Antihyperalgesic effect of levetiracetam in neuropathic pain models in rats

Levetiracetam ameliorates epileptogenesis by modulating the adenosinergic pathway in a kindling model of epilepsy in mice

Background

Levetiracetam (LEV) has been found to have an antihyperalgesic effect via acting on the adenosine system. However, the effects of LEV on the modulation of the adenosine system in the brain have not been elucidated in the prevention of seizures and epilepsy. The present study aimed to explore the possible LEV mechanisms of action in the adenosine signaling systems in an animal model of epilepsy.

Methodology

A docking study was initially performed to determine the possible interaction of LEV with adenosine A1 receptors (A1Rs) and equilibrative nucleoside transporters-1 (ENT1). The experimental study was divided into an acute seizure test (32 mice distributed into 4 groups) and a chronic kindling model study (40 mice distributed into 5 groups), followed by gene expression analysis and immunohistochemistry. The kindling model lasted 26 days and took 13 subconvulsive doses of pentylenetetrazole (PTZ) to completely kindle the mice in the PTZ control group. Gene expression changes in the A1Rs, potassium inwardly-rectifying channel 3.2 (Kir3.2), and ENT1 in the brain tissue samples of the mice following treatment with LEV were analyzed using reverse transcription-quantitative polymerase chain reaction, and immunohistochemistry was performed for the A1R protein expression.

Results

Docking studies predicted a significant interaction of LEV with A1Rs and ENT1 proteins. Results from the acute testing revealed that caffeine (100 mg/kg) and 8-cyclopentyl-1,3-dipropylxanthine (25 mg/kg) significantly reversed the antiseizure effects of LEV by reversing the percent protection and shortening the onset of the first myoclonic jerk (FMJ) and generalized clonic seizures (GCSs). In the PTZ-induced kindling, LEV demonstrated an increased gene expression of A1Rs and Kir3.2 in the brain. LEV also significantly reduced the gene expression of ENT1. Furthermore, the immunohistochemical analysis showed that LEV increased the protein expression of A1Rs in the brain.

Conclusion

Based on these results, it can be concluded that LEV modulates epileptogenesis by acting on the adenosine pathway in the central nervous system.

Levetiracetam treatment in an experimental model of sciatic nerve injury: A randomized controlled trial

AIM

This study examined whether levetiracetam contributes to improvements in the axon-nerve damage in an experimental rat model.

MATERIALS AND METHODS

Forty-eight Wistar albino adult male rats weighing 250-300 gr were randomized into six groups having or not having sciatic nerve damages and receiving different (none, 300 and 600 mg/kg) levetiracetam doses, and control (non-levetiracetam). Functional gait analysis and tissue sample analysis with the aid of light microscopy and hematoxylin-eosin dye were evaluated between the groups. Additionally, scanning electron microscopy (SEM) was used for the detailed examination of sciatic nerves. S-100 (Schwann cell marker) immunoreactivities in sciatic nerve was detected by immunohistochemistry.

RESULTS

Sciatic functional index of the injured rats receiving 300 mg/kg levetiracetam was -65.59 ± 29.48 and -47.13 ± 21.36 in the 2nd and 6th weeks, respectively (p < 0.001). Also, IMA and TOS levels were significantly higher in the control group compared to those receiving levetiracetam (p = 0.001 and p < 0.001, respectively).      The most significant nerve regeneration was in the group injured and treated with LEV 600 mg/kg (p < 0.05).

CONCLUSION

There was a significant improvement in the sciatic functional index, histopathological findings, and parameters showing tissue oxidant status in rats with sciatic nerve injury receiving levetiracetam treatment. Further investigations should be performed to evaluate the contribution of levetiracetam as a treatment modality in sciatic nerve injuries.

Preemptive Levetiracetam Decreases Postoperative Pain: A Double-Blind, Randomised, Control Trial

Background Previously many studies have found the use of anti-epileptic drugs such as pregabalin, carbamazepine, and gabapentin in pain management. In addition, levetiracetam (LEV), an effective anti-epileptic drug, has shown analgesic effects in animal models. We aimed to evaluate the effect of oral LEV as pre-emptive analgesia in patients who underwent laparoscopic cholecystectomy under general anaesthesia and postoperative fentanyl requirements. Material and methods Forty-two patients of the American Society of Anaesthesiologists (ASA) grade I and II of either gender posted for elective laparoscopic cholecystectomy surgery were included in this double-blind, randomised, placebo-controlled study. Patients were divided into two equal groups of 21 each to receive either tablet LEV 500 mg or a matching placebo tablet, given 1 hour before surgery. Postoperative pain was assessed by a visual analogue scale (0-100 mm), where 0 meant no pain and 100, worst pain. In addition, patients received IV fentanyl as rescue analgesia during the first 24 hours of the postoperative period. Results Nineteen patients in the LEV group and 20 in the placebo group completed the study. Patients in the LEV group had significantly lower pain scores at all time intervals except 0 hours and reduced fentanyl consumption postoperatively in the first 24 hours (p<0.05). Side effects were comparable in both groups. Conclusion A single, preoperative dose of oral LEV 500 mg significantly decreases post-surgical pain and fentanyl demand as rescue analgesia in elective laparoscopic cholecystectomy.

