L-dihydroxyphenylserine (Droxidopa): a new therapy for neurogenic orthostatic hypotension: The US experience

Postural Orthostatic Tachycardia Syndrome Associated with COVID-19: A Narrative Review

Postural orthostatic tachycardia syndrome (POTS) is a complex condition marked by an atypical autonomic response to standing, leading to orthostatic intolerance and significant tachycardia without accompanying hypotension. In recent studies, a considerable number of individuals recovering from COVID-19 have been reported to experience POTS within 6 to 8 months post-infection. Key symptoms of POTS include fatigue, difficulty with orthostatic tolerance, tachycardia, and cognitive challenges. The underlying causes of POTS following COVID-19 remain unknown, with various theories proposed such as renin-angiotensin-aldosterone system (RAAS) dysregulation, hyperadrenergic reaction, and direct viral infection. Healthcare professionals should be vigilant for POTS in patients who have recovered from COVID-19 and are experiencing signs of autonomic dysfunction and use diagnostic procedures such as the tilt-up table test for confirmation. COVID-19-related POTS should be approached with a holistic strategy. Although many patients show improvement with initial non-drug treatments, for subjects who do not respond and exhibit more severe symptoms, medication-based therapies may be necessary. The current understanding of COVID-19-related POTS is limited, underscoring the need for more research to increase knowledge and enhance treatment approaches.

Non-pharmacological and drug treatment of autonomic dysfunction in multiple system atrophy: current status and future directions

Multiple system atrophy (MSA) is a sporadic, fatal, and rapidly progressive neurodegenerative disease of unknown etiology that is clinically characterized by autonomic failure, parkinsonism, cerebellar ataxia, and pyramidal signs in any combination. Early onset and extensive autonomic dysfunction, including cardiovascular dysfunction characterized by orthostatic hypotension (OH) and supine hypertension, urinary dysfunction characterized by overactive bladder and incomplete bladder emptying, sexual dysfunction characterized by sexual desire deficiency and erectile dysfunction, and gastrointestinal dysfunction characterized by delayed gastric emptying and constipation, are the main features of MSA. Autonomic dysfunction greatly reduces quality of life and increases mortality. Therefore, early diagnosis and intervention are urgently needed to benefit MSA patients. In this review, we aim to discuss the systematic treatment of autonomic dysfunction in MSA, and focus on the current methods, starting from non-pharmacological methods, such as patient education, psychotherapy, diet change, surgery, and neuromodulation, to various drug treatments targeting autonomic nerve and its projection fibers. In addition, we also draw attention to the interactions among various treatments, and introduce novel methods proposed in recent years, such as gene therapy, stem cell therapy, and neural prosthesis implantation. Furthermore, we elaborate on the specific targets and mechanisms of action of various drugs. We would like to call for large-scale research to determine the efficacy of these methods in the future. Finally, we point out that studies on the pathogenesis of MSA and pathophysiological mechanisms of various autonomic dysfunction would also contribute to the development of new promising treatments and concepts.

Ampreloxetine Versus Droxidopa in Neurogenic Orthostatic Hypotension: A Comparative Review

Neurogenic orthostatic hypotension (nOH) is a disabling problem of autonomic dysfunction in patients with Parkinson's disease, which is associated with poor quality of life and higher mortality rates. The purpose of this literature review was to explore and compare the efficacy and safety of droxidopa (an existing treatment) and ampreloxetine (a newer medication) in the treatment of nOH. We used a mixed-method literature review that addresses the epidemiology, pathophysiology, and pharmacological and non-pharmacological management of nOH in Parkinson's disease in a general way, with a more exploratory approach to droxidopa- and ampreloxetine-controlled trial studies. We included a total of 10 studies of randomized controlled trials with eight studies focused on droxidopa and two studies focused on ampreloxetine. These two drugs were analyzed and compared based on the collected individual study results. Treatment of nOH in Parkinson's disease patients with droxidopa or ampreloxetine showed clinically meaningful and statistically significant improvements relative to placebo on the components of the OHSA (Orthostatic Hypotension Symptom Assessment) composite score and OHDAS (Orthostatic Hypotension Daily Activity Scale composite scores) composite score. Droxidopa had an improved effect on daily activities, with an associated increase in standing systolic blood pressure (BP), but the long-term efficacy of droxidopa has not been documented. Standing systolic BP was maintained by ampreloxetine and worsened after the withdrawal phase. This highlights the importance of conducting further research which will help us to improve the therapeutic approach for patients with nOH and Parkinson's disease.

Autonomic and Depression Symptoms in Parkinson's Disease: Clinical Evidence for Overlapping Physiology

BACKGROUND

Autonomic dysfunction and depression are common non-motor symptoms of Parkinson's disease (PD) that confer poorer prognosis. These PD symptoms may have overlapping pathophysiologic underpinnings.

OBJECTIVE

To investigate associations between autonomic and depression symptoms in early PD, and their evolution over time.

METHODS

We obtained data from the Parkinson's Progression Markers Initiative, a prospective open-access database of early PD. Regression analyses were used to model effects of depression on autonomic symptoms in controls and in PD at baseline, visit 6 (24 months after baseline), and visit 12 (60 months after baseline), correcting for multiple comparisons.

RESULTS

Data from 421 people with PD at baseline, 360 at visit 6, 300 at visit 12, and 193 controls were included. When controlling for age, depression, and anti-hypertensive medications, depression predicted autonomic symptoms in all groups. Accounting for motor symptoms did not alter these associations. When comparing groups, the influence of depression on autonomic symptoms was stronger in all PD groups compared to controls, and strongest in PD at visit 12. Depression predicted the presence of orthostatic hypotension only in the PD group at visit 12.

