Gabapentin is effective in treating nocturnal painful spasms in multiple sclerosis

Suppression of neuropathic pain in the circadian clock-deficient Per2m/m mice involves up-regulation of endocannabinoid system

Neuropathic pain often results from injuries and diseases that affect the somatosensory system. Disruption of the circadian clock has been implicated in the exacerbation of the neuropathic pain state. However, in this study, we report that mice deficient in a core clock component Period2 (Per2m/m mice) fail to develop tactile pain hypersensitivity even following peripheral nerve injury. Similar to male wild-type mice, partial sciatic nerve ligation (PSL)-Per2m/m male mice showed activation of glial cells in the dorsal horn of the spinal cord and increased expression of pain-related genes. Interestingly, α1D-adrenergic receptor (α1D-AR) expression was up-regulated in the spinal cord of Per2m/m mice, leading to increased production of 2-arachidonoylglycerol (2-AG), an endocannabinoid receptor ligand. This increase in 2-AG suppressed the PSL-induced tactile pain hypersensitivity. Furthermore, intraspinal dorsal horn injection of adeno-associated viral vectors expressing α1D-AR also attenuated pain hypersensitivity in PSL-wild-type male mice by increasing 2-AG production. Our findings reveal an uncovered role of the circadian clock in neuropathic pain disorders and suggest a link between α1D-AR signaling and the endocannabinoid system.

Basis for diurnal exacerbation of neuropathic pain hypersensitivity and its application for drug development

In addition to diurnal rhythms in physiology and behavior, a variety of pathological conditions also exhibit marked day-night changes in symptom intensity, exemplified by allergic rhinitis, arthritis, asthma, myocardial infarction, congestive heart failure, stroke, and chronic pain disorders. Currently, novel therapeutic approaches are facilitated by the development of chemical compounds targeted to key proteins that cause diurnal exacerbation of pathological events. Neuropathic pain is a chronic condition that occurs by tumor-induced nerve compression, cancer cell infiltration into the nerve, diabetes, and herpes virus infection. One troublesome hallmark symptom of neuropathic pain is hypersensitivity to normally innocuous stimuli known as "mechanical allodynia" that is often refractory to common analgesic therapies. Millions of patients worldwide presently endure neuropathic pain. We summarize the recent insights gained into the mechanism of diurnal exacerbation of neuropathic pain hypersensitivity and introduce the strategy of circadian clock-based drug development.

Non‐Stationary Outcome of Alternating Hemiplegia of Childhood into Adulthood

Background

Objectives

Methods

Results

Conclusions

Circadian rhythms and pain

The goal of this review is to provide a perspective on the nature and importance of the relationship between the circadian and pain systems. We provide: 1) An overview of the circadian and pain systems, 2) a review of direct and correlative evidence that demonstrates diurnal and circadian rhythms within the pain system; 3) a perspective highlighting the need to consider the role of a proposed feedback loop of circadian rhythm disruption and maladaptive pain; 4) a perspective on the nature of the relationship between circadian rhythms and pain. In summary, we propose that there is no single locus responsible for producing the circadian rhythms of the pain system. Instead, circadian rhythms of pain are a complex result of the distributed rhythms present throughout the pain system, especially those of the descending pain modulatory system, and the rhythms of the systems with which it interacts, including the opioid, endocrine, and immune systems.

Emerging Role of Serum Glucocorticoid-Regulated Kinase 1 in Pathological Pain

Currently, the management of acute and chronic pain in clinical practice remains unsatisfactory due to the existence of limited effective treatments, and novel therapeutic strategies for pathological pain are urgently needed. In the past few decades, the role of serum and glucocorticoid-inducible kinase 1 (SGK1) in the development of pain and diurnal rhythms has been implicated in numerous studies. The expression levels of SGK1 mRNA and protein were found to be elevated in the spinal cord and brain in various pathological pain models. Blocking SGK1 significantly attenuated pain-like responses and the development of pathological pain. These studies provide strong evidence that SGK1 plays a role in the development of various types of pathological pain and that targeting SGK1 may be a novel therapeutic strategy for pain management. In this review article, we provide evidence from animal models for the potential role of SGK1 in the regulation of pathological pain caused by inflammation, nerve injury, psychiatric disorders, and chronic opioid exposure.

