The diverse therapeutic actions of pregabalin: is a single mechanism responsible for several pharmacological activities?

Mirogabalin inhibits scratching behavior of spontaneous model mouse of atopic dermatitis

Introduction: Atopic dermatitis (AD) is one of the most prevalent intractable chronic itch diseases worldwide. In recent years, new molecular-targeted drugs have emerged, but side effects and economic challenges remain. Therefore, since it is important for AD patients to have a wider range of treatment options, it is important to explore new therapeutic agents. Gabapentinoids, gabapentin and pregabalin, have been shown to be effective for the clinical treatment of several chronic itch. Recently, mirogabalin (MGB) was developed as a novel gabapentinoid. MGB is a drug for neuropathic pain and has a margin of safety between its side effects and the analgesic effect for animal experiments. Herein, we showed that MGB exhibited an antipruritic effect in a mouse model of AD using NC/Nga mice. Methods and results: The oral administration of MGB (10 mg/kg) inhibited spontaneous scratching behavior in AD mice and its effect was dose dependently. Then, when MGB (10 mg/kg) was orally administrated to healthy mice, it did not affect motor function, including locomotor activity, wheel activity, and coordinated movement. Moreover, gabapentin (100 mg/kg) and pregabalin (30 mg/kg), inhibited spontaneous scratching behavior in AD mice and decreased motor function in healthy mice. Furthermore, intracisternal injection of MGB (10 μg/site) significantly suppressed spontaneous scratching behavior in AD mice. Discussion: In summary, our results suggest that MGB exerts an antipruritic effect via the spinal dorsal horn using NC/Nga mice. We hope that MGB is a candidate for a novel therapeutic agent for AD with relatively few side effects.

An extract of phase II and III trials on recent developments in managing neuropathic pain syndromes: diabetic peripheral neuropathy, trigeminal neuralgia, and postherpetic neuralgia

INTRODUCTION

Neuropathic pain (NP) conditions involve lesions to the somatosensory nervous system leading to chronic and debilitating pain. Many patients suffering from NP utilize pharmacological treatments with various drugs that seek to reduce pathologic neuronal states. However, many of these drugs show poor efficacy as well as cause significant adverse effects. Because of this, there is a major need for the development of safer and more efficacious drugs to treat NP.

AREAS COVERED

In this review, we analyzed current treatments being developed for a variety of NP conditions. Specifically, we sought drugs in phase II/III clinical trials with indications for NP conditions. Various databases were searched including Google Scholar, PubMed, and clinicaltrials.gov.

EXPERT OPINION

All the mentioned targets for treatments of NP seem to be promising alternatives for existing treatments that often possess poor side effect profiles for patients. However, gene therapy potentially offers the unique ability to inject a plasmid containing growth factors leading to nerve growth and repair. Because of this, gene therapy appears to be the most intriguing new treatment for NP.

Mechanism of Analgesia by Gabapentinoid Drugs: Involvement of Modulation of Synaptogenesis and Trafficking of Glutamate-Gated Ion Channels

Gabapentinoids have clinically been used for treating epilepsy, neuropathic pain, and several other neurologic disorders for >30 years; however, the definitive molecular mechanism responsible for their therapeutic actions remained uncertain. The conventional pharmacological observation regarding their efficacy in chronic pain modulation is the weakening of glutamate release at presynaptic terminals in the spinal cord. While the α2/δ-1 subunit of voltage-gated calcium channels (VGCCs) has been identified as the primary drug receptor for gabapentinoids, the lack of consistent effect of this drug class on VGCC function is indicative of a minor role in regulating this ion channel's activity. The current review targets the efficacy and mechanism of gabapentinoids in treating chronic pain. The discovery of interaction of α2/δ-1 with thrombospondins established this protein as a major synaptogenic neuronal receptor for thrombospondins. Other findings identified α2/δ-1 as a powerful regulator of N-methyl-D-aspartate receptor (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) by potentiating the synaptic expression, a putative pathophysiological mechanism of neuropathic pain. Further, the interdependent interactions between thrombospondin and α2/δ-1 contribute to chronic pain states, while gabapentinoid ligands efficaciously reverse such pain conditions. Gabapentin normalizes and even blocks NMDAR and AMPAR synaptic targeting and activity elicited by nerve injury. SIGNIFICANCE STATEMENT: Gabapentinoid drugs are used to treat various neurological conditions including chronic pain. In chronic pain states, gene expression of cacnα2/δ-1 and thrombospondins are upregulated and promote aberrant excitatory synaptogenesis. The complex trait of protein associations that involve interdependent interactions between α2/δ-1 and thrombospondins, further, association of N-methyl-D-aspartate receptor and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor with the C-tail of α2/δ-1, constitutes a macromolecular signaling complex that forms the crucial elements for the pharmacological mode of action of gabapentinoids.

IL-10/β-Endorphin-Mediated Neuroimmune Modulation on Microglia during Antinociception

Microglia are glial cells centrally related to pathophysiology and neuroimmunological regulation of pain through microglia-neuron crosstalk mechanisms. In contrast, anti-inflammatory mechanisms guided by immunological effectors such as IL-10 trigger the secretion of analgesic substances, culminating in the differential expression of genes encoding endogenous opioid peptides, especially β-endorphin. Thus, when β-endorphin binds to the µ-opioid receptor, it generates neuronal hyperpolarization, inhibiting nociceptive stimuli. This review aimed to summarize the recent advances in understanding the mechanism by which IL-10/β-endorphin can reduce pain. For this, databases were searched for articles from their inception up until November 2022. Two independent reviewers extracted the data and assessed the methodological quality of the included studies, and seventeen studies were considered eligible for this review. Several studies have demonstrated the impact of IL-10/β-endorphin in reducing pain, where IL-10 can stimulate GLP-1R, GRP40, and α7nAChR receptors, as well as intracellular signaling pathways, such as STAT3, resulting in increased β-endorphin expression and secretion. In addition, molecules such as gabapentinoids, thalidomide, cynandione A, morroniside, lemairamin, and cinobufagin, as well as non-pharmacological treatments such as electroacupuncture, reduce pain through IL-10 mediated mechanisms, reflecting a microglia-dependent β-endorphin differential increase. This process represents a cornerstone in pain neuroimmunology knowledge, and the results obtained by different studies about the theme are presented in this review.

A randomized, active-controlled, parallel, open-label, multicenter, phase 4 study to compare the efficacy and safety of pregabalin sustained release tablet and pregabalin immediate release capsule in type II diabetic patients with peripheral neuropathic pain

BACKGROUND

Diabetic peripheral polyneuropathy is the most common chronic complication of type 2 diabetes. Neuropathic pain is challenging to manage, and various drugs are required to control it, decreasing treatment adherence. Pregabalin, a ligand that binds to alpha-2-delta subunits of the presynaptic calcium channel, has been approved by the Food and Drug Administration for the treatment of diabetic neuropathic pain. In this study, we will compare the efficacy, safety, treatment satisfaction, and compliance between pregabalin sustained-release (SR) tablets and pregabalin immediate-release (IR) capsules in type 2 diabetic patients with peripheral neuropathic pain.

METHODS

This study is a randomized, active-controlled, parallel, open-label, multicenter, phase 4 clinical trial (trial registration NCT05624853). Type 2 diabetic patients with glycosylated hemoglobin below 10% and peripheral neuropathic pain who have been taking pregabalin 150 mg/d or more for more than 4 weeks will be randomly assigned to pregabalin SR tablet (150 mg once a day, n = 65) or pregabalin IR capsule (75 mg twice a day, n = 65) therapy for 8 weeks. The primary outcome will be the efficacy of SR pregabalin after 8 weeks of treatment, which will be assessed by visual analog scale measurements. The secondary outcomes will include changes in several parameters, such as quality of life, treatment satisfaction, quality of sleep, and drug compliance.

DISCUSSION

In thus study, we aim to demonstrate that pregabalin SR tablets are associated with better compliance and satisfaction compared with pregabalin IR capsules, despite similar efficacy.

Risk of parkinsonism and related movement disorders with gabapentinoids or tramadol: A case-crossover study

INTRODUCTION

A safety signal concerning parkinsonism and related movement disorders with gabapentinoids (gabapentin and pregabalin) or tramadol was detected by reviewing individual case reports and data mining in spontaneous report databases. Well-designed pharmacoepidemiological studies are needed to assess the signal.

