Droxidopa: A Review of Its Use in Symptomatic Neurogenic Orthostatic Hypotension

Prodrugs as empowering tools in drug discovery and development: recent strategic applications of drug delivery solutions to mitigate challenges associated with lead compounds and drug candidates

The delivery of a drug to a specific organ or tissue at an efficacious concentration is the pharmacokinetic (PK) hallmark of promoting effective pharmacological action at a target site with an acceptable safety profile. Sub-optimal pharmaceutical or ADME profiles of drug candidates, which can often be a function of inherently poor physicochemical properties, pose significant challenges to drug discovery and development teams and may contribute to high compound attrition rates. Medicinal chemists have exploited prodrugs as an informed strategy to productively enhance the profiles of new chemical entities by optimizing the physicochemical, biopharmaceutical, and pharmacokinetic properties as well as selectively delivering a molecule to the site of action as a means of addressing a range of limitations. While discovery scientists have traditionally employed prodrugs to improve solubility and membrane permeability, the growing sophistication of prodrug technologies has enabled a significant expansion of their scope and applications as an empowering tool to mitigate a broad range of drug delivery challenges. Prodrugs have emerged as successful solutions to resolve non-linear exposure, inadequate exposure to support toxicological studies, pH-dependent absorption, high pill burden, formulation challenges, lack of feasibility of developing solid and liquid dosage forms, first-pass metabolism, high dosing frequency translating to reduced patient compliance and poor site-specific drug delivery. During the period 2012-2022, the US Food and Drug Administration (FDA) approved 50 prodrugs, which amounts to 13% of approved small molecule drugs, reflecting both the importance and success of implementing prodrug approaches in the pursuit of developing safe and effective drugs to address unmet medical needs.

Orthostatic hypotension: Review and expert position statement

Orthostatic hypotension is defined as a drop in systolic blood pressure of at least 20mmHg or a drop in diastolic blood pressure of at least 10mmHg within 3minutes of standing. It is a common disorder, especially in high-risk populations such as elderly subjects and patients with neurological diseases, and is associated with markedly increased morbidity and mortality. Its management can be challenging, particularly in cases where supine hypertension is associated with severe orthostatic hypotension. Education of the patient, non-pharmacological measures, and drug adaptation are the cornerstones of treatment. Pharmacological treatment should be individualized according to the severity, underlying cause, 24-hour blood pressure profile, and associated coexisting conditions. First-line therapies are midodrine and fludrocortisone, which may need to be combined for optimal care of severe cases.

Acute orthostatic responses during early mobilisation of patients with acquired brain injury - Innowalk pro versus standing frame

Introduction

Early mobilisation is paramount in the rehabilitation of patients with acquired brain injuries. However, the effectiveness of mobilisation to standing combined with passive leg movement in mitigating orthostatic intolerance remains uncertain. Hence, we investigated whether participants exhibited better tolerance standing in a motorized standing device with passive leg movements, Innowalk Pro, compared to a traditional standing frame.

Methods

17 patients with acquired brain injury (<1 year post-injury) performed two sessions in each standing device on four separate days. Maximum standing time was 30 min, less when symptoms of syncope or volitional exhaustion occurred. Besides total standing time, electromyography of thigh muscles, and changes in mean arterial pressure and heart rate were monitored at rest and during standing.

Results

No significant differences were found in standing time, changes in mean arterial pressure or heart rate between standing in Innowalk Pro and the standing frame. However, participants had significantly more thigh muscle activation (p = 0.006) when standing in Innowalk Pro.

Conclusions

Mobilising participants with a subacute acquired brain injury in a standing frame with motorised passive movements of the lower limbs did, despite higher thigh muscle activation, not lead to better orthostatic tolerance or prolonged standing time compared to a traditional standing frame.

Cobalt(II)-Catalyzed Selective Three-Component Oxyalkylation of N-Aryl Glycinates: A Route to CF3-Labeled Threonine Analogues

Glycinates, protected enols, and an electrophilic trifluoromethylating reagent were employed to assemble CF3-labeled threonine analogues through a radical addition cascade. To suppress the competing oxidation of the oxyalkyl radical intermediate, various redox catalysts were evaluated and Co(II) exhibited supreme selectivity control with a proper counterion. A series of glycinate and related peptides were thus successfully modified under Co-catalysis. Mechanistic studies revealed that a N-aryl glycinate could be preferentially oxidized by cobalt over the oxyalkyl radical to generate an imine intermediate, and the key to this selectivity could be ascribed to the prechelation of glycinate, as well as a weakly basic carboxylate counterion.