Mechanisms Underlying the Selective Therapeutic Efficacy of Carbamazepine for Attenuation of Trigeminal Nerve Injury Pain

Different peripheral nerve injuries cause neuropathic pain through distinct mechanisms. Even the site of injury may impact underlying mechanisms, as indicated by the clinical finding that the antiseizure drug carbamazepine (CBZ) relieves pain because of compression injuries of trigeminal but not somatic nerves. We leveraged this observation in the present study hypothesizing that because CBZ blocks voltage-gated sodium channels (VGSCs), its therapeutic selectivity reflects differences between trigeminal and somatic nerves with respect to injury-induced changes in VGSCs. CBZ diminished ongoing and evoked pain behavior in rats with chronic constriction injury (CCI) to the infraorbital nerve (ION) but had minimal effect in rats with sciatic nerve CCI. This difference in behavior was associated with a selective increase in the potency of CBZ-induced inhibition of compound action potentials in the ION, an effect mirrored in human trigeminal versus somatic nerves. The increase in potency was associated with a selective increase in the efficacy of the Na_V1.1 channel blocker ICA-121431 and Na_V1.1 protein in the ION, but no change in Na_V1.1 mRNA in trigeminal ganglia. Importantly, local ICA-121431 administration reversed ION CCI-induced hypersensitivity. Our results suggest a novel therapeutic target for the treatment of trigeminal neuropathic pain.SIGNIFICANCE STATEMENT This study is based on evidence of differences in pain and its treatment depending on whether the pain is above (trigeminal) or below (somatic) the neck, as well as evidence that voltage-gated sodium channels (VGSCs) may contribute to these differences. The focus of the present study was on channels underlying action potential propagation in peripheral nerves. There were differences between somatic and trigeminal nerves in VGSC subtypes underlying action potential propagation both in the absence and presence of injury. Importantly, because the local block of Na_V1.1 in the trigeminal nerve reverses nerve injury-induced mechanical hypersensitivity, the selective upregulation of Na_V1.1 in trigeminal nerves suggests a novel therapeutic target for the treatment of pain associated with trigeminal nerve injury.

Brivaracetam attenuates pain behaviors in a murine model of neuropathic pain

Background

The antiseizure racetams may provide novel molecular insights into neuropathic pain due to their unique mechanism involving synaptic vesicle glycoprotein 2A. Anti-allodynic effects of levetiracetam have been shown in animal models of neuropathic pain. Here, we studied the effect of brivaracetam, which binds to synaptic vesicle glycoprotein 2A with 20-fold greater affinity, and has fewer off-target effects.

Methods

Mice underwent unilateral sciatic nerve cuffing and were evaluated for mechanical sensitivity using von Frey filaments. Pain behaviors were assessed with prophylactic treatment using levetiracetam (100 or 10 mg/kg) or brivaracetam (10 or 1 mg/kg) beginning after surgery and continuing for 21 days, or with therapeutic treatment using brivaracetam (10 or 1 mg/kg) beginning on day 14, after allodynia was established, and continuing for 28 or 63 days. Spinal cord tissues from the prophylaxis experiment with10 mg/kg brivaracetam were examined for neuroinflammation (Iba1 and tumor necrosis factor), T-lymphocyte (CD3) infiltration, and synaptic vesicle glycoprotein 2A expression.

Results

When used prophylactically, levetiracetam, 100 mg/kg, and brivaracetam, 10 mg/kg, prevented the development of allodynia, with lower doses of each being less effective. When used therapeutically, brivaracetam extinguished allodynia, requiring 10 days with 10 mg/kg, and six weeks with 1 mg/kg. Brivaracetam was associated with reduced neuroinflammation and reduced T-lymphocyte infiltration in the dorsal horn. After sciatic nerve cuffing, synaptic vesicle glycoprotein 2A expression was identified in neurons, activated astrocytes, microglia/macrophages, and T lymphocytes in the dorsal horn.

Conclusion

Synaptic vesicle glycoprotein 2A may represent a novel target for neuropathic pain. Brivaracetam may warrant study in humans with neuropathic pain due to peripheral nerve injury.

Psychopharmacology of chronic pain

Chronic pain is a frequent condition that affects an estimated 20% of people worldwide, accounting for 15%-20% of doctors' appointments (Treede et al., 2015). It lacks the acute warning function of physiologic nociception, and instead involves the activation of multiple neurophysiologic mechanisms in the somatosensory system, a complex neuronal network under the control of powerful autoregulatory loops and able to undergo rapid neuroplastic alteration (Verdu et al., 2008). There is a growing body of research suggesting that some such pathways are shared by major psychologic disorders such as depression and anxiety, opening new avenues in co-treatment strategies. In particular, besides anticonvulsants, which are today used as analgesics, other psychopharmaceuticals, such as the tricyclic antidepressants, are displaying efficacy in the treatment of neuropathic and nociceptive chronic pain. The state of the art regarding the mechanisms of nociception and the pharmacology of both the neurotransmitters involved and the wide range of psychoactive compounds that may be useful in the treatment of chronic pain are discussed.

Levetiracetam synergizes with gabapentin, pregabalin, duloxetine and selected antioxidants in a mouse diabetic painful neuropathy model

RATIONALE

We have reported that levetiracetam, a novel anticonvulsant with analgesic properties, synergizes with ibuprofen/aspirin/paracetamol in a model of diabetic painful neuropathy (DPN). Most guidelines recommend gabapentin, pregabalin, and duloxetine as first- or second-line agents for DPN.

OBJECTIVE

We examined the effects of combination treatment of first-/second-line analgesics with levetiracetam in a model of DPN. Additionally, the levetiracetam's combinations with antioxidants, low dose of aspirin, coenzyme Q10, or α-lipoic acid were evaluated.

METHODS

Diabetes was induced in C57BL/6 mice with a single high dose of streptozotocin. The antinociceptive effects of orally administered levetiracetam, gabapentin, pregabalin, duloxetine (acute treatment) and aspirin, coenzyme Q10, and α-lipoic acid (preventive 7-day treatment), as well as combinations of levetiracetam with individual drugs were examined in the tail-flick test. In combination experiments, the drugs were coadministered in fixed-dose fractions of single-drug ED₅₀; the type of interaction was determined by isobolographic analysis.

RESULTS

About 60-, 32-, 30-, 26-, 18-, and 6-fold reductions of doses of both drugs in levetiracetam combinations with pregabalin, gabapentin, coenzyme Q10, aspirin, duloxetine, and α-lipoic acid, respectively, were detected.

CONCLUSIONS

Combinations of levetiracetam with gabapentin/pregabalin/duloxetine that target different mechanisms/sites of action involved in DPN, as well as combinations of levetiracetam and low-dose aspirin/coenzyme Q10/α-lipoic acid that target underlying causes of DPN, produce marked synergistic interactions in reducing nociception in diabetic mice. This suggests that these combination treatments might be of great benefit for diabetic patients and should be explored further in clinical trials.

The Post-mastectomy Pain Syndrome-A Systematic Review of the Treatment Modalities

Post-mastectomy pain syndrome (PMPS) is a chronic neuropathic pain condition, affecting many women who have undergone breast cancer surgery. The development of PMPS is complex and the treatment options are limited. In this systematic review, we have analyzed the existing treatment modalities of PMPS. Six studies on five treatments were carefully selected, critically evaluated, and presented. The treatments were: antidepressants, anti-epileptics, topical capsaicin, and autologous fat grafting. Four of these treatments had a significant effect on PMPS. However, most of the studies had several flaws and therefore larger studies of high quality should be performed in the future.

Brivaracetam: Rationale for discovery and preclinical profile of a selective SV2A ligand for epilepsy treatment

Despite availability of effective antiepileptic drugs (AEDs), many patients with epilepsy continue to experience refractory seizures and adverse events. Achievement of better seizure control and fewer side effects is key to improving quality of life. This review describes the rationale for the discovery and preclinical profile of brivaracetam (BRV), currently under regulatory review as adjunctive therapy for adults with partial-onset seizures. The discovery of BRV was triggered by the novel mechanism of action and atypical properties of levetiracetam (LEV) in preclinical seizure and epilepsy models. LEV is associated with several mechanisms that may contribute to its antiepileptic properties and adverse effect profile. Early findings observed a moderate affinity for a unique brain-specific LEV binding site (LBS) that correlated with anticonvulsant effects in animal models of epilepsy. This provided a promising molecular target and rationale for identifying selective, high-affinity ligands for LBS with potential for improved antiepileptic properties. The later discovery that synaptic vesicle protein 2A (SV2A) was the molecular correlate of LBS confirmed the novelty of the target. A drug discovery program resulted in the identification of anticonvulsants, comprising two distinct families of high-affinity SV2A ligands possessing different pharmacologic properties. Among these, BRV differed significantly from LEV by its selective, high affinity and differential interaction with SV2A as well as a higher lipophilicity, correlating with more potent and complete seizure suppression, as well as a more rapid brain penetration in preclinical models. Initial studies in animal models also revealed BRV had a greater antiepileptogenic potential than LEV. These properties of BRV highlight its promising potential as an AED that might provide broad-spectrum efficacy, associated with a promising tolerability profile and a fast onset of action. BRV represents the first selective SV2A ligand for epilepsy treatment and may add a significant contribution to the existing armamentarium of AEDs.

Levetiracetam synergises with common analgesics in producing antinociception in a mouse model of painful diabetic neuropathy

Painful diabetic neuropathy is difficult to treat. Single analgesics often have insufficient efficacy and poor tolerability. Combination therapy may therefore be of particular benefit, because it might provide optimal analgesia with fewer adverse effects. This study aimed to examine the type of interaction between levetiracetam, a novel anticonvulsant with analgesic properties, and commonly used analgesics (ibuprofen, aspirin and paracetamol) in a mouse model of painful diabetic neuropathy. Diabetes was induced in C57BL/6 mice with a single high dose of streptozotocin, applied intraperitoneally (150 mg/kg). Thermal (tail-flick test) and mechanical (electronic von Frey test) nociceptive thresholds were measured before and three weeks after diabetes induction. The antinociceptive effects of orally administered levetiracetam, analgesics, and their combinations were examined in diabetic mice that developed thermal/mechanical hypersensitivity. In combination experiments, the drugs were co-administered in fixed-dose fractions of single drug ED50 and the type of interaction was determined by isobolographic analysis. Levetiracetam (10-100 mg/kg), ibuprofen (2-50 mg/kg), aspirin (5-75 mg/kg), paracetamol (5-100 mg/kg), and levetiracetam-analgesic combinations produced significant, dose-dependent antinociceptive effects in diabetic mice in both tests. In the tail-flick test, isobolographic analysis revealed 15-, and 19-fold reduction of doses of both drugs in the combination of levetiracetam with aspirin/ibuprofen, and paracetamol, respectively. In the von Frey test, approximately 7- and 9-fold reduction of doses of both drugs was detected in levetiracetam-ibuprofen and levetiracetam-aspirin/levetiracetam-paracetamol combinations, respectively. These results show synergism between levetiracetam and ibuprofen/aspirin/paracetamol in a model of painful diabetic neuropathy and might provide a useful approach to the treatment of patients suffering from painful diabetic neuropathy.

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.

An observational trial to investigate the efficacy and tolerability of levetiracetam in trigeminal neuralgia

OBJECTIVE

To explore the efficacy and tolerability of levetiracetam in medical treatment of trigeminal neuralgia.

BACKGROUND

Antiepileptic drugs (AEDs) are considered as first-line treatment for trigeminal neuralgia, although their use is often limited due to incomplete efficacy and tolerability. Newer AEDs with improved safety profile may be useful in this disorder.

METHODS

Patients suffering from trigeminal neuralgia (either primary or secondary) refractory to previous treatments were recruited to be treated with levetiracetam (3-4 g/day) for 16 weeks as add-on therapy, after a 2-week baseline period. Rescue medication was allowed in both the baseline and treatment phases. The primary efficacy measure was the number of attacks per day. The patients' efficacy evaluation, the patients' global evaluation for both safety and efficacy, changes in the Hamilton Depression Scale, the Hamilton Anxiety Scale, and the Quality of Life Measure Short Form-36 were secondary parameters.

RESULTS

Twenty-three patients were included in the analysis. After treatment and compared to the baseline phase, the number of daily attacks decreased by 62.4%. All secondary parameters changed significantly with the exception of the Quality of Life Measure Short Form-36 score. Seven patients withdrew from the study. Five patients (21.7%) reported side effects and 2 withdrew.

CONCLUSIONS

Levetiracetam may be effective and safe in trigeminal neuralgia treatment. Confirmation in a randomized controlled study is needed.

Specific effect of levetiracetam in experimental human pain models*

BACKGROUND

Levetiracetam is a new antiepileptic drug. There is only limited experience with levetiracetam in clinical neuropathic pain.

AIM

To test the analgesic effect of levetiracetam in a human experimental pain model in order to obtain preclinical evidence for its potential effect in neuropathic pain.

METHODS

Sixteen healthy volunteers completed a randomized, double-blind, cross-over trial with a single oral dose of 1500 mg levetiracetam against placebo. Pain tests included pain detection and tolerance to single electrical stimulation and temporal pain summation threshold to repetitive electrical stimulation (3 Hz) of the sural nerve.

RESULTS

Levetiracetam significantly increased the pain tolerance thresholds (p=0.04), and the pain detection thresholds tended to be increased (p=0.06), whereas levetiracetam had no effect on temporal pain summation thresholds (p=0.30).

CONCLUSION

Levetiracetam has an analgesic effect in the electrical sural nerve stimulation pain model, but it did not increase temporal pain summation threshold. Levetiracetam may still be effective in clinical neuropathic pain.

Levetiracetam in chronic daily headache: a double-blind, randomised placebo-controlled study. (The Australian KEPPRA Headache Trial [AUS-KHT])

INTRODUCTION

Chronic daily headache (CDH) represents a temporal profile of headache (15+ days/month; 4+ hours/day; >6 months). We report the first comprehensive and largest levetiracetam (LEV) trial in CDH.

METHODS

A 27-week, multi-centre, randomised, placebo-controlled, cross-over, phase III B study assessed efficacy of a target of 3 g/day LEV of 6 placebo tablets/day in CDH. Primary efficacy was headache-free rate (HFR) while secondary parameters were loss of diagnostic criteria; severity; duration; disability; associated features; pain; and quality of life.

RESULTS

Ninety-six patients were recruited (baseline HFR 10.4 ± 14.6%; median 0%). At onset of history 73 (74.1%) had migraine +/- aura and 35 (36.5%) had tension-type headache (TTH). Over the six months preceding recruitment 54 (56.3%) had migraine and 42 (43.8%) had TTH. Headache history was 22.6 ± 15.0 years (median 20.0). Eighty-eight received placebo and 89 received LEV with >80 receiving stable dose in either arm. LEV achieved 3.9% increased HFR over placebo, showing a trend but not significance. There was 9.9% increase in loss of CDH diagnostic criteria re: headache days/month for LEV over placebo (p = .0325), reduced disability (p = .0487) and reduced pain severity for LEV (p = .0162). The Short-Form Quality of Life assessment instrument (SF-36) showed impaired mental health on LEV (p = .001).

DISCUSSION

These findings conflict with reports of LEV efficacy, mandating placebo control in headache trials. Primary efficacy equated to one extra headache-free day/month with reduced disability and pain intensity. Mental health was reduced on LEV. The 10% loss of diagnostic criteria, decreased intensity and disability suggest a subpopulation with CDH where LEV remains a therapeutic option.

Painful and involuntary multiple sclerosis

INTRODUCTION

Pain, dysphagia, respiratory problems, sexual and cardiovascular dysfunctions may occur in patients with MS.

AREAS COVERED

In the present review, we attempt to summarize the current knowledge on the impact pain, dysphagia, respiratory problems, sexual and cardiovascular dysfunctions have in patients with MS.

EXPERT OPINION

To effectively manage MS, it is essential that these symptoms are recognized as early as possible and treated by a rehabilitative multidisciplinary approach, based on proven scientific evidence.

Antinociceptive action of carbamazepine on thermal hypersensitive pain at spinal level in a rat model of adjuvant-induced chronic inflammation

PURPOSE

Systemic carbamazepine, a voltage-gated sodium channel blocker, has been reported to dose-dependently reduce inflammatory hyperalgesia. However, the antinociceptive effects of carbamazepine on the spinal cord in inflammatory conditions are unclear. The aim of the present study was to evaluate the antinociceptive effects of carbamazepine on the spinal cord in a chronic inflammatory condition.

METHODS

In Sprague-Dawley rats, a chronic inflammatory condition was induced by complete Freund's adjuvant (CFA) inoculation into the tail. Tail flick (TF) latencies were measured following intraperitoneal carbamazepine, or intrathecal carbamazepine or tetrodotoxin injection in intact rats and in the chronic inflammatory rats. From the values of TF latency at 60 min after drug injection, the effective dose required to produce 50% response (ED(50)) of each drug was derived.

RESULTS

Carbamazepine attenuated thermal responses with both systemic and intrathecal administration. The effect was more evident in rats with chronic inflammation than in intact rats; the ED(50s) of intraperitoneal carbamazepine in intact and inflamed rats were 12.39 and 1.54 mg/kg, and those of intrathecal carbamazepine were 0.311 and 0.048 nmol, respectively. Intrathecal tetrodotoxin also clearly inhibited the response, with ED(50s) of 1.006 pmol in intact rats and 0.310 pmol in inflamed rats. The relative potencies of intrathecal carbamazepine versus tetrodotoxin for inhibition were approximately 1:150-1:300 in intact and inflamed rats.

CONCLUSION

These results indicate that the inhibition of voltage-gated sodium channels, at least tetrodotoxin-sensitive channels, may contribute to the antinociceptive effect of carbamazepine on CFA-induced inflammatory pain, since lower doses of intrathecal carbamazepine and tetrodotoxin attenuated thermal responses to a greater extent in inflamed rats than in intact rats.

The antihyperalgesic effect of levetiracetam in an inflammatory model of pain in rats: mechanism of action

BACKGROUND AND PURPOSE

Levetiracetam, a novel antiepileptic drug, has recently been shown to have antinociceptive effects in various animal models of pain. The purpose of this study was to investigate the antihyperalgesic effect of levetiracetam and its mechanism of action, by examining the involvement of GABAergic, opioidergic, 5-hydroxytryptaminergic (5-HTergic) and adrenergic systems in its effect, in a rat model of inflammatory pain.

EXPERIMENTAL APPROACH

Rats were intraplantarly injected with the pro-inflammatory compound carrageenan. A paw pressure test was used to determine: (i) the effect of levetiracetam on carrageenan-induced hyperalgesia; and (ii) the effects of bicuculline (selective GABA(A) receptor antagonist), naloxone (non-selective opioid receptor antagonist), methysergide (non-selective 5-HT receptor antagonist) and yohimbine (selective alpha(2)-adrenoceptor antagonist) on the antihyperalgesic action of levetiracetam.

RESULTS

Levetiracetam (10-200 mg.kg(-1); p.o.) significantly reduced, in a dose-dependent manner, the inflammatory hyperalgesia induced by carrageenan. The antihyperalgesic effect of levetiracetam was significantly decreased after administration of bicuculline (0.5-2 mg.kg(-1); i.p.), naloxone (1-3 mg.kg(-1); i.p.), methysergide (0.25-1 mg.kg(-1); i.p.) and yohimbine (1-3 mg.kg(-1); i.p.).

CONCLUSIONS AND IMPLICATIONS

These results show that levetiracetam produced antihyperalgesia which is at least in part mediated by GABA(A), opioid, 5-HT and alpha(2)-adrenergic receptors, in an inflammatory model of pain. The efficacy of levetiracetam in this animal model of inflammatory pain suggests that it could be a potentially important agent for treating inflammatory pain conditions in humans.

SVOP is a nucleotide binding protein

Background

Synaptic Vesicle Protein 2 (SV2) and SV2-related protein (SVOP) are transporter-like proteins that localize to neurotransmitter-containing vesicles. Both proteins share structural similarity with the major facilitator (MF) family of small molecule transporters. We recently reported that SV2 binds nucleotides, a feature that has also been reported for another MF family member, the human glucose transporter 1 (Glut1). In the case of Glut1, nucleotide binding affects transport activity. In this study, we determined if SVOP also binds nucleotides and assessed its nucleotide binding properties.