OBJECTIVE

This study aimed to investigate the association of exposure to gabapentinoids or tramadol with the risk of parkinsonism and related movement disorders.

METHODS

We conducted a case-crossover study using a Japanese electronic medical records database. Patients with newly diagnosed parkinsonism or related movement disorders between January 1, 2007, and April 14, 2019, were identified. The diagnosis date of outcomes was defined as the index date. We assessed the exposure of each patient to gabapentinoids or tramadol during a 90-day hazard period ending 1 day before the index date and in three 90-day reference periods. Multivariable conditional logistic regression models were employed to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). To confirm the robustness of the primary findings, we also performed sensitivity analyses using a case-case-time-control design, a different time window for hazard and reference periods, a different definition of outcome, and different number of reference periods.

RESULTS

A total of 28,972 eligible cases were included in the primary analysis. Exposure to gabapentinoids (aOR, 2.12; 95% CI, 1.73-2.61) and tramadol (aOR, 2.04; 95% CI, 1.57-2.64) was associated with increased risk. Results were consistent across sensitivity analyses.

CONCLUSION

Our findings serve as a caution to physicians who prescribe gabapentinoids or tramadol in routine clinical practice.

The Novel Gabapentinoid Mirogabalin Prevents Upregulation of α2δ-1 Subunit of Voltage-Gated Calcium Channels in Spinal Dorsal Horn in a Rat Model of Spinal Nerve Ligation

Gabapentinoids are specific ligands for the α₂δ-1 subunit of voltage-gated calcium channels. This class of drugs, including gabapentin and pregabalin, exert various pharmacological effects and are widely used for the treatment of epilepsy, anxiety, and chronic pain. The mechanism of action of gabapentinoids involves both direct modulation of calcium channel kinetics and inhibition of channel trafficking and expression, which contribute to the above pharmacological effects. In the present study, we investigated the effects of mirogabalin, a novel potent gabapentinoid, on expression levels of the α₂δ-1 subunit in the spinal dorsal horn in a rat model of spinal nerve ligation (SNL) as an experimental animal model for peripheral neuropathic pain. The neuropathic pain state was induced by SNL in male Sprague - Dawley rats. After the development of mechanical hypersensitivity, the animals received 10 mg/kg mirogabalin or vehicle orally for 5 consecutive days and were subjected to immunohistochemical analysis of α₂δ-1 subunit expression in the spinal cord. In the SNL model rats, expression of the α₂δ-1 subunit significantly increased in the spinal dorsal horn at the ipsilateral side of nerve injury, while mirogabalin inhibited this increase. In conclusion, the α₂δ-1 subunit was upregulated in the spinal dorsal horn of SNL model rats, and repeated administration of mirogabalin inhibited this upregulation. The inhibitory effect of mirogabalin on upregulation of the α₂δ-1 subunit after nerve injury is considered to contribute to its analgesic effects in peripheral neuropathic pain.

Pregabalin Mediates Retinal Ganglion Cell Survival From Retinal Ischemia/Reperfusion Injury Via the Akt/GSK3β/β-Catenin Signaling Pathway

Purpose

Progressive retinal ganglion cell (RGC) loss induced by retinal ischemia/reperfusion (RIR) injury leads to irreversible visual impairment. Pregabalin (PGB) is a promising drug for neurodegenerative diseases. However, with regard to RGC survival, its specific role and exact mechanism after RIR injury remain unclear. In this study, we sought to investigate whether PGB could protect RGCs from mitochondria-related apoptosis induced by RIR and explore the possible mechanisms.

Methods

C57BL/6J mice and primary RGCs were pretreated with PGB prior to ischemia/reperfusion modeling. The retinal structure and cell morphology were assessed by immunochemical assays and optical coherence tomography. CCK8 was used to assay cell viability, and an electroretinogram was performed to detect RGC function. Mitochondrial damage was assessed by a reactive oxygen species (ROS) assay kit and transmission electron microscopy. Western blot and immunofluorescence assays quantified the expression of proteins associated with the Akt/GSK3β/β-catenin pathway.

Results

Treatment with PGB increased the viability of RGCs in vitro. Consistently, PGB preserved the normal thickness of the retina, upregulated Bcl-2, reduced the ratio of cleaved caspase-3/caspase-3 and the expression of Bax in vivo. Meanwhile, PGB improved mitochondrial structure and prevented excessive ROS production. Moreover, PGB restored the amplitudes of oscillatory potentials and photopic negative responses following RIR. The mechanisms underlying its neuroprotective effects were attributed to upregulation of the Akt/GSK3β/β-catenin pathway. However, PGB-mediated neuroprotection was suppressed when using MK2206 (an Akt inhibitor), whereas it was preserved when treated with TWS119 (a GSK3β inhibitor).

Conclusions

PGB exerts a protective effect against RGC apoptosis induced by RIR injury, mediated by the Akt/GSK3β/β-catenin pathway.

Gabapentin reduces stress and does not affect ocular parameters in clinically normal cats

OBJECTIVE

To describe the effects of gabapentin on ocular and behavioral parameters following oral administration in healthy cats.

MATERIALS AND METHODS

Masked, placebo-controlled, randomized crossover-design study. Ten young, healthy cats were scheduled for two veterinary visits 7 days apart and randomly assigned to receive a compounded capsule containing 100 mg of gabapentin or placebo (100 mg lactose powder) at the first visit and the opposite treatment at the second visit. Respiratory rate, heart rate, stress score, sedation score, compliance score, horizontal pupil diameter, intraocular pressure, and Schirmer tear test-1 were measured prior to and 1.5, 3, and 6 h following capsule administration. Stress score, sedation score, and compliance score were assigned based on established behavioral scales. Results of the two treatments were statistically compared with a p-value <0.05 considered significant.

RESULTS

Respiratory rate was significantly reduced at 1.5 (p = 0.049) and 3 (p = 0.03) hours following gabapentin administration. Stress score was significantly reduced at 1.5 (p = 0.01) hours following gabapentin administration. Sedation score was significantly increased at 1.5 (p = 0.015) and 3 (p = 0.03) hours following gabapentin administration. Gabapentin had no significant effect on heart rate, compliance score, or ocular values measured in this study.

CONCLUSIONS

Gabapentin reduces stress and increases sedation at 1.5 h after treatment, with no significant effect on horizontal pupil diameter, intraocular pressure or Schirmer tear test-1 results.

Does gabapentin impact response to anticholinergics for overactive bladder?

INTRODUCTION AND HYPOTHESIS

It is unknown whether gabapentin modulates the therapeutic effect of anticholinergics (AC) in patients with overactive bladder. We hypothesized that pre-existing gabapentin use would improve response rates in these patients.

METHODS

Female patients treated with AC between 2010-2018 were identified. Data were collected on gabapentin use, indication, dose and duration of use as well as demographic and clinical characteristics. Patients were stratified by those that only took AC and those that took both AC and gabapentin ("combination therapy"). Response was determined through chart review. Descriptive statistics were expressed as medians and interquartile ranges (IQR). Pairwise analysis was performed using Wilcoxon rank-sum. Multivariable logistic regression was used to identify independent variables predicting response. A subgroup analysis was performed in patients with chronic pain disorders.

RESULTS

Seven hundred fifty-six subjects met all criteria; 16.5% (n = 125) were on combination therapy. Those taking gabapentin were more likely to have chronic (49.6% vs. 22.5%, p < 0.001) or neuropathic pain (25.6% vs. 9.4%, p < 0.001) and to use narcotics (41.6% vs. 15.5%, p < 0.001). Patients taking combination therapy were not more likely to improve compared to patients taking AC alone (41.6% vs. 47.7%, p = 0.211), which persisted after adjusting for confounders (aOR = 1.02, 95% CI: 0.63-1.65). In the 182 patients with chronic pain, those receiving combination therapy were more likely to respond than those taking AC alone (35.2% vs. 21.9%, p = 0.0015), although this did not persist after adjusting for confounders (aOR = 1.15, 95% CI: 0.70-1.90).