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.

Epilepsy and Attention Deficit Hyperactivity Disorder: Connection, Chance, and Challenges

Comorbidities are common in children with epilepsy, with nearly half of the patients having at least one comorbidity. Attention deficit hyperactivity disorder (ADHD) is a psychiatric disorder characterized by hyperactivity and inattentiveness level disproportional to the child’s developmental stage. The burden of ADHD in children with epilepsy is high and can adversely affect the patients’ clinical outcomes, psychosocial aspects, and quality of life. Several hypotheses were proposed to explain the high burden of ADHD in childhood epilepsy; the well-established bidirectional connection and shared genetic/non-genetic factors between epilepsy and comorbid ADHD largely rule out the possibility of a chance in this association. Stimulants are effective in children with comorbid ADHD, and the current body of evidence supports their safety within the approved dose. Nonetheless, safety data should be further studied in randomized, double-blinded, placebo-controlled trials. Comorbid ADHD is still under-recognized in clinical practice. Early identification and management of comorbid ADHD are crucial to optimize the prognosis and reduce the risk of adverse long-term neurodevelopmental outcomes. The identification of the shared genetic background of epilepsy and ADHD can open the gate for tailoring treatment options for these patients through precision medicine.

Droxidopa in the Management of Hepatorenal Syndrome

PURPOSE

Hepatorenal syndrome (HRS) is renal dysfunction associated with the hemodynamic consequences of advanced liver disease and cirrhosis. HRS is associated with a high mortality, and there remain high failure rates with first-line therapy aimed at improving perfusion. We report the use of droxidopa, an oral norepinephrine precursor, to aid in the management of HRS-AKI refractory to first-line therapy.

SUMMARY

A 51-year-old Caucasian male with alcohol-related cirrhosis presented with 1-week history of pre-syncope and falls. He was found to have acute kidney injury meeting diagnostic criteria of HRS based on absence of identifiable contributing factors. After no response to volume expansion, medical management was initiated with midodrine and octreotide and eventually escalated to norepinephrine intravenous infusion. The patient's renal function and urine output improved initially on norepinephrine, but worsened when attempting to wean to a suitable outpatient regimen, becoming dependent upon norepinephrine. On day 13 of hospitalization, droxidopa was initiated at a dose of 100 mg three times daily and titrated to a dose of 400 mg three times daily. Norepinephrine infusion was weaned and discontinued on day 16 of hospitalization. The patient remained hemodynamically stable and was able to be discharged on droxidopa 400 mg three times daily, midodrine 20 mg three times day, and octreotide 200 mcg three times daily.

CONCLUSION

Droxidopa, an oral norepinephrine precursor, presents a novel adjunctive agent for management of HRS refractory to first-line medical management.

Treatment strategies for clozapine-induced hypotension: a systematic review

BACKGROUND

Clozapine is the most effective medication for treatment-refractory schizophrenia but is associated with significant adverse drug effects, including hypotension and dizziness, which have a negative impact on quality of life and treatment compliance. Available evidence for the management of clozapine-induced hypotension is scant.

OBJECTIVES

Due to limited guidance on the safety and efficacy of pharmacological treatments for clozapine-induced hypotension, we set out to systematically review and assess the evidence for the management of clozapine-induced hypotension and provide guidance to clinicians, patients, and carers.

DESIGN

We undertook a systematic review of the safety and efficacy of interventions for clozapine-induced hypotension given the limited available evidence.

DATA SOURCES AND METHODS

PubMed, Embase, PsycINFO, CINAHL, and the Cochrane trial Registry were searched from inception to November 2021 for literature on the treatment strategies for clozapine-induced hypotension and dizziness using a PROSPERO pre-registered search strategy. For orthostatic hypotension, we developed a management framework to assist in the choice of intervention.

RESULTS

We identified nine case studies and four case series describing interventions in 15 patients. Hypotension interventions included temporary clozapine dose reduction, non-pharmacological treatments, and pharmacological treatments. Midodrine, fludrocortisone, moclobemide and Bovril^® combination, and etilefrine were associated with improvement in symptoms or reduction in orthostatic hypotension. Angiotensin II, arginine vasopressin, and noradrenaline successfully restored and maintained mean arterial pressure in critical care situations. A paradoxical reaction of severe hypotension was reported with adrenaline use.

