L-threo-dihydroxyphenylserine (L-threo-DOPS; droxidopa) in the management of neurogenic orthostatic hypotension: a multi-national, multi-center, dose-ranging study in multiple system atrophy and pure autonomic failure

Multiple system atrophy

BACKGROUND

It has been almost 4 decades since the descriptions of the 3 parts of multiple system atrophy (MSA) have taken place, characterized clinically by dysautonomia, parkinsonism, and cerebellar dysfunction. The discovery of a distinctive pathologic maker has finally provided the conceptual synthesis of these 3 entities into the universal designation of MSA as a distinct disease process with a complex combination of clinical presentations. Although advances have been made in terms of awareness and knowledge concerning the clinical features and pathophysiology of MSA, it remains challenging for neurologists who treat these patients to differentiate MSA from its mimics as well as providing them with effective treatment.

REVIEW SUMMARY

The aim of this review is to provide an overview of the advances in the knowledge of the disease, to highlight typical features useful for the recognition of its entity, and to enlist different treatment options.

CONCLUSION

Despite the fact that there is still no treatment modality that can alter the disease progression, a number of useful symptomatic treatment measures are available and should be offered to patients to ameliorate the nonmotor features of MSA and even the motor features that may at least transiently respond to treatment.

Management of neurogenic orthostatic hypotension: an update

Orthostatic hypotension (OH) is common in elderly people and in patients with disorders such as diabetes and Parkinson's disease. Grading of the severity of OH and its effect on the patient's quality of life are important. The symptoms vary with orthostatic stress, and subtle symptoms such as tiredness and cognitive impairment should be recognised. Standard drug treatment for OH is effective but worsens supine hypertension, whereas pyridostigmine can improve OH slightly but significantly without worsening of supine hypertension. Because orthostatic stress varies from moment to moment and drug treatment is suboptimal, drug treatment of OH needs to be combined with non-pharmacological approaches, such as compression of venous capacitance beds, use of physical counter-manoeuvres, and intermittent water-bolus treatment.

L-dihydroxyphenylserine (Droxidopa) in the treatment of orthostatic hypotension: the European experience

Neurogenic orthostatic hypotension is a cardinal feature of generalised autonomic failure and commonly is the presenting sign in patients with primary autonomic failure. Orthostatic hypotension can result in considerable morbidity and even mortality and is a major management problem in disorders such as pure autonomic failure, multiple system atrophy and also in Parkinson's disease. Treatment is ideally two pronged, using non-pharmacological and pharmacological measures. Drug treatment ideally is aimed at restoring adequate amounts of the neurotransmitter noradrenaline. This often is not achievable because of damage to sympathetic nerve terminals, to autonomic ganglia or to central autonomic networks. An alternative is the use of sympathomimetics (that mimic the effects of noradrenaline, but are not identical to noradrenaline), in addition to other agents that target physiological mechanisms that contribute to blood pressure control.L-threo-dihydroxyphenyslerine (Droxidopa) is a pro-drug which has a structure similar to noradrenaline, but with a carboxyl group. It has no pressor effects in this form. It can be administered orally, unlike noradrenaline, and after absorption is converted by the enzyme dopa decarboxylase into noradrenaline thus increasing levels of the neurotransmitter which is identical to endogenous noradrenaline. Experience in Caucasians and in Europe is limited mainly to patients with dopamine beta hydroxylase deficiency. This review focuses on two studies performed in Europe, and provides information on its efficacy, tolerability and safety in patients with pure autonomic failure, multiple system atrophy and Parkinson's disease. It also addresses the issue of whether addition of dopa decarboxylase inhibitors, when combined with l-dopa in the treatment of the motor deficit in Parkinson's disease, impairs the pressor efficacy of Droxidopa.

Prise en charge médicale des patients atteints de syndromes parkinsoniens atypiques dégénératifs

Atypical degenerative parkinsonian syndromes (progressive supranuclar palsy, multiple system atrophy, corticobasal degeneration, Lewy body dementia) are an important differential diagnosis to idiopathic Parkinson's disease. However, because these disorders are characterized by the degeneration of multiple neuronal populations, treatment approaches are much less specific than in Parkinson's disease, where dopamimetic drugs represent the mainstay of therapy. Thus, and because the progression of these disorders is usually more aggressive than Parkinson's disease, many physicians face a form of therapeutic resignation when confronted with patients suffering from atypical degenerative parkinsonian syndromes. However, in the present article, we wish to show that a symptom-by-symptom approach can substantially relieve the patients and their caregivers by providing an overview of pharmacologic and non-pharmacologic treatment options.

EFNS guidelines on the diagnosis and management of orthostatic hypotension

Orthostatic (postural) hypotension (OH) is a common, yet under diagnosed disorder. It may contribute to disability and even death. It can be the initial sign, and lead to incapacitating symptoms in primary and secondary autonomic disorders. These range from visual disturbances and dizziness to loss of consciousness (syncope) after postural change. Evidence based guidelines for the diagnostic workup and the therapeutic management (non-pharmacological and pharmacological) are provided based on the EFNS guidance regulations. The final literature research was performed in March 2005. For diagnosis of OH, a structured history taking and measurement of blood pressure (BP) and heart rate in supine and upright position are necessary. OH is defined as fall in systolic BP below 20 mmHg and diastolic BP below 10 mmHg of baseline within 3 min in upright position. Passive head-up tilt testing is recommended if the active standing test is negative, especially if the history is suggestive of OH, or in patients with motor impairment. The management initially consists of education, advice and training on various factors that influence blood pressure. Increased water and salt ingestion effectively improves OH. Physical measures include leg crossing, squatting, elastic abdominal binders and stockings, and careful exercise. Fludrocortisone is a valuable starter drug. Second line drugs include sympathomimetics, such as midodrine, ephedrine, or dihydroxyphenylserine. Supine hypertension has to be considered.

L-Dihydroxyphenylserine (L-DOPS): A Norepinephrine Prodrug

L-threo-3,4-dihydroxyphenylserine (L-DOPS, droxydopa) is a synthetic catecholamino acid. When taken orally, L-DOPS is converted to the sympathetic neurotransmitter, norepinephrine (NE), via decarboxylation catalyzed by L-aromatic-amino-acid decarboxylase (LAAAD). Plasma L-DOPS levels peak at about 3 h, followed by a monoexponential decline with a half-time of 2 to 3 h. Plasma levels of NE and of its main neuronal metabolite, dihydroxyphenylglycol (DHPG) peak approximately concