Randomized trials of dopamine agonists in restless legs syndrome: a systematic review, quality assessment, and meta-analysis

Dopamine agonists in restless leg syndrome treatment and their effects on sleep parameters: A systematic review and meta-analysis

BACKGROUND

Dopamine agonists (DAs) constitute the standard therapeutic scheme for restless leg syndrome (RLS) because they have been proven to be effective. However, DAs may change sleep parameters, thus having adverse effects on patient condition. This meta-analysis clarified the effects of DAs used in RLS treatment on the sleep architecture.

METHODS

PubMed, Embase, and Cochrane Central databases were searched for randomized control trials (RCT) (up to October 2023) that discussed the effects of DAs on sleep architecture in patients with RLS. A meta-analysis employing a random-effects model was conducted. The patients were divided into subgroups according to individual DAs and treatment duration (1 day or ≥4 weeks).

RESULTS

Thirteen eligible randomized placebo-controlled trials were included in the assessment. The effects of three DAs (i.e., pramipexole, ropinirole, and rotigotine) on rapid eye movement (REM) sleep, slow-wave sleep (SWS), and sleep efficiency (SE) were analyzed. Overall, pramipexole significantly improved SE but decreased the percentage of REM sleep among treated patients. Ropinirole also enhanced SE compared with the placebo group. Rotigotine did not affect SE and REM sleep. Subgroup analysis found that pramipexole used for 1 day and ≥4 weeks significantly diminished the percentage of REM sleep. Ropinirole used for 1 day showed similar REM sleep patterns. Finally, none of the three DAs affected SWS.

CONCLUSIONS

This meta-analysis demonstrated that DAs significantly affect sleep parameters.

Huzursuz bacak sendromunun kan parametreleri ile olan ilişkisi

sağlıklı kontrol grubu ile bazı laboratuvar parametreleri açısından karşılaştırarak etyopatogenezi etkileyen faktörleri araştırmak amaçlanmıştır. Gereç ve Yöntem: Huzursuz bacak sendromu tanısı konulan hastalar çalışmaya dahil edildi. Yaş ve cinsiyet açısından benzer kontrol grubu oluşturuldu. Her iki grup demir, ferritin, demir bağlama kapasitesi, folat, vitamin B12, vitamin D, kalsiyum, magnezyum, ALT, AST, hemogram, kreatinin, açlık kan şekeri, tiroid hormon seviyeleri açısından karşılaştırıldı. Bulgular: Çalışmaya 37 huzursuz bacak sendromu hastası, 41 tane de kontrol dahil edildi. Huzursuz bacak sendromu grubunda hemoglobin, ferritin, demir, açlık kan şekeri, D vitamini ve fT4 değerleri sırasıyla 12.7 (10.3-16.0) g/dL, 37.3 (3.7-89.4) mg/L, 62 (21-195) μg/dL, 96 (65-250) mg/L, 11.26 (4.20-41.57) ug/L ve 1.24 (0.73-2.14) µg/dL iken kontrol grubunda sırasıyla 14.8 (12.3-16.1) g/dL, 56 (9-189) mg/L, 90 (30-245) µg/dL, 91 (70-107) mg/L, 17.31 (5.73-32.90) µg/L ve 1.08 (0.63-2.04) µg/dL idi. Hemoglobin, ferritin, demir, açlık kan şekeri, vitamin D ve T4 seviyeleri açısından gruplar arasında istatistiksel olarak anlamlı farklılıklar saptandı. Sonuç: Huzursuz bacak sendromlu hastalarda hemoglobin ve demir parametreleri, vitamin D düzeyleri, açlık kan şekeri ve T4 seviyeleri eksiklikleri açısından mutlaka değerlendirilmeli, gereklilik halinde mutalaka replase edilmelidir. Eksikliklerin düzeltilmesi hastaların klinikleri açısından yararlı olabilir.

Restless legs syndrome

Restless legs syndrome (RLS) is a common sensorimotor disorder characterized by an urge to move that appears during rest or is exacerbated by rest, that occurs in the evening or night and that disappears during movement or is improved by movement. Symptoms vary considerably in age at onset, frequency and severity, with severe forms affecting sleep, quality of life and mood. Patients with RLS often display periodic leg movements during sleep or resting wakefulness. RLS is considered to be a complex condition in which predisposing genetic factors, environmental factors and comorbidities contribute to the expression of the disorder. RLS occurs alone or with comorbidities, for example, iron deficiency and kidney disease, but also with cardiovascular diseases, diabetes mellitus and neurological, rheumatological and respiratory disorders. The pathophysiology is still unclear, with the involvement of brain iron deficiency, dysfunction in the dopaminergic and nociceptive systems and altered adenosine and glutamatergic pathways as hypotheses being investigated. RLS is poorly recognized by physicians and it is accordingly often incorrectly diagnosed and managed. Treatment guidelines recommend initiation of therapy with low doses of dopamine agonists or α₂δ ligands in severe forms. Although dopaminergic treatment is initially highly effective, its long-term use can result in a serious worsening of symptoms known as augmentation. Other treatments include opioids and iron preparations.

Quantitative Comparison of the Efficacies of 5 First-Line Drugs for Primary Restless Leg Syndrome

Comparative analyses of the efficacies of dopaminergic agonists (pramipexole, ropinirole, and rotigotine patch) and α-2-δ ligands (gabapentin enacarbil and pregabalin) for treatment of primary restless leg syndrome (RLS) are lacking because of the few head-to-head clinical trials. A model-based meta-analysis approach was employed to quantitatively compare the efficacies of these 5 first-line RLS drugs. Longitudinal efficacy data of RLS drugs were collected from published eligible literature. Mean changes in both the International Restless Leg Syndrome Study Group (IRLS) rating scale and Clinical Global Impression Improvement (CGI-I) scale response rate were analyzed. A study-level population pharmacodynamic model was used to fit the dose-effect relationship and to describe the therapeutic effect over time for RLS drugs and placebo, and the typical efficacies of these drugs were compared. The onset of action was rapid for RLS drugs. In the placebo group, typical maximum IRLS reduction (E_max,IRLS ) and CGI-I response rate (E_max,CGI-I ) were -9.34 points and 48.2%, respectively. After deducting placebo effects, we found that the baseline IRLS score was significantly correlated with the E_max,IRLS of dopaminergic agonists. Typical E_max,IRLS of dopaminergic agonists was expressed as - 7.7 - 0.682 × ( baseline IRLS score - 24 ) points. Typical E_max,IRLS values of pregabalin and gabapentin enacarbil were -5.95 points and -4.00 points, respectively. The therapeutic effect of dopaminergic agonists was found to be associated with baseline symptom severity. In RLS patients with more severe symptoms, the therapeutic effect of dopaminergic agonists tended to be better than that of α-2-δ ligands.

Novel and Potent Dopamine D2 Receptor Go-Protein Biased Agonists

The discovery of functionally biased and physiologically beneficial ligands directed toward G-protein coupled receptors (GPCRs) has provided the impetus to design dopamine D₂ receptor (D₂R) targeted molecules that may be therapeutically advantageous for the treatment of certain neuropsychiatric or basal ganglia related disorders. Here we describe the synthesis of a novel series of D₂R agonists linking the D₂R unbiased agonist sumanirole with privileged secondary molecular fragments. The resulting ligands demonstrate improved D₂R affinity and selectivity over sumanirole. Extensive in vitro functional studies and bias factor analysis led to the identification of a novel class of highly potent Go-protein biased full D₂R agonists with more than 10-fold and 1000-fold bias selectivity toward activation of specific G-protein subtypes and β-arrestin, respectively. Intracellular electrophysiological recordings from midbrain dopamine neurons demonstrated that Go-protein selective agonists can elicit prolonged ligand-induced GIRK activity via D₂Rs, which may be beneficial in the treatment of dyskinesias associated with dopamine system dysfunction.

Does the medical literature remain inadequately described despite having reporting guidelines for 21 years? - A systematic review of reviews: an update

PURPOSE

Reporting guidelines (eg, Consolidated Standards of Reporting Trials [CONSORT] statement) are intended to improve reporting standards and enhance the transparency and reproducibility of research findings. Despite accessibility of such guidelines, researchers are not required to adhere to them. Our goal was to determine the current status of reporting quality in the medical literature and examine whether adherence of reporting guidelines has improved since the inception of reporting guidelines.

MATERIALS AND METHODS

Eight reporting guidelines, such as CONSORT, Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), STrengthening the Reporting of OBservational studies in Epidemiology (STROBE), Quality of Reporting of Meta-analysis (QUOROM), STAndards for Reporting of Diagnostic accuracy (STARD), Animal Research: Reporting In Vivo Experiments (ARRIVE), Consolidated Health Economic Evaluation Reporting Standards (CHEERS), and Meta-analysis of Observational Studies in Epidemiology (MOOSE) were examined. Our inclusion criteria included reviews published between January 1996 to September 2016 which investigated the adherence to reporting guidelines in the literature that addressed clinical trials, systematic reviews, observational studies, meta-analysis, diagnostic accuracy, economic evaluations, and preclinical animal studies that were in English. All reviews were found on Web of Science, Excerpta Medical Database (EMBASE), MEDLINE, and Cumulative Index to Nursing and Allied Health Literature (CINAHL).

RESULTS

Among the general searching of 26,819 studies by using the designed searching method, 124 studies were included post screening. We found that 87.9% of the included studies reported suboptimal adherence to reporting guidelines. Factors associated with poor adherence included non-pharmacological interventions, year of publication, and trials concluding with significant results. Improved adherence was associated with better study designs such as allocation concealment, random sequence, large sample sizes, adequately powered studies, multiple authorships, and being published in journals endorsing guidelines.