Methodology/Principal Findings

We performed in vitro photoaffinity labeling experiments with the photoreactive ATP analogue, 8-azido-ATP[γ] biotin and purified recombinant SVOP-FLAG fusion protein. We found that SVOP is a nucleotide-binding protein, although both its substrate specificity and binding site differ from that of SV2. Within the nucleotides tested, ATP, GTP and NAD show same level of inhibition on SVOP-FLAG labeling. Dose dependent studies indicated that SVOP demonstrates the highest affinity for NAD, in contrast to SV2, which binds both NAD and ATP with equal affinity. Mapping of the binding site revealed a single region spanning transmembrane domains 9–12, which contrasts to the two binding sites in the large cytoplasmic domains in SV2A.

Conclusions/Significance

SVOP is the third MF family member to be found to bind nucleotides. Given that the binding sites are unique in SVOP, SV2 and Glut1, this feature appears to have arisen separately.

Effect of antiepileptic agent, levetiracetam, on urodynamic parameters and neurogenic bladder overactivity in chronically paraplegic rats

OBJECTIVES

To investigate the effects of different levetiracetam (LEV) doses on urodynamic parameters in an animal model of neurogenic detrusor overactivity (NDO).

METHODS

A total of 54 female rats were studied. Of the 54 rats, 6 served as normal controls, and 48 underwent T10 spinal cord transection (SCT). Of the latter 48 rats, 12 were paraplegic controls, and the remaining 36 rats were divided into 3 equal subgroups that received LEV by way of a subcutaneous osmotic minipump at a dose of 17, 54, and 108 mg/kg daily, respectively. The paraplegic control and treatment groups were further subdivided (n = 6), and cystometry was performed at 3 and 4 weeks after SCT, respectively.

RESULTS

All paraplegic controls developed NDO, with spontaneous contractions. At 3 and 4 weeks after SCT, the mean frequency of the contractions was 1.6 +/- 0.3/min and 1.7 +/- 0.2/min. The contraction amplitude and bladder capacity were not significantly different. After 1 week of LEV treatment, these urodynamic parameters improved significantly in a dose-dependent manner, and the changes were more striking at 2 weeks. At a LEV dosage of 17, 54, and 108 mg/kg, respectively, the NDO frequency increased from 1.7 +/- 0.3 to 0.7 +/- 0.2 contractions/min (P = .01), 0.48 +/- 0.16 contractions/min (P = .009), and 0.5 +/- 0.17 contractions/min (P = .01). The bladder capacity increased from 0.51 +/- 0.1 mL to 1.5 +/- 0.2 mL (P = .0001), 2.5 +/- 1.7 mL (P = .006), and 2.6 +/- 0.3 mL (P = .0003), and the micturition pressure improved from 105.8 +/- 6.9 to 73.8 +/- 6.8 cm H(2)O (P = .01), 58.6 +/- 8.9 cm H(2)O (P = .006), and 49.7 +/- 8.9 cm H(2)O (P = .002).

CONCLUSIONS

The results of our study have shown that LEV is an effective treatment of NDO after SCT in rats. It might prove to be a novel, alternative therapeutic approach to NDO. The follow-up of these experimental results with a clinical trial is warranted.

Antinociceptive efficacy of levetiracetam in a mice model for painful diabetic neuropathy

BACKGROUND AND OBJECTIVE

Despite important advances in available knowledge, management of neuropathic pain remains incomplete, and results from experimental and clinical studies indicate that some anticonvulsants show promise for treating neuropathic pain. The aim of this study was to assess the antinociceptive efficacy of levetiracetam (LEV, ucb L059) in a mice model for painful diabetic neuropathy using the in vivo nociceptive behavioral 'hot-plate test.'

METHODS

The hot-plate test consisted of placing individual mice (adult male Balb/C) on the hot plate at 50+/-0.1 degrees C and timing the delay for the first hind paw lift (nociceptive threshold). After obtaining control values, diabetes was induced by injection of streptozotocin [200 mg/kg intraperitoneally (i.p.)] and 2 weeks after induction of diabetes (serum glucose > or =400 mg/dL) LEV was administered i.p. and hot-plate tests were repeated. Pain threshold values were determined and analyzed by Kruskal-Wallis one-way analysis of variance (ANOVA) followed by a pairwise comparison using a Dunnett's t-test on the ranked data.

RESULTS

LEV (60, 300 and 900 mg/kg) had no significant effect on the nociceptive threshold in normal mice (n=8 for each dose, P>0.05). There were significant decreases in pain threshold latency in diabetic mice compared with the normal healthy group and these were significantly and dose-dependently restored by much lower doses of LEV (20, 100 and 200 mg/kg) in a reversible manner.

CONCLUSION

Results obtained from the in vivo behavioral test lend support to the validation of the promising therapeutic potential of the novel antiepileptic agent LEV in the treatment of neuropathic pain.

Pharmaco-EEG-based assessment of interaction between ethanol and levetiracetam

Recent research suggests a potential role for a new generation of anticonvulsant drugs, including levetiracetam, in the treatment of alcohol dependence. Some elements of the central mechanism of action that levetiracetam has in common with ethanol, give rise to the question of whether there is an interaction between these two agents and whether there is any risk associated with the enhanced depressive effect of these agents on the central nervous system. In this study, we have used a pharmaco-electroencephalographic (EEG) method to examine the interaction of ethanol with levetiracetam. The influence of levetiracetam on the effect of ethanol on EEG of rabbits (midbrain reticular formation, hippocampus, frontal cortex) was determined. Levetiracetam was administered p.o. as a single dose (50mg/kg or 200mg/kg) or repeatedly at a dose of 100mg/kg/day for 14 days. Ethanol was injected i.v. at a dose of 0.8 g/kg 60 min after the administration of levetiracetam. Ethanol caused an increase in the low frequencies (0.5-4 Hz) in the recording, as well as a marked decrease in the higher frequencies (13-30 Hz and 30-45 Hz). Changes in the EEG recordings after levetiracetam alone were more significant when the drug was given in repeated doses. Combined administration of ethanol and levetiracetam (200mg/kg) resulted in a markedly synergistic effect in the frontal cortex and the midbrain reticular formation. The drug decreases the sensitivity of the hippocampus to ethanol, an observation that may be important in the treatment of alcohol addiction.