CONCLUSIONS

Pre-existing gabapentin use does not seem to influence response to AC in patients with overactive bladder.

Pharmacological use of gamma-aminobutyric acid derivatives in osteoarthritis pain management: a systematic review

Background

Pain is the major complication of osteoarthritis (OA) patients and is a decisive symptom for medical intervention. Gamma-aminobutyric acid (GABA) derivatives are optional painkillers but not widely used in pain management of OA patients. We synthesized the efficacy and safety of GABA derivatives for OA pain management.

Methods

We searched Medline, Cochrane CENTRAL, Embase, and ClinicalTrals.gov from inception to 13 October 2021 and included randomized controlled trials (RCTs) comparing the efficacy and safety of GABA derivatives with placebo or standard control in OA pain management. Two independent reviewers extracted data and assessed these studies for risk of bias using Cochrane Collaboration’s tool for RCT.

Results

In total, three eligible RCTs (n = 3) meeting the eligibility criteria were included. Among these RCTs, one focused on hand OA pain management, while two RCTs focused on knee OA. In hand OA, pregabalin reduced numerical rating scale (NRS) score and the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) pain score significantly compared with placebo, and caused 55 AEs. In knee OA, pregabalin reduced visual analogue scale (VAS) score and the Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain score significantly with no recorded adverse event (AE). Meanwhile, in knee OA, gabapentin reduced both VAS score and WOMAC pain score compared with acetaminophen and caused 9 AEs.

Conclusions

GABA derivatives seem to be effective and safe in OA pain management. However, future researches with large sample size are needed to further prove the efficacy of GABA derivatives in OA pain control.

Trial registration: CRD42021240225.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41927-022-00257-z.

Systematic Review of Voltage-Gated Calcium Channel α2δ Subunit Ligands for the Treatment of Chronic Neuropathic Pain and Insight into Structure-Activity Relationship (SAR) by Pharmacophore Modeling

BACKGROUND

Neuropathic pain (NP) is a complex symptom related to the nerve damage. The discovery of new drugs for treating chronic NP has been continuing for several decades, while more progress is still needed to be made because of the unsatisfactory efficacy and the side effects of the currently available drugs. Among all the approved drugs for chronic NP, voltage-gated calcium channel (VGCC) α2δ subunit ligands, also known as gabapentinoids, are among the first-line treatment and represent a class of efficacious and relatively safe therapeutic agents. However, new strategies are still needed to be explored due to the unsatisfied response rate.

OBJECTIVES

To review the latest status of the discovery and development of gabapentinoids for the treatment of chronic NP by covering both the marketed and the preclinical/clinical ones. To analyze the structure-activity relationship (SAR) of gabapentinoids to facilitate the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

METHODS

We searched PubMed Central, Embase, Cochrane Library, Web of Science, Scopus and Espacenet for the literature and patents of diabetic peripheral neuropathic pain, postherpetic neuralgia, fibromyalgia, voltage-gated calcium channel α2δ subunit and related therapeutic agents from incipient to June 10, 2021. The SAR of gabapentinoids were analyzed by pharmacophore modeling using Phase module in Schrödinger suite.

RESULTS

A variety of gabapentinoids were identified as VGCC α2δ ligands that have ever been under development for the treatment of chronic NP. Among them, four gabapentinoids are marketed, one is at the active late clinical trials, and eight have been discontinued. Pharmacophore models were generated by using Phase module in Schrödinger suite, and common pharmacophores were predicted based on pharmacophoric features and analyzed.

CONCLUSION

The latest progress of the discovery and development of gabapentinoids for the treatment of chronic NP was reviewed. Moreover, the structure-activity relationship (SAR) of gabapentinoids is analyzed by pharmacophore modeling, which will be valuable for the future design of structurally novel therapeutic agents targeting VGCC α2δ subunit.

The teratogenic effect of pregabalin on heart, liver and kidney in rats: a light microscopic, electron microscopic and immunohistochemical study

BACKGROUND

Pregabalin (PGB) was approved as new anti-epileptic drugs with little information about its teratogenic effect.

AIM OF THE WORK

to evaluate the developmental toxicity of PGB.

MATERIALS AND METHODS

60 pregnant albino rats were divided into three groups. PGB (500 mg/kg body weight/day) was given to group II, PGB (1250 mg/kg body weight/day) was given to Group III and no medications were given to group I. The pups were normally delivered. Liver, kidney and heart specimens were prepared for histological, immunohistochemical, and morphometric studies.

RESULTS

A dose of 500 mg of PGB had minimal toxic effects in the form of mild collagen deposition and moderate positive caspase-3 immunoexpression. PGB dose of 1250 mg/kg induced gross toxic effects in form of degenerated cardiac myofibres, ruptured blood vessels, vacuolations in the renal cortex, fibrosis and strong positive caspase-3 immunoexpression.

CONCLUSION

PGB at dose of 500 mg/kg revealed minimal toxic changes. PGB cause embryotoxicity in a dose-dependent manner, as the higher dose induced more degenerative changes.

The σ1 Receptor and the HINT1 Protein Control α2δ1 Binding to Glutamate NMDA Receptors: Implications in Neuropathic Pain

Nerve injury produces neuropathic pain through the binding of α2δ1 proteins to glutamate N-methyl-D-aspartate receptors (NMDARs). Notably, mice with a targeted deletion of the sigma 1 receptor (σ1R) gene do not develop neuropathy, whereas mice lacking the histidine triad nucleotide-binding protein 1 (Hint1) gene exhibit exacerbated allodynia. σ1R antagonists more effectively diminish neuropathic pain of spinal origin when administered by intracerebroventricular injection than systemically. Thus, in mice subjected to unilateral sciatic nerve chronic constriction injury (CCI), we studied the participation of σ1Rs and HINT1 proteins in the formation of α2δ1-NMDAR complexes within the supraspinal periaqueductal gray (PAG). We found that δ1 peptides required σ1Rs in order to interact with the NMDAR NR1 variant that contains the cytosolic C1 segment. σ1R antagonists or low calcium levels provoke the dissociation of σ1R-NR1 C1 dimers, while they barely affect the integrity of δ1-σ1R-NR1 C1 trimers. However, HINT1 does remove δ1 peptides from the trimer, thereby facilitating the subsequent dissociation of σ1Rs from NMDARs. In σ1R-/- mice, CCI does not promote the formation of NMDAR-α2δ1 complexes and allodynia does not develop. The levels of α2δ1-σ1R-NMDAR complexes increase in HINT1-/- mice and after inducing CCI, degradation of α2δ1 proteins is observed. Notably, σ1R antagonists but not gabapentinoids alleviate neuropathic pain in these mice. During severe neuropathy, the metabolism of α2δ1 proteins may account for the failure of many patients to respond to gabapentinoids. Therefore, σ1Rs promote and HINT1 proteins hinder the formation α2δ1-NMDAR complexes in the PAG, and hence, the appearance of mechanical allodynia depends on the interplay between these proteins.

An Update on Postoperative Opioid Use and Alternative Pain Control Following Spine Surgery

Opioids are commonly prescribed postoperatively for pain control, especially in spine surgery. Not only does this pose concerns for potential abuse, but it also has been shown to worsen certain outcomes. Risk factors for increased use include preoperative opioid use, female sex, psychiatric diagnoses, and drug and alcohol use. Over the past few decades, there have been increasing efforts mostly spearheaded by governmental agencies to decrease postoperative opioid use via opioid prescription limitation laws regulating the number of days and amounts of analgesics prescribed and promotion of the use of enhanced recovery after surgery (ERAS) protocols, multimodal pain regimens, epidural catheters, and ultrasound-guided peripheral nerve blocks. These strategies collectively have been efficacious in decreasing overall opioid use and better controlling patients' postoperative pain while simultaneously improving other outcomes such as postoperative nausea, vomiting, and length of stay. With an aging population undergoing an increasing number of spinal surgeries each year, it is now more important than ever to continue these efforts to improve the quality and safety of pain control methods after spinal surgery and limit the transition of acute management to the development of opioid dependence and addiction long-term.

