Pregabalin for the treatment of fibromyalgia

The Antinociceptive Effects and Sex-Specific Neurotransmitter Modulation of Metformin in a Mouse Model of Fibromyalgia

Fibromyalgia (FM) is a chronic and debilitating condition characterized by diffuse pain, often associated with symptoms such as fatigue, cognitive disturbances, and mood disorders. Metformin, an oral hypoglycemic agent, has recently gained attention for its potential benefits beyond glucose regulation. It has shown promise in alleviating neuropathic and inflammatory pain, suggesting that it could offer a novel approach to managing chronic pain conditions like FM. This study aimed to further explore metformin's analgesic potential by evaluating its effects in an experimental FM model induced by reserpine in both male and female mice. After the administration of 200 mg/kg metformin to male and female mice, the FM-related symptoms were assessed, including mechanical allodynia, thermal hyperalgesia, and depressive-like behaviors. A histological examination of the thalamus, hippocampus, and spinal cord was conducted using haematoxylin and eosin staining. The neurotransmitter and proinflammatory cytokines levels were measured in the brains and spinal cords. Our results have shown that metformin treatment for seven days significantly reversed these FM-like symptoms, reducing pain sensitivity and improving mood-related behaviors in both the male and female mice. Additionally, metformin exhibited neuroprotective effects, mitigating reserpine-induced damage in the hippocampus, thalamus, and spinal cord. It also significantly lowered the levels of the proinflammatory cytokine interleukin 1-beta (IL-1β) in the brain and spinal cord. Notably, metformin modulated the neurotransmitter levels differently between the sexes, decreasing glutamate and increasing serotonin and norepinephrine in the male mice, but not in the females. These findings underscore metformin's potential as an alternative therapy for FM, with sex-specific differences suggesting distinct mechanisms of action.

Short‑term effects of pregabalin plus exercise therapy on pain, emotional status, physical function and nociceptive responses in patients with fibromyalgia

The aim of the present study was to investigate the effects of pregabalin plus exercise vs. pregabalin treatment alone on the electromyographic nociceptive flexion reflex (NFR) threshold in patients with fibromyalgia (FM). For this purpose, the present study included a total of 40 patients diagnosed with FM according to the American College of Rheumatology 2010 criteria. The patients were divided into two groups as follows: Group 1 received pregabalin treatment only and group 2 received exercise therapy in addition to pregabalin treatment. Assessments were made at baseline and at the 1st month using a visual analog scale (VAS) to measure pain, the Fibromyalgia Impact Questionnaire (FIQ) to measure the severity of FM, Beck's Depression Inventory (BDI) to measure depression and the NFR to measure the compressive forces on peripheral nerves. In both groups, the NFR threshold following treatment was significantly higher than that at the baseline results (P#x003C;0.001). There was no significant difference between the groups as regards the difference from pre- to post-treatment NFR threshold values (P=0.610 and P=0.555, respectively). There was a strong, negative correlation between the pre-treatment NFR threshold and VAS resting, VAS motion and FIQ scores (Rho=-0.62, Rho=-0.69 and Rho=-0.60, respectively). There was a moderate negative correlation between the pre-treatment NFR threshold and BDI scores (Rho=-0.35). On the whole, the present study demonstrates that in the treatment of FM, pregabalin improves the clinical scores and leads to an increase in the NFR threshold. Herewith, it should be noted that short-term exercise therapy does not appear to provide additional benefits.

Fibromyalgia Concomitant with Seropositive Rheumatoid Arthritis in a Tertiary Hospital in South-Western Saudi Arabia: Prevalence and Treatment Patterns

Introduction:

Rheumatoid arthritis (RA) patients with fibromyalgia syndrome (FMS) report worse functional status and quality of life hence the association has important clinical implications. FMS can be challenging to treat, and the current evidence recommends a multidisciplinary treatment approach focused on symptom management.