Sulfasalazine alleviates neuropathic pain hypersensitivity in mice through inhibition of SGK-1 in the spinal cord

Diurnal variations in pain hypersensitivity are common in chronic pain disorders. Temporal exacerbation of neuropathic pain hypersensitivity is dependent on diurnal variations in glucocorticoid secretion from the adrenal glands. We previously demonstrated that spinal expression of serum- and glucocorticoid-inducible kinase-1 (SGK-1) is associated with glucocorticoid- induced exacerbation of pain hypersensitivity, but there are no available strategies to inhibit SGK-1 in the spinal cord. By screening a clinically approved drug library (more than 1,200 drugs), we found that sulfasalazine (SSZ) has inhibitory effects on SGK-1. SSZ is a prodrug composed of 5-aminosalicylic acid and sulfapyridine linked by NN bond, which is therapeutically effective for inflammatory bowel diseases. However, the NN bond in SSZ was necessary for its inhibitory action against SGK-1. Although intrathecal injection of SSZ to nerve-injured mice significantly alleviated mechanical pain hypersensitivity, no significant anti- neuropathic pain effects of SSZ were detected after oral administration due to its low bioavailability and limited spinal distribution, which were associated with efflux by the xenobiotic transporter breast cancer resistance protein (BCRP). Concomitant oral administration of SSZ with febuxostat (FBX), which is an approved drug to inhibit BCRP, improved the distribution of SSZ to the spinal cord. The concomitant oral administration with FBX also increased the anti-neuropathic pain effects of SSZ. Our study revealed a previously unrecognized pharmacological effect of SSZ to alleviate SGK-1-induced painful peripheral neuropathy, and concomitant oral administration of SSZ with FBX may also be a preventative option for diurnal exacerbation of neuropathic pain hypersensitivity.

Pharmacotherapeutic Options for Managing Pain in Multiple Sclerosis

Pain is a major matter for patients with multiple sclerosis; treatment response is frequently inadequate, with a significant impact on quality of life. The estimated prevalence of pain in multiple sclerosis ranges widely (26-86%), and different subtypes of pain, mediated by specific pathophysiological mechanisms, are described. The aim of this narrative review, performed using a systematic search methodology, was to provide current, evidence-based, knowledge about the pharmacological treatment of the different kinds of pain in multiple sclerosis. We searched for relevant papers within PubMed, EMBASE, the Cochrane Database of Systematic Reviews, and the Clinical Trials database (ClinicalTrials.gov), considering publications up to November 2019. Two authors independently selected studies for inclusion, data extraction, and bias assessment. A total of 27 randomized controlled trials were identified, but in only a few cases, patients with different pain qualities were stratified. Following a mechanism-based approach, treatment of paroxysmal pain and painful tonic spasms should be based on sodium-channel blockers, whereas treatment of ongoing extremity pain should be based on gabapentinoids and antidepressants.

Glucocorticoid regulation of ATP release from spinal astrocytes underlies diurnal exacerbation of neuropathic mechanical allodynia

Diurnal variations in pain hypersensitivity are common in chronic pain disorders, but the underlying mechanisms are enigmatic. Here, we report that mechanical pain hypersensitivity in sciatic nerve-injured mice shows pronounced diurnal alterations, which critically depend on diurnal variations in glucocorticoids from the adrenal glands. Diurnal enhancement of pain hypersensitivity is mediated by glucocorticoid-induced enhancement of the extracellular release of ATP in the spinal cord, which stimulates purinergic receptors on microglia in the dorsal horn. We identify serum- and glucocorticoid-inducible kinase-1 (SGK-1) as the key molecule responsible for the glucocorticoid-enhanced release of ATP from astrocytes. SGK-1 protein levels in spinal astrocytes are increased in response to glucocorticoid stimuli and enhanced ATP release by opening the pannexin-1 hemichannels. Our findings reveal an unappreciated circadian machinery affecting pain hypersensitivity caused by peripheral nerve injury, thus opening up novel approaches to the management of chronic pain.