CONCLUSION

We conclude that the level of adherence to reporting guidelines remains suboptimal. Endorsement of reporting guidelines by journals is important and recommended.

Perceived sleep deficit is a strong predictor of RLS in multisite pain - A population based study in middle aged females

BACKGROUND

Chronic pain conditions as well as Restless Legs Syndrome (RLS) are known to be associated with subjectively and objectively disturbed sleep. RLS has been recently described as highly prevalent in multisite pain and the role of sleep as a modifying factor in this RLS phenotype is unknown. This study aimed to investigate if perceived sleep deficit and other sleep related parameters predict RLS in subjects with multisite pain.

CURRENT KNOWLEDGE/STUDY RATIONALE

We have recently demonstrated a strong association between Restless Legs Syndrome (RLS) and number of pain locations. In the current analysis we hypothesized that impaired sleep predicts RLS in subjects with multisite pain.

METHOD

Questionnaire-based data from 2727 randomly selected women aged 18-64 years were used to analyze RLS symptoms, self-reported sleep quality, and the degree of daytime sleepiness (Epworth Sleepiness Scale (ESS)) in relation to type, degree and localization of body pain. Potential confounders including anthropometrics, pain localization, co-morbidities, and medication were adjusted for in the Generalized Linear Models (GLM).

RESULTS

Perceived sleep deficit ≥90min (OR 2.4 (1.5-3.8), p<0.001) and frequent nocturnal awakenings (OR 2.3 (1.4-3.6), p<0.001) were the strongest sleep related predictors for RLS in subjects with multisite pain. Additional factors include prolonged sleep latency (≥30min, OR 1.8 (1.1-2.8), p=0.01) and daytime symptoms like elevated daytime sleepiness (ESS score ≥9, OR 1.8 (1.2-2.7), p=0.005). Accordingly, RLS diagnosis was associated with impaired sleep quality (TST (Total Sleep Time) -8.2min, sleep latency +8.0min, and number of awakenings from sleep +0.4, p<0.01). ESS score increased with RLS diagnosis (+0.74, p<0.01) and number of pain locations (0.5, 1.7, and 1.8 for 1, 3, and 5 pain areas, p<0.001). In addition, confounders like pain severity, the history of psychiatric disease, and current smoking were associated with impaired sleep quality in this group of females.

CONCLUSIONS

Perceived sleep deficit and sleep fragmentation are the strongest sleep related predictors of RLS in multisite pain. Potential implication of our results are that clinical management programmes of RLS in subjects with multisite pain need to consider both sleep quality and sleep quantity for individually tailored treatment regimes.

STUDY IMPACT

RLS, pain, and sleep disorders are highly interrelated. Our study strongly suggests that clinical management of RLS in patients with multisite pain needs to consider sleep quality as an independent risk factor.

Novel Bivalent Ligands Based on the Sumanirole Pharmacophore Reveal Dopamine D2 Receptor (D2R) Biased Agonism

The development of bivalent ligands has attracted interest as a way to potentially improve the selectivity and/or affinity for a specific receptor subtype. The ability to bind two distinct receptor binding sites simultaneously can allow the selective activation of specific G-protein dependent or β-arrestin-mediated cascade pathways. Herein, we developed an extended SAR study using sumanirole (1) as the primary pharmacophore. We found that substitutions in the N-1- and/or N-5-positions, physiochemical properties of those substituents, and secondary aromatic pharmacophores can enhance agonist efficacy for the cAMP inhibition mediated by G_i/o-proteins, while reducing or suppressing potency and efficacy toward β-arrestin recruitment. Compound 19 was identified as a new lead for its selective D₂ G-protein biased agonism with an EC₅₀ in the subnanomolar range. Structure-activity correlations were observed between substitutions in positions N-1 and/or N-5 of 1 and the capacity of the new bivalent compounds to selectively activate G-proteins versus β-arrestin recruitment in D₂R-BRET functional assays.

Pramipexole Increases Go Timeouts but Not No-go Errors in Healthy Volunteers

Parkinson's disease (PD) is characterized by motor symptoms, such as resting tremor, bradykinesia and rigidity, but also features non-motor complications. PD patients taking dopaminergic therapy, such as levodopa but especially dopamine agonists (DAs), evidence an increase in impulse control disorders (ICDs), suggesting a link between dopaminergic therapy and impulsive pursuit of pleasurable activities. However, impulsivity is a multifaceted construct. Motor impulsivity refers to the inability to overcome automatic responses or cancel pre-potent responses. Previous research has suggested that PD patients, on dopaminergic medications, have decreased motor impulsivity. Whether effects on impulsivity are main effects of dopaminergic therapies or are specific to PD is unclear. Using a Go No-go task, we investigated the effect of a single dose of the DA pramipexole on motor impulsivity in healthy participants. The Go No-go task consisted of Go trials, for which keystroke responses were made as quickly as possible, and lesser frequency No-go trials, on which motor responses were to be inhibited. We hypothesized that pramipexole would decrease motor impulsivity. This would manifest as: (a) fewer No-go errors (i.e., fewer responses on trials in which a response ought to have been inhibited); and (b) more timed-out Go trials (i.e., more trials on which the deadline elapsed before a decision to make a keystroke occurred). Healthy volunteers were treated with either 0.5 mg of pramipexole or a standard placebo (randomly determined). During the 2-h wait period, they completed demographic, cognitive, physiological and affective measures. The pramipexole group had significantly more Go timeouts (p < 0.05) compared to the placebo group though they did not differ in percent of No-go errors. In contrast to its effect on pursuit of pleasurable activities, pramipexole did not increase motor impulsivity. In fact, in line with findings in PD and addiction, dopaminergic therapy might increase motor impulse control. In these patient groups, by enhancing function of the dorsal striatum (DS) of the basal ganglia in contrast to its effect on impulsive pursuit of pleasurable activities. These findings have implications for use and effects of pramipexole in PD as well as in other conditions (e.g., restless leg, dystonia, depression, addiction-related problems).

Novel Analogues of (R)-5-(Methylamino)-5,6-dihydro-4H-imidazo[4,5,1-ij]quinolin-2(1H)-one (Sumanirole) Provide Clues to Dopamine D2/D3 Receptor Agonist Selectivity

Novel 1-, 5-, and 8-substituted analogues of sumanirole (1), a dopamine D2/D3 receptor (D2R/D3R) agonist, were synthesized. Binding affinities at both D2R and D3R were higher when determined in competition with the agonist radioligand [(3)H]7-hydroxy-N,N-dipropyl-2-aminotetralin (7-OH-DPAT) than with the antagonist radioligand [(3)H]N-methylspiperone. Although 1 was confirmed as a D2R-preferential agonist, its selectivity in binding and functional studies was lower than previously reported. All analogues were determined to be D2R/D3R agonists in both GoBRET and mitogenesis functional assays. Loss of efficacy was detected for the N-1-substituted analogues at D3R. In contrast, the N-5-alkyl-substituted analogues, and notably the n-butyl-arylamides (22b and 22c), all showed improved affinity at D2R over 1 with neither a loss of efficacy nor an increase in selectivity. Computational modeling provided a structural basis for the D2R selectivity of 1, illustrating how subtle differences in the highly homologous orthosteric binding site (OBS) differentially affect D2R/D3R affinity and functional efficacy.

Intractable restless legs syndrome: role of prolonged-release oxycodone-naloxone

Restless legs syndrome (RLS) is a common neurological disorder characterized by an irresistible urge to move the legs accompanied by uncomfortable sensations that occur at night or at time of rest. Pharmacological therapy should be limited to patients who suffer from clinically relevant symptoms. Chronic RLS is usually treated with either a dopamine agonist (pramipexole, ropinirole, rotigotine) or an α2δ calcium-channel ligand (gabapentin, gabapentin enacarbil, pregabalin). Augmentation is the main complication of long-term dopaminergic treatment, and frequently requires a reduction of current dopaminergic dose or a switch to non-dopaminergic medications. Opioids as monotherapy or add-on treatment should be considered when alternative satisfactory regimens are unavailable and the severity of symptoms warrants it. In a recent Phase III trial, oxycodone-naloxone prolonged release (PR) demonstrated a significant and sustained effect on patients with severe RLS inadequately controlled by previous treatments. The adverse-event profile was consistent with the safety profile of opioids. The most frequent adverse events were fatigue, constipation, nausea, headache, hyperhidrosis, somnolence, dry mouth, and pruritus. Adverse events were usually mild or moderate in intensity. No cases of augmentation were reported. Oxycodone-naloxone PR is approved for the second-line symptomatic treatment of adults with severe to very severe idiopathic RLS after failure of dopaminergic treatment. Further studies are needed to evaluate if oxycodone-naloxone PR is equally efficacious as a first-line treatment. Moreover, long-term comparative studies between opioids, dopaminergic drugs and α2δ ligands are needed.

Efficacy of Pramipexole for the Treatment of Primary Restless Leg Syndrome: A Systematic Review and Meta-analysis of Randomized Clinical Trials

PURPOSE

The objective of this meta-analysis was to systematically evaluate the efficacy of pramipexole for the treatment of primary moderate-to-severe restless leg syndrome (RLS).

METHODS

Databases of PubMed, OVID, ScienceDirect, SpringerLink, Thomson Reuters Web of Science, the Cochrane Library, the Wiley Online Library, ArticleFirst, CALIS, Study, CNKI, and WanFang were searched to identify randomized controlled trials (RCTs) investigating pramipexole for the treatment of primary moderate-to-severe RLS. A meta-analysis was then conducted to pool results.

