Treatment of restless legs syndrome

Ropinirole-Associated Orthostatic Hypotension as Cause of a Prescribing Cascade in an Elderly Man

Ropinirole is an overall well-tolerated antiparkinsonian medication that is also used to treat restless leg syndrome (RLS). The incidence of side effects is low, with orthostatic hypotension (OH) only anecdotally reported. Additionally, it is known that the elderly population is very susceptible to adverse drug effects and the prevalence of prescribing cascades that these can trigger is unknown.

A 71-year-old male with history of atrial fibrillation, well-controlled diabetes on oral agents, hyperlipidemia, hypertension, ischemic heart failure status post (s/p) implantable cardioverter-defibrillator (ICD) placement with improved ejection fraction (EF), transient ischemic attack (TIA), rheumatoid arthritis, RLS, aortic stenosis s/p mechanical aortic valve replacement on anticoagulation, deep venous thrombosis (DVT), and right knee replacement, presented to the ED with generalized weakness, with difficulty standing from seated position, followed by a fall without head trauma. Over the eight months prior to this presentation, the patient had had similar symptoms that resulted in four falls, two hospital admissions, and new prescriptions of midodrine and compression stockings.

On admission, vital signs were remarkable for positive orthostatics with blood pressure (BP) 110/74 mmHg, heart rate (HR) of 86 bpm in supine position and BP 87/51 mmHg, HR of 70 bpm while in standing position. Physical exam was unremarkable except for a known ejection murmur and dry oral mucous membranes. Labs included a creatinine 3.6 mg/dl, blood urea nitrogen (BUN) 66 mg/dl, international normalized ration (INR) of 4.1, B-natriuretic peptide (BNP) of 313 pg/mL, troponin <0.03 ng/mL. A kidney ultrasound was normal, and a transthoracic echocardiogram showed left ventricle ejection fraction (LVEF) of 55-65%, improved compared to a prior study. Furosemide, carvedilol and canagliflozin were discontinued and IV fluids were administered. In the subsequent days, his creatinine improved, and so did the patient's volume status, but he continued to be orthostatic despite midodrine and stockings. On further interview, the patient disclosed starting ropinirole 0.25 mg three times daily approximately 10 months prior to this admission, due to asymptomatic RLS that was reported in a sleep study. Decision was made to discontinue this medication, which resulted in improvement of symptoms. We were able to discontinue IV fluids, midodrine and stockings, and reintroduce carvedilol, furosemide and canagliflozin in a stepwise manner. In a follow-up visit one month after discharge, the patient was symptom-free.

This case illustrates two major points. First, this prescribing cascade potentially induced by ropinirole, as well as the increase in health care costs associated to iatrogenic admissions, is major preventable problem faced mostly by the geriatric population. Second, although OH associated with ropinirole has only been reported in patients treated for Parkinson’s disease, this side effect should be considered when prescribing ropinirole for other indications, with cautious assessment of risks and benefits. Further studies need to be conducted to establish the frequency of OH related to ropinirole.

Gabapentin Enacarbil: A Review in Restless Legs Syndrome

Gabapentin enacarbil is an extended-release prodrug of gabapentin that is approved in the USA (Horizant(®)) and Japan (Regnite(®)) for the treatment of moderate to severe primary restless legs syndrome (RLS) in adults [featured indication]. This article summarizes pharmacological, efficacy and tolerability data relevant to the use of oral gabapentin enacarbil in this indication. In double-blind, multicentre trials, treatment with gabapentin enacarbil 600 mg/day for 12 weeks significantly improved the symptoms of moderate to severe primary RLS in adults. Gabapentin enacarbil also significantly improved RLS pain scores and generally improved sleep and mood outcomes. These data are supported by retrospective pooled analyses of three of these trials (XP081, PIVOT RLS I and PIVOT RLS II), with gabapentin enacarbil generally improving symptoms irrespective of disease severity, associated sleep disturbance or prior dopamine agonist use. Responses to gabapentin enacarbil were sustained in longer-term trials, with lower relapse rates in gabapentin enacarbil than placebo recipients in a longer-term maintenance study. Overall, in short and longer-term trials, relatively few patients discontinued treatment, adverse events were mostly mild to moderate in severity, and somnolence/sedation and dizziness were the most commonly reported adverse events. Notably, there were no reports of augmentation or QT-interval prolongation. Gabapentin enacarbil is an important agent for the treatment of adults with moderate to severe primary RLS.

Oxycodone/Naloxone PR: A Review in Severe Refractory Restless Legs Syndrome

An oral, fixed-dose combination of prolonged-release (PR) oxycodone with PR naloxone (Targin(®), Targiniq(®), Targinact(®); hereafter referred to as oxycodone/naloxone PR) is approved in Europe for the second-line symptomatic treatment of patients with severe to very severe idiopathic restless legs syndrome (RLS), after failure of dopaminergic therapy. Coadministration of naloxone represents a targeted approach to counteracting opioid-induced bowel dysfunction without compromising therapeutic efficacy; because of its very low oral bioavailability, naloxone blocks the action of oxycodone at opioid receptors locally in the gut. The efficacy of oxycodone/naloxone PR in patients with severe RLS inadequately controlled by previous (mainly dopaminergic) treatment has been demonstrated in RELOXYN, a 12-week, randomized, double-blind study with a 40-week open-label extension. In this pivotal study, oxycodone/naloxone PR significantly improved RLS symptoms compared with placebo from week 2 onwards; a beneficial effect of oxycodone/naloxone PR was maintained through 1 year of treatment. Furthermore, improvements in RLS symptoms in oxycodone/naloxone PR recipients were accompanied by similarly sustained improvements in disease-specific quality of life and subjective sleep variables. Oxycodone/naloxone PR was generally well tolerated, with a treatment-related adverse event profile (e.g. gastrointestinal disorders, CNS disorders, fatigue and pruritus) that was consistent with that expected for opioid therapy. Notably, there were no confirmed cases of augmentation among oxycodone/naloxone PR recipients throughout the course of the study. Results from the well-designed RELOXYN trial have thus demonstrated the value of oxycodone/naloxone PR as a second-line therapy for severe refractory RLS; further investigation of this combination product as a first-line treatment for severe RLS is now warranted.

Depolarized inactivation overcomes impaired activation to produce DRG neuron hyperexcitability in a Nav1.7 mutation in a patient with distal limb pain

Sodium channel Nav1.7, encoded by SCN9A, is expressed in DRG neurons and regulates their excitability. Genetic and functional studies have established a critical contribution of Nav1.7 to human pain disorders. We have now characterized a novel Nav1.7 mutation (R1279P) from a female human subject with distal limb pain, in which depolarized fast inactivation overrides impaired activation to produce hyperexcitability and spontaneous firing in DRG neurons. Whole-cell voltage-clamp recordings in human embryonic kidney (HEK) 293 cells demonstrated that R1279P significantly depolarizes steady-state fast-, slow-, and closed-state inactivation. It accelerates deactivation, decelerates inactivation, and facilitates repriming. The mutation increases ramp currents in response to slow depolarizations. Our voltage-clamp analysis showed that R1279P depolarizes channel activation, a change that was supported by our multistate structural modeling. Because this mutation confers both gain-of-function and loss-of-function attributes on the Nav1.7 channel, we tested the impact of R1279P expression on DRG neuron excitability. Current-clamp studies reveal that R1279P depolarizes resting membrane potential, decreases current threshold, and increases firing frequency of evoked action potentials within small DRG neurons. The populations of spontaneously firing and repetitively firing neurons were increased by expressing R1279P. These observations indicate that the dominant proexcitatory gating changes associated with this mutation, including depolarized steady-state fast-, slow-, and closed-state inactivation, faster repriming, and larger ramp currents, override the depolarizing shift of activation, to produce hyperexcitability and spontaneous firing of nociceptive neurons that underlie pain.

The higher prevalence of non-right handers among patients with restless leg syndrome

Restless leg syndrome (RLS) is a common disorder described as an urge to move the legs. Dopamine, the main neuro-transmitter in the pathophysiology of RLS, is likely related to the development of brain laterality and human handedness. We aimed to compare the prevalence of RLS in right and non-right handers. A checklist including Edinburgh questioner for handedness, questions for RLS diagnosis and basic characteristics was filled out by a sample of population. The exclusion criteria included prolonged use of dopaminergic or psychologic drugs and having diseases with similar symptoms to RLS. The frequency of non-right handers in RLS patients was compared with the controls by Chi square test. P value less than 0.05 was considered significant. 164 persons were divided into RLS patients (69) and non-RLS controls (95). There was no significant difference between demographic characteristics. The prevalence of non-right handers in RLS patients was significantly more than non-RLS controls (P: 0.03). Our finding regarding the higher prevalence of non-right handers in RLS patients needs more justifications based on neuroscientists' guides. RLS as a disease in which dopaminergic system involves is highly assumed to be linked with handedness. This is just a hypothesis that impaired modulation of immune system in left handers may be accompanied with lower dopamine levels in RLS.

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.

Parkinson disease: an update

BACKGROUND

Over the past decade, the treatment of Parkinson disease (PD) has undergone tremendous changes. New drugs have been introduced to manage the cardinal motor symptoms of PD, and other agents have been borrowed to treat the nonmotor manifestations of the illness. For neurologists faced with the task of treating PD patients, the available array of medications may be confusing and intimidating.

REVIEW SUMMARY

In this review, I summarize the newest approved medications for the treatment of PD, including the new dopamine agonists and catechol-O-methyl-transferase inhibitors. I also describe agents that are used to treat common problems in PD patients, including hallucinations, orthostasis, nausea, erectile dysfunction, depression, and memory loss. Guidelines for handling common scenarios in PD patients will be illustrated by 10 case histories. Finally, the most promising PD drugs that are currently in development will be reviewed.

CONCLUSIONS

Neurologists have a vast armamentarium to treat both motor and nonmotor manifestations of PD. Understanding this array allows the astute clinician to improve the lives of their patients with PD.