Neuropathic pain hypersensitivity is known to undergo diurnal variations, although the underlying mechanisms are not clear. Using a sciatic nerve-injury mouse model, the authors find such diurnal changes are mediated by glucocorticoid induced enhancement of ATP release from astrocytes via pannexin-1 hemichannels.

Pharmacological management of spasticity in multiple sclerosis: Systematic review and consensus paper

Background and objectives:

Treatment of spasticity poses a major challenge given the complex clinical presentation and variable efficacy and safety profiles of available drugs. We present a systematic review of the pharmacological treatment of spasticity in multiple sclerosis (MS) patients.

Methods:

Controlled trials and observational studies were identified. Scientific evidence was evaluated according to pre-specified levels of certainty.

Results:

The evidence supports the use of baclofen, tizanidine and gabapentin as first-line options. Diazepam or dantrolene could be considered if no clinical improvement is seen with the previous drugs. Nabiximols has a positive effect when used as add-on therapy in patients with poor response and/or tolerance to first-line oral treatments. Despite limited evidence, intrathecal baclofen and intrathecal phenol show a positive effect in severe spasticity and suboptimal response to oral drugs.

Conclusion:

The available studies on spasticity treatment offer some insight to guide clinical practice but are of variable methodological quality. Large, well-designed trials are needed to confirm the effectiveness of antispasticity agents and to produce evidence-based treatment algorithms.

Synaptopathy connects inflammation and neurodegeneration in multiple sclerosis

Multiple sclerosis (MS) has long been regarded as a chronic inflammatory disease of the white matter that leads to demyelination and eventually to neurodegeneration. In the past decade, several aspects of MS pathogenesis have been challenged, and degenerative changes of the grey matter, which are independent of demyelination, have become a topic of interest. CNS inflammation in MS and experimental autoimmune encephalomyelitis (EAE; a disease model used to study MS in rodents) causes a marked imbalance between GABAergic and glutamatergic transmission, and a loss of synapses, all of which leads to a diffuse 'synaptopathy'. Altered synaptic transmission can occur early in MS and EAE, independently of demyelination and axonal loss, and subsequently causes excitotoxic damage. Inflammation-driven synaptic abnormalities are emerging as a prominent pathogenic mechanism in MS-importantly, they are potentially reversible and, therefore, represent attractive therapeutic targets. In this Review, we focus on the connection between inflammation and synaptopathy in MS and EAE, which sheds light not only on the pathophysiology of MS but also on that of primary neurodegenerative disorders in which inflammatory processes contribute to disease progression.

Fighting insomnia and battling lethargy: the yin and yang of palliative care

There is an interdependent relationship between insomnia and fatigue in the medical literature, but both remain distinct entities. Insomnia entails problematic sleep initiation, maintenance, or restoration with an accompanying decrease in perceived daytime function. Lethargy is a symptom that has a wide differential diagnosis that heavily overlaps with cancer-related fatigue; however, insomnia may contribute to worsened fatigue and lethargy in cancer patients. Insomnia is a major risk factor for mood disturbances such as depression, which may also contribute to lethargy in this at-risk population. The pathophysiology of fatigue and insomnia is discussed in this review, including their differential diagnoses as well as the emerging understanding of the roles of neurotransmitters, branched-chain amino acids, and inflammatory cytokines. Treatment approaches for insomnia and fatigue are also discussed and reviewed, including the role of hypnotics, psychotropics, hormonal agents, and alternative therapies.

Diurnal and twenty-four hour patterning of human diseases: acute and chronic common and uncommon medical conditions

The symptom intensity and mortality of human diseases, conditions, and syndromes exhibit diurnal or 24 h patterning, e.g., skin: atopic dermatitis, urticaria, psoriasis, and palmar hyperhidrosis; gastrointestinal: esophageal reflux, peptic ulcer (including perforation and hemorrhage), cyclic vomiting syndrome, biliary colic, hepatic variceal hemorrhage, and proctalgia fugax; infection: susceptibility, fever, and mortality; neural: frontal, parietal, temporal, and occipital lobe seizures, Parkinson's and Alzheimer's disease, hereditary progressive dystonia, and pain (cancer, post-surgical, diabetic neuropathic and foot ulcer, tooth caries, burning mouth and temporomandibular syndromes, fibromyalgia, sciatica, intervertebral vacuum phenomenon, multiple sclerosis muscle spasm, and migraine, tension, cluster, hypnic, and paroxysmal hemicranial headache); renal: colic and nocturnal enuresis and polyuria; ocular: bulbar conjunctival redness, keratoconjunctivitis sicca, intraocular pressure and anterior ischemic optic neuropathy, and recurrent corneal erosion syndrome; psychiatric/behavioral: major and seasonal affective depressive disorders, bipolar disorder, parasuicide and suicide, dementia-associated agitation, and addictive alcohol, tobacco, and heroin cravings and withdrawal phenomena; plus autoimmune and musculoskeletal: rheumatoid arthritis, osteoarthritis, axial spondylarthritis, gout, Sjögren's syndrome, and systemic lupus erythematosus. Knowledge of these and other 24 h patterns of human pathophysiology informs research of their underlying circadian and other endogenous mechanisms, external temporal triggers, and more effective patient care entailing clinical chronopreventive and chronotherapeutic strategies.

Pharmacological treatment of pain in multiple sclerosis

Pain is a common symptom in multiple sclerosis (MS) and was recently estimated to be experienced by up to 75% of patients. Nociceptive and neuropathic pain in MS may be present concurrently and at different stages of the disease and may be associated with other symptoms. Evidence for treating pain in MS is limited. Many clinical features of pain are often unrecognized by clinicians and are difficult for patients to describe. Treatment is often based on anecdotal reports and clinical experience. We present a review of treatment options for pain in MS that should serve to update current knowledge, highlight shortcomings in clinical research and provide indications towards achieving evidence-based treatment of pain in MS.

Treating pain in multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory, demyelinating, central nervous system disease that frequently causes pain.

AREAS COVERED

This article reviews the current literature and describes the therapeutic options for treating MS-related pain. The reader will be provided with current, evidence-based knowledge about the treatment of MS-related pain, and the review will take a practical approach to the various drugs for treating pain, including starting dose, titration and side effects.

EXPERT OPINION

Only cannabinoids have been assessed in randomized, controlled trials. Because of the concern regarding the risk of abuse and psychiatric adverse events, published guidelines as well as expert recommendations suggest using them as second-line therapy only. Hence, current treatment should be based on the general principles for treating peripheral neuropathic pain, taking into account drug-induced adverse effects.

Role of cannabinoids in multiple sclerosis

Although extracts from the cannabis plant have been used medicinally for thousands of years, it is only within the last 2 decades that our understanding of cannabinoid physiology and the provision of evidence for therapeutic benefit of cannabinoids has begun to accumulate. This review provides a background to advances in our understanding of cannabinoid receptors and the endocannabinoid system, and then considers how cannabinoids may help in the management of multiple sclerosis (MS). The relative paucity of treatments for MS-related symptoms has led to experimentation by patients with MS in a number of areas including the use of cannabis extracts. An increasing amount of evidence is now emerging to confirm anecdotal reports of symptomatic improvement, particularly for muscle stiffness and spasms, neuropathic pain and sleep and bladder disturbance, in patients with MS treated with cannabinoids. Trials evaluating a role in treating other symptoms such as tremor and nystagmus have not demonstrated any beneficial effects of cannabinoids. Safety profiles of cannabinoids seem acceptable, although a slow prolonged period of titration improves tolerability. No serious safety concerns have emerged. Methodological issues in trial design and treatment delivery are now being addressed. In addition, recent experimental evidence is beginning to suggest an effect of cannabinoids on more fundamental processes important in MS, with evidence of anti-inflammation, encouragement of remyelination and neuroprotection. Trials are currently under way to test whether cannabinoids may have a longer term role in reducing disability and progression in MS, in addition to symptom amelioration, where indications are being established.

Pharmacological management of pain in patients with multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating, autoimmune disease of the CNS. There are currently a number of disease-modifying medications for MS that modulate or suppress the immune system; however, these medications do not directly relieve MS symptoms, which include visual deficits, gait problems, sensory deficits, weakness, tremor, spasticity and pain, among others. Pain is a common symptom in MS which has recently been estimated to be experienced by more than 40% of patients. Nociceptive pain occurs as an appropriate physiological response transmitted to a conscious level when nociceptors in bone, muscle or any body tissue are activated, warning the organism of tissue damage. Neuropathic pain is initiated as a direct consequence of a lesion or disease affecting the somatosensory system, with no physiological advantage. Nociceptive and neuropathic pain in MS may be present concurrently and at different stages of the disease, and may be associated with other symptoms. Central neuropathic pain has been reported to be among the most common pain syndromes in MS. It is described as constant, often spontaneous, burning occurring more frequently in the lower limbs. Treatment typically includes tricyclic antidepressants and antiepileptic medications, although studies have been conducted in relatively small samples and optimal dosing has not been confirmed. Cannabinoids have been among the few treatments studied in well designed, randomized, placebo-controlled trials for central neuropathic pain. In the largest of these trials, which included 630 subjects, a 15-week comparison between Delta9-tetrahydrocannabinol and placebo was performed. More patients receiving active treatment perceived an improvement in pain than those receiving placebo, although approximately 20% of subjects reported worsening of pain while on active treatment. Trigeminal neuralgia, while affecting less than 5% of patients with MS, is the most studied pain syndrome. The pain can be extreme and is typically treated with carbamazepine, although adverse effects can mimic an MS exacerbation. Painful topic spasms occur in approximately 11% of the MS population and are treated with antispasticity medications such as baclofen and benzodiazepines. Gabapentin has also demonstrated efficacy, but all studies have included small sample sizes. In general, evidence for treating pain in MS is limited. Many clinical features of pain are often unrecognized by clinicians and are difficult for patients to describe. Treatment is often based on anecdotal reports and clinical experience. We present a review of treatment options for pain in MS, which should serve to update current knowledge, highlight shortcomings in clinical research and provide indications towards achieving evidence-based treatment of pain in MS.

Current management of pain associated with multiple sclerosis

While pain is a common problem in patients with multiple sclerosis (MS), it is not frequently mentioned by patients and a more direct approach is required in order to obtain information about pain from patients. Many patients with MS experience more than one pain syndrome; combinations of dysaesthesia, headaches and/or back or muscle and joint pain are frequent. For each pain syndrome a clear diagnosis and therapeutic concept needs to be established. Pain in MS can be classified into four diagnostically and therapeutically relevant categories: (i) neuropathic pain due to MS (pain directly related to MS); (ii) pain indirectly related to MS; (iii) MS treatment-related pain; and (iv) pain unrelated to MS. Painful paroxysmal symptoms such as trigeminal neuralgia (TN), or painful tonic spasms are treated with antiepileptics as first choice, e.g. carbamazepine, oxcarbazepine, lamotrigine, gabapentin, pregabalin, etc. Painful 'burning' dysaesthesias, the most frequent chronic pain syndrome, are treated with TCAs such as amitriptyline, or antiepileptics such as gabapentin, pregabalin, lamotrigine, etc. Combinations of drugs with different modes of action can be particularly useful for reducing adverse effects. While escalation therapy may require opioids, there are encouraging results from studies regarding cannabinoids, but their future role in the treatment of MS-related pain has still to be determined. Pain related to spasticity often improves with adequate physiotherapy. Drug treatment includes antispastic agents such as baclofen or tizanidine and in patients with phasic spasticity, gabapentin or levetiracetam are administered. In patients with severe spasticity, botulinum toxin injections or intrathecal baclofen merit consideration. While physiotherapy may ameliorate malposition-induced joint and muscle pain, additional drug treatment with paracetamol (acetaminophen) or NSAIDs may be useful. Moreover, painful pressure lesions should be avoided by using optimally adjusted aids. Treatment-related pain associated with MS can occur with subcutaneous injections of interferon-beta or glatiramer acetate, and may be reduced by optimizing the injection technique and by local cooling. Systemic (particularly 'flu-like') adverse effects of interferons, e.g. myalgias, can be reduced by administering paracetamol, ibuprofen or naproxen. A potential increase in the frequency of pre-existing headaches after starting treatment with interferons may require optimization of headache attack therapy or even prophylactic treatment. Pain unrelated to MS, such as back pain or headache, is common in patients with MS and may deteriorate as a result of the disease. In summary, a careful analysis of each pain syndrome will allow the design of the appropriate treatment plan using various medical and nonmedical options (multimodal therapy), and will thus help to improve the quality of life (QOL) of the patients.

