Clonidine for the treatment of supine hypertension and pressure natriuresis in autonomic failure

Norepinephrine Reuptake Inhibition, an Emergent Treatment for Neurogenic Orthostatic Hypotension

The NET (norepinephrine transporter) is situated in the prejunctional plasma membrane of noradrenergic neurons. It is responsible for >90% of the norepinephrine uptake that is released in the autonomic neuroeffector junction. Inhibitors of this cell membrane transporter, known as norepinephrine reuptake inhibitors (NRIs), are commercially available for the treatment of depression and attention deficit hyperactivity disorder. These agents increase norepinephrine levels, potentiating its action in preganglionic and postganglionic adrenergic neurons, the latter through activation of α-1 adrenoreceptors. Previous studies found that patients with neurogenic orthostatic hypotension can improve standing blood pressure and reduce symptoms of neurogenic orthostatic hypotension after a single administration of the selective NRI atomoxetine. This effect was primarily observed in patients with impaired central autonomic pathways with otherwise normal postganglionic sympathetic fibers, known as multiple system atrophy. Likewise, patients with normal or high norepinephrine levels may benefit from NRIs. The long-term efficacy of NRIs for the treatment of neurogenic orthostatic hypotension-related symptoms is currently under investigation. In summary, an in-depth understanding of the pathophysiology of neurogenic orthostatic hypotension resulted in the discovery of a new therapeutic pathway targeted by NRI.

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.

Continuous Positive Airway Pressure for the Treatment of Supine Hypertension and Orthostatic Hypotension in Autonomic Failure

BACKGROUND

Supine hypertension affects most patients with orthostatic hypotension (OH) due to autonomic failure, but it is often untreated for fear of worsening OH. We hypothesized that increasing intrathoracic pressure with continuous positive airway pressure (CPAP) had a Valsalva-like blood-pressure-lowering effect that could be used to treat nocturnal supine hypertension in these patients, while reducing nocturnal pressure diuresis and improving daytime OH.

METHODS

In Protocol 1, we determined the acute hemodynamic effects of increasing levels of CPAP (0, 4, 8, 12, and 16 cm H2O, 3 minutes each) in 26 patients with autonomic failure and supine hypertension studied while awake and supine. In Protocol 2 (n=11), we compared the effects of overnight therapy with CPAP (8-12 cm H2O for 8 hours) versus placebo on nocturnal supine hypertension, nocturnal diuresis and daytime OH in a 2-night crossover study.

RESULTS

In Protocol 1, acute CPAP (4-16 cm H2O) decreased systolic blood pressure in a dose-dependent manner (maximal drop 22±4 mmHg with CPAP 16) due to reductions in stroke volume (-16+3%) and cardiac output (-14±3%). Systemic vascular resistance and heart rate remained unchanged. In Protocol 2, overnight CPAP lowered nighttime systolic blood pressure (maximal change -23±5 versus placebo -1±7 mmHg; P=0.023) and was associated with lower nighttime diuresis (609±84 versus placebo 1004±160 mL; P=0.004) and improved morning orthostatic tolerance (AUC upright SBP 642±121 versus placebo 410±109 mmHg*min; P=0.014).

CONCLUSIONS

CPAP is a novel nonpharmacologic approach to treat the supine hypertension of autonomic failure while improving nocturia and daytime OH.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT03312556.

Short-term Outcomes of Hypertensive Crises in Patients with Orthostatic Hypotension

Supine hypertension-orthostatic hypotension disease poses a management challenge to clinicians. Data on short term outcomes of patients with orthostatic hypotension (OH) who are hospitalized with hypertensive (HTN) crises is lacking. The Nationwide Readmission Database 2016-2019 was queried for all hospitalizations of HTN crises. Hospitalizations were stratified according to whether OH was present or not. We employed propensity score to match hospitalizations for patients with OH to those without, at 1:1 ratio. Outcomes evaluated were 30-days readmission with HTN crises or falls, as well as hospital outcomes of in-hospital mortality, acute kidney injury, acute congestive heart failure, acute coronary syndrome, type 2 myocardial infarction, aortic dissection, stroke, length of stay (LOS), discharge to nursing home and hospitalization costs. We included a total of 9451 hospitalization (4735 in the OH group vs 4716 in the control group). OH group was more likely to be readmitted with falls (Odds ratio [OR]:3.27, P < 0.01) but not with HTN crises (P = 0.05). Both groups had similar likelihood of developing acute kidney injury (P = 0.08), stroke/transient ischemic attack (P = 0.52), and aortic dissection (P = 0.66). Alternatively, OH group were less likely to develop acute heart failure (OR:0.54, P < 0.01) or acute coronary syndrome (OR:0.39, P < 0.01) in the setting of HTN crises than non-OH group. OH group were more likely to have longer LOS and have higher hospitalization costs. Patients with OH who are admitted with HTN crises tend to have similar or lower HTN-related complications to non-OH group while having higher likelihood of readmission with falls, LOS and hospitalization costs. Further studies are needed to confirm such findings.

Orthostatic Hypotension in Hypertensive Adults: Harry Goldblatt Award for Early Career Investigators 2021

Orthostatic hypotension affects roughly 10% of individuals with hypertension and is associated with several adverse health outcomes, including dementia, cardiovascular disease, stroke, and death. Among adults with hypertension, orthostatic hypotension has also been shown to predict patterns of blood pressure dysregulation that may not be appreciated in the office setting, including nocturnal nondipping. Individuals with uncontrolled hypertension are at particular risk of orthostatic hypotension and may meet diagnostic criteria for the condition with a smaller relative reduction in blood pressure compared with normotensive individuals. Antihypertensive medications are commonly de-prescribed to address orthostatic hypotension; however, this approach may worsen supine or seated hypertension, which may be an important driver of adverse events in this population. There is significant variability between guidelines for the diagnosis of orthostatic hypotension with regards to timing and position of blood pressure measurements. Clinically relevant orthostatic hypotension may be missed when standing measurements are delayed or when taken after a seated rather than supine position. The treatment of orthostatic hypotension in patients with hypertension poses a significant management challenge for clinicians; however, recent evidence suggests that intensive blood pressure control may reduce the risk of orthostatic hypotension. A detailed characterization of blood pressure variability is essential to tailoring a treatment plan and can be accomplished using both in-office and out-of-office monitoring.

Orthostatic Hypotension: Management of a Complex, But Common, Medical Problem

Orthostatic hypotension (OH), a common, often overlooked, disorder with many causes, is associated with debilitating symptoms, falls, syncope, cognitive impairment, and risk of death. Chronic OH, a cardinal sign of autonomic dysfunction, increases with advancing age and is commonly associated with neurodegenerative and autoimmune diseases, diabetes, hypertension, heart failure, and kidney failure. Management typically involves a multidisciplinary, patient-centered, approach to arrive at an appropriate underlying diagnosis that is causing OH, treating accompanying conditions, and providing individually tailored pharmacological and nonpharmacological treatment. We propose a novel streamlined pathophysiological classification of OH; review the relationship between the cardiovascular disease continuum and OH; discuss OH-mediated end-organ damage; provide diagnostic and therapeutic algorithms to guide clinical decision making and patient care; identify current gaps in knowledge and try to define future research directions. Using a case-based learning approach, specific clinical scenarios are presented highlighting various presentations of OH to provide a practical guide to evaluate and manage patients who have OH.

Advances in the Pathophysiology and Management of Supine Hypertension in Patients with Neurogenic Orthostatic Hypotension

PURPOSE OF REVIEW

Patients with neurogenic orthostatic hypotension (OH) frequently have hypertension in the supine position (sHTN). We review the controversies surrounding the need and safety of treating sHTN in patients with OH.

RECENT FINDINGS

The presence of sHTN complicates the management of OH because treatment of one can worsen the other. New approaches have been developed to treat OH without worsening sHTN by preferentially improving standing blood pressure, such as medications that harness the patient's residual sympathetic tone like pyridostigmine and atomoxetine, and devices such as an automated abdominal binder that targets the inappropriate splanchnic venous pooling causing OH. There is a reluctance to treat sHTN for fear of increasing the risks of falls and syncope associated with OH, thought to be more immediate and dangerous than the late complications of organ damage associated with sHTN. This, however, does not take into account that nighttime sHTN induces natriuresis, volume loss, and begets daytime orthostatic hypotension. It is possible to treat sHTN in ways that reduce the risk of worsening OH. Furthermore, novel approaches, such as the use of local heat can control nighttime sHTN, reduce nocturia, and improve OH. Although continued progress is needed, recent findings offer hope that we can treat nocturnal sHTN and at the same time improve daytime OH, lessening the controversy whether to treat or not sHTN.

The Pathogenesis and Treatment of Cardiovascular Autonomic Dysfunction in Parkinson's Disease: What We Know and Where to Go

Cardiovascular autonomic dysfunctions (CAD) are prevalent in Parkinson’s disease (PD). It contributes to the development of cognitive dysfunction, falls and even mortality. Significant progress has been achieved in the last decade. However, the underlying mechanisms and effective treatments for CAD have not been established yet. This review aims to help clinicians to better understand the pathogenesis and therapeutic strategies. The literatures about CAD in patients with PD were reviewed. References for this review were identified by searches of PubMed between 1972 and March 2021, with the search term “cardiovascular autonomic dysfunctions, postural hypotension, orthostatic hypotension (OH), supine hypertension (SH), postprandial hypotension, and nondipping”. The pathogenesis, including the neurogenic and non-neurogenic mechanisms, and the current pharmaceutical and non-pharmaceutical treatment for CAD, were analyzed. CAD mainly includes four aspects, which are OH, SH, postprandial hypotension and nondipping, among them, OH is the main component. Both non-neurogenic and neurogenic mechanisms are involved in CAD. Failure of the baroreflex circulate, which includes the lesions at the afferent, efferent or central components, is an important pathogenesis of CAD. Both non-pharmacological and pharmacological treatment alleviate CAD-related symptoms by acting on the baroreflex reflex circulate. However, pharmacological strategy has the limitation of failing to enhance baroreflex sensitivity and life quality. Novel OH treatment drugs, such as pyridostigmine and atomoxetine, can effectively improve OH-related symptoms via enhancing residual sympathetic tone, without adverse reactions of supine hypertension. Baroreflex impairment is a crucial pathological mechanism associated with CAD in PD. Currently, non-pharmacological strategy was the preferred option for its advantage of enhancing baroreflex sensitivity. Pharmacological treatment is a second-line option. Therefore, to find drugs that can enhance baroreflex sensitivity, especially via acting on its central components, is urgently needed in the scientific research and clinical practice.

Management of Orthostatic Hypotension in Parkinson's Disease

Orthostatic hypotension (OH) is a common non-motor feature of Parkinson's disease that may cause unexplained falls, syncope, lightheadedness, cognitive impairment, dyspnea, fatigue, blurred vision, shoulder, neck, or low-back pain upon standing. Blood pressure (BP) measurements supine and after 3 minutes upon standing screen for OH at bedside. The medical history and cardiovascular autonomic function tests ultimately distinguish neurogenic OH, which is due to impaired sympathetic nerve activity, from non-neurogenic causes of OH, such as hypovolemia and BP lowering drugs. The correction of non-neurogenic causes and exacerbating factors, lifestyle changes and non-pharmacological measures are the cornerstone of OH treatment. If these measures fail, pharmacological interventions (sympathomimetic agents and/or fludrocortisone) should be introduced stepwise depending on the severity of symptoms. About 50% of patients with neurogenic OH also suffer from supine and nocturnal hypertension, which should be monitored for with in-office, home and 24 h-ambulatory BP measurements. Behavioral measures help prevent supine hypertension, which is eventually treated with non-pharmacological measures and bedtime administration of short-acting anti-hypertensive drugs in severe cases. If left untreated, OH impacts on activity of daily living and increases the risk of syncope and falls. Supine hypertension is asymptomatic, but often limits an effective treatment of OH, increases the risk of hypertensive emergencies and, combined with OH, facilitates end-organ damage. A timely management of both OH and supine hypertension ameliorates quality of life and prevents short and long-term complications in patients with Parkinson's disease.