CONCLUSION

We demonstrated the important impact of depression on autonomic symptoms in early and middle stages of PD, which are independent of motor symptoms. Though the physiologic basis of these two PD symptoms are not fully understood, our findings add to pathologic evidence of a shared mechanistic substrate, separate from that responsible for PD motor symptoms. These findings may influence clinical management and development of novel therapies.

The role of noradrenaline in cognition and cognitive disorders

Many aspects of cognition and behaviour are regulated by noradrenergic projections to the forebrain originating from the locus coeruleus, acting through alpha and beta adrenoreceptors. Loss of these projections is common in neurodegenerative diseases and contributes to their cognitive and behavioural deficits. We review the evidence for a noradrenergic modulation of cognition in its contribution to Alzheimer's disease, Parkinson's disease and other cognitive disorders. We discuss the advances in human imaging and computational methods that quantify the locus coeruleus and its function in humans, and highlight the potential for new noradrenergic treatment strategies.

Cardiology meets neurology: clinical presentation and management of patients with primary neurogenic disorders and orthostatic intolerance

Patients with primary neurogenic disorders such as pure autonomic failure or multiple system atrophy may initially present with cardiocirculatory symptoms such as orthostatic intolerance or fluctuations in heart rate with symptomatic tachycardia. It is therefore clinically important to identify such patients since circulatory manifestations are only one of a series of symptoms resulting from autonomic dysfunction in various organ systems. These patients require a multimodal diagnostic and therapeutic approach and should undergo extensive evaluation in a specialized autonomic nervous system (ANS) outpatient unit. Based on a clinical case presentation, the current review summarizes the diagnostic and therapeutic approach to key cardiovascular symptoms of primary autonomic disorders and their neurological work-up in a specialized autonomic function laboratory.

Neurogenic Orthostatic Hypotension: State of the Art and Therapeutic Strategies

Neurogenic orthostatic hypotension (nOH) is a subtype of orthostatic hypotension in which patients have impaired regulation of standing blood pressure due to autonomic dysfunction. Several primary and secondary causes of this disease exist. Patients may present with an array of symptoms making diagnosis difficult. This review article addresses the epidemiology, pathophysiology, causes, clinical features, and management of nOH. We highlight various pharmacological and non-pharmacological approaches to treatment, and review the recent guidelines and our approach to nOH.

Management of neurogenic orthostatic hypotension in the heart failure patient

Neurogenic orthostatic hypotension (nOH) is a common comorbidity in patients with neurodegenerative diseases. It is associated with an increased risk of falls, incident cardiovascular disease, and all-cause mortality. There are over 5 million individuals in the U.S. with heart failure (HF) with an associated 50% mortality rate at 5 years. The prevalence of nOH and HF increase with age and, as the population continues to age, will be increasingly common comorbid conditions. Thus, the effective management of these conditions has important implications for public health. The management of orthostatic hypotension in the context of congestive heart failure is challenging due to the fact that the fundamental principles of management of these disease states are in opposition to each other. In this review, we will discuss the principles of management of nOH and HF and outline strategies for the effective treatment of these comorbid conditions.

Rapid Systolic Blood Pressure Changes After Standing Up Associate With Impaired Physical Performance in Geriatric Outpatients

Background

Orthostatic hypotension is a prevalent condition in older adults and is associated with impaired physical performance and falls. The ability of older adults to compensate for rapid changes in systolic blood pressure (SBP; ie, SBP decline rate and SBP variability) may be important for physical performance. This study investigates the association of rapid SBP changes after standing up with physical performance.

Methods and Results

Consecutive patients who visited the Center of Geriatrics Amsterdam in 2014 and 2015 were included. The following SBP parameters were computed in 2 intervals (0–15 and 15–180 seconds) after standing up: steepness of steepest SBP decline; ratio of standing/supine SBP variability; and magnitude of largest SBP decline. Physical performance was assessed using the following measures: chair stand time, timed up and go time, walking speed, handgrip strength, and tandem stance performance. A total of 109 patients (45% men; age, mean, 81.7 years [standard deviation, 7.0 years]) were included. Steepness of steepest SBP decline (0–15 seconds) was associated with slower chair stand time (P<0.001), timed up and go time (P=0.022), and walking speed (P=0.024). Ratio of standing/supine SBP variability (0–15 seconds) was associated with slower chair stand time (P=0.005). Magnitude of largest SBP decline was not associated with physical performance.

Conclusions

SBP parameters reflecting rapid SBP changes were more strongly associated with physical performance compared with SBP decline magnitude in geriatric outpatients. These results support the hypothesis of an inadequate cerebral autoregulation during rapid SBP changes and advocate the use of continuous blood pressure measurements.

Postural orthostatic tachycardia syndrome: clinical presentation, aetiology and management

Postural orthostatic tachycardia syndrome (POTS) is a variant of cardiovascular autonomic disorder characterized by an excessive heart rate increase on standing and orthostatic intolerance. POTS affects younger individuals 15-45 years old with a distinct female predominance (≈80%). The prevalence ranges between 0.2% and 1.0% in developed countries. The onset of POTS is typically precipitated by immunological stressors such as viral infection, vaccination, trauma, pregnancy, surgery or psychosocial stress. The most common complaints are dizziness, weakness, rapid heartbeat and palpitation on standing. Moreover, patients often report physical deconditioning and reduced exercise capacity as well as headache, 'brain fog', dyspnoea, gastrointestinal disorders and musculoskeletal pain. The aetiology of POTS is largely unknown and three main hypotheses include an autoimmune disorder, abnormally increased sympathetic activity and catecholamine excess, and sympathetic denervation leading to central hypovolaemia and reflex tachycardia. The golden standard for POTS diagnosis is head-up tilt test with a non-invasive beat-to-beat haemodynamic monitoring. Although long-term prognosis of POTS is poorly explored, around 50% of patients spontaneously recover within 1-3 years. After the diagnosis has been established, patient should be thoroughly educated about non-pharmacological measures alleviating the symptoms. Exercise training may be very effective and counteract deconditioning. In more symptomatic patients, different drugs directed at controlling heart rate, increasing peripheral vasoconstriction and intravascular volume can be tested. However, the overall effects of pharmacological therapy are modest and the most affected patients remain handicapped. Future efforts should focus on better understanding of POTS pathophysiology and designing randomized controlled trials for selection of more effective therapy.

Droxidopa for the treatment of neurogenic orthostatic hypotension in neurodegenerative diseases

INTRODUCTION

L-threo-3,4-dihydroxyphenylserine (droxidopa), a pro-drug metabolized to norepinephrine in nerve endings and other tissues, has been commercially available in Japan since 1989 for treating orthostatic hypotension symptoms in Parkinson's disease (PD) patients with a Hoehn & Yahr stage III rating, as well as patients with Multiple System Atrophy (MSA), familial amyloid polyneuropathy, and hemodialysis. Recently, the FDA has approved its use in symptomatic neurogenic orthostatic hypotension (NOH). Areas covered: The authors review the effects of droxidopa in NOH with a focus on the neurodegenerative diseases PD, MSA, and pure autonomic failure (PAF). Expert opinion: A few small and short placebo-controlled clinical trials in NOH showed significant reductions in the manometric drop in blood pressure (BP) after posture changes or meals. Larger Phase III studies showed conflicting results, with two out of four trials meeting their primary outcome and thus suggesting a positive yet short-lasting effect of the drug on OH Questionnaire composite score, light-headedness/dizziness score, and standing BP during the first two treatment-weeks. Results appear essentially similar in PD, MSA, and PAF. The FDA granted droxidopa approval in the frame of an 'accelerated approval program' provided further studies are conducted to assess its long-term effects on OH symptoms.

Autonomic dysfunction: Diagnosis and management

The autonomic nervous system is designed to maintain physiologic homeostasis. Its widespread connections make it vulnerable to disruption by many disease processes including primary etiologies such as Parkinson's disease, multiple system atrophy, dementia with Lewy bodies, and pure autonomic failure and secondary etiologies such as diabetes mellitus, amyloidosis, and immune-mediated illnesses. The result is numerous symptoms involving the cardiovascular, gastrointestinal, and urogenital systems. Patients with autonomic dysfunction (AUD) often have peripheral and/or cardiac denervation leading to impairment of the baroreflex, which is known to play a major role in determining hemodynamic outcome during orthostatic stress and low cardiac output states. Heart rate and plasma norepinephrine responses to orthostatic stress are helpful in diagnosing impairment of the baroreflex in patients with orthostatic hypotension (OH) and suspected AUD. Similarly, cardiac sympathetic denervation diagnosed with MIBG scintigraphy or ¹⁸F-DA PET scanning has also been shown to be helpful in distinguishing preganglionic from postganglionic involvement and in diagnosing early stages of neurodegenerative diseases. In this chapter, we review the causes of AUD, the pathophysiology and resulting cardiovascular manifestations with emphasis on the diagnosis and treatment of OH.

Orthostatic hypotension: A review

Orthostatic hypotension, defined by a drop in blood pressure of at least 20mmHg for systolic blood pressure and at least 10mmHg for diastolic blood pressure within 3minutes of standing up, is a frequent finding, particularly in elderly patients. It is associated with a significant increase in morbidity and mortality. Although it is often multifactorial, the first favoring factor is medications. Other etiologies are divided in neurogenic orthostatic hypotension, characterized by autonomic failure due to central or peripheral nervous system disorders, and non-neurogenic orthostatic hypotension, mainly favoured by hypovolemia. Treatment always requires education of the patient regarding triggering situations and physiological countermanoeuvers. Pharmacological treatment may sometimes be necessary and mainly relies on volume expansion by fludrocortisone and/or a vasopressor agents such as midodrine. There is no predefined blood pressure target, the goal of therapy being the relief of symptoms and fall prevention.

Refractory orthostatic hypotension in a patient with a spinal cord injury: Treatment with droxidopa

CONTEXT

Orthostatic hypotension (OH) is a common complication in patients with a spinal cord injury, mainly affecting complete injuries above neurological level T6. It is generally more severe during the acute phase but can remain symptomatic for several years.

FINDINGS

A 65-year-old male with a grade ASIA A post-traumatic cervical spinal cord injury, at neurological level C4, presenting with symptomatic refractory OH. Increased blood pressure (BP) levels and an overall clinical improvement was observed after administering an increasing dose of droxidopa. Treatment was started at a dose of 100 mg twice daily (bid), one to be taken upon rising in the morning and another one in the afternoon, at least three hours before bedtime. According to the patient's symptomatic response, each individual dose was increased by 100 mg at 48-hour intervals. Both increased mean BP levels and a subjective symptomatic improvement were evidenced at a dose of 300 mg bid.

CLINICAL RELEVANCE

Treatment with droxidopa increases BP levels and improves symptoms related to refractory OH using all physical and pharmacological measures available. It could therefore constitute an effective alternative treatment for OH in patients with a spinal cord injury.