Nonepileptic uses of antiepileptic drugs in children and adolescents

Antiepileptic drugs are often prescribed for nonepileptic neurologic and psychiatric conditions. The United States Food and Drug Administration has approved several antiepileptic drugs for the treatment of neuropathic pain, migraine, and mania in adults. For pediatric patients, use of antiepileptic drugs for non-seizure-related purposes is supported mainly by adult studies, open-label trials, and case reports. Summarized here is the published literature for or against the use of antiepileptic drugs for neuropathic pain, migraine, movement disorders, bipolar disorder, aggressive behavior, and pervasive developmental disorders in children and adolescents. Using the American Academy of Neurology's four-tiered classification scheme for a therapeutic article and translation to a recommendation rating, there are no nonepileptic disorders for which antiepileptic drugs have been established as effective for pediatric patients. Valproate and carbamazepine are "possibly effective" in the treatment of Sydenham chorea, and valproate is "probably effective" in decreasing aggressive behavior. Carbamazepine is "probably ineffective" in the treatment of aggression, and lamotrigine is "possibly ineffective" in improving the core symptom of pervasive developmental disorders. Despite the frequent use of antiepileptic drugs in the treatment of juvenile bipolar disorder, migraine, and neuropathic pain, the data are insufficient to make recommendations regarding the efficacy of antiepileptics in these conditions in children and adolescents.

How pain and analgesics disturb sleep

OBJECTIVE

Clinical experiences as well as specific investigations show that pain and sleep disturbances are closely correlated. The aims of this review are first to describe sleep disturbances related to painful medical diseases and analgesics and secondly to propose management possibilities for these sleep disturbances.

METHOD

The viewpoints presented were based mainly on objective rest activity and sleep studies using actigraphy and polysomnography.

RESULTS

Polysomnographic and actigraphic studies have described significant sleep disturbances in patients suffering from different pain disorders. These disturbances are: reduced sleep efficiency and altered sleep architecture characterized by increased wakefulness and stage 1 non-rapid eye movement sleep, associated with diminished slow wave sleep and rapid eye movement sleep. Sleep disturbances may be related to pain and to the analgesic or sedative medications administered.

CONCLUSION

If many factors, including pain, disease process per se, as well as medication, could disturb sleep, sleep disturbances may also adversely affect the natural course of the painful disease. Improving sleep quantity and quality in patients with painful disorders may break this vicious circle and as consequence enhance the patients' overall health and quality of life.

Gabapentin: pharmacology and its use in pain management

Although its exact mode of action is not known, gabapentin appears to have a unique effect on voltage-dependent calcium ion channels at the postsynaptic dorsal horns and may, therefore, interrupt the series of events that possibly leads to the experience of a neuropathic pain sensation. Gabapentin is especially effective at relieving allodynia and hyperalgesia in animal models. It has been shown to be efficacious in numerous small clinical studies and case reports in a wide variety of pain syndromes. Gabapentin has been clearly demonstrated to be effective for the treatment of neuropathic pain in diabetic neuropathy and postherpetic neuralgia. This evidence, combined with its favourable side-effect profile in various patient groups (including the elderly) and lack of drug interactions, makes it an attractive agent. Therefore, gabapentin should be considered an important drug in the management of neuropathic pain syndromes.