Local Passive Heat for the Treatment of Hypertension in Autonomic Failure

Background

Supine hypertension affects a majority of patients with autonomic failure; it is associated with end‐organ damage and can worsen daytime orthostatic hypotension by inducing pressure diuresis and volume loss during the night. Because sympathetic activation prevents blood pressure (BP) from falling in healthy subjects exposed to heat, we hypothesized that passive heat had a BP‐lowering effect in patients with autonomic failure and could be used to treat their supine hypertension.

Methods and Results

In Protocol 1 (n=22), the acute effects of local heat (40–42°C applied with a heating pad placed over the abdomen for 2 hours) versus sham control were assessed in a randomized crossover fashion. Heat acutely decreased systolic BP by −19±4 mm Hg (versus 3±4 with sham, P<0.001) owing to decreases in stroke volume (−18±5% versus −4±4%, P=0.013 ) and cardiac output (−15±5% versus −2±4%, P=0.013). In Protocol 2 (proof‐of‐concept overnight study; n=12), we compared the effects of local heat (38°C applied with a water‐perfused heating pad placed under the torso from 10 pm to 6 am) versus placebo pill. Heat decreased nighttime systolic BP (maximal change −28±6 versus −2±6 mm Hg, P<0.001). BP returned to baseline by 8 am. The nocturnal systolic BP decrease correlated with a decrease in urinary volume (r=0.57, P=0.072) and an improvement in the morning upright systolic BP (r=−0.76, P=0.007).

Conclusions

Local heat therapy effectively lowered overnight BP in patients with autonomic failure and supine hypertension and offers a novel approach to treat this condition. Future studies are needed to assess the long‐term safety and efficacy in improving nighttime fluid loss and daytime orthostatic hypotension.

Registration

URL: https://www.clinicaltrials.gov; Unique identifiers: NCT02417415 and NCT03042988.

My Treatment Approach to Multiple System Atrophy

Multiple system atrophy (MSA) is a neurodegenerative disorder primarily characterized by autonomic failure plus parkinsonism or cerebellar ataxia. The diagnosis may be challenging and is usually made at a tertiary care center. The long-term management issues are equally challenging and frequently require collaboration with the patient's local care providers. Whereas there is currently no cure for MSA, treatment focuses on the most problematic symptoms experienced by the patient. Autonomic symptoms may include severe orthostatic hypotension with syncope, urinary symptoms culminating in incontinence, constipation, anhidrosis, and erectile dysfunction. Motor symptoms include parkinsonism, cerebellar ataxia, and falls. Although certain motor symptoms may respond partially to medications, some of these medications may exacerbate autonomic problems. In this manuscript, we seek to bridge the gap between tertiary care providers and the patient's local care providers to provide multidisciplinary care to the MSA patient. Patients are often best served by management of their chronic and evolving complex problems with a team approach involving their primary care providers and subspecialists. Treatment guidelines typically list myriad therapeutic options without clarifying the most efficacious and simplest treatment strategies. Herein, we provide a guideline based on what has worked in our MSA clinic, a clinic designed to provide care throughout the disease course with subspecialty integration with the goal of empowering a partnership with the patient's home primary care providers.

Pharmacologic treatment of orthostatic hypotension

Neurogenic orthostatic hypotension (OH) is a disabling disorder caused by impairment of the normal autonomic compensatory mechanisms that maintain upright blood pressure. Nonpharmacologic treatment is always the first step in the management of this condition, but a considerable number of patients will require pharmacologic therapies. Denervation hypersensitivity and impairment of baroreflex buffering makes these patients sensitive to small doses of pressor agents. Understanding the underlying pathophysiology can help in selecting between treatment options. In general, patients with low "sympathetic reserve", i.e., those with peripheral noradrenergic degeneration (pure autonomic failure, Parkinson's disease) and low plasma norepinephrine, tend to respond better to "norepinephrine replacers" (midodrine and droxidopa). On the other hand, patients with relatively preserved "sympathetic reserve", i.e., those with impaired central autonomic pathways but spared peripheral noradrenergic fibers (multiple system atrophy) and normal or slightly reduced plasma norepinephrine, tend to respond better to "norepinephrine enhancers" (pyridostigmine, atomoxetine, and yohimbine). There is, however, a spectrum of responses within these extremes, and treatment should be individualized. Other nonspecific treatments include fludrocortisone and octreotide. The presence of associated clinical conditions, such as supine hypertension, heart failure, postprandial hypotension, PD, MSA, and diabetes need to be considered in the pharmacologic management of these patients.

Management of supine hypertension in patients with neurogenic orthostatic hypotension: scientific statement of the American Autonomic Society, European Federation of Autonomic Societies, and the European Society of Hypertension

: Supine hypertension commonly occurs in patients with neurogenic orthostatic hypotension due to autonomic failure. Supine hypertension promotes nocturnal sodium excretion and orthostatic hypotension, thus, interfering with quality of life. Perusal of the literature on essential hypertension and smaller scale investigations in autonomic failure patients also suggest that supine hypertension may predispose to cardiovascular and renal disease. These reasons provide a rationale for treating supine hypertension. Yet, treatment of supine hypertension, be it through nonpharmacological or pharmacological approaches, may exacerbate orthostatic hypotension when patients get up during the night. Fall-related complications may occur. More research is needed to define the magnitude of the deleterious effects of supine hypertension on cardiovascular, cerebrovascular, and renal morbidity and mortality. Integration of more precise cardiovascular risk assessment, efficacy, and safety data, and the prognosis of the underlying condition causing autonomic failure is required for individualized management recommendations.