Effectiveness of droxidopa compared to midodrine in standing blood pressure and orthostatic tolerance in adults with neurogenic orthostatic hypotension: a systematic review protocol

REVIEW QUESTION

The question of this review is: what is the effectiveness of droxidopa compared to midodrine on standing blood pressure and orthostatic intolerance symptoms in adults with neurogenic orthostatic hypotension?

Restoring Spinal Noradrenergic Inhibitory Tone Attenuates Pain Hypersensitivity in a Rat Model of Parkinson's Disease

In the present study, we investigated whether restoring descending noradrenergic inhibitory tone can attenuate pain in a PD rat model, which was established by stereotaxic infusion of 6-hydroxydopamine (6-OHDA) into the bilateral striatum (CPu). PD rats developed thermal and mechanical hypersensitivity at the 4th week after surgery. HPLC analysis showed that NE content, but not dopamine or 5-HT, significantly decreased in lumbar spinal cord in PD rats. Additional noradrenergic depletion by injection of N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) aggravated pain hypersensitivity in PD rats. At the 5th week after injection of 6-OHDA, systemic treatment with pharmacological norepinephrine (NE) precursor droxidopa (L-DOPS) or α2 adrenoceptor agonist clonidine significantly attenuated thermal and mechanical pain hypersensitivity in PD rats. Furthermore, application of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) reuptake inhibitors duloxetine, but not 5-HT selective reuptake inhibitors sertraline, significantly inhibited thermal and mechanical pain hypersensitivity in PD rats. Systemic administration of Madopar (L-DOPA) or the D2/D3 agonist pramipexole slightly inhibited the thermal, but not mechanical, hypersensitivity in PD rats. Thus, our study revealed that impairment of descending noradrenergic system may play a key role in PD-associated pain and restoring spinal noradrenergic inhibitory tone may serve as a novel strategy to manage PD-associated pain.

New insights into orthostatic hypotension in multiple system atrophy: a European multicentre cohort study

OBJECTIVES

Orthostatic hypotension (OH) is a key feature of multiple system atrophy (MSA), a fatal progressive neurodegenerative disorder associated with autonomic failure, parkinsonism and ataxia. This study aims (1) to determine the clinical spectrum of OH in a large European cohort of patients with MSA and (2) to investigate whether a prolonged postural challenge increases the sensitivity to detect OH in MSA.

METHODS

Assessment of OH during a 10 min orthostatic test in 349 patients with MSA from seven centres of the European MSA-Study Group (age: 63.6 ± 8.8 years; disease duration: 4.2 ± 2.6 years). Assessment of a possible relationship between OH and MSA subtype (P with predominant parkinsonism or C with predominant cerebellar ataxia), Unified MSA Rating Scale (UMSARS) scores and drug intake.

RESULTS

187 patients (54%) had moderate (> 20 mm Hg (systolic blood pressure (SBP)) and/or > 10 mm Hg (diastolic blood pressure (DBP)) or severe OH (> 30 mm Hg (SBP) and/or > 15 mm Hg (DBP)) within 3 min and 250 patients (72%) within 10 min. OH magnitude was significantly associated with disease severity (UMSARS I, II and IV), orthostatic symptoms (UMSARS I) and supine hypertension. OH severity was not associated with MSA subtype. Drug intake did not differ according to OH magnitude except for antihypertensive drugs being less frequently, and antihypotensive drugs more frequently, prescribed in severe OH.

CONCLUSIONS

This is the largest study of OH in patients with MSA. Our data suggest that the sensitivity to pick up OH increases substantially by a prolonged 10 min orthostatic challenge. These results will help to improve OH management and the design of future clinical trials.

Neurogenic orthostatic hypotension: roles of norepinephrine deficiency in its causes, its treatment, and future research directions

BACKGROUND

Although a diversity of neurotransmitters and hormones participate in controlling blood pressure, norepinephrine released from postganglionic sympathetic nerve terminals is an important mediator of the rapid regulation of cardiovascular function required for homeostasis of cerebral perfusion. Hence, neurogenic orthostatic hypotension (NOH) often represents a deficiency of noradrenergic responsiveness to postural change.

RESEARCH DESIGN AND METHODS

PubMed searches with 'orthostatic hypotension' and 'norepinephrine' as conjoint search terms and no restriction on language or date, so as to survey the pathophysiologic and clinical relevance of norepinephrine deficiency for current NOH interventions and for future directions in treatment and research.

RESULTS

Norepinephrine deficiency in NOH can arise peripherally, due to cardiovascular sympathetic denervation (as in pure autonomic failure, Parkinson's disease, and a variety of neuropathies), or centrally, due to a failure of viscerosensory signals to generate adequate sympathetic traffic to intact sympathetic nerve endings (as in multiple system atrophy). Nonpharmacologic countermeasures such as pre-emptive water intake may yield blood-pressure increases exceeding those achieved pharmacologically. For patients with symptomatic NOH unresponsive to such strategies, a variety of pharmacologic interventions have been administered off-label on the basis of drug mechanisms expected to increase blood pressure via blood-volume expansion or vasoconstriction. Two pressor agents have received FDA approval: the sympathomimetic midodrine and more recently the norepinephrine prodrug droxidopa.

CONCLUSIONS

Pressor agents are important for treating symptomatic NOH in patients unresponsive to lifestyle changes alone. However, the dysautonomia underlying NOH often permits blood-pressure excursions toward both hypotension and hypertension. Future research should aim to shed light on the resulting management issues, and should also explore the possibility of pharmacotherapy selectively targeting orthostatic blood-pressure decreases.

Structural analysis of enzymes used for bioindustry and bioremediation

Microbial enzymes have been widely applied in the large-scale, bioindustrial manufacture of food products and pharmaceuticals due to their high substrate specificity and stereoselectivity, and their effectiveness under mild conditions with low environmental burden. At the same time, bioremedial techniques using microbial enzymes have been developed to solve the problem of industrial waste, particularly with respect to persistent chemicals and toxic substances. And finally, structural studies of these enzymes have revealed the mechanistic basis of enzymatic reactions, including the stereoselectivity and binding specificity of substrates and cofactors. The obtained structural insights are useful not only to deepen our understanding of enzymes with potential bioindustrial and/or bioremedial application, but also for the functional improvement of enzymes through rational protein engineering. This review shows the structural bases for various types of enzymatic reactions, including the substrate specificity accompanying cofactor-controlled and kinetic mechanisms.

New developments in the management of neurogenic orthostatic hypotension

Orthostatic hypotension (OH) is defined as a sustained reduction of ≥ 20 mmHg systolic blood pressure or ≥ 10 mmHg diastolic blood pressure upon standing for ≤ 3 min. Orthostatic hypotension is commonly associated with hypertension, and its prevalence is highest in those with uncontrolled hypertension compared to those with controlled hypertension or normotensive community elderly subjects. Orthostatic hypotension can cause significant disability, with patients experiencing dizziness, lightheadedness or syncope, and other problems that potentially have a profound negative impact on activities of daily living that require standing or walking. Furthermore, OH increases the risk of falls and, importantly, is an independent risk factor of mortality. Despite its importance, there is a paucity of treatment options for this condition. Most of the advances in treatment options have relied on small studies of repurposed drugs done in patients with severe OH due to rare neurodegenerative conditions. Midodrine, an oral prodrug converted to the selective α1-adrenoceptor agonist desglymidodrine, was approved by the FDA for the treatment of OH in 1996. For almost two decades, no other pharmacotherapy was developed specifically for the treatment of OH until 2014, when droxidopa was approved by the FDA for the treatment of neurogenic OH associated with primary autonomic neuropathies including Parkinson disease, multiple system atrophy, and pure autonomic failure. These are neurodegenerative diseases ultimately characterized by failure of the autonomic nervous system to generate norepinephrine responses appropriate to postural challenge. Droxidopa is a synthetic amino acid that is converted to norepinephrine by dopa-decarboxylase, the same enzyme that converts levodopa into dopamine in the treatment of Parkinson disease. We will review this and other advances in the treatment of OH in an attempt to provide a practical guide to its management.

Syncope due to Autonomic Dysfunction: Diagnosis and Management

Syncope is one of several disorders that cause transient loss of consciousness. Cerebral hypoperfusion is the proximate cause of syncope. Transient or fixed autonomic nervous system dysfunction is a major contributor in many causes. A structured approach to the evaluation of syncope allows for more effective therapy.

Neurogenic orthostatic hypotension - management update and role of droxidopa

Orthostatic hypotension (OH) is defined as a significant decrease in blood pressure (BP) during the first 3 minutes of standing or a head up on a tilt table. Symptoms of OH are highly variable, ranging from mild light-headedness to recurrent syncope. OH occurs due to dysfunction of one or more components of various complex mechanisms that interplay closely to maintain BP in a normal range during various physiological and associated disease states. Various biochemical and electrophysiological studies are often undertaken to assess the severity and etiology of OH. In addition to the lifestyle modifications, various medications that stimulate the adrenergic receptors or increase central blood volume are used in patients with OH. Droxidopa is a newer agent that increases the levels of norepinephrine in postganglionic sympathetic neurons. Management strategies for OH are presented, including the mechanism of action of droxidopa and various studies performed to assess its efficacy.

Diagnosing and treating neurogenic orthostatic hypotension in primary care

In response to a change in posture from supine or sitting to standing, autonomic reflexes normally maintain blood pressure (BP) by selective increases in arteriovenous resistance and by increased cardiac output, ensuring continued perfusion of the central nervous system. In neurogenic orthostatic hypotension (NOH), inadequate vasoconstriction and cardiac output cause BP to drop excessively, resulting in inadequate perfusion, with predictable symptoms such as dizziness, lightheadedness and falls. The condition may represent a central failure of baroreceptor signals to modulate cardiovascular function, a peripheral failure of norepinephrine release from cardiovascular sympathetic nerve endings, or both. Symptomatic patients may benefit from both non-pharmacologic and pharmacologic interventions. Among the latter, two pressor agents have been approved by the US Food and Drug Administration: the sympathomimetic prodrug midodrine, approved in 1996 for symptomatic orthostatic hypotension, and the norepinephrine prodrug droxidopa, approved in 2014, which is indicated for the treatment of symptomatic neurogenic orthostatic hypotension caused by primary autonomic failure (Parkinson's disease, multiple system atrophy and pure autonomic failure). A wide variety of off-label options also have been described (e.g. the synthetic mineralocorticoid fludrocortisone). Because pressor agents may promote supine hypertension, NOH management requires monitoring of supine BP and also lifestyle measures to minimize supine BP increases (e.g. head-of-bed elevation). However, NOH has been associated with cognitive impairment and increases a patient's risk of syncope and falls, with the potential for serious consequences. Hence, concerns about supine hypertension - for which the long-term prognosis in patients with NOH is yet to be established - must sometimes be balanced by the need to address a patient's immediate risks.

Current Concepts in the Treatment of Multiple System Atrophy

MSA is a progressive neurodegenerative disorder characterized by autonomic failure and a variable combination of poor levodopa-responsive parkinsonism and cerebellar ataxia (CA). Current therapeutic management is based on symptomatic treatment. Almost one third of MSA patients may benefit from l-dopa for the symptomatic treatment of parkinsonism, whereas physiotherapy remains the best therapeutic option for CA. Only midodrine and droxidopa were found to be efficient for neurogenic hypotension in double-blind, controlled studies, whereas other symptoms of autonomic failure may be managed with off-label treatments. To date, no curative treatment is available for MSA. Recent results of neuroprotective and -restorative trials have provided some hope for future advances. Considerations for future clinical trials are also discussed in this review.

Neurotransmitter-based strategies for the treatment of cognitive dysfunction in Down syndrome

Down syndrome (DS) is a multisystem disorder affecting the cardiovascular, respiratory, gastrointestinal, neurological, hematopoietic, and musculoskeletal systems and is characterized by significant cognitive disability and a possible common pathogenic mechanism with Alzheimer's disease. During the last decade, numerous studies have supported the notion that the triplication of specific genes on human chromosome 21 plays a significant role in cognitive dysfunction in DS. Here we reviewed studies in trisomic mouse models and humans, including children and adults with DS. In order to identify groups of genes that contribute to cognitive disability in DS, multiple mouse models of DS with segmental trisomy have been generated. Over-expression of these particular genes in DS can lead to dysfunction of several neurotransmitter systems. Therapeutic strategies for DS have either focused on normalizing the expression of triplicated genes with important roles in DS or restoring the function of these systems. Indeed, our extensive review of studies on the pathogenesis of DS suggests that one plausible strategy for the treatment of cognitive dysfunction is to target the cholinergic, serotonergic, GABA-ergic, glutamatergic, and norepinephrinergic system. However, a fundamental strategy for treatment of cognitive dysfunction in DS would include reducing to normal levels the expression of specific triplicated genes in affected systems before the onset of neurodegeneration.

Structural optimization of SadA, an Fe(II)- and α-ketoglutarate-dependent dioxygenase targeting biocatalytic synthesis of N-succinyl-L-threo-3,4-dimethoxyphenylserine

L-threo-3,4-Dihydroxyphenylserine (l-DOPS, Droxidopa) is a psychoactive drug and synthetic amino acid precursor that acts as a prodrug to the neurotransmitters. SadA, a dioxygenase from Burkholderia ambifaria AMMD, is an Fe(II)- and α-ketoglutarate (KG)-dependent enzyme that catalyzes N-substituted branched-chain or aromatic l-amino acids. SadA is able to produce N-succinyl-l-threo-3,4-dimethoxyphenylserine (NSDOPS), which is a precursor of l-DOPS, by catalyzing the hydroxylation of N-succinyl-3,4-dimethoxyphenylalanine (NSDOPA). However, the catalytic activity of SadA toward NSDOPS is much lower than that toward N-succinyl branched-chain l-amino acids. Here, we report an improved biocatalytic synthesis of NSDOPS with SadA. Structure-based protein engineering was applied to improve the α-KG turnover activity for the synthesis of NSDOPS. The G79A, G79A/F261W or G79A/F261R mutant showed a more than 6-fold increase in activity compared to that of the wild-type enzyme. The results provide a new insight into the substrate specificity toward NSDOPA and will be useful for the rational design of SadA mutants as a target of industrial biocatalysts.

Multiple system atrophy of the cerebellar type: clinical state of the art

Multiple system atrophy (MSA) is a late-onset, sporadic neurodegenerative disorder clinically characterized by autonomic failure and either poorly levodopa-responsive parkinsonism or cerebellar ataxia. It is neuropathologically defined by widespread and abundant central nervous system α-synuclein-positive glial cytoplasmic inclusions and striatonigral and/or olivopontocerebellar neurodegeneration. There are two clinical subtypes of MSA distinguished by the predominant motor features: the parkinsonian variant (MSA-P) and the cerebellar variant (MSA-C). Despite recent progress in understanding the pathobiology of MSA, investigations into the symptomatology and natural history of the cerebellar variant of the disease have been limited. MSA-C presents a unique challenge to both clinicians and researchers alike. A key question is how to distinguish early in the disease course between MSA-C and other causes of adult-onset cerebellar ataxia. This is a particularly difficult question, because the clinical framework for conceptualizing and studying sporadic adult-onset ataxias continues to undergo flux. To date, several investigations have attempted to identify clinical features, imaging, and other biomarkers that may be predictive of MSA-C. This review presents a clinically oriented overview of our current understanding of MSA-C with a focus on evidence for distinguishing MSA-C from other sporadic, adult-onset ataxias.

Management of neurogenic orthostatic hypotension in patients with autonomic failure

The maintenance of blood pressure in the upright position requires intact autonomic cardiovascular reflexes. Diseases that affect the sympathetic innervation of the cardiovascular system result in a sustained fall in blood pressure upon standing (i.e., neurogenic orthostatic hypotension) that can impair the blood supply to the brain and other organs and cause considerable morbidity and mortality. Here we review treatment options for neurogenic orthostatic hypotension and include an algorithm for its management that emphasizes the importance of non-pharmacologic measures and provides guidance on pharmacologic treatment options.

Orthostatic hypotension in Parkinson’s disease

SUMMARY Orthostatic hypotension (OH) is a frequent non-motor symptom in Parkinson’s disease (PD), affecting between 22.9 and 38.4% of patients. In PD, OH is related to an increased risk of falls, and possibly to cognitive dysfunction and increased mortality. These data emphasize the importance of its prompt recognition and treatment. OH is related to pre- and post-ganglionic adrenergic denervation, but other factors, such as drugs, heat, meals or alcohol intake, might also induce or aggravate it. Evidence about the efficacy and safety of pharmacological or nonpharmacological strategies for OH treatment in PD is weak. Nonpharmacological measures include liberal addition of salt to the diet, exercise, compression stockings or physical maneuvers. Severe cases may be treated with midodrine or fludrocortisone. Some results suggest that droxidopa and fipamezole may be effective treatments. We finish this review article by discussing the most important unanswered questions about PD-related OH, which may be the focus of future research.