Aim:

Information regarding the current prevalence of FMS in RA patients is lacking. Thus, this study aims to address the prevalence and predictors of FMS in seropositive RA patients and demonstrate our clinical practice in the management of FMS.

Methods:

Participants’ data was gathered from Aseer central hospital (ACH) rheumatology clinics and daycare units over a period of 2 years. Subjects were assessed using the 2010 American College of Rheumatology (ACR) criteria for FMS. Data were collected from medical records, including patient demographics, comorbidities and concomitant FMS-related data.

Results:

Out of 310 seropositive RA patients, 15% (n = 47) fulfilled the diagnostic criteria for FMS. Of them, 29, 11 and 7 were on pregabalin, amitriptyline and duloxetine, respectively. Half of FMS patients showed one or more therapy changes. A significant difference between RA patients with and without concomitant FMS was observed, including age, gender and comorbidities.

Conclusion:

In this retrospective study, a high prevalence of FMS in individuals with seropositive RA was identified. This study explores real-world practice in the treatment of FMS with remarkable findings regarding underdosing and lower discontinuation rate of pregabalin.

Gabapentin and pregabalin to treat aggressivity in dementia: a systematic review and illustrative case report

AIMS

The prevalence of dementia is rising as life expectancy increases globally. Behavioural and psychological symptoms of dementia (BPSD), including agitation and aggression, are common, presenting a challenge to clinicians and caregivers.

METHODS

Following PRISMA guidelines, we systematically reviewed evidence for gabapentin and pregabalin against BPSD symptoms of agitation or aggression in any dementia, using six databases (Pubmed, CINHL, PsychINFO, HealthStar, Embase, and Web of Science). Complementing this formal systematic review, an illustrative case of a patient with BPSD in mixed Alzheimer's/vascular dementia, who appeared to derive benefits in terms of symptom control and functioning from the introduction of gabapentin titrated up to 3600 mg day^-1 alongside other interventions, is presented.

RESULTS

Twenty-four relevant articles were identified in the systematic review. There were no randomized trials. Fifteen papers were original case series/case reports of patients treated with these compounds, encompassing 87 patients given gabapentin and six given pregabalin. In 12 of 15 papers, drug treatment was effective in the majority of cases. The remaining nine papers were solely reviews, of which two were described as systematic but predated PRISMA guidelines. Preliminary low-grade evidence based on case series and case reviews suggests possible benefit of gabapentin and pregabalin in patients with BPSD in Alzheimer's disease. These benefits cannot be confirmed until well-powered randomized controlled trials are undertaken. Evidence in frontotemporal dementia is lacking.

CONCLUSION

Gabapentin and pregabalin could be considered for BPSD when medications having stronger evidence bases (risperidone, other antipsychotics, carbamazepine and citalopram) have been ineffective or present unacceptable risks of adverse outcomes.

The Effect of Preoperative Pregabalin on Postoperative Nausea and Vomiting: A Meta-analysis

BACKGROUND

Nonopioid adjuvant medications are increasingly included among perioperative Enhanced Recovery After Surgery protocols. Preoperative pregabalin has been shown to improve postoperative pain and limit reliance on opioid analgesia. Our group investigated the ability of preoperative pregabalin to also prevent postoperative nausea and vomiting (PONV).

METHODS

Our group performed a meta-analysis of randomized trials that report outcomes on the effect of preoperative pregabalin on PONV endpoints in patients undergoing general anesthesia.

RESULTS

Among all included trials (23 trials; n = 1693), preoperative pregabalin was associated with a significant reduction in PONV (risk ratio [RR] = 0.53; 95% confidence interval [CI], 0.39-0.73; P = 0.0001), nausea (RR = 0.62; 95% CI, 0.46-0.83; P = 0.002), and vomiting (RR = 0.68; 95% CI, 0.52-0.88; P = 0.003) at 24 hours. Subgroup analysis designed to account for major PONV confounders, including the exclusion trials with repeat dosing, thiopental induction, nitrous oxide maintenance, and prophylactic antiemetics and including high-risk surgery, resulted in similar antiemetic efficacy. Preoperative pregabalin is also associated with significantly increased rates of postoperative visual disturbance (RR = 3.11; 95% CI, 1.34-7.21; P = 0.008) compared with a control.

CONCLUSIONS

Preoperative pregabalin is associated with significant reduction of PONV and should not only be considered as part of a multimodal approach to postoperative analgesia but also for prevention of PONV.

Targeting ASIC3 for Relieving Mice Fibromyalgia Pain: Roles of Electroacupuncture, Opioid, and Adenosine

Many scientists are seeking better therapies for treating fibromyalgia (FM) pain. We used a mouse model of FM to determine if ASIC3 and its relevant signaling pathway participated in FM pain. We demonstrated that FM-induced mechanical hyperalgesia was attenuated by electroacupuncture (EA). The decrease in fatigue-induced lower motor function in FM mice was also reversed by EA. These EA-based effects were abolished by the opioid receptor antagonist naloxone and the adenosine A1 receptor antagonist rolofylline. Administration of opioid receptor agonist endomorphin (EM) or adenosine A1 receptor agonist N⁶-cyclopentyladenosine (CPA) has similar results to EA. Similar results were also observed in ASIC3^−/− or ASIC3 antagonist (APETx2) injected mice. Using western blotting, we determined that pPKA, pPI3K, and pERK were increased during a dual acidic injection priming period. Nociceptive receptors, such as ASIC3, Nav1.7, and Nav1.8, were upregulated in the dorsal root ganglion (DRG) and spinal cord (SC) of FM mice. Furthermore, pPKA, pPI3K, and pERK were increased in the central thalamus. These aforementioned mechanisms were completely abolished in ASIC3 knockout mice. Electrophysiological results also indicated that acid potentiated Nav currents through ASIC3 and ERK pathway. Our results highlight the crucial role of ASIC3-mediated mechanisms in the treatment of FM-induced mechanical hyperalgesia.

Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology

Voltage‐gated calcium channels are essential players in many physiological processes in excitable cells. There are three main subdivisions of calcium channel, defined by the pore‐forming α₁ subunit, the Ca_V1, Ca_V2 and Ca_V3 channels. For all the subtypes of voltage‐gated calcium channel, their gating properties are key for the precise control of neurotransmitter release, muscle contraction and cell excitability, among many other processes. For the Ca_V1 and Ca_V2 channels, their ability to reach their required destinations in the cell membrane, their activation and the fine tuning of their biophysical properties are all dramatically influenced by the auxiliary subunits that associate with them. Furthermore, there are many diseases, both genetic and acquired, involving voltage‐gated calcium channels. This review will provide a general introduction and then concentrate particularly on the role of auxiliary α₂δ subunits in both physiological and pathological processes involving calcium channels, and as a therapeutic target.

Effects of electroacupuncture in a mouse model of fibromyalgia: role of N-methyl-D-aspartate receptors and related mechanisms

Objective

N-methyl-D-aspartate receptor (NMDAR) activation and downstream transduction pathways are crucial for pain signalling. Fibromyalgia (FM) is a common pain syndrome of unclear aetiology that is often drug-refractory but may benefit from treatment with electroacupuncture (EA). We examined the contributions of NMDAR signalling to FM pain and EA responses in a mouse model.

Methods

A model of FM was established by acid saline injection in 32 mice and subgroups (n=8 each) were treated with EA (2 Hz, 15 min daily for 4 days) or minimal acupuncture (MA). Expression of NMDAR subunits, calmodulin-dependent protein kinase II (CaMKII), cyclic AMP response element binding protein (pCREB) and their corresponding phospho-activated forms were measured by Western blotting and immunohistochemistry.