CONCLUSION

Orthostatic hypotension is a common side effect during clozapine titration. Following an assessment of the titration schedule, salt and fluid intake, and review of hypertensive and nonselective α1-adrenergic agents, first-line treatment should be a temporary reduction in clozapine dose or non-pharmacological interventions. If orthostatic hypotension persists, fludrocortisone should be trialled with monitoring of potassium levels and sodium and fluid intake. Midodrine may be considered second-line or where fludrocortisone is contraindicated or poorly tolerated. For patients on clozapine with hypotension in critical care settings, the use of adrenaline to maintain mean arterial pressure should be avoided.

REGISTRATION

PROSPERO (Registration No. CRD42020191530).

Management of Hypertension and Blood Pressure Dysregulation in Patients with Parkinson's Disease-a Systematic Review

PURPOSE OF REVIEW

The aim of this review article was to summarize the cardiovascular and blood pressure profile regarding Parkinson disease patients and to provide an update on the recent advancements in the field of the diagnosis and management of blood pressure abnormalities in these patients. Our goal was to guide physicians to avoid pitfalls in current practice while treating patients with Parkinson disease and blood pressure abnormalities. For this purpose, we searched bibliographic databases (PubMed, Google Scholar) for all publications published on blood pressure effects in Parkinson disease until May 2020. Furthermore, we highlight some thoughts and potential perspectives for the next possible steps in the field.

RECENT FINDINGS

Blood pressure dysregulation in patients with Parkinson's disease has several implications in clinical practice and presents an ongoing concern. Compared with chronic essential hypertension, the syndrome of combined neurogenic orthostatic hypotension and supine hypertension in Parkinson's disease has received little attention. If left untreated, hypertension may lead to cardiovascular disease whereas hypotension may lead to fall-related complications, with tremendous impact on the quality of life of affected individuals. The effect of blood Epressure control and the risk of death from cardiovascular disease in Parkinson disease are largely unexplored. Blood pressure abnormalities in Parkinson disease present bidirectional relationship and the rationale for treating and controlling hypertension in persons with Parkinson disease and concurrent neurogenic orthostatic hypotension and/or supine hypertension is compelling. Further research is warranted in order to clarify the mechanisms, clinical implications, and potential reversibility of compromised cardiovascular function, in persons with Parkinson disease.

New insights in diagnostics and therapies in syncope: a novel approach to non-cardiac syncope

This article aims to give advice on how to identify and manage patients with syncope who are at risk of severe outcomes, that is, at risk of trauma, potentially life-threatening episodes or frequent recurrences reducing quality of life. The first step of syncope diagnostic assessment is to identify patients with cardiac syncope, and once established, these patients must receive the adequate mechanism-specific treatment. If cardiac syncope is unlikely, reflex (neurally mediated) syncope and orthostatic hypotension are the most frequent causes of transient loss of consciousness. For these presentations, efficacy of therapy is largely determined by the mechanism of syncope rather than its aetiology or clinical features. The identified mechanism of syncope should be carefully assessed and assigned either to hypotensive or bradycardic phenotype, which will determine the choice of therapy (counteracting hypotension or counteracting bradycardia). The results of recent trials indicate that 'mechanism-specific therapy' is highly effective in preventing recurrences. Established mechanism-specific treatment strategies include withdrawal of hypotensive drugs, applying fludrocortisone and midodrine for the hypotensive phenotype and cardiac pacing in the bradycardic phenotype.

Drug-Related Orthostatic Hypotension: Beyond Anti-Hypertensive Medications

Orthostatic hypotension (OH) is an abnormal blood pressure response to standing, which is associated with an increased risk of adverse outcomes such as syncope, falls, cognitive impairment, and mortality. Medical therapy is one the most common causes of OH, since numerous cardiovascular and psychoactive medications may interfere with the blood pressure response to standing, leading to drug-related OH. Additionally, hypotensive medications frequently overlap with other OH risk factors (e.g., advanced age, neurogenic autonomic dysfunction, and comorbidities), thus increasing the risk of symptoms and complications. Consequently, a medication review is recommended as a first-line approach in the diagnostic and therapeutic work-up of OH, with a view to minimizing the risk of drug-related orthostatic blood pressure impairment. If symptoms persist after the review of hypotensive medications, despite adherence to non-pharmacological interventions, specific drug treatment for OH can be considered. In this narrative review we present an overview of drugs acting on the cardiovascular and central nervous system that may potentially impair the orthostatic blood pressure response and we provide practical suggestions that may be helpful to guide medical therapy optimization in patients with OH. In addition, we summarize the available strategies for drug treatment of OH in patients with persistent symptoms despite non-pharmacological interventions.

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.