Levetiracetam Reduces Anesthetic-Induced Hyperalgesia in Rats

BACKGROUND

As part of an increase in excitability, small doses of pentobarbital, propofol, and midazolam induce an increased sensitivity to pain. Specific therapy to prevent or reduce this excitability may offer advantages over current clinical management with analgesics and sedatives. The pharmacological profile of the novel antiepileptic drug, levetiracetam, suggests that it may reduce the intensity of the excitatory stages of anesthesia.

METHODS

We examined the influence of levetiracetam on the reduction of the nociceptive reflex threshold in rats by sedative doses of pentobarbital, propofol, and midazolam. Measurements of nociceptive reflex threshold to pressure and heat were made and then repeated after intraperitoneal injection of saline or one of three doses of levetiracetam (100, 200, 500 mg/kg). Pentobarbital (30 mg/kg), propofol (30 mg/kg), or midazolam (1.9 mg/kg) were then administered. The reflex threshold was measured every 10 min, starting at 5 min after the sedative injection, until 65 min had elapsed.

RESULTS

Levetiracetam did not alter nociceptive reflex threshold in nonsedated animals (P = 0.11) or influence the degree or duration of sedation. The three anesthetic/sedative drugs reduced the nociceptive reflex threshold by 20%-30% of control values. Levetiracetam reduced the hyperreflexia associated with pentobarbital and midazolam (P < 0.05), but not propofol.

CONCLUSIONS

These findings support further investigation into the role of levetiracetam in the prevention of anesthetic-induced excitability.

Antinociceptive efficacy of lacosamide in a rat model for painful diabetic neuropathy

Lacosamide was tested in the streptozotocin rat model of diabetic neuropathic pain in comparison to drugs which are commonly used in the treatment of diabetic neuropathic pain, i.e. antidepressants and anticonvulsants. In diabetic rats, lacosamide attenuated cold (10, 30 mg/kg, i.p.), warm (3, 10, 30 mg/kg, i.p.) and mechanical allodynia (30 mg/kg, i.p.). Streptozotocin-induced thermal and mechanical hyperalgesia were reduced by lacosamide at doses of 10 and 30 mg/kg, i.p. Morphine (3 mg/kg) showed similar efficacy on allodynia and hyperalgesia. Amitriptyline (10 mg/kg), venlafaxine (15 mg/kg), levetiracetam (180 mg/kg) and pregabalin (100 mg/kg) exhibited significant effects on thermal allodynia and mechanical hyperalgesia. Only treatment with amitriptyline (30 mg/kg, i.p.) produced full reversal of thermal allodynia comparable to lacosamide. Lamotrigine (45 mg/kg, i.p.) had no effect on both behavioral readouts. Lacosamide's potency and efficacy in reversing pain behavior might be due to its new, yet unknown mechanism of action.

Characterization of [(3)H]ucb 30889 binding to synaptic vesicle protein 2A in the rat spinal cord

The novel antiepileptic drug levetiracetam ((2S-(2-oxo-1-pyrrolidinyl)butanamide, KEPPRA possesses a specific binding site in brain, which has very recently been identified as the synaptic vesicle protein SV 2 A. The aim of this study was to evaluate the presence of a levetiracetam binding site in the spinal cord and compare its properties to that in rat brain. We used [(3)H]ucb 30889 ((2S)-2-[4-(3-azidophenyl)-2-oxopyrrolidin-1-yl]butanamide), a levetiracetam analogue, to perform binding assays, photoaffinity labelling and autoradiography experiments, and revealed the presence of SV 2 A by Western-blot analysis. [(3)H]ucb 30889 binding kinetics at 4 degrees C were biphasic and saturation binding curves were compatible with the labelling of a homogenous population of binding sites with a K(d) similar to that in brain. Competition curves with ligands known to interact with levetiracetam binding sites and photolabelling experiments indicated that [(3)H]ucb 30889 labels the same 90 kDa protein in both spinal cord and brain. Levetiracetam binding site was localised in the grey matter of the spinal cord and its expression was not modified in a model of neuropathic pain. This study demonstrates the presence of a specific levetiracetam binding site in the rat spinal cord, which is similar to that found in rat brain.

Comparison of the effects of anticonvulsant drugs with diverse mechanisms of action in the formalin test in rats

The purpose of the present studies was to compare anticonvulsant drugs with diverse mechanisms of action in a persistent pain model, the formalin test. In addition, the anticonvulsant effects of the compounds were determined in the threshold electroshock tonic seizure test and the 6-Hz limbic seizure test. The effects of the compounds were also determined on locomotor activity. Carbamazepine, oxcarbazepine, lamotrigine, gabapentin and ethosuximide all produced statistically significant analgesic effects in the formalin test whereas phenytoin, topiramate, zonisamide, phenobarbital, tiagabine, valproate and levetiracetam did not. All compounds were anticonvulsant. In addition, morphine and phenobarbital increased locomotor activity while ethosuximide had no effect and all other compounds decreased locomotor activity. For those compounds that were analgesic, the doses required to produce analgesia were larger in magnitude than the anticonvulsant ED50 values in the threshold electroshock and 6-Hz tests, as well as larger than doses that altered locomotor activity. The present results demonstrate that the anticonvulsant and analgesic effects of clinically used antiepileptic drugs do not necessarily correlate and therefore suggest that the anticonvulsant and analgesic efficacy of these drugs may be due to different pharmacologic mechanisms.

Interactions between anandamide-induced anterograde amnesia and post-training memory modulatory systems

Rats were bilaterally implanted with indwelling cannulae in the CA1 region of the dorsal hippocampus. After recovery from surgery, they were trained in a one-trial, step-down inhibitory avoidance task using a 0.5 mA foot shock. The animals received intrahippocampal infusions of either vehicle or anandamide (100 microM, 0.5 microl/side) 30 min before training. Then, either immediately post-training or 3 h later, they received infusions of saline, noradrenaline (0.5 microg/side), SKF 38393 (1.5 microg/side), oxotremorine (0.6 microg/side) or Sp-cAMPs (0.5 microg/side) also in the hippocampus. All animals were tested for retention 24-h post-training. Anandamide produced anterograde amnesia. Immediate, but not delayed, post-training treatment with Sp-cAMPs and noradrenaline reversed this effect. SKF 38393 and oxotremorine had no influence on the amnesia caused by anandamide either when given immediately or 3 h after training. The results suggest that the amnesic effect of anandamide is related to the known noradrenergic regulation of cAMP-dependent protein kinase (PKA) activity previously described in the hippocampus immediately after avoidance training, which is crucial to long-term memory (LTM) formation.

Progress report on new antiepileptic drugs: a summary of the Seventh Eilat Conference (EILAT VII)

The Seventh Eilat Conference on New Antiepileptic Drugs (AEDs) (EILAT VII) took place in Villasimius, Sardinia, Italy from the 9th to 13th May 2004. Basic scientists, clinical pharmacologists and neurologists from 24 countries attended the conference,whose main themes included advances in pathophysiology of drug resistance, new AEDs in pediatric epilepsy syndromes, modes of AED action and spectrum of adverse effects and a re-appraisal of comparative responses to AED combinations. Consistent with previous formats of this conference, the central part of the conference was devoted to a review of AEDs in development, as well as updates on second-generation AEDs. This article summarizes the information presented on drugs in development, including atipamezole, BIA-2-093, fluorofelbamate, NPS 1776, pregabalin, retigabine, safinamide, SPM 927, stiripentol, talampanel,ucb 34714 and valrocemide (TV 1901). Updates on felbamate, gabapentin, lamotrigine, levetiracetam, oxcarbazepine, tiagabine,topiramate, vigabatrin, zonisamide, new oral and parenteral formulations of valproic acid and SPM 927 and the antiepileptic vagal stimulator device are also presented.

Efficacy and safety of levetiracetam in pediatric migraine

BACKGROUND

Headache is a frequent occurrence among children and adolescents. Chronic headaches can be severe and disabling, and require prophylactic treatment; however, additional data on the use of prophylactic medications for migraine in children are needed.

OBJECTIVE

To review the efficacy and safety of levetiracetam (Keppra) in pediatric patients with a history of recurrent headache.

DESIGN/METHODS

Data from 19 pediatric patients were retrospectively reviewed. The initial dose of levetiracetam was usually 125 or 250 mg twice daily, but varied depending upon clinical judgment.

RESULTS

Charts of 9 girls and 10 boys (mean age, 11.9 years) were reviewed. A variety of medications, including triptans, had been used before initiating treatment with levetiracetam. Mean headache frequency before treatment was 6.3 per month (standard deviation [SD], 3.8; confidence interval [CI], 4.4 to 8.1). Duration of headaches ranged from 0.25 to 8 years. Migraine (63.2%) and migraine with aura (15.8%) were the most common types of headache reported. Most patients (89.5%) had headaches that were severe. After treatment, the mean headache frequency decreased to 1.7 per month (SD, 2.7; CI, 0.4 to 3.0), representing a reduction compared with baseline (P <.0001). Levetiracetam eliminated headaches in 10 patients (52.6%), and 7 patients (36.8%) had less severe and less frequent headaches. Levetiracetam did not have an effect on headaches in 2 patients (10.5%). Mean duration of treatment with levetiracetam was 4.1 months. Doses ranged from 125 to 750 mg twice daily. Sixteen patients (84.2%) reported no side effects on levetiracetam. One patient experienced asthenia/somnolence and dizziness, and irritable, hyperactive, and hostile behavior led to discontinuation of levetiracetam in another patient. A third patient experienced irritability and moodiness that attenuated after 1 month of treatment and did not require discontinuation.

CONCLUSIONS

In this small retrospective review, levetiracetam was found to be generally well tolerated and appears to be a promising candidate for additional evaluation in well-controlled clinical trials of pediatric patients with migraine.