Results

Acid saline injection induced significant mechanical hyperalgesia (paw withdrawal threshold 2.18±0.27 g, p<0.05 vs controls), which was reversed by EA (4.23±0.33 g, p<0.05 vs FM group) but not by MA (2.37±0.14 g, p<0.05 vs EA group). Expression levels of phosphorylated N-methyl-D-aspartate receptor (pNR)1 and pNR2B were significantly increased in the dorsal root ganglion of FM model mice (132.21±14.4% and 116.69±3.22% of control values), whereas NR1 and NR2B levels were unchanged (97.31±3.79% and 97.07%±2.27%, respectively). Expression levels of pCaMKIIα and pCREB were also higher in the FM group, and these changes were reversed by EA but not by MA. Similar changes in expression were observed in spinal cord neurons.

Conclusions

Reduced NMDAR−CaMKIIα−pCREB signalling is implicated in the positive effects of EA in FM. NMDAR signalling components may represent promising therapeutic targets for FM treatment.

Treatment Patterns Associated with ACR-Recommended Medications in the Management of Fibromyalgia in the United States

BACKGROUND

Fibromyalgia (FM) affects up to 6% of U.S. adults, resulting in a significant burden on the health care system and poor quality of life for patients. Duloxetine, pregabalin, and milnacipran are approved for management of FM; however, consensus is lacking regarding optimal therapy. Patients with FM taking approved medications often do not experience meaningful symptom relief, and many experience intolerable adverse events.

OBJECTIVE

To assess treatment patterns associated with available and commonly used medications for the management of FM using U.S. health insurance claims.

METHODS

This retrospective analysis used the MarketScan claims database to identify adults with a first diagnosis of FM (ICD-9-CM code 729.1) between 2009 and 2011 with continuous health plan enrollment for 12 months pre- and post-index. Medications of interest were pregabalin, gabapentin, duloxetine, milnacipran, cyclobenzaprine, and tramadol. These are 6 of the 8 medications recommended by the American College of Rheumatology (ACR) for treating FM; the other 2 (amitriptyline and venlafaxine) were only included in some initial assessments. The Charlson Comorbidity Index (CCI) was used to assess overall comorbidity burden. Endpoints included proportion of patients treated within 1 year after first diagnosis; initial treatment pattern; adherence over the first-year follow-up period for the medications of interest; and discontinuation, switching, and combination therapy patterns among pain medications of interest at different time points. Proportion of days covered (PDC; defined as number of days in the period when the patient had drug supply divided by the number of days in the period) was used to define adherence, which was categorized as low (PDC < 50%), medium (PDC 50% to < 80%), or high (PDC ≥ 80%). The time to discontinuation (defined as the first drug supply gap ≥ 90 days) was estimated using Kaplan-Meier analysis.

RESULTS

Overall, 240,144 patients met the inclusion criteria. Patients were predominantly women (68%), had preferred provider organization insurance coverage (68%), and had a CCI score < 1 at baseline (69%). Only 31% (n = 74,738) initiated a treatment with a prescription medication listed in the ACR guidelines, and many patients received less than the recommended dose. Most (n = 70,919) patients initially received monotherapy with one of the 8 prescription medications. Of those who started with ≥ 2 medications (n = 3,819), cyclobenzaprine plus tramadol was the most frequent combination. Adherence was suboptimal for all 6 medications of interest. Duloxetine had the highest mean PDC (59%); for all other agents, mean PDC was < 50%. With the exception of duloxetine, discontinuation rates at 6 months were > 50% for all agents. Alterations in therapy were common. Among patients who discontinued their initial treatment of duloxetine, pregabalin, or milnacipran, approximately one-third had switched treatments within 90 days after their first prescription. For those who maintained their initial treatment agent, approximately 50% of patients added a second pain medication within 1 year of treatment initiation.

CONCLUSIONS

The evidence suggests that patients with FM often do not receive 1 of the prescription medications recommended by ACR guidelines, and those who do are commonly prescribed lower-than-recommended doses, potentially resulting in poor effectiveness and tolerability. Discontinuation, switching, and addition of new pain medications are common, which may indicate low levels of satisfaction with initial treatment. New therapies with improved effectiveness and better tolerability are urgently needed for patients with FM.