Pure Autonomic Failure with Asymptomatic Hypertensive Urgency: A Case Report and Literature Review

We report the case study of a 70-year-old gentleman who presented with isolated, slowly progressive dizziness after prolonged standing and was eventually diagnosed with pure autonomic failure. Initially, his symptoms improved with the use of midodrine and fludrocortisone, but gradually became refractory and disabling. Despite multiple therapeutic interventions, his symptoms persisted along with worsening supine hypertension. We discuss the challenges faced in the treatment of an uncommon condition and discuss the clinical utility of performing serial 24-h ambulatory monitoring to detect subclinical blood pressure fluctuations.

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?

Prevalence, risk factors, and prognosis of orthostatic hypotension in diabetic patients: A systematic review and meta-analysis

BACKGROUND

Orthostatic hypotension (OH) is a major clinical sign of cardiovascular autonomic dysfunction in diabetic patients. Our aim was to quantitatively evaluate the prevalence and risk factors of OH in patients with diabetes mellitus (DM) and assess its prognosis.

METHODS

A comprehensive search of the PubMed, Embase, China National Knowledge Infrastructure, VIP Chinese Journal, Wanfang, and SINOMED databases was conducted for related published work up to September 25, 2016, and manually searched eligible studies from the references in accordance with the inclusion criteria.

RESULTS

We included 21 studies in the analysis, with a total sample size of 13,772. The pooled prevalence of OH in DM was 24% (95% confidence interval [CI]: 19-28%). Potential risk factors, that is, glycosylated hemoglobin A (HbA1c) (odds ratio [OR], 1.13, 95% CI, 1.07-1.20), hypertension (OR, 1.02, 95% CI, 1.01-1.02), and diabetic nephropathy (OR, 2.37, 95% CI, 1.76-3.19), were significantly associated with OH in DM. In addition, the prognosis of OH in DM was associated with higher risk of total mortality and cardiovascular events.

CONCLUSION

The pooled prevalence of OH in DM appears high. HbA1c, hypertension, and diabetic nephropathy are risk factors for OH in DM. OH indicates poor prognosis in diabetic patients. Attention should be focused on diabetic patients with the stated risk factors to prevent OH.

The Treatment of Primary Orthostatic Hypotension

OBJECTIVE

To review the efficacy and safety of pharmacological and nonpharmacological strategies used to treat primary orthostatic hypotension (OH).

DATA SOURCES

A literature review using PubMed and MEDLINE databases searching hypotension, non-pharmacological therapy, midodrine, droxidopa, pyridostigmine, fludrocortisone, atomoxetine, pseudoephedrine, and octreotide was performed.

STUDY SELECTION AND DATA EXTRACTION

Randomized or observational studies, cohorts, case series, or case reports written in English between January 1970 and November 2016 that assessed primary OH treatment in adult patients were evaluated.

DATA SYNTHESIS

Based on the chosen criteria, it was found that OH patients make up approximately 15% of all syncope patients, predominantly as a result of cardiovascular or neurological insults, or offending medication. Nonpharmacological strategies are the primary treatment, such as discontinuing offending medications, switching medication administration to bedtime, avoiding large carbohydrate-rich meals, limiting alcohol, maintaining adequate hydration, adding salt to diet, and so on. If these fail, pharmacotherapy can help ameliorate symptoms, including midodrine, droxidopa, fludrocortisone, pyridostigmine, atomoxetine, sympathomimetic agents, and octreotide.

CONCLUSIONS

Midodrine and droxidopa possess the most evidence with respect to increasing blood pressure and alleviating symptoms. Pyridostigmine and fludrocortisone can be used in patients who fail to respond to these agents. Emerging evidence with low-dose atomoxetine is promising, especially in those with central autonomic failure, and may prove to be a viable alternative treatment option. Data surrounding other therapies such as sympathomimetic agents or octreotide are minimal. Medication management of primary OH should be guided by patient-specific factors, such as tolerability, adverse effects, and drug-drug and drug-disease interactions.