FINDINGS

Twelve RCTs involving 3286 participants were included in this study. The mean (SD) treatment duration was 11.12 (5.72) weeks/person. The meta-analysis found that the post-treatment change in the International Restless Leg Syndrome Study Group Rating Scale (IRLS) score of the pramipexole group was significantly superior to that of the placebo group (weighted mean difference [WMD] = -4.64; 95% CI, -5.95 to -3.33; n = 8). More patients in the pramipexole group reported at least a 50% reduction in the IRLS score after treatment (risk ratio [RR] = 1.57; 95% CI, 1.43 to 1.73; n = 8). In terms of the scores for the Clinical Global Impression of Improvement scale (RR = 1.48; 95% CI, 1.31 to 1.66; n = 11) and the Patient Global Impression scale (RR = 1.54; 95% CI, 1.31 to 1.81; n = 9), treatment outcomes of the pramipexole group were significantly superior to those of the placebo group. In terms of the change in quality of life (WMD = 5.39; 95% CI, 2.28 to 8.50; n = 4), the change in daytime tiredness (WMD = -0.61; 95% CI, -1.21 to -0.01; n = 4), the change in the number of periodic limb movements per hour of sleep (WMD = -35.95; 95% CI, -56.42 to -15.48; n = 3), and the change in the quality of sleep (WMD = 3.60; 95% CI, 1.69 to 5.50; n = 6), the treatment outcomes of the pramipexole group were significantly superior to those of the placebo group.

IMPLICATIONS

This meta-analysis study indicated that pramipexole could effectively improve the symptoms of patients with primary moderate-to-severe RLS, although the quality of evidence was relatively low. Future clinical trials focusing on the medium-term and long-term treatment outcomes and using mainly objective indicators for evaluation are warranted. It is also necessary to pay close attention to augmentation during medication.

In the Clinic. Restless Legs Syndrome

This issue provides a clinical overview of restless legs syndrome, focusing on diagnosis, treatment, and practice improvement. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including MKSAP (Medical Knowledge and Self-Assessment Program). Annals of Internal Medicine editors develop In the Clinic in collaboration with the ACP's Medical Education and Publishing divisions and with the assistance of additional science writers and physician writers.

The development of a short route to the API ropinirole hydrochloride

A four-step, three-stage synthesis of the API ropinirole hydrochloride has been developed from a commercially available naphthalene derivative.

Possible association between vitamin D deficiency and restless legs syndrome

BACKGROUND AND AIM

Restless legs syndrome (RLS) is a distressing sleep disorder that occurs worldwide. Although there have been recent developments in understanding the pathophysiology of RLS, the exact mechanism of the disease has not been well elucidated. An increased prevalence of neurologic and psychiatric diseases involving dopaminergic dysfunction in vitamin D-deficient patients led us to hypothesize that vitamin D deficiency might result in dopaminergic dysfunction and consequently, the development of RLS (in which dopaminergic dysfunction plays a pivotal role). Thus, the aim of this study was to evaluate the relationship between vitamin D deficiency and RLS.

METHODS

One hundred and fifty-five consecutive patients, 18-65 years of age, who were admitted to the Department of Internal Medicine with musculoskeletal symptoms and who subsequently underwent neurological and electromyography (EMG) examination by the same senior neurologist, were included in this study. The patients were divided into two groups according to serum 25-hydroxyvitamin D (25(OH)D) (a vitamin D metabolite used as a measure of vitamin D status) level: 36 patients with serum 25(OH)D levels ≥20 ng/mL comprised the normal vitamin D group, and 119 patients with serum 25(OH)D levels <20 ng/mL comprised the vitamin D deficiency group. The two groups were compared for the presence of RLS and associated factors.

RESULTS

The two groups were similar in terms of mean age, sex, mean body mass index (BMI), and serum levels of calcium, phosphate, alkaline phosphatase (ALP), and ferritin. The presence of RLS was significantly higher in the vitamin D deficiency group (χ (2)=12.87, P<0.001). Regression analysis showed vitamin D deficiency and serum 25(OH)D level to be significantly associated with the presence of RLS (odds ratio [OR] 5.085, P<0.001 and OR 1.047, P=0.006, respectively).

CONCLUSION

The present study demonstrated a possible association between vitamin D deficiency and RLS. Given the dopaminergic effects of vitamin D, 25(OH)D depletion may lead to dopaminergic dysfunction and may have a place in the etiology of RLS. Prospective vitamin D treatment studies are needed to confirm this relationship and to evaluate the efficacy of vitamin D as a treatment for RLS patients.

What treatment works best for restless legs syndrome? Meta-analyses of dopaminergic and non-dopaminergic medications

BACKGROUND

At the time of writing only dopamine agonists are licensed for the treatment of restless legs syndrome (RLS) in various countries, but randomized controlled trials (RCTs) have been performed with other treatments. We performed comprehensive meta-analyses and indirect comparisons of RCTs for all currently recommended treatments of RLS.