Effect of Pregabalin on Cardiovascular Responses to Exercise and Postexercise Pain and Fatigue in Fibromyalgia: A Randomized, Double-Blind, Crossover Pilot Study

Pregabalin, an approved treatment for fibromyalgia (FM), has been shown to decrease sympathetic nervous system (SNS) activity and inhibit sympathetically maintained pain, but its effects on exercise responses have not been reported. Methods. Using a randomized double-blind crossover design, we assessed the effect of 5 weeks of pregabalin (versus placebo) on acute cardiovascular and subjective responses to moderate exercise in 19 FM patients. Blood pressure (BP), heart rate (HR), and ratings of perceived exertion (RPE) during exercise and ratings of pain, physical fatigue, and mental fatigue before, during, and for 48 hours after exercise were compared in patients on pregabalin versus placebo and also versus 18 healthy controls. Results. On placebo, exercise RPE and BP were significantly higher in FM patients than controls (p < 0.04). Pregabalin responders (n = 12, defined by patient satisfaction and symptom changes) had significantly lower exercise BP, HR, and RPE on pregabalin versus placebo (p < 0.03) and no longer differed from controls (p > 0.26). Cardiovascular responses of nonresponders (n = 7) were not altered by pregabalin. In responders, pregabalin improved ratings of fatigue and pain (p < 0.04), but negative effects on pain and fatigue were seen in nonresponders. Conclusions. These preliminary findings suggest that pregabalin may normalize cardiovascular and subjective responses to exercise in many FM patients.

Pregabalin for chronic pain: does one medication fit all?

BACKGROUND

Pregabalin is frequently prescribed for chronic non-cancer pain. No previous study has examined its off-label use.

OBJECTIVES

Our primary aim was to assess the proportion of patients taking pregabalin for conditions approved by Health Canada ('on-label') and compare their perspectives on its use to those who use pregabalin for other conditions ('off-label').

METHODS

Patients who have used pregabalin within the past year were recruited from two registries of chronic non-cancer pain patients treated in tertiary care clinics: the Quebec Pain Registry and the Fibromyalgia Patients Registry. Data on the use of pregabalin and its perceived benefits were collected from the registries and from completed questionnaires.

RESULTS

Out of 4339 screened chronic non-cancer pain patients, 355 (8.18%) met the study selection criteria. Three-quarters of them (268/355) used pregabalin for pain conditions not approved by Health Canada and were therefore regarded as off-label users. The most prevalent condition for pregabalin use was lumbar back pain (103/357; 28.85%). There were no significant differences between on- and off-label users in their perceived satisfaction from pregabalin therapy and its effect on function and quality of life. Among former users, the most prevalent reason for discontinuation was adverse effects, mainly dry mouth and weight gain.

CONCLUSIONS

We conclude that despite specific indications for pregabalin prescription, it is mainly used off-label, notably for low back pain. Nevertheless, off-label users were equally satisfied with its clinical effects. Although formal exploration of the broader analgesic properties of pregabalin is warranted, treating heterogeneous chronic pain conditions with pregabalin may be legitimate.

LIMITATIONS

The main limitations of the study are patients' low response rate, the recruitment of participants solely from a tertiary pain center and not from the general patient population and a possible recall bias that may have arisen from the retrospective nature of the study.

Targeting angiotensin II type 2 receptor pathways to treat neuropathic pain and inflammatory pain

INTRODUCTION

Neuropathic pain and chronic inflammatory pain are large unmet medical needs. Over the past two decades, numerous 'pain targets' have been identified for analgesic drug discovery. Despite promising results in rodent pain models, many compounds modulating such targets lacked efficacy in clinical trials. An exception is oral EMA401, a small-molecule angiotensin II type 2 receptor (AT2R) antagonist.