What do we really know about supine hypertension in patients with orthostatic hypotension

PURPOSE OF REVIEW

Patients with severe orthostatic hypotension due to autonomic failure may be hypertensive in the supine position. Until recently, there were no internationally recognized diagnostic criteria for supine hypertension. This review covers diagnostic criteria, mechanisms, and management of supine hypertension in autonomic failure patients.

RECENT FINDINGS

Recently, an international consensus group defined supine hypertension in patients with neurogenic orthostatic hypotension as brachial SBP at least 140 mmHg and/or DBP at least 90 mmHg while supine. Using these criteria, a large proportion of patients with orthostatic hypotension is diagnosed with supine hypertension. Recent research supports the concept that the hypertension can be mediated through residual sympathetic nervous system function and independently from sympathetic activity, for example via mineralocorticoid receptor activation.

SUMMARY

The clear definition of supine hypertension is an important step that will hopefully foster clinical research in this area. Supine hypertension promotes renal sodium excretion, thus, worsening orthostatic hypotension the next morning. Supine hypertension may promote cardiovascular and renal disease. Yet, long-term benefits of treating supine hypertension be it through non pharmacological or pharmacological means have not been proven by sufficiently large clinical trials.

Orthostatic hypotension: pathophysiology, assessment, treatment and the paradox of supine hypertension

Both hypertension and orthostatic hypotension (OH) are strongly age-associated and are common management problems in older people. However, unlike hypertension, management of OH has unique challenges with few well-established treatments. Not infrequently, they both coexist, further compounding the management. This review provides comprehensive information on OH, including pathophysiology, diagnostic workup and treatment, with a view to provide a practical guide to its management. Special references are made to patients with supine hypertension and postprandial hypotension and older hypertensive patients.

Management of Supine Hypertension Complicating Neurogenic Orthostatic Hypotension

Neurogenic orthostatic hypotension (NOH) can be present in a number of disorders, including synucleinopathies, autoimmune disorders, and various genetic disorders. All are characterized by defective norepinephrine release from sympathetic terminals upon standing, resulting in impaired vasoconstriction. NOH is defined as a drop in systolic blood pressure ≥20 mmHg or diastolic blood pressure ≥10 mmHg, or both, within 3 minutes of standing or head up-tilt at a minimum of 60°. However, approximately 50% of patients have associated supine hypertension, which greatly complicates treatment. Supine hypertension not only is a common side effect of many anti-hypotensive agents but is also present in untreated patients, suggesting it is, in part, innate to the pathophysiology of autonomic dysfunction. Pathological mechanisms differ depending on the underlying autonomic disorder. In central neurodegenerative disorders, residual post-ganglionic sympathetic activity is likely the primary mechanism, whereas plasma angiotensin, aldosterone, and inappropriate mineralocorticoid receptor activity may contribute in peripheral autonomic lesions. Baroreflex failure/loss of baroreflex buffering is common to both. More work is required. Clinically, there is much dispute regarding the treatment of supine hypertension when there is a risk of exacerbating orthostatic hypotension. However, given the similar levels of end-organ damage (i.e., heart attack and stroke) seen with transient hypertension, it seems clear that treatment is important. Current therapies for both NOH and supine hypertension include a combination of pharmacological and conservative measures. However, in addition to the current standard of care, protocols may consider 24-h blood pressure monitoring and potential future examination of the peripheral post-ganglionic sympathetic nerves in order to apply individualized adjunct therapies. Finally, no anti-hypertensive agents are currently approved for use in this patient population, and development of novel therapies should focus on short-acting agents, selective to the supine position, that act primarily at night when hypertension is most severe/prolonged.

The Pharmacology of Autonomic Failure: From Hypotension to Hypertension

Primary neurodegenerative autonomic disorders are characterized clinically by loss of autonomic regulation of blood pressure. The clinical picture is dominated by orthostatic hypotension, but supine hypertension is also a significant problem. Autonomic failure can result from impairment of central autonomic pathways (multiple system atrophy) or neurodegeneration of peripheral postganglionic autonomic fibers (pure autonomic failure, Parkinson's disease). Pharmacologic probes such as the ganglionic blocker trimethaphan can help us in the understanding of the underlying pathophysiology and diagnosis of these disorders. Conversely, understanding the pathophysiology is crucial in the development of effective pharmacotherapy for these patients. Autonomic failure patients provide us with an unfortunate but unique research model characterized by loss of baroreflex buffering. This greatly magnifies the effect of stimuli that would not be apparent in normal subjects. An example of this is the discovery of the osmopressor reflex: ingestion of water increases blood pressure by 30-40 mm Hg in autonomic failure patients. Animal studies indicate that the trigger of this reflex is related to hypo-osmolality in the portal circulation involving transient receptor potential vanilloid 4 receptors. Studies in autonomic failure patients have also revealed that angiotensin II can be generated through noncanonical pathways independent of plasma renin activity to contribute to hypertension. Similarly, the mineralocorticoid receptor antagonist eplerenone produces acute hypotensive effects, highlighting the presence of non-nuclear mineralocorticoid receptor pathways. These are examples of careful clinical research that integrates pathophysiology and pharmacology to advance our knowledge of human disease.

Nocturia in Parkinson's Disease: Why Does It Occur and How to Manage?

BACKGROUND

Nocturia is one of the commonest nonmotor symptoms in Parkinson's disease (PD) and has a significant impact on quality of life both for patients and their carers. There exists a relation between nocturia and poor sleep quality, falls, and institutionalization. Nocturia may manifest as a result of reduced functional bladder capacity or nocturnal polyuria; however, most often the cause is multifactorial. Disorders of circadian rhythm regulation are known to occur with sleep disturbances in PD may also contribute to nocturia.

METHODS AND RESULTS

In this review, an overview of the assessment and management of nocturia in patients with PD is presented. History taking, medication review, and a bladder diary form the cornerstone of the evaluation. Urinalysis, ultrasonography, and urodynamic studies help to assess the cause for lower urinary tract symptoms and exclude concomitant pathologies, such as bladder outlet obstruction. Antimuscarinic medications are the first-line treatment for the overactive bladder; however, caution is needed when using these medications in individuals predisposed to cognitive impairment. Desmopressin is effective for managing nocturnal polyuria.