METHODS

We searched the Central, Medline, Embase, PsycINFO and CINAHL databases. Outcome measures were the international RLS study group severity scale (IRLS), clinical global impression-improvement, (CGI-I), periodic limb movement index (PLMI), and psychosocial parameters such as quality of life (QoL). We also conducted indirect comparisons by testing for heterogeneity between the substance groups.

RESULTS

Placebo (58 trials) and actively (4 trials) controlled RCTs with dopamine agonists (38 trials), levodopa (4 trials), anticonvulsants (13 trials), most of them with α₂δ ligands (11 trials), opioids (1 trial), and iron treatments (6 trials) were included (9596 patients). Although treatment effects showed large variations, changes in the IRLS in the substance groups were comparable (P = 0.78), with a mean reduction in the IRLS of -5.47 points for dopamine agonists, -5.12 points for anticonvulsants (α₂δ ligands and levetiracetam), and -4.59 points for iron treatments. The CGI-I indicated slightly different treatment effects between the substance groups, while PLMI changes during treatment differed (P = 0.002), showing a marked decrease with dopamine agonists (-22.50/h), levodopa (-26.01/h), and oxycodone (-34.46/h) compared with a slight decrease for anticonvulsants (α₂δ ligands and levetiracetam; -8.48/h) and iron treatments (-13.10/h). Quality of sleep and QoL improved moderately in most of the RCTs investigating these parameters (standardized mean difference, SMD) 0.40 and 0.33, respectively). In the few studies evaluating the change of depressive (n = 4) or anxiety symptoms (n = 3), these symptoms improved slightly (SMD -0.24, and -0.21). Adverse effects and dropouts were comparable in number across all substance groups. In meta-regressions, the treatment effect was predicted by the design of the trial (the more sites involved in a trial the lower the effect) and by the duration of action of a medication (the longer the duration of action, expressed as the half-life time of a substance, the greater the improvement), the latter indicating potential superiority of treatments with stable blood concentration.

CONCLUSION

This first meta-analysis of all RCTs for the pharmacological treatment of RLS provides evidence that, besides the well-defined efficacy of dopaminergic treatment, other treatments with different pharmacological principles show efficacy in small samples and may be well-tolerated alternatives for the treatment of RLS. In the group of anticonvulsants, only the trials performed with α₂δ ligands such as gabapentin, gabapentin enacarbil, and pregabalin showed good efficacy. This indicates a specific mechanism of action of these substances in RLS. The group of iron treatments consisted of a few trials with different compounds in oral and intravenous application form, respectively. For a more differentiated evaluation of the efficacy of iron treatments further studies are necessary. The large efficacy of one opioid RCT in RLS has to be confirmed in further studies.

A systematic scoping review of adherence to reporting guidelines in health care literature

Background

Reporting guidelines have been available for the past 17 years since the inception of the Consolidated Standards of Reporting Trials statement in 1996. These guidelines were developed to improve the quality of reporting of studies in medical literature. Despite the widespread availability of these guidelines, the quality of reporting of medical literature remained suboptimal. In this study, we assess the current adherence practice to reporting guidelines; determine key factors associated with better adherence to these guidelines; and provide recommendations to enhance adherence to reporting guidelines for future studies.

Methods

We undertook a systematic scoping review of systematic reviews of adherence to reporting guidelines across different clinical areas and study designs. We searched four electronic databases (Cumulative Index to Nursing and Allied Health Literature, Web of Science, Embase, and Medline) from January 1996 to September 2012. Studies were included if they addressed adherence to one of the following guidelines: Consolidated Standards of Reporting Trials (CONSORT), Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), Quality of Reporting of Meta-analysis (QUOROM), Transparent Reporting of Evaluations with Nonrandomized Designs (TREND), Meta-analysis Of Observational Studies in Epidemiology (MOOSE) and Strengthening the Reporting of Observational Studies in Epidemiology (STROBE). A protocol for this study was devised. A literature search, data extraction, and quality assessment were performed independently by two authors in duplicate. This study reporting follows the PRISMA guidelines.

Results

Our search retrieved 5159 titles, of which 50 were eligible. Overall, 86.0% of studies reported suboptimal levels of adherence to reporting guidelines. Factors associated with better adherence included journal impact factor and endorsement of guidelines, publication date, funding source, multisite studies, pharmacological interventions and larger studies.

Conclusion

Reporting guidelines in the clinical literature are important to improve the standards of reporting of clinical studies; however, adherence to these guidelines remains suboptimal. Action is therefore needed to enhance the adherence to these standards. Strategies to enhance adherence include journal editorial policies endorsing these guidelines.

Motor restlessness, sleep disturbances, thermal sensory alterations and elevated serum iron levels in Btbd9 mutant mice

Restless legs syndrome (RLS), also known as Willis-Ekbom disease, is a sensory-motor neurological disorder with a circadian component. RLS is characterized by uncomfortable sensations in the extremities, generally at night or during sleep, which often leads to an uncontrollable urge to move them for relief. Recently, genomic studies identified single-nucleotide polymorphisms in BTBD9, along with three other genes, as being associated with a higher risk of RLS. Little is known about the function of BTBD9 or its potential role in the pathophysiology of RLS. We therefore examined a line of Btbd9 mutant mice we recently generated for phenotypes similar to symptoms found in RLS patients. We observed that the Btbd9 mutant mice had motor restlessness, sensory alterations likely limited to the rest phase, and decreased sleep and increased wake times during the rest phase. Additionally, the Btbd9 mutant mice had altered serum iron levels and monoamine neurotransmitter systems. Furthermore, the sensory alterations in the Btbd9 mutant mice were relieved using ropinirole, a dopaminergic agonist widely used for RLS treatment. These results, taken together, suggest that the Btbd9 mutant mice model several characteristics similar to RLS and would therefore be the first genotypic mouse model of RLS. Furthermore, our data provide further evidence that BTBD9 is involved in RLS, and future studies of the Btbd9 mutant mice will help shine light on its role in the pathophysiology of RLS. Finally, our data argue for the utility of Btbd9 mutant mice to discover and screen novel therapeutics for RLS.

Efficacy and safety of pramipexole in chinese patients with restless legs syndrome: results from a multi-center, randomized, double-blind, placebo-controlled trial

BACKGROUND

We performed a six-week study of pramipexole vs. a placebo in Chinese restless legs syndrome patients.

METHODS

Overall, 305 enrolled patients were assigned randomly in a 2:1 ratio to the pramipexole group (N=202) and the placebo group (N=103).

RESULTS

Of 287 patients in the full analysis set, the pramipexole group showed significant improvement compared with the placebo group in the change of their International Restless Legs Syndrome Study Group Rating Scale of Severity (IRLS) total score from baseline to week 6 after adjustment of centers and baseline characters (-15.87±0.66 vs. -11.35±0.92, p<0.0001) and in the proportion of patients who were "much improved" and "very much improved" when measured by Clinical Global Impressions-Improvement (81.9% vs. 54.3%, p<0.0001). At week 6, the IRLS responder rate was 73.8% (pramipexole) and 48.9% (placebo) (p<0.0001) and the patient global impression responder rate was 68.6% (pramipexole) and 43.5% (placebo) (p<0.0001). The proportion of adverse events was 62.9% in the pramipexole group and 43.7% in the placebo group, respectively. No deaths occurred.

CONCLUSION

Pramipexole was effective and well-tolerated in Chinese patients with restless legs syndrome.

Dopamine agonists for restless legs syndrome

BACKGROUND

According to clinical guidelines, dopamine agonists are the first-line treatment of restless legs syndrome (RLS).

OBJECTIVES

To evaluate efficacy and safety of dopamine agonists for RLS.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2008, Issue 4), MEDLINE, EMBASE, PsycINFO and CINAHL, from January 1985 to December 2008, plus reference lists of articles. We contacted pharmaceutical companies.

SELECTION CRITERIA

We included double-blind randomised controlled trials (RCTs) of dopamine agonist treatment versus placebo or other treatment for a period of at least seven days in patients with RLS (≥ 18 years). Outcomes included the International RLS Severity Rating Scale (IRLS), Clinical Global Impressions (CGI-I), polysomnography and self rated sleep quality, quality of life, daytime functioning, and safety parameters.

DATA COLLECTION AND ANALYSIS

Two reviewers extracted data separately; assessed risk of bias; and contacted pharmaceutical companies and authors for additional information. We collected dropout rates due to adverse events and experience of adverse events.

MAIN RESULTS

We included 35 placebo controlled and three active controlled RCTs (N = 7365). The mean reduction on the IRLS was -5.7 points lower in dopamine agonist treatment compared to placebo (95% confidence interval (CI) -6.7 to -4.7). Periodic limb movements in sleep per hour of sleep (PLMS-Index; PLMSI) were -22.4/h lower than in placebo (95% CI -27.8 to -16.9). Self rated quality of sleep and disease specific quality of life were improved by a standardised mean difference (SMD) of 0.40 (95% CI 0.33 to 0.47) and 0.34 (95% CI 0.23 to 0.44), respectively. Patients were more likely to drop out (odds ratio (OR) 1.82, 95% CI 1.35 to 2.45) and experienced more adverse events under dopamine agonist treatment than with placebo (OR 1.82, 95% CI 1.59 to 2.08). Visual inspection of forest plots showed the highest efficacy in three studies investigating cabergoline and pergolide (N = 3). Active controlled trials investigated effects of cabergoline, pergolide, and pramipexole in a number of outcomes. The IRLS score was lower with cabergoline and pramipexole compared to levodopa (MD -5.3, 95% CI -8.4 to -2.1). Only four studies investigated treatment efficacy up to seven months. The most severe side effect, augmentation, was not assessed reliably.