Input-dependent synaptic suppression by pregabalin in the central amygdala in male mice with inflammatory pain

Pregabalin (PGB) is a synthetic amino acid compound most widely prescribed for chronic peripheral and central neuropathic pain. PGB is a ligand for the α2δ1 subunit of voltage-dependent calcium channels, and its binding reduces neurotransmitter release and thus inhibits synaptic transmission. The central nucleus of the amygdala (CeA) is a kernel site for the enhanced nociception-emotion link in chronic pain. The nociceptive information is conveyed to the CeA via the following two pathways: 1) the pathway arising from the basolateral amygdala (BLA), which carries nociceptive information mediated by the thalamocortical system, and 2) that arising from the external part of the pontine lateral parabrachial nucleus (LPB), that forms the final route of the spino-parabrachio-amygdaloid pathway that conveys nociceptive information directly from the superficial layer of the spinal dorsal horn. We compared the effects of PGB on the excitatory postsynaptic currents of neurons in the right CeA in response to electrical stimulation of BLA and LPB pathways using the whole-cell patch-clamp technique. Inflammatory pain was induced by intraplantar injection of formalin solution at the left hind paw. At eight hours post-formalin, PGB reduced EPSCs amplitude of the BLA-to-CeA synaptic transmission, accompanied by a significant increase in the PPR, suggesting a decreased release probability from the presynaptic terminals. In addition, these effects of PGB were only seen in inflammatory conditions. PGB did not affect the synaptic transmission at the LPB-to-CeA pathway, even in formalin-treated mice. These results suggest PGB improves not simply the aberrantly enhanced nociception but also various pain-associated cognitive and affective consequences in patients with chronic nociplastic pain.

Drug Repositioning: Antimalarial Activities of GABA Analogs in Mice Infected with Plasmodium berghei

BACKGROUND

Drug repositioning is becoming popular due to the development of resistance to almost all the recommended antimalarials. Pregabalin and gabapentin are chemical analogs of gamma- aminobutyric acid (GABA) approved for the treatment of epilepsy and neuropathic pain.

OBJECTIVE

This study investigates acute toxicities and antimalarial activities of pregabalin and gabapentin in the murine malarial model.

METHODS

Acute toxicities were assessed using the method of Lorke, while curative activities were assessed by the administration of serial doses of pregabalin and gabapentin to Plasmodium berghei infected mice. Pregabalin was further investigated for its prophylactic activity, and curative potential when combined with either artesunate or amodiaquine. All drugs were freshly prepared and administered orally. Thin films were collected, stained, and observed under the microscope for the estimation of parasitemia and calculation of percentage chemoinhibition or chemoprevention. In pregabalin -artesunate or -amodiaquine combination aspect of this study, survival day post-infection (SDPI) was recorded, while parasitemia was re-estimated for animals that survived till day 28.

RESULTS

The oral LD50 of gabapentin, as well as pregabalin, was >5,000 mg/kg. Gabapentin at 100 and 200 mg/Kg demonstrated 35.64% and -12.78% chemoinhibition, respectively, while pregabalin demonstrated 75.60% and 100.00% chemoinhibition at doses of 12.5 and 25 mg/Kg, respectively. Moreover, pregabalin at individual doses of 25, 50 mg/Kg, and in combination with either artesunate or amodiaquine demonstrated 100.00% chemoinhibition. In its prophylactic study, pregabalin was found to be 100% chemopreventive at individual doses of 12.5 and 25 mg/Kg.

CONCLUSION

Both GABA analogs have antimalarial properties, but pregabalin proved to be more efficacious.

Microglial IL-10 and β-endorphin expression mediates gabapentinoids antineuropathic pain

Gabapentinoids are recommended first-line treatments for neuropathic pain. They are neuronal voltage-dependent calcium channel α2δ-1 subunit ligands and have been suggested to attenuate neuropathic pain via interaction with neuronal α2δ-1 subunit. However, the current study revealed their microglial mechanisms underlying antineuropathic pain. Intrathecal injection of gabapentin, pregabalin and mirogabalin rapidly inhibited mechanical allodynia and thermal hyperalgesia, with projected ED₅₀ values of 30.3, 6.2 and 1.5 µg (or 176.9, 38.9 and 7.2 nmol) and E_max values of 66%, 61% and 65% MPE respectively for mechanical allodynia. Intrathecal gabapentinoids stimulated spinal mRNA and protein expression of IL-10 and β-endorphin (but not dynorphin A) in neuropathic rats with the time point parallel to their inhibition of allodynia, which was observed in microglia but not astrocytes or neurons in spinal dorsal horns by using double immunofluorescence staining. Intrathecal gabapentin alleviated pain hypersensitivity in male/female neuropathic but not male sham rats, whereas it increased expression of spinal IL-10 and β-endorphin in male/female neuropathic and male sham rats. Treatment with gabapentin, pregabalin and mirogabalin specifically upregulated IL-10 and β-endorphin mRNA and protein expression in primary spinal microglial but not astrocytic or neuronal cells, with EC₅₀ values of 41.3, 11.5 and 2.5 µM and 34.7, 13.3 and 2.8 µM respectively. Pretreatment with intrathecal microglial metabolic inhibitor minocycline, IL-10 antibody, β-endorphin antiserum or μ-opioid receptor antagonist CTAP (but not κ- or δ-opioid receptor antagonists) suppressed spinal gabapentinoids-inhibited mechanical allodynia. Immunofluorescence staining exhibited specific α2δ-1 expression in neurons but not microglia or astrocytes in the spinal dorsal horns or cultured primary spinal cells. Thus the results illustrate that gabapentinoids alleviate neuropathic pain through stimulating expression of spinal microglial IL-10 and consequent β-endorphin.

Electroacupuncture prevents cocaine-induced conditioned place preference reinstatement and attenuates ΔFosB and GluR2 expression

Acupuncture has been used for treating drug addiction since the 1970s, but little is known about the mechanisms by which acupuncture affects drug cue-induced relapse. The transcription factor delta-FosB (ΔFosB) plays a critical role in behavior and pathology after chronic use of cocaine. ΔFosB regulates glutamate receptor signaling and dendritic spine morphology in animal models. This experimental study compared the effects of electroacupuncture (EA) at acupoints LI4 and LI11 with those of another potentially beneficial intervention, gabapentin (GBP), alone or in combination, on reinstatement of cocaine-induced conditioned place preference (CPP) and levels of ΔFosB and glutamate receptor subunit 2 (GluR2) expression in the nucleus accumbens (NAc). EA at LI4 and LI11 significantly prevented cue-induced cocaine CPP reinstatement, whereas needle insertion without electrical stimulation at these acupoints had no such effect. EA also significantly attenuated cocaine-induced increases in ΔFosB and GluR2 expression in the NAc. Unexpectedly, these effects were reversed when GBP was combined with EA. Treatment with EA at LI4 and LI11 prevented cocaine-induced increases in dendritic spine density in the NAc core and shell. Our results suggest that EA at LI4 and LI11 may prevent cocaine relapse by modulating ΔFosB and GluR2 expression, as well as dendritic spine density.

Stem Cell Therapy for Modulating Neuroinflammation in Neuropathic Pain

Neuropathic pain (NP) is a complex, debilitating, chronic pain state, heterogeneous in nature and caused by a lesion or disease affecting the somatosensory system. Its pathogenesis involves a wide range of molecular pathways. NP treatment is extremely challenging, due to its complex underlying disease mechanisms. Current pharmacological and nonpharmacological approaches can provide long-lasting pain relief to a limited percentage of patients and lack safe and effective treatment options. Therefore, scientists are focusing on the introduction of novel treatment approaches, such as stem cell therapy. A growing number of reports have highlighted the potential of stem cells for treating NP. In this review, we briefly introduce NP, current pharmacological and nonpharmacological treatments, and preclinical studies of stem cells to treat NP. In addition, we summarize stem cell mechanisms—including neuromodulation in treating NP. Literature searches were conducted using PubMed to provide an overview of the neuroprotective effects of stem cells with particular emphasis on recent translational research regarding stem cell-based treatment of NP, highlighting its potential as a novel therapeutic approach.