AREAS COVERED

Herein, angiotensin II/AT2R signaling-induced hyperexcitability and abnormal sprouting of cultured dorsal root ganglion neurons, together with radioligand binding, pharmacokinetics, analgesic efficacy and mode of action of small-molecule AT2R antagonists in rodent models of peripheral neuropathic and chronic inflammatory pain, are reviewed. The findings of a successful Phase IIa clinical trial of EMA401 in patients with neuropathic pain are presented in brief.

EXPERT OPINION

The functional importance of angiotensin II/AT2R signaling has remained enigmatic for decades, and there are no clinically available medications that target the AT2R. However, on the basis of preclinical findings and recent clinical trial data showing that the peripherally restricted, small-molecule AT2R antagonist, EMA401, successfully alleviated neuropathic pain in a Phase II clinical trial, the AT2R is receiving considerable attention as a new therapeutic target with human validation for the relief of peripheral neuropathic and chronic inflammatory pain conditions.

Milnacipran for fibromyalgia: a useful addition to the treatment armamentarium

INTRODUCTION

Antidepressants are used to treat a variety of chronic pain conditions including peripheral neuropathy, headache, and more recently, fibromyalgia. The antidepressant milnacipran blocks the reuptake of norepinephrine and serotonin and is used for the management of fibromyalgia.

AREAS COVERED

The article contains data primarily obtained from the MEDLINE database using a PubMed search of the keywords including milnacipran, fibromyalgia and depression. Of the available serotonin norepinephrine reuptake inhibitors, milnacipran has greater potency in inhibiting reuptake of norepinephrine relative to serotonin and is proposed to work by attenuating pain signals. Milnacipran is well tolerated and effective for fibromyalgia pain when given in divided doses of 100 - 200 mg daily. Studies show that milnacipran may be effective for fibromyalgia-associated symptoms including depression and fatigue.

EXPERT OPINION

Milnacipran provides modest fibromyalgia pain relief and is best used as part of a multidisciplinary treatment approach. While milnacipran was not studied in fibromyalgia patients with major depression, it may be a wise choice for fibromyalgia patients with depressive symptoms and patients for whom sedation, dizziness, edema or weight gain with gabapentin and pregabalin is a problem. Milnacipran has been found to be beneficial for treating some troublesome fibromyalgia-associated symptoms, including fatigue and cognitive dysfunction.

Impact of animal-assisted therapy for outpatients with fibromyalgia

OBJECTIVES

Animal-assisted therapy using dogs trained to be calm and provide comfort to strangers has been used as a complementary therapy for a range of medical conditions. This study was designed to evaluate the effects of brief therapy dog visits for fibromyalgia patients attending a tertiary outpatient pain management facility compared with time spent in a waiting room.

DESIGN

Open label with waiting room control.

SETTING

Tertiary care, university-based, outpatient pain management clinic.

SUBJECTS

A convenience sample of fibromyalgia patients was obtained through advertisements posted in the clinic.

INTERVENTIONS

Participants were able to spend clinic waiting time with a certified therapy dog instead of waiting in the outpatient waiting area. When the therapy dog was not available, individuals remained in the waiting area. OUTCOME MEASURES.: Self-reported pain, fatigue, and emotional distress were recorded using 11-point numeric rating scales before and after the therapy dog visit or waiting room time.

RESULTS

Data were evaluated from 106 therapy dog visits and 49 waiting room controls, with no significant between-group demographic differences in participants. Average intervention duration was 12 minutes for the therapy dog visit and 17 minutes for the waiting room control. Significant improvements were reported for pain, mood, and other measures of distress among patients after the therapy dog visit, but not the waiting room control. Clinically meaningful pain relief (≥2 points pain severity reduction) occurred in 34% after the therapy dog visit and 4% in the waiting room control. Outcome was not affected by the presence of comorbid anxiety or depression.

CONCLUSIONS

Brief therapy dog visits may provide a valuable complementary therapy for fibromyalgia outpatients.