIENTS AND METHODS

Post hoc analysis of PGB- vs. non- PGB-treated patients in a 2-month epidemiological, prospective, multicentre study to assess NP prevalence and management in cancer pain patients visiting radiotherapy oncologic units. Patients undertook the Brief Pain Inventory (BPI), Hospital Anxiety and Depression Scale (HADS), the Medical Outcomes Sleep Scale (MOS-Sleep) and the short form (SF-12) Health Survey.

RESULTS

A total of 273 patients with no previous PGB treatment: 162 were treated with PGB polytherapy and 111 with other treatments. At 8 weeks, satisfaction with treatment was 92.6% (PGB) vs. 78.9% (non-PGB), p=0.0024, and benzodiazepine use 37.8% (non-PGB) vs. 19.8% (PGB), p=0.0009. The decreases in BPI total pain intensity and total interference with activities and in MOS overall sleep problems index were significantly larger in the PGB group.

CONCLUSIONS

The addition of more specific NP-targeting drugs to usual treatment, such as PGB, in NP cancer patients provides more satisfaction with treatment and better outcomes in terms of pain intensity, interference with activities and sleep than treatments without specific NP-targeting drugs. Anxiolytic profile of PGB could allow for less use of benzodiazepines.