Mirogabalin, a novel ligand for α2δ subunit of voltage-gated calcium channels, improves cognitive impairments in repeated intramuscular acidic saline injection model rats, an experimental model of fibromyalgia

Mirogabalin is a novel potent and selective ligand for the α₂δ subunit of voltage-gated calcium channels, and shows potent and sustained analgesic effects in neuropathic pain and fibromyalgia models. Fibromyalgia is often associated with multiple comorbid symptoms, such as anxiety, depression and cognitive impairment. In the present study, we investigated the effects of mirogabalin on cognitive impairments in an experimental animal model for fibromyalgia, repeated intramuscular acidic saline injection model (Sluka model) rats. Male rats received two repeated intramuscular injections of pH 4 acidic saline into their gastrocnemius muscle. After developing mechanical hypersensitivity as identified in the von Frey test, the animals received the test substance orally once daily for 13 days and were subjected to four cognitive function tests, (Y-maze, novel object recognition, Morris water maze and step-through passive avoidance). Sluka model rats showed cognitive impairments in all four tests. Oral administration of mirogabalin (3 and 10 mg/kg) improved the cognitive impairments in these rats. In conclusion, mirogabalin improved the impaired cognitive function in Sluka model rats. It may thus also alleviate cognitive impairments as well as painful symptoms in fibromyalgia patients.

Do gabapentin or pregabalin directly modulate the µ receptor?

BACKGROUND

Pregabalin and gabapentin improve neuropathic pain symptoms but there are emerging concerns regarding their misuse. This is more pronounced among patients with substance use disorder, particularly involving opioids. Co-ingestion of gabapentinoids with opioids is increasingly identified in opioid related deaths, however, the molecular mechanism behind this is still unclear. We have sought to determine whether pregabalin or gabapentin directly modulates acute μ receptor signaling, or μ receptor activation by morphine.

METHODS

The effects of pregabalin and gabapentin were assessed in HEK 293 cells stably transfected with the human μ receptor. Their effect on morphine induced hyperpolarization, cAMP production and ERK phosphorylation were studied using fluorescent-based membrane potential assay, bioluminescence based CAMYEL assay and ELISA assay, respectively. Pregabalin/gabapentin effects on morphine-induced hyperpolarization were also investigated in AtT20 cells.

RESULTS

Pregabalin or gabapentin (1 µM, 100 µM each) did not activate the µ receptor or affect K channel activation or ERK phosphorylation produced by morphine. Neither drug affected the desensitization of K channel activation produced by prolonged (30 min) application of morphine. Gabapentin (1 µM, 100 µM) and pregabalin (1 µM) did not affect inhibition of forskolin-stimulated cAMP production by morphine. However, pregabalin (100 µM) potentiated forskolin mediated cAMP production, although morphine still inhibited cAMP levels with a similar potency to control.

DISCUSSION

Pregabalin or gabapentin did not activate or modulate µ receptor signaling in three different assays. Our data do not support the hypothesis that gabapentin or pregabalin augment opioid effects through direct or allosteric modulation of the µ receptor. Pregabalin at a high concentration increases cAMP production independent of morphine. The mechanism of enhanced opioid-related harms from co-ingestion of pregabalin or gabapentin with opioids needs further investigation.

A Critical Review on Analytical Methods for Recently Approved FDC Drugs: Pregabalin and Etoricoxib

Fixed-dose combinations (FDCs) refer to products containing two or more active ingredients combined in a single dosage form. The FDCs are justified because of several advantages. These are a) potentiating therapeutic efficacy, b) reducing the incidences of adverse drug effects, c) having pharmacokinetic advantages, d) reducing pills burden, e) reducing the dose of individual drugs and f) decreasing the drug resistance development. A recently approved FDC of Pregabalin IP (75 mg) and Etoricoxib (60 mg) recommended to control neuropathic chronic back pain. Analytical methods are available for individual quantitation of pregabalin (PGB) and etoricoxib (ETC), but an effective and reliable analytical method has not been reported for their combination. Thus, the objective of this literature survey was to gather information on various analytical instrumental methods used so far for the individual quantitation of PGB and ETC in various matrices. Such data would be useful to the scientific community to develop a novel analytical method for the analysis of recently approved FDC of PGB and ETC. Various scientific databases were explored to meet the objectives, and the information is synchronized. The reported methods are high-performance liquid chromatography (48% & 53%), hyphenated techniques (54% & 21%), spectroscopy (50% & 34%), and high-performance thin-layer chromatography, or thin-layer chromatography (6% & 13%) for pregabalin and etoricoxib, respectively. All these methods were specific and selective for the analysis of individual drugs.

Retinal teratogenicity of pregabalin in chick embryo model

BACKGROUND

Pregabalin is a gamma-aminobutyric acid analog that binds to the α2-δ subunits of the pre-synaptic voltage-dependent calcium channels of nerves with a high affinity and selectivity. In this study, the retinal teratogenic potential of pregabalin was investigated in a chick embryo model.

MATERIALS AND METHODS

Fertilised chicken eggs were divided into groups for administration with different doses of pregabalin. All eggs were opened on the 10th day of incubation. The embryos were dissected and the effects of pregabalin on the retina were investigated histopathologically, morphometrically, and immunohistochemically (Caspase-3).

RESULTS

There was no statistically significant difference between the low dose pregabalin, control, or vehicle control groups in terms of the number of retina layers and retinal thickness. Medium and high dose pregabalin caused a statistically significant decrease in the number of retina layers, as well as sensory retinal and pigment epithelium layer thicknesses. The outer nuclear and outer plexiform layer did not form in the group administered a medium dose. Similarly, the outer nuclear, outer plexiform, inner nuclear, and inner plexiform layer did not form in the high-dose group. No statistically significant difference was observed between the groups in terms of cellular damage and Caspase-3 expression.

CONCLUSION

The use of pregabalin during pregnancy compromises retinal development in a dose-dependent manner. The use of pregabalin in pregnancy causes the aforementioned defects in this system and it may have developmental effects that needs to be further evaluated.

ALIAmides Update: Palmitoylethanolamide and Its Formulations on Management of Peripheral Neuropathic Pain

Neuropathic pain results from lesions or diseases of the somatosensory nervous system and it remains largely difficult to treat. Peripheral neuropathic pain originates from injury to the peripheral nervous system (PNS) and manifests as a series of symptoms and complications, including allodynia and hyperalgesia. The aim of this review is to discuss a novel approach on neuropathic pain management, which is based on the knowledge of processes that underlie the development of peripheral neuropathic pain; in particular highlights the role of glia and mast cells in pain and neuroinflammation. ALIAmides (autacoid local injury antagonist amides) represent a group of endogenous bioactive lipids, including palmitoylethanolamide (PEA), which play a central role in numerous biological processes, including pain, inflammation, and lipid metabolism. These compounds are emerging thanks to their anti-inflammatory and anti-hyperalgesic effects, due to the down-regulation of activation of mast cells. Collectively, preclinical and clinical studies support the idea that ALIAmides merit further consideration as therapeutic approach for controlling inflammatory responses, pain, and related peripheral neuropathic pain.

Evaluation of the Efficacy of Prolonged Pregabalin Administration Before and After Surgery in Patients Undergoing Arthroscopic Anterior Cruciate Ligament Repair: A Prospective, Randomized, Double-blind Study

CONTEXT AND OBJECTIVE

Reconstruction of the knee ligament causes postoperative pain and delayed rehabilitation.

OBJECTIVE

The primary objective of this study was to evaluate the effect of a prolonged preoperative and postoperative pregabalin use for arthroscopic anterior cruciate ligament repair.

MATERIALS AND METHODS

Group 1 (N=25) patients received pregabalin 75 mg/d, and group 2 (N=25) received placebo, 7 days before and 7 days after surgery. Spinal anesthesia was performed using 0.5% hyperbaric bupivacaine (15 mg). The following were evaluated: pain intensity immediately after the surgery, and 12 hours, 24 hours, 1 week, 2 weeks, 1 month, and 2 months after the surgery using a Numerical Rating Scale; dose of postoperative supplementary analgesic for 2 months; time to first analgesic requirement; and side effects during 2 months. For supplementation, the participants received 1 g dipyrone; if there was no pain control, 100 mg ketoprofen was administered; if there was no effect, 100 mg tramadol was administered; and if there was no pain control, 5 mg intravenous morphine was administered until pain control.

RESULTS

There was no difference between the groups with regard to pain intensity (P=0.077). In the pregabalin group, morphine consumption was lower at 12 hours (P=0.039) and 24 hours (P=0.044) after surgery, and the consumption of tramadol and ketoprofen was lower 24 hours after surgery. There was no significant difference in the incidence of nausea and vomiting. Dizziness was higher in the pregabalin group (group 1=12 patients; group 2=3 patients; P=0.005).

DISCUSSION

A prolonged preoperative and postoperative pregabalin prescription for anterior cruciate ligament repair decreased the need for supplementary analgesics during the first 24 postoperative hours but increased dizziness.

Pregabalin as a Pain Therapeutic: Beyond Calcium Channels

Initially developed to generate new treatments for epilepsy, gabapentin, and pregabalin (“gabapentinoids”) were engineered to mimic the action of GABA and to modulate GABA metabolism. Rather than their intended pharmacological action on GABA neurotransmission, instead, they exhibit a high affinity for the α2δ-1 and α2δ-2 subunits of voltage-activated calcium channels, wherein binding of gabapentinoids inhibits cellular calcium influx and attenuates neurotransmission. Despite a lack of activity on GABA levels, gabapentin and pregabalin are effective at suppressing seizures and subsequently approved as a new class of antiepileptic therapy for partial-onset epilepsy. Through the same hypothesized molecular mechanism and by controlling neuronal hyperexcitability, gabapentinoids demonstrate clear efficacy in pain management, which has arguably been their most extensively prescribed application to date. In this review, we focus on pregabalin as a second-generation gabapentinoid widely employed in the treatment of a variety of pain conditions. We also discuss the wider functional roles of α2δ subunits and the contributions that pregabalin might play in affecting physiological and pathophysiological processes.

Pregabalin-associated movement disorders: A literature review

Central nervous system adverse effects are commonly reported with pregabalin (PGB). On the other hand, movement disorders (MDs) associated with this drug were rarely described. However, their occurrence could significantly affect the quality of life of PGB users. This literature review aims to evaluate the clinical epidemiological profile, pathological mechanisms, and management of PGB-associated MDs. Relevant reports in six databases were identified and assessed by two reviewers without language restriction. A total of 46 reports containing 305 cases from 17 countries were assessed. The MDs encountered were as follows: 184 individuals with ataxia, 61 with tremors, 39 with myoclonus, 8 with parkinsonism, 1 with restless legs syndrome, 1 with dystonia, 1 with dyskinesia, and 1 with akathisia. The mean age was 62 years (range: 23-94). The male sex was slightly predominant with 54.34%. The mean PGB dose when the MD occurred was 238 mg, and neuropathic pain was the most common indication of PGB. The time from PGB start to MD was < 1 month at 75%. The time from PGB withdrawal to recovery was < 1 week at 77%. All the individuals where the follow-up was reported had a full recovery. The most common management was PGB withdrawal. In the literature, the majority of the cases did not report information about timeline events, neurological examination details, or electrodiagnostic studies. The best management for all MDs is probably PGB withdrawal. If the patient is on dialysis program, perhaps an increased number of sessions will decrease recovery time. Furthermore, the addition of a benzodiazepine could accelerate recovery.

Repurposed molecules for antiepileptogenesis: Missing an opportunity to prevent epilepsy?

Prevention of epilepsy is a great unmet need. Acute central nervous system (CNS) insults such as traumatic brain injury (TBI), cerebrovascular accidents (CVA), and CNS infections account for 15%-20% of all epilepsy. Following TBI and CVA, there is a latency of days to years before epilepsy develops. This allows treatment to prevent or modify postinjury epilepsy. No such treatment exists. In animal models of acquired epilepsy, a number of medications in clinical use for diverse indications have been shown to have antiepileptogenic or disease-modifying effects, including medications with excellent side effect profiles. These include atorvastatin, ceftriaxone, losartan, isoflurane, N-acetylcysteine, and the antiseizure medications levetiracetam, brivaracetam, topiramate, gabapentin, pregabalin, vigabatrin, and eslicarbazepine acetate. In addition, there are preclinical antiepileptogenic data for anakinra, rapamycin, fingolimod, and erythropoietin, although these medications have potential for more serious side effects. However, except for vigabatrin, there have been almost no translation studies to prevent or modify epilepsy using these potentially "repurposable" medications. We may be missing an opportunity to develop preventive treatment for epilepsy by not evaluating these medications clinically. One reason for the lack of translation studies is that the preclinical data for most of these medications are disparate in terms of types of injury, models within different injury type, dosing, injury-treatment initiation latencies, treatment duration, and epilepsy outcome evaluation mode and duration. This makes it difficult to compare the relative strength of antiepileptogenic evidence across the molecules, and difficult to determine which drug(s) would be the best to evaluate clinically. Furthermore, most preclinical antiepileptogenic studies lack information needed for translation, such as dose-blood level relationship, brain target engagement, and dose-response, and many use treatment parameters that cannot be applied clinically, for example, treatment initiation before or at the time of injury and dosing higher than tolerated human equivalent dosing. Here, we review animal and human antiepileptogenic evidence for these medications. We highlight the gaps in our knowledge for each molecule that need to be filled in order to consider clinical translation, and we suggest a platform of preclinical antiepileptogenesis evaluation of potentially repurposable molecules or their combinations going forward.

[A double blind placebo controlled randomized clinical trial of the efficacy and safety of pregabalin in induction of remission in patients with alcohol dependence]

AIM

To study the efficacy of pregabalin for relapse prevention and reduction of drinking in patients with alcohol dependence.

MATERIAL AND METHODS

One hundred recently detoxified out-patients with alcohol dependence were randomly assigned to one of two treatment groups. Patients of the first group (n=50; 38 men, 12 women, age 43.0±1.27) received pregabalin (150 mg once a day at night time) for 3 months, while patients of the second group (n=50; 45 men, 5 women, age 45.92±1.4) received identically looking placebo. All patients received standardized manualized weekly counseling (medical management). Drinking was measured on the weekly basis with Time Line Follow Back technique and GGT enzyme activity. Also, craving for alcohol, depression, and anxiety were measured weekly with the number of scales.

RESULTS

Kaplan-Meier survival analysis demonstrated significantly higher retention in treatment and in remission in the pregabalin group (lower drop out and relapse rate) mediana (CL)-12 (10.4-13.6) weeks in the pregabalin group vs. 6 (4.5-7.5) in the placebo group, Log Rank Mantel-Cox test = 0.005). Proportion of patients, who completed treatment in the pregabalin group, was significantly higher compared to the placebo group: 50% vs. 24%. Mean duration of participation in the treatment program was also higher in the pregabalin group: 9.1±0.5 weeks vs. 7.1±0.5 in the placebo group. General linear model demonstrated the significant treatment group effect on: (1) total alcohol consumption (TAC) (mean grams of alcohol per day) with lower TAC in the pregabalin group and (2) on the number of heavy drinking days (NHDD) with lower NHDD in the pregabalin group. Mean NHDD per patient for the period of participation in the study was lower in the pregabalin group (3.6±0.7 vs. 6.4±0.8; p=0.009), while the mean number of abstinent (sober) days was higher (55.9±3.6 vs. 40.0±3.3; p=0.001). No significant differences between the two groups were found in the scores on craving for alcohol, depression and anxiety scales. GGT activity was also similar in both groups throughout the study with no significant between group differences. The rate of adverse events (sleepiness, dizziness, and headache) was insignificantly higher in the pregabalin group compared with the placebo group. All adverse events were mild, gradually disappeared, and did not require any medication.

CONCLUSION

Results of this study provide evidence that pregabalin in a low dose of 150 mg per day is an effective and safe medication for relapse prevention and reduction of drinking in patients with alcohol dependence.

Anxiolytic effects of the novel α2δ ligand mirogabalin in a rat model of chronic constriction injury, an experimental model of neuropathic pain

RATIONALE

Psychiatric disorders such as anxiety and depression are frequently observed in neuropathic pain patients, and negatively impact their quality of life. Mirogabalin is a novel ligand for the α₂δ subunit of voltage-gated calcium channels and has unique binding characteristics to α₂δ subunits and potent and long-lasting analgesic effects in neuropathic pain models.