CONCLUSIONS

An individualized approach is recommended to optimize the management of nocturia in PD.

Clinical Relevance of Orthostatic Hypotension in Neurodegenerative Disease

The autonomic nervous system appears to be uniquely susceptible to degeneration in disorders of α-synuclein pathology. Clinically, autonomic dysfunction in these disorders manifests as neurogenic orthostatic hypotension (nOH), a condition that results in substantial morbidity and mortality. nOH results from pathology affecting either the central autonomic pathways or peripheral autonomic nerve fibers. Determining the localization and pathophysiology of nOH is critical in effectively managing this disorder and selecting appropriate treatment options. In this review, we discuss the pathophysiology of nOH with respect to the various α-synuclein-related neurodegenerative conditions. We highlight the associated clinical features, including gait instability, rapid eye movement behavior disorder, and hyposmia. We also review the current pharmacologic treatment options for nOH. Overall, the goals of therapy are to improve symptoms and prevent syncope and falls. Non-pharmacologic interventions should be introduced first, followed by carefully selected pharmacologic therapies. Treatment decisions should be directed by an understanding of the underlying pathophysiology, as well as the comorbidities and potential contributing factors present in each individual patient.

Mineralocorticoid Receptor Activation Contributes to the Supine Hypertension of Autonomic Failure

Primary autonomic failure is characterized by disabling orthostatic hypotension, but at least half of these patients have paradoxical supine hypertension. Renin-angiotensin mechanisms were not initially thought to contribute to this hypertension because plasma renin activity is often undetectable in autonomic failure. Plasma aldosterone levels are normal, however, and we recently showed that plasma angiotensin II is elevated and acts at AT1 (angiotensin type 1) receptors to contribute to hypertension in these patients. Because aldosterone and angiotensin II can also bind mineralocorticoid receptors to elevate blood pressure, we hypothesized that mineralocorticoid receptor activation plays a role in the hypertension of autonomic failure. To test this hypothesis, we determined the acute effects of the mineralocorticoid receptor antagonist eplerenone (50 mg, oral) versus placebo on supine blood pressure in a randomized, double-blind, crossover study. Medications were given at 8:00 pm with blood pressure recorded every 2 hours for 12 hours. Ten primary autonomic failure patients with supine hypertension completed this study (7 pure autonomic failure, 2 multiple system atrophy, 1 parkinson's disease; 7 male; 70±2 years of age). Eplerenone maximally reduced supine systolic blood pressure by 32±6 mm Hg at 8 hours after administration (versus 8±10 mm Hg placebo, P=0.016), with no effect on nocturia (12-hour urine volume: 985±134 mL placebo versus 931±94 mL eplerenone, P=0.492; nocturnal weight loss: -1.19±0.15 kg placebo versus -1.18±0.15 kg eplerenone, P=0.766). These findings suggest that inappropriate mineralocorticoid receptor activation contributes to the hypertension of autonomic failure, likely independent of canonical mineralocorticoid effects, and provides rationale for use of eplerenone in these patients.

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.

Multiple system atrophy: using clinical pharmacology to reveal pathophysiology

Despite similarities in their clinical presentation, patients with multiple system atrophy (MSA) have residual sympathetic tone and intact post-ganglionic noradrenergic fibers, whereas patients with pure autonomic failure (PAF) and Parkinson disease have efferent post-ganglionic autonomic denervation. These differences are apparent biochemically, as well as in neurophysiological testing, with near normal plasma norephrine in MSA but very low levels in PAF. These differences are also reflected in the response patients have to drugs that interact with the autonomic nervous system. For example, the ganglionic blocker trimethaphan reduces residual sympathetic tone and lowers blood pressure in MSA, but less so in PAF. Conversely, the α2-antagonist yohimbine produces a greater increase in blood pressure in MSA compared to PAF, although significant overlap exists. In normal subjects, the norepinephrine reuptake (NET) inhibitor atomoxetine has little effect on blood pressure because the peripheral effects of NET inhibition that result in noradrenergic vasoconstriction are counteracted by the increase in brain norepinephrine, which reduces sympathetic outflow (a clonidine-like effect). In patients with autonomic failure and intact peripheral noradrenergic fibers, only the peripheral vasoconstriction is apparent. This translates to a significant pressor effect of atomoxetine in MSA, but not in PAF patients. Thus, pharmacological probes can be used to understand the pathophysiology of the different forms of autonomic failure, assist in the diagnosis, and aid in the management of orthostatic hypotension.

Efficacy of atomoxetine versus midodrine for the treatment of orthostatic hypotension in autonomic failure

The clinical presentation of autonomic failure is orthostatic hypotension. Severely affected patients require pharmacological treatment to prevent presyncopal symptoms or frank syncope. We previously reported in a proof of concept study that pediatric doses of the norepinephrine transporter blockade, atomoxetine, increases blood pressure in autonomic failure patients with residual sympathetic activity compared with placebo. Given that the sympathetic nervous system is maximally activated in the upright position, we hypothesized that atomoxetine would be superior to midodrine, a direct vasoconstrictor, in improving upright blood pressure and orthostatic hypotension-related symptoms. To test this hypothesis, we compared the effect of acute atomoxetine versus midodrine on upright systolic blood pressure and orthostatic symptom scores in 65 patients with severe autonomic failure. There were no differences in seated systolic blood pressure (means difference=0.3 mm Hg; 95% confidence [CI], -7.3 to 7.9; P=0.94). In contrast, atomoxetine produced a greater pressor response in upright systolic blood pressure (means difference=7.5 mm Hg; 95% CI, 0.6 to 15; P=0.03) compared with midodrine. Furthermore, atomoxetine (means difference=0.4; 95% CI, 0.1 to 0.8; P=0.02), but not midodrine (means difference=0.5; 95% CI, -0.1 to 1.0; P=0.08), improved orthostatic hypotension-related symptoms as compared with placebo. The results of our study suggest that atomoxetine could be a superior therapeutic option than midodrine for the treatment of orthostatic hypotension in autonomic failure.