Development and validation of a UPLC-MS/MS method for quantitation of droxidopa in human plasma: Application to a pharmacokinetic study

In this study, a simple and sensitive ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for quantitation of droxidopa in human plasma for the first time. A simple plasma protein precipitation method using methanol containing 3% formic acid was selected, and the separation was achieved by an Acquity UPLC™ BEH Amide column (2.1mm×50mm, 1.7μm) with a gradient elution using acetonitrile, ammonium formate buffer and formic acid as mobile phase. The detection of droxidopa and benserazide (internal standard, IS) was performed using positive-ion electrospray tandem mass spectrometry via multiple reaction monitoring (MRM). The precursor-to-product ion transitions m/z 214.2→m/z 152.0 for droxidopa, and m/z 258.1→m/z 139.1 for IS were used for quantification. A lower limit of quantification of 5.00ng/mL was achieved and the linear curve range was 5.00-4000ng/mL using a weighted (1/x(2)) linear regression model. Intra-assay and inter-assay precision was less than 10.2%, and the accuracy ranged from 0.1% to 2.1%. Stability, recovery and matrix effects were within the acceptance criteria recommended by the regulatory bioanalytical guidelines. The method was successfully applied to a pharmacokinetic study of droxidopa in healthy Chinese volunteers.

Autonomic Dysfunction: How to Identify and When to Treat?

Cardiovascular autonomic dysfunction (AD) is a particular condition that can be detected by means of ambulatory blood pressure monitoring (ABPM). ABPM is helpful to identify some specific characteristics of haemodynamic AD, including non-dipping/reverse-dipping pattern, orthostatic and post-prandial hypotension and elevated blood pressure variability. These characteristics may be misdiagnosed with traditional, clinic blood pressure measurements. AD is relatively common in the real world. By analysing about 1000 recordings in a Cardiology unit, AD was found in 6.8 % of the exams. Several diseases may be the underlying causes of AD. In our sample half of the subjects were diabetic (54.4 %), 17.7 % were patients with alpha-synucleinopathy (Parkinson disease or multiple system atrophy), and 27.9 % had other underlying causes of AD including chronic kidney disease, α-lytic drug assumption and AD from unknown causes. According to the different aetiology, different clinical characteristics can be found, in particular in diabetics these peculiar aspects are less pronounced compared to the other subgroups. These characteristics have been found to be predictors of cardiovascular events, organ damage, and mortality. For these reasons, early identification of these behaviours is important, in order to better define patient's cardiovascular risk profile. As regard treatment of AD, several drugs have been tested, however none of this showed efficacy in all kinds of patients. Another open aspect is "safe" reference values for supine hypertension.

Causes, consequences, and cures for neuroinflammation mediated via the locus coeruleus: noradrenergic signaling system

Aside from its roles in as a classical neurotransmitter involved in regulation of behavior, noradrenaline (NA) has other functions in the CNS. This includes restricting the development of neuroinflammatory activation, providing neurotrophic support to neurons, and providing neuroprotection against oxidative stress. In recent years, it has become evident that disruption of physiological NA levels or signaling is a contributing factor to a variety of neurological diseases and conditions including Alzheimer's disease (AD) and Multiple Sclerosis. The basis for dysregulation in these diseases is, in many cases, due to damage occurring to noradrenergic neurons present in the locus coeruleus (LC), the major source of NA in the CNS. LC damage is present in AD, multiple sclerosis, and a large number of other diseases and conditions. Studies using animal models have shown that experimentally induced lesion of LC neurons exacerbates neuropathology while treatments to compensate for NA depletion, or to reduce LC neuronal damage, provide benefit. In this review, we will summarize the anti-inflammatory and neuroprotective actions of NA, summarize examples of how LC damage worsens disease, and discuss several approaches taken to treat or prevent reductions in NA levels and LC neuronal damage. Further understanding of these events will be of value for the development of treatments for AD, multiple sclerosis, and other diseases and conditions having a neuroinflammatory component. The classical neurotransmitter noradrenaline (NA) has critical roles in modulating behaviors including those involved in sleep, anxiety, and depression. However, NA can also elicit anti-inflammatory responses in glial cells, can increase neuronal viability by inducing neurotrophic factor expression, and can reduce neuronal damage due to oxidative stress by scavenging free radicals. NA is primarily produced by tyrosine hydroxylase (TH) expressing neurons in the locus coeruleus (LC), a relatively small brainstem nucleus near the IVth ventricle which sends projections throughout the brain and spinal cord. It has been known for close to 50 years that LC neurons are lost during normal aging, and that loss is exacerbated in neurological diseases including Parkinson's disease and Alzheimer's disease. LC neuronal damage and glial activation has now been documented in a variety of other neurological conditions and diseases, however, the causes of LC damage and cell loss remain largely unknown. A number of approaches have been developed to address the loss of NA and increased inflammation associated with LC damage, and several methods are being explored to directly minimize the extent of LC neuronal cell loss or function. In this review, we will summarize some of the consequences of LC loss, consider several factors that likely contribute to that loss, and discuss various ways that have been used to increase NA or to reduce LC damage. This article is part of the 60th Anniversary special issue.