OBJECTIVES

To provide further information on the pharmacological profile of mirogabalin and its utility for chronic pain therapy, we investigated its anxiolytic effects in an experimental animal model for neuropathic pain.

METHODS

In chronic constriction injury (CCI) model rats, mechanical hypersensitivity was determined by the von Frey test. Anxiety- and depression-related behaviours were evaluated using the elevated plus maze test and forced swimming test, respectively.

RESULTS

CCI model rats showed sustained tactile allodynia followed by anxiety-related behaviours, not depression-related behaviours. The tactile allodynia (significant decreases in paw withdrawal threshold) developed within 2 weeks after model preparation, whereas the anxiety-related behaviours (significant decreases in the number of entries and time spent in open arms and significant increases in time spent in closed arms) were observed at 5 weeks but not 4 weeks after model preparation. Single oral administration of mirogabalin (3 or 10 mg/kg) dose-dependently alleviated the above-mentioned anxiety-related behaviours and tactile allodynia.

CONCLUSIONS

CCI model rats showed anxiety-related behaviours in a time-dependent manner in the elevated plus maze test. Mirogabalin alleviated both the anxiety-related behaviours and tactile allodynia in CCI model rats. Mirogabalin may provide effective anxiety relief as well as pain relief in patients with neuropathic pain.

Immediate and controlled-release pregabalin for the treatment of epilepsy

Introduction: Epilepsy is a common neurological disease requiring complex therapies, which are unable to achieve seizure control in 30% of patients. Poor adherence has been recognized as a possible determinant of drug-resistance. Prolonged-release formulations of antiepileptic drugs might help increase adherence and minimize side effects.Areas covered: Pregabalin (PGB) has peculiar pharmacodynamics and almost ideal pharmacokinetics, except for a short half-life and therefore requiring multiple daily dosing. PGB immediate-release (IR) is effective in focal-onset epilepsy (FOE), neuropathic pain, generalized anxiety disorder, and fibromyalgia, despite some tolerability issues, especially at higher doses. The controlled-release formulation (CR) shares PGB IR advantages and requires slight dose adjustments to guarantee bioavailability. In 2014, PGB CR (165 and 330 mg/day) failed to prove superior to placebo in a randomized placebo-controlled trial on 323 subjects with drug-resistant FOE, although it was just as tolerable. Therefore, PGB CR is not currently licensed for epilepsy.Expert opinion: Considering the disappointing results of the only controlled trial, PGB CR is unlikely to become an established epilepsy treatment anytime soon. Nevertheless, given its peculiar properties and potential advantages, PGB (in either formulation) should be further evaluated in specific populations of patients, especially fragile subjects with several comorbidities and complex polytherapies.

An update for epilepsy research and antiepileptic drug development: Toward precise circuit therapy

Epilepsy involves neuronal dysfunction at molecular, cellular, and circuit levels. The understanding of the mechanism of the epilepsies has advanced greatly in the last three decades, especially in terms of their cellular and molecular basis. However, despite the availability of ~30 anti-epileptic drugs (AEDs) with diverse molecular targets, there are still many challenges (e.g. drug resistance, side effects) in pharmacological treatment of epilepsies today. Because molecular mechanisms are integrated at the level of neuronal circuits, we suggest a shift in epilepsy treatment and research strategies from the "molecular" level to the "circuit" level. Recent technological advances have facilitated circuit mechanistic discovery at each level and have paved the way for many opportunities of novel therapeutic strategies and AED development toward precise circuit therapy.

Sensitivity of functional targeted neuropeptide evaluation in testing pregabalin analgesic efficacy in a rat model of osteoarthritis pain

The monosodium iodoacetate (MIA)-induced joint degeneration in rats is the most used animal model to screen analgesic drugs to alleviate osteoarthritis (OA) pain. This study aimed to evaluate the analgesic efficacy of pregabalin (PGB) in an MIA-induced OA model in rodents by using functional and neuroproteomic pain assessment methods. Treatment group included PGB in curative intent over 9 days compared to gold standard therapy (positive controls) and placebo (negative control). Functional assessments of pain (quantitative sensory testing and operant test) were performed concomitantly with spinal neuropeptides quantification. At day 21 post-OA induction, PGB in MIA rats reduced tactile allodynia (P = 0.028) and improved the place escape/avoidance behaviour (P = 0.04) compared to values recorded at last time-point before initiating analgesic therapy. All spinal neuropeptide concentrations, such as substance P, calcitonin gene-related peptide, bradykinin and somatostatin, came back to normal (non-affected) rat values, compared to their increase observed in MIA rats receiving the placebo (P < 0.0001). Initiated 13 days after chemical OA induction, repeated medication with PGB provided analgesia according to quantitative sensory testing, operant test and targeted neuropeptides pain assessment methods. This report highlights the interest of using reliable and sensitive methods like targeted neuropeptide quantification to detect the analgesic effects of a test article with concomitant functional assessments of pain when studying OA pain components.

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.

Analgesic effects of mirogabalin, a novel ligand for α2δ subunit of voltage-gated calcium channels, in experimental animal models of fibromyalgia

Mirogabalin, a novel ligand for the α₂δ subunit of voltage-gated calcium channels, is under the development for the treatment of neuropathic pain. Mirogabalin specifically and potently binds to α₂δ subunits, and it shows analgesic effects in both peripheral and central neuropathic pain models in rats. To expand pharmacological findings on mirogabalin and provide additional information of its potential for chronic pain therapy, we examined the effects of mirogabalin in 2 experimental models of fibromyalgia, namely, the intermittent cold stress model (ICS model) and the unilateral intramuscular acidic saline injection model (Sluka model). To induce chronic mechanical hypersensitivity, mice were placed under ICS conditions for 3 days, whereas rats were injected twice with acidic saline (pH 4) into the gastrocnemius muscle in a 4-day interval. The pain sensitivity was evaluated by the von Frey test. Long-lasting increases in pain response score or decreases in pain threshold to the von Frey stimulation were observed in both the ICS and Sluka models. Mirogabalin (1, 3, or 10 mg/kg, p.o.) dose-dependently alleviated the mechanical hypersensitivity, with significant effects persisting at 6 or 8 h following administration. The standard α₂δ ligand, pregabalin (30 mg/kg, p.o.), also significantly reduced the mechanical hypersensitivity. In summary, mirogabalin showed analgesic effects in the ICS model mice and in the Sluka model rats. Therefore, mirogabalin may have the potential to provide effective pain relief in patients with fibromyalgia.

Influence of pregabalin on post-operative pain after laparoscopic cholecystectomy: A meta-analysis of randomised controlled trials

Background:

Pregabalin may have some potential in reducing post-operative pain after laparoscopic cholecystectomy. However, the results remain controversial. We conduct a systematic review and meta-analysis to explore the influence of pregabalin on post-operative pain after laparoscopic cholecystectomy.

Materials and Methods:

PubMed, Embase, Web of science, EBSCO and Cochrane Library databases have been systematically searched. Randomised controlled trials (RCTs) assessing the effect of pregabalin versus placebo on post-operative pain after laparoscopic cholecystectomy are included. The primary outcomes are pain scores at 8–12 h and 20–24 h. Secondary outcomes include sedation score, intraoperative fentanyl requirement, post-operative analgesic requirement, operative duration, post-operative nausea and vomiting, as well as respiratory depression. This meta-analysis is performed using the random-effect model.

Results:

Eight RCTs involving 528 patients were included in the meta-analysis. Overall, compared with control intervention after laparoscopic cholecystectomy, pregabalin treatment is found to significantly reduce pain scores at 20–24 h (Standard Mean difference [Std. MD] = −0.46; 95% confidence interval [CI] = −0.82–−0.10), and post-operative analgesic requirement (Std. MD = −2.64; 95% CI = −3.94–−1.33), but cannot substantially decrease pain scores at 8–12 h (Std. MD = −0.71; 95% CI = −1.70–0.27). In addition, pregabalin results in improved sedation score (Std. MD = 0.92; 95% CI = 0.55–1.29), but has no remarkable influence on intraoperative fentanyl requirement (Std. MD = 0.04; 95% CI = −0.30–0.39), operative duration (Std. MD = 0.34; 95% CI = −0.10–0.77), post-operative nausea and vomiting (Std. MD = 0.79; 95% CI = 0.59–1.11) as well as respiratory depression (Std. MD = 0.71; 95% CI = 0.17–3.02).

Conclusions:

Compared to control intervention after laparoscopic cholecystectomy, pregabalin treatment can significantly decrease pain scores at 20–24 h and post-operative analgesic requirement, with no increase in adverse events.

[Pharmacological, pharmacodynamics, and clinical profile of mirogabalin besylate (Tarlige® tablets 2.5 mg∙5 mg∙10 mg∙15 mg)]

Mirogabalin, a novel ligand for the α₂δ subunit of voltage-gated calcium channels, has been approved for the treatment of peripheral neuropathic pain including painful diabetic peripheral neuropathy (DPNP) and postherpetic neuralgia (PHN) in Japan. Mirogabalin showed potent and selective binding affinities for the α₂δ subunits, and slower dissociation rates for the α₂δ-1 subunit than for the α₂δ-2 subunit. It also showed potent and long-lasting analgesic effects in rat models of neuropathic pain, and wider safety margins for the central nervous system side effects. A pharmacological study using mutant mice demonstrated that the analgesic effects of mirogabalin were mediated by binding of the drug to the α₂δ-1 subunit, not the α₂δ-2 subunit. The pharmacological properties of mirogabalin can be associated with its unique binding characteristics. The bioavailability of mirogabalin is high and its plasma exposure increases dose-proportionally. Mirogabalin is mainly excreted via the kidneys in an unchanged form, thus, mirogabalin has a low possibility of undergoing drug-drug interaction, while dose adjustment based on the creatinine clearance level is specified in patients with renal impairment. In double-blind, placebo-controlled phase 3 studies in Asian patients with DPNP and PHN, mirogabalin showed significant and dose-dependent pain relief, and all tested doses of mirogabalin were well tolerated. In summary, mirogabalin has a balanced efficacy versus safety profile, and can provide an alternative therapeutic option for the treatment of peripheral neuropathic pain.

Duloxetine in patients with diabetic peripheral neuropathic pain in Japan: a randomized, doubleblind, noninferiority comparative study with pregabalin

Purpose

Duloxetine and pregabalin are recommended as first-line treatments for diabetic peripheral neuropathic pain (DPNP). However, studies have not reported a direct comparison between duloxetine and pregabalin. We conducted a postmarketing, randomized, double-blind study to assess the noninferiority of duloxetine compared with pregabalin after 12 weeks of treatment in adult patients with DPNP in Japan (NCT02417935).

Patients and methods

Patients (N = 303) with distal symmetrical DPNP were randomized to and were administered duloxetine (40–60 mg/day) or pregabalin (300–600 mg/day). The primary endpoint was the change from baseline in weekly mean of the 24-hour average pain score (numeric rating scale [NRS]). Noninferiority of duloxetine compared with pregabalin was assessed with the primary endpoint at week 12. Secondary measures, including night pain and worst pain, Brief Pain Inventory-Severity and Interference rating short form (BPI-SF), Clinical Global Impression of Improvement (CGI-I), Patient Global Impression of Improvement (PGI-I), and Neuropathic Pain Symptom Inventory (NPSI), health outcome measures (EuroQol 5-Dimension index and VAS), and safety were also assessed.

Results

For the 24-hour NRS average pain score, the difference between the duloxetine and pregabalin groups was 0.072 (95% CI: – 0.295, 0.439), and the upper bound of the 95% CI (0.439) did not exceed the predefined noninferiority margin (0.51), at the end of the study period. For secondary outcome measures (night pain, worst pain, BPI-SF, CGI-I, PGI-I, NPSI) and health outcome measures, both the duloxetine and pregabalin treatment groups showed an improvement from baseline with no significant between-group difference. Duloxetine and pregabalin were well tolerated and the safety profiles were consistent with previously reported results.

Conclusion

This study demonstrated the noninferior efficacy of duloxetine compared with pregabalin in the treatment of adult patients with DPNP. The safety analyses showed an acceptable tolerability based on safety profiles of duloxetine and pregabalin.

Cerebral Biochemical Effect of Pregabalin in Patients with Painful Diabetic Neuropathy: A Randomized Controlled Trial

INTRODUCTION

With the development of new neuroimaging tools it has become possible to assess neurochemical alterations in patients experiencing chronic pain and to determine how these factors change during pharmacological treatment. The goal of this study was to examine the exact neurochemical mechanism underlying pregabalin treatment, utilizing magnetic resonance spectroscopy (¹H-MRS), in a population of patients with painful diabetic polyneuropathy (PDN), with the overall aim to ultimately objectify the clinical effect of pregabalin.

METHODS

A double blind, randomized, placebo-controlled study was conducted. A total of 27 patients with PDN were enrolled in the study, of whom 13 received placebo treatment (control group) and 14 received pregabalin (intervention group). Pregabalin treatment consisted of stepwise dose escalation over the study period from 75 mg daily ultimately to 600 mg daily. ¹H-MRS was performed at 3T on four regions of interest in the brain: the rostral anterior cingulate cortex (rACC), left and right thalamus and prefrontal cortex. The absolute concentrations of N-acetyl aspartate, glutamate, glutamine, gamma-amino-butyric-acid (GABA), glucose (Glc) and myo-inositol (mINS) were determined using LCModel.

RESULTS

The concentration of most neurometabolites in the placebo and pregabalin group did not significantly differ over time, with only a small significant difference in Glc level in the left thalamus (p = 0.049). Comparison of the effects of the different doses revealed significant differences for mINS in the rACC (baseline 2.42 ± 1.21 vs. 450 mg 1.58 ± 0.94; p = 0.022) and dorsolateral prefrontal cortex (75 mg 2.38 ± 0.89 vs. 450 mg 1.59 ± 0.85; p = 0.042) and also for GABA in the rACC (75 mg 0.53 ± 0.51 vs. 225 mg 0.28 ± 0.19; p = 0.014).

CONCLUSION

No differences were found in metabolite concentrations between the placebo (control) and intervention groups, but some differences, although small, were found between the different doses.

TRIAL REGISTRATION

This study is registered at ClinicalTrials.gov (NCT01180608).

FUNDING

Lyrica Independent Investigator Research Award (LIIRA) 2010 (Pfizer) funded the study.

The α2δ Subunit and Absence Epilepsy: Beyond Calcium Channels?

Background:

Spike-wave discharges, underlying absence seizures, are generated within a cortico-thalamo-cortical network that involves the somatosensory cortex, the reticular thalamic nucleus, and the ventrobasal thalamic nuclei. Activation of T-type voltage-sensitive calcium channels (VSCCs) contributes to the pathological oscillatory activity of this network, and some of the first-line drugs used in the treatment of absence epilepsy inhibit T-type calcium channels. The α2δ subunit is a component of high voltage-activated VSCCs (i.e., L-, N-, P/Q-, and R channels) and studies carried out in heterologous expression systems suggest that it may also associate with T channels. The α2δ subunit is also targeted by thrombospondins, which regulate synaptogenesis in the central nervous system.

Objective:

To discuss the potential role for the thrombospondin/α2δ axis in the pathophysiology of absence epilepsy.

Methods:

We searched PubMed articles for the terms “absence epilepsy”, “T-type voltage-sensitive calcium channels”, “α2δ subunit”, “ducky mice”, “pregabalin”, “gabapentin”, “thrombospondins”, and included papers focusing this Review's scope.

Results:

We moved from the evidence that mice lacking the α2δ-2 subunit show absence seizures and α2δ ligands (gabapentin and pregabalin) are detrimental in the treatment of absence epilepsy. This suggests that α2δ may be protective against absence epilepsy via a mechanism that does not involve T channels. We discuss the interaction between thrombospondins and α2δ and its potential relevance in the regulation of excitatory synaptic formation in the cortico-thalamo-cortical network.

Conclusion:

We speculate on the possibility that the thrombospondin/α2δ axis is critical for the correct functioning of the cortico-thalamo-cortical network, and that abnormalities in this axis may play a role in the pathophysiology of absence epilepsy.