A retrospective review of the ambulatory blood pressure patterns and diurnal urine production in subgroups of spinal cord injured patients

STUDY DESIGN

Retrospective study.

OBJECTIVES

To quantify diurnal blood pressure (BP) patterns and nocturnal hypertension and to measure diurnal urine production in spinal cord injury (SCI) patients with clinically significant disorders of BP control.

SETTING

A specialist state-based spinal cord service in Victoria, Australia.

METHODS

Medical records of patients with traumatic SCI who were referred to a specialist service for management of a BP disorder were examined. Ambulatory BP and nocturnal urine production were compared between groups of patients classified according to level, completeness and chronicity of SCI. Patients with night:day systolic BP <90% were classified as dippers, 90-100% as non-dippers and >100% as reversed dippers.

RESULTS

Patients (44 tetraplegic, 10 paraplegic) were predominantly males (92.6%) aged 41±2.5 years (mean±s.e.m.). Referral was for orthostatic intolerance (n=37), autonomic dysreflexia (n=6), nocturnal polyuria (n=4), elevated BP (n=1) and peripheral oedema (n=1). The average BP was 111.1±1.4/65.0±1.2 mm Hg. In 56% of patients (n=30), BP at night was higher than during the day and another 37% (n=20) were non-dippers. Nocturnal hypertension was present in 31% (n=17) of the patients. In the tetraplegic patients, urine flow rate was greater during the night than day (121±9.5 ml h(-1) vs 89±8.2 ml h(-1), P=0.025).

CONCLUSION

Ambulatory BP monitoring in patients with SCI and clinically significant BP disorders detected a high incidence of reversed dipping and nocturnal hypertension. We postulate elevated nocturnal BP may contribute to nocturnal diuresis that might cause relative volume depletion and thereby contribute to daytime orthostatic hypotension.

Current concepts in orthostatic hypotension management

Orthostatic hypotension is a condition commonly affecting the elderly and is often accompanied by disabling presyncopal symptoms, syncope and impaired quality of life. The pathophysiology of orthostatic hypotension is linked to abnormal blood pressure regulatory mechanisms and autonomic insufficiency. As part of its diagnostic evaluation, a comprehensive history and medical examination focused on detecting symptoms and physical findings of autonomic neuropathy should be performed. In individuals with substantial falls in blood pressure upon standing, autonomic function tests are recommended to detect impairment of autonomic reflexes. Treatment should always follow a stepwise approach with initial use of nonpharmacologic interventions including avoidance of hypotensive medications, high-salt diet and physical counter maneuvers. If these measures are not sufficient, medications such as fludrocortisone and midodrine can be added. The goals of treatment are to improve symptoms and to make the patient as ambulatory as possible instead of targeting arbitrary blood pressure values.

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.

Management of neurogenic orthostatic hypotension

The burden of orthostatic hypotension (OH) on public health is a universally recognized enigmatic clinical condition that is associated with significant increases on morbidity and mortality rates, and can take a major toll on one's quality of life. Orthostatic hypotension is predictive of vascular deaths from acute myocardial infarction, strokes in the middle aged population, and increases mortality rates when associated with diabetes, hypertension, Parkinson's disease, and patients receiving renal dialysis. The consensus definition for OH is a fall in systolic blood pressure of at least 20 mm Hg and/or diastolic blood pressure of at least 10 mm Hg within 3 minutes of quiet standing. Because neurogenic OH is often accompanied by supine hypertension, the treatment program should aim toward minimizing OH and the potential fall injuries related to cerebral hypoperfusion without exacerbating nocturnal hypertension that may lead to excessive cardiovascular complications.

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.

Management approaches to hypertension in autonomic failure

PURPOSE OF REVIEW

Supine hypertension is a common finding in autonomic failure that can worsen orthostatic hypotension and predispose to end-organ damage. This review focuses on nonpharmacologic and pharmacologic approaches to manage hypertension in these patients in the face of disabling orthostatic hypotension.

RECENT FINDINGS

The hypertension of autonomic failure can be driven by sympathetic-dependent or independent mechanisms, contingent on the site of autonomic lesions. Management of supine hypertension should include simple nonpharmacologic approaches including avoiding the supine position during the daytime and sleeping in a head-up tilt position at night. Most patients, however, require pharmacologic treatment. Several antihypertensive therapies lower nighttime pressure in autonomic failure, but none improve nocturnal volume depletion or morning orthostatic tolerance. Regardless, treatment may still be beneficial in some patients but must be decided on an individual basis. Blood pressure monitoring is helpful in this regard, as well as titration of doses, as these patients are hypersensitive to depressor agents due to loss of baroreceptor reflexes.

SUMMARY

Autonomic failure provides a unique opportunity to study blood pressure regulation independent of autonomic influences. Understanding mechanisms driving supine hypertension will have important implications for the treatment of autonomic failure and will improve our knowledge of cardiovascular regulation in other populations, including essential hypertension and elderly hypertensive individuals with comorbid orthostatic hypotension.

Angiotensin II, independent of plasma renin activity, contributes to the hypertension of autonomic failure

At least half of primary autonomic failure patients exhibit supine hypertension, despite profound impairments in sympathetic activity. Although the mechanisms underlying this hypertension are unknown, plasma renin activity is often undetectable, suggesting renin-angiotensin (Ang) pathways are not involved. However, because aldosterone levels are preserved, we tested the hypothesis that Ang II is intact and contributes to the hypertension of autonomic failure. Indeed, circulating Ang II was paradoxically increased in hypertensive autonomic failure patients (52±5 pg/mL, n=11) compared with matched healthy controls (27±4 pg/mL, n=10; P=0.002), despite similarly low renin activity (0.19±0.06 versus 0.34±0.13 ng/mL per hour, respectively; P=0.449). To determine the contribution of Ang II to supine hypertension in these patients, we administered the AT(1) receptor blocker losartan (50 mg) at bedtime in a randomized, double-blind, placebo-controlled study (n=11). Losartan maximally reduced systolic blood pressure by 32±11 mm Hg at 6 hours after administration (P<0.05), decreased nocturnal urinary sodium excretion (P=0.0461), and did not worsen morning orthostatic tolerance. In contrast, there was no effect of captopril on supine blood pressure in a subset of these patients. These findings suggest that Ang II formation in autonomic failure is independent of plasma renin activity, and perhaps Ang-converting enzyme. Furthermore, these studies suggest that elevations in Ang II contribute to the hypertension of autonomic failure, and provide rationale for the use of AT(1) receptor blockers for treatment of these patients.