The management of orthostatic hypotension in Parkinson's disease

Orthostatic hypotension (OH) is a common and disabling symptom affecting Parkinson's disease (PD) patients. We present the effect of the different therapies commonly used to manage PD on this clinical manifestation. For this purpose, we describe the relationship between OH and the current treatments employed in PD, such as L-DOPA, dopaminergic agonists, and continuous dopaminergic stimulation therapies. Additionally, we review the therapeutic measures that could be used to ameliorate OH. There are different approaches to deal with this manifestation, including pharmacological and non-pharmacological treatments, although none of them is specifically aimed for treating OH in PD.

Common syndromes of orthostatic intolerance

The autonomic nervous system, adequate blood volume, and intact skeletal and respiratory muscle pumps are essential components for rapid cardiovascular adjustments to upright posture (orthostasis). Patients lacking sufficient blood volume or having defective sympathetic adrenergic vasoconstriction develop orthostatic hypotension (OH), prohibiting effective upright activities. OH is one form of orthostatic intolerance (OI) defined by signs, such as hypotension, and symptoms, such as lightheadedness, that occur when upright and are relieved by recumbence. Mild OI is commonly experienced during intercurrent illnesses and when standing up rapidly. The latter is denoted "initial OH" and represents a normal cardiovascular adjustment to the blood volume shifts during standing. Some people experience episodic acute OI, such as postural vasovagal syncope (fainting), or chronic OI, such as postural tachycardia syndrome, which can significantly reduce quality of life. The lifetime incidence of ≥1 fainting episodes is ∼40%. For the most part, these episodes are benign and self-limited, although frequent syncope episodes can be debilitating, and injury may occur from sudden falls. In this article, mechanisms for OI having components of adrenergic hypofunction, adrenergic hyperfunction, hyperpnea, and regional blood volume redistribution are discussed. Therapeutic strategies to cope with OI are proposed.

Hemodynamic effects of L-threo-3,4-dihydroxyphenylserine (Droxidopa) in hypotensive individuals with spinal cord injury

OBJECTIVES

To determine the effect of an escalating dose of droxidopa (100, 200, and 400 mg) compared with placebo on seated blood pressure (BP) in hypotensive individuals with spinal cord injury (SCI). Secondarily, we aimed to determine the effect of droxidopa on (1) supine BP and heart rate, (2) the change in BP and heart rate when these individuals were transferred from the supine to the seated position, and (3) adverse event (AE) reporting.

DESIGN

Open-label dose titration trial.

SETTING

A Veterans Administration Medical Center.

PARTICIPANTS

Participants with SCI (C3-T12) (N=10) were studied during 4 laboratory visits. Subjects visited the laboratory for about 5 hours on each visit, which incorporated a 30-minute seated baseline, a 30- to 60-minute supine, and a 4-hour seated postdrug observation.

INTERVENTIONS

Placebo on visit 1, droxidopa 100 mg on visit 2, droxidopa 200 mg on visit 3, and droxidopa 400 mg on visit 4.

MAIN OUTCOME MEASURES

BP and heart rate changes from baseline to the postdrug period, orthostatic heart rate and BP responses, and subjective AE reporting.

RESULTS

Seated BP was significantly elevated with 400 mg droxidopa compared with placebo and 100 mg droxidopa for 3 hours and was elevated for 2 hours compared with 200 mg droxidopa. Increase in supine BP was not worsened following droxidopa, and the expected fall in BP when transferred to the seated position was prevented with droxidopa 200 and 400 mg. There were no significant differences in the heart rate response or AE reporting among the study visits.

CONCLUSIONS

Our preliminary findings suggest that droxidopa, at the doses tested, does not cause excessive increases in supine BP and the 400-mg dose appears to be effective at increasing seated BP for up to 3 hours in persons with SCI.

Syndromes of orthostatic intolerance: a hidden danger

Orthostatic hypotension (OH) is a relatively common heterogenous and multifactorial disorder, traditionally classified as neurogenic (less common but often more severe) or nonneurogenic (more common, with no direct signs of autonomic nervous system disease). The different clinical variants of orthostatic intolerance include initial, classical and delayed OH as well as postural tachycardia syndrome. Orthostatic instability may induce syncopal attacks either alone or in combination with other mechanisms, and is often dismissed as a precipitating factor. Moreover, prevalent OH is an independent risk factor for all-cause mortality and cardiovascular morbidity, and the majority of patients with OH are asymptomatic or have few nonspecific symptoms. Management of symptomatic orthostatic intolerance includes both nonpharmacological and pharmacological methods, but it is not always successful and may lead to complications. Future studies of OH should focus on mechanisms that lead to neurogenic and nonneurogenic OH, novel diagnostic methods and more effective therapeutic modalities.

Orthostatic Hypotension in the Patient with Diabetes: A Broad Review of Pharmacologic Treatment Options

Objective:

To provide an evidence-based broad review of the pharmacologic management of orthostatic hypotension (OH) in the patient with diabetes.

Data Sources:

A search of PubMed, MD Consult, International Pharmaceutical Abstracts, and the Cochrane Register of Clinical Trials and Systematic Reviews was performed using the key words diabetes, autonomic neuropathy, orthostatic hypotension, midodrine, fludrocortisone, pyridostigmine, xamoterol, octreotide, pindolol, dihydroergotamine, erythropoietin, clonidine, acarbose, desmopressin, and droxidopa. Literature published between 1976 and August 2012 was included.

Study Selection and Data Extraction:

All articles in English and studies in humans including clinical trials, meta-analyses, practice guidelines, randomized controlled trials, and review articles were identified and evaluated. Studies not including patients with diabetes were excluded. The selection of materials was focused on those that would aid the pharmacist in caring for patients with orthostatic hypotension resulting from diabetic neuropathy.

Data Synthesis:

Definitive guidelines on the pharmacologic management of OH in the patient with diabetes are not available and recommendations must be assessed from available evidence-based sources. Ten trials of medications used in the patient with diabetes were assessed for efficacy and safety. From these trials, evidence-based therapy options were recommended. If nonpharmacologic measures are insufficient in ameliorating symptoms, fludrocortisone or midodrine should be considered as first-line agents in the absence of contraindications. Pyridostigmine, octreotide, or recombinant erythropoietin may be useful as adjunct or alternative agents. Combination therapy may be considered, based on coexisting conditions or response. When recommending both nonpharmacologic and pharmacologic therapy, careful attention should be paid to comorbid conditions such as congestive heart failure, supine hypertension, and kidney disease.

Conclusions:

There is insufficient evidence to recommend the routine use of medications other than the first-line agents fludrocortisone or midodrine in this patient population. Further trials with existing and new therapeutic options in patients with diabetes are warranted.

Is there room for non-dopaminergic treatment in Parkinson disease?

Although levodopa and dopaminergic drugs remain the mainstay of therapy for the motor symptoms of Parkinson disease (PD), they fail to address many of the non-motor symptoms of PD including orthostatic hypotension, freezing of gait (FOG) and difficulty with balance, drug-induced paranoia and hallucinations, and drug-induced dyskinesias. Droxidopa, a drug that increases norepinephrine, treats orthostatic hypotension, cholinomimetic drugs sometimes help with FOG and difficulty with balance, pimavanserin, a drug that blocks serotonin receptors, treats paranoia and hallucinations, and anti-glutaminergic drugs treat dyskinesias. Thus, there are ample opportunities for non-dopaminergic drugs in PD.

Droxidopa, an oral norepinephrine precursor, improves hemodynamic and renal alterations of portal hypertensive rats

We aimed to evaluate the effects of droxidopa (an oral synthetic precursor of norepinephrine) on the hemodynamic and renal alterations of portal hypertensive rats. Sham, portal vein-ligated (PVL), and 4-week biliary duct-ligated (BDL) rats received a single oral dose of droxidopa (25-50 mg/kg) or vehicle and hemodynamic parameters were monitored for 2 hours. Two groups of BDL and cirrhotic rats induced by carbon tetrachloride (CCl(4) ) were treated for 5 days with droxidopa (15 mg/kg, twice daily, orally); hemodynamic parameters and blood and urinary parameters were assessed. The droxidopa effect on the Rho kinase (RhoK) / protein kinase B (AKT) / endothelial nitric oxide synthase (eNOS) pathways was analyzed by western blot in superior mesenteric artery (SMA). The acute administration of droxidopa in PVL and BDL rats caused a significant and maintained increase in arterial pressure and mesenteric arterial resistance, with a significant decrease of mesenteric arterial and portal blood flow, without changing portal pressure and renal blood flow. Two-hour diuresis greatly increased. Carbidopa (DOPA decarboxylase inhibitor) blunted all effects of droxidopa. Chronic droxidopa therapy in BDL rats produced the same beneficial hemodynamic effects observed in the acute study, did not alter liver function parameters, and caused a 50% increase in 24-hour diuresis volume (7.4 ± 0.9 mL/100g in BDL vehicle versus 11.8 ± 2.5 mL/100g in BDL droxidopa; P = 0.01). Droxidopa-treated rats also showed a decreased ratio of p-eNOS/eNOS and p-AKT/AKT and increased activity of RhoK in SMA. The same chronic treatment in CCl(4) rats caused similar hemodynamic effects and produced significant increases in diuresis volume and 24-hour natriuresis (0.08 ± 0.02 mmol/100g in CCl(4) vehicle versus 0.23 ± 0.03 mmol/100g in CCl(4) droxidopa; P = 0.014).

CONCLUSION

Droxidopa might be an effective therapeutic agent for hemodynamic and renal alterations of liver cirrhosis and should be tested in cirrhosis patients.

Upcoming treatments in Parkinson's disease, including gene therapy

Progress is being made in the development of three categories of therapy for Parkinson's disease: (1) Symptomatic, (2) Neuroprotective, (3) Neurorestorative. Evolving approaches to symptomatic therapy, already in clinical trials, include the use of adenosine 2(A) antagonists, novel glutamate antagonists, and serotonin receptor antagonists, the latter for the therapy of Parkinson's psychosis and/or levodopa-induced dyskinesias. Examples of promising neuroprotective therapies under evaluation include the administration of creatine, urate-inducing compounds, calcium channel blockers, and pioglitazone, a peroxisome proliferator-activated receptor agonist. Cell-based restorative therapies are not the subject of this presentation, but various forms of gene therapy have shown promise in human Parkinson's disease trials. These protocols typically involve gene transfer into the CNS through the use of viral vectors. Currently, the most advanced studies of this technique involve delivery of an adeno-associated viral vector encoding glutamic acid decarboxylase into the subthalamic nucleus. This treatment has shown modest benefit in early clinical trials. Other gene therapies, in various stages of human clinical trials, include gene transfer for the production of trophic factors, for aromatic amino acid decarboxylase alone, and most recently, a lentiviral vector transfer of an enzymatic dopamine "factory" consisting of three essential enzymes required for production for this neurotransmitter.