AUTHORS' CONCLUSIONS

The meta-analyses show the superiority of dopamine agonists over placebo in RCTs up to seven months. Cabergoline and pramipexole showed larger efficacy compared to levodopa in some but not all outcomes.

The physiology, signaling, and pharmacology of dopamine receptors

G protein-coupled dopamine receptors (D1, D2, D3, D4, and D5) mediate all of the physiological functions of the catecholaminergic neurotransmitter dopamine, ranging from voluntary movement and reward to hormonal regulation and hypertension. Pharmacological agents targeting dopaminergic neurotransmission have been clinically used in the management of several neurological and psychiatric disorders, including Parkinson's disease, schizophrenia, bipolar disorder, Huntington's disease, attention deficit hyperactivity disorder (ADHD(1)), and Tourette's syndrome. Numerous advances have occurred in understanding the general structural, biochemical, and functional properties of dopamine receptors that have led to the development of multiple pharmacologically active compounds that directly target dopamine receptors, such as antiparkinson drugs and antipsychotics. Recent progress in understanding the complex biology of dopamine receptor-related signal transduction mechanisms has revealed that, in addition to their primary action on cAMP-mediated signaling, dopamine receptors can act through diverse signaling mechanisms that involve alternative G protein coupling or through G protein-independent mechanisms via interactions with ion channels or proteins that are characteristically implicated in receptor desensitization, such as β-arrestins. One of the future directions in managing dopamine-related pathologic conditions may involve a transition from the approaches that directly affect receptor function to a precise targeting of postreceptor intracellular signaling modalities either directly or through ligand-biased signaling pharmacology. In this comprehensive review, we discuss dopamine receptor classification, their basic structural and genetic organization, their distribution and functions in the brain and the periphery, and their regulation and signal transduction mechanisms. In addition, we discuss the abnormalities of dopamine receptor expression, function, and signaling that are documented in human disorders and the current pharmacology and emerging trends in the development of novel therapeutic agents that act at dopamine receptors and/or on related signaling events.

Levodopa for restless legs syndrome

BACKGROUND

Levodopa plus dopamine decarboxylase inhibitor is a common treatment for restless legs syndrome (RLS).

OBJECTIVES

To evaluate efficacy and safety of levodopa for RLS compared to placebo and other active agents.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library 2008, Issue 4), MEDLINE, EMBASE, PsycINFO and CINAHL, from January 1985 to December 2008, reference lists of articles, and contacted pharmaceutical companies.

SELECTION CRITERIA

We included double-blind randomised controlled trials (RCT) investigating levodopa treatment versus placebo or other treatment for at least seven days in patients with RLS (age ≥ 18 years). Outcomes included symptom severity, CGI-I, objective as well as self rated sleep parameters, quality of life, and safety parameters.

DATA COLLECTION AND ANALYSIS

Two authors extracted data, assessed risk of bias, and contacted pharmaceutical companies and authors for additional information. We collected dropouts due to adverse events and patients experiencing adverse events.

MAIN RESULTS

Six placebo controlled and three active controlled RCTs were included (521 participants). Symptom severity (11 point rating scale, 0 points indicating no symptoms, 10 points indicating maximally severe symptoms) was more reduced with levodopa than placebo in two studies (mean difference (MD) -1.34, 95% confidence interval (CI) -2.18 to -0.5, P = 0.002). Periodic limb movements in sleep per hour of sleep (PLMS-Index; PLMSI) improved by -26.28/h compared to placebo (95% CI -30.53 to -22.02, P < 0.00001).The CGI-I changed more with levodopa than placebo in two studies (MD -1.25, 95% CI -1.89 to -0.62, P = 0.0001). In two studies, sleep quality (sleep questionnaire, visual analogue scale) showed a large effect (standardised mean difference (SMD) 0.92, 95% CI 0.52 to 1.33, P < 0.00001) whereas quality of life (50 mm Visual Analogue Scales) improved by 3.23 compared to placebo (95% CI 1.64 to 4.82, P < 0.0001). Few patients dropped out of treatment (3 of 218 patients) but more levodopa treated patients experienced adverse events than with placebo (odds ratio 2.61, 95% CI 1.35 to 5.04, P = 0.004). Two dopamine agonist controlled studies showed smaller effects with levodopa than cabergoline and pramipexole on the IRLS (MD 5.25, 95% CI 2.10 to 8.40, P =0.001), CGI-I (MD 0.62, 95% CI 0.37 to 0.87, P < 0.00001), and quality of life (MD 5.54, 95% CI 2.65 to 8.43, P = 0.0002).

AUTHORS' CONCLUSIONS

Levodopa is efficacious for the short-term treatment of RLS. Augmentation, the clinically most relevant adverse event, was not investigated sufficiently.