Arterial hypertension, a tricky side of Parkinson's disease: physiopathology and therapeutic features

The role of arterial hypertension (HT) as risk factor for Parkinson's disease (PD) is still debated. Case-control and retrospective studies do not support an association between HT and PD and the risk of PD seems to be lower in hypertensive than in normotensive subjects. In addition, the use of calcium-channel blockers (CCBs) and angiotensin-converting enzyme inhibitors seems to have a protective effect on the risk of developing PD. In clinical practice, a crucial finding in subjects with PD is the high supine systolic blood pressure (SBP) coupled with orthostatic hypotension (OH). It is not clear whether this SBP load could be a risk factor for target organ damage as this load can be largely due to the drugs used to treat OH (i.e., fludrocortisone acetate, midodrine) or PD itself (i.e., monoamine oxidase inhibitors, dopamine D2-receptor antagonists). This blood pressure (BP) load is largely independent of medications as the 40 % of subjects with PD have a non-dipping pattern of BP during 24 h ambulatory monitoring (24-h ABPM). In PD, nocturnal HT is usually asymptomatic and 24-h ABPM should be used to track both supine HT and OH. Treatment of HT in PD is difficult because the reduction of supine BP could worsen OH. To avoid this, short-acting dihydropyridine CCBs, clonidine or nitrates are recommended, assuming between meals, in late afternoon or in the evening in avoiding an aggravation in the post-prandial hypotension characteristic of PD.

Mechanisms of orthostatic hypotension and supine hypertension in Parkinson disease

Non-motor aspects of Parkinson disease (PD) are now recognized to be important both clinically and scientifically. Among these facets are abnormalities in blood pressure regulation. As much as 40% of PD patients have orthostatic hypotension (OH), which is usually associated with supine hypertension (SH). Symptoms of OH range from light-headedness to falls with serious trauma. SH, while typically asymptomatic, poses a significant increased risk for cardiovascular morbidity and mortality. Neuroimaging, neurochemical, and neuropharmacological studies indicate cardiac and extra-cardiac sympathetic noradrenergic denervation and baroreflex failure in virtually all PD patients with OH, and cardiac sympathetic denervation has been confirmed histopathologically. Mechanisms of SH in PD+OH remain poorly understood. The diurnal blood pressure profile shows increased variability that is correlated with decreased baroreflex gain and with increased morbidity and mortality. Treatment should be individually tailored according to the timing of OH or SH, using primarily short-acting sympathomimetic medications in the daytime for OH and short-acting antihypertensive in the nighttime for SH. Future research is needed to understand better and attenuate blood pressure fluctuations through manipulations that improve baroreflex function.

Pharmacotherapy of autonomic failure

The clinical picture of autonomic failure is characterized by severe and disabling orthostatic hypotension. These disorders can develop as a result of damage of central neural pathways or peripheral autonomic nerves, caused either by a primary autonomic neurodegenerative disorder or secondary to systemic illness. Treatment should be focused on decreasing pre-syncopal symptoms instead of achieving blood pressure goals. Non-pharmacologic strategies such as physical counter-maneuvers, dietary changes (i.e. high salt diet, rapid water drinking or compression garments) are the first line therapy. Affected patients should be screened for co-morbid conditions such as post-prandial hypotension and supine hypertension that can worsen orthostatic hypotension if not treated. If symptoms are not controlled with these conservative measures the next step is to start pharmacological agents; these interventions should be aimed at increasing intravascular volume either by promoting water and salt retention (fludrocortisone) or by increasing red blood cell mass when anemia is present (recombinant erythropoietin). When pressor agents are needed, direct pressor agents (midodrine) or agents that potentiate sympathetic activity (atomoxetine, yohimbine, pyridostigmine) can be used. It is preferable to use short-acting pressor agents that can be taken on as needed basis in preparation for upright activities.

Treatment of dysautonomia in extrapyramidal disorders

Although extrapyramidal diseases are commonly thought to solely affect the extrapyramidal motor system, nonmotor symptoms such as behavioural abnormalities, dysautonomia, sleep disturbances and sensory dysfunctions are also frequently observed. Autonomic dysfunction as an important clinical component of extrapyramidal disease (idiopathic Parkinson's disease, multiple system atrophy, progressive supranuclear palsy, dementia with Lewy bodies) is often not formally assessed and thus frequently misdiagnosed. Symptoms of autonomic dysfunction in general impact more on quality of life than motor symptoms. Appropriate symptom-oriented diagnosis and symptomatic treatment as part of an interdisciplinary approach can greatly benefit the patient. Unfortunately, double-blind, randomized, controlled studies are scarce with the consequence that most recommendations are not based on the highest level of evidence. This review elaborates a limited overview on the treatment of cardiovascular, gastrointestinal, urogenital and sudomotor autonomic dysfunction in various extrapyramidal syndromes.

Nocturnal blood pressure dipping in the hypertension of autonomic failure

Blood pressure (BP) normally decreases during the night. Absence of this phenomenon (nondipping) is associated with increased cardiovascular risk. Altered autonomic and endocrine circadian rhythms are suspected to play a role. Patients with peripheral autonomic failure offer a unique opportunity to study this phenomenon, because approximately 50% develop supine hypertension despite very low autonomic function. The purpose of this study was to define the prevalence of dipping in these patients and to determine whether dipping is associated with less severe autonomic impairment or exaggerated nocturnal sodium excretion. We collected BP and urine from 8:00 pm to 8:00 am in 41 peripheral autonomic failure patients with supine hypertension. Dipping (systolic BP fall >or=10% during 12 am to 6 am from baseline [8 pm to 10 pm]) occurred in 34% of patients, with an average decrease of -44+/-4 mm Hg at 4 am. Systolic BP, averaged from 12 am to 6 am, decreased to normotensive levels in 50% (n=7) of dippers and 15% (n=7) of nondippers. There were no significant differences in the severity of autonomic failure, nocturnal diuresis, or natriuresis (0.18+/-0.01 in dippers versus 0.18+/-0.01 mEq/mg of creatinine in nondippers; P=0.522) between groups. At 8:00 am, orthostatic hypotension was similar between groups (-84/-35+/-9/4 mm Hg in dippers versus -93/-39+/-6/3 mm Hg in nondippers; P=0.356 for systolic BP). In conclusion, dipping was observed in one third of patients with peripheral autonomic failure, so that a significant percentage of patients would not require treatment for supine hypertension. Dipping was not associated with increased nocturnal urinary sodium or volume excretion or less severe autonomic failure. Thus, mechanisms independent of autonomic pathways contribute to BP dipping in these patients.

Potentiation by yohimbine of alpha-adrenoceptor-mediated vasoconstriction in response to clonidine in the rabbit ear vein

We investigated the pharmacological profile of the vasoconstrictive response to clonidine in the isolated rabbit ear vein, and compared the characteristics of clonidine with those of noradrenaline and moxonidine. The maximal vasoconstrictive responses to clonidine and moxonidine in the rabbit ear vein were 35.94+/-11.18% and 88.78+/-11.54% of the maximum response to noradrenaline, respectively. Prazosin 0.1 microM inhibited the vasoconstriction induced by lower concentrations of noradrenaline, and the concentration-dependent response curve for noradrenaline was significantly shifted to the right by 1 microM prazosin. Yohimbine (0.1 and 0.5 microM) only decreased the vasoconstrictive response to lower concentrations of noradrenaline, but did not affect the response to higher concentrations. Vasoconstrictive responses to lower but not higher concentrations of clonidine and moxonidine were inhibited by 0.1 microM yohimbine. In contrast, the same concentration of yohimbine significantly potentiated the maximal response to a high concentration of clonidine by 24.06%. In isolated rabbit ear vein pretreated with 0.1 microM yohimbine, prazosin competitively inhibited the concentration-response curve for clonidine with a pA(2) value of 8.05+/-0.06. We conclude that clonidine acts mainly on alpha(2)-adrenoceptors to produce vasoconstriction in the rabbit ear vein; however, in the preparation pretreated with yohimbine, the clonidine-induced vasoconstriction is mediated via alpha(1)-adrenoceptors and its maximal vasoconstriction is significantly potentiated.

Pathophysiology, diagnosis, and treatment of orthostatic hypotension and vasovagal syncope

Orthostatic hypotension (OH) occurs in 0.5% of individuals and as many as 7-17% of patients in acute care settings. Moreover, OH may be more prevalent in the elderly due to the increased use of vasoactive medications and the concomitant decrease in physiologic function, such as baroreceptor sensitivity. OH may result in the genesis of a presyncopal state or result in syncope. OH is defined as a reduction of systolic blood pressure (SBP) of at least 20 mm Hg or diastolic blood pressure (DBP) of at least 10 mm Hg within 3 minutes of standing. A review of symptoms, and measurement of supine and standing BP with appropriate clinical tests should narrow the differential diagnosis and the cause of OH. The fall in BP seen in OH results from the inability of the autonomic nervous system (ANS) to achieve adequate venous return and appropriate vasoconstriction sufficient to maintain BP. An evaluation of patients with OH should consider hypovolemia, removal of offending medications, primary autonomic disorders, secondary autonomic disorders, and vasovagal syncope, the most common cause of syncope. Although further research is necessary to rectify the disease process responsible for OH, patients suffering from this disorder can effectively be treated with a combination of nonpharmacologic treatment, pharmacologic treatment, and patient education. Agents such as fludrocortisone, midodrine, and selective serotonin reuptake inhibitors have shown promising results. Treatment for recurrent vasovagal syncope includes increased salt and water intake and various drug treatments, most of which are still under investigation.

Norepinephrine Transporter Blockade With Atomoxetine Induces Hypertension in Patients With Impaired Autonomic Function

Atomoxetine, a selective norepinephrine transporter blocker, could increase blood pressure by elevating norepinephrine concentration in peripheral sympathetic neurons. This effect may be masked in healthy subjects by central sympatholytic mechanisms. To test this hypothesis we studied the pressor effect of 18 mg of atomoxetine (pediatric dose) in 21 patients with damage of the central (10 subjects) and peripheral (11 subjects) autonomic nervous system. Atomoxetine was administered in a randomized, crossover, placebo-controlled fashion, and blood pressure and heart rate were measured at baseline and for 60 minutes after drug intake. Atomoxetine acutely increased seated and standing systolic blood pressure in patients with central autonomic failure by 54+/-26 (mean+/-standard deviation; P=0.004) and 45+/-23 mm Hg (P=0.016), respectively, as compared with placebo. At the end of the observation period the mean seated systolic blood pressure in the atomoxetine group was in the hypertensive range (149+/-26, range 113 to 209 mm Hg). However, in patients with peripheral autonomic failure, atomoxetine did not elicit a pressor response; seated and standing systolic blood pressure increased by 4+/-18 mm Hg (P=0.695) and 0.6+/-8 mm Hg (P=0.546) with atomoxetine as compared with placebo. In conclusion, atomoxetine induces a dramatic increase in blood pressure in patients with central autonomic failure even at very low doses. These findings suggest that a functional central sympatholytic pathway is essential to avoid hypertension in patients treated with this drug. Caution should be exercised when this medication is used in patients with milder form of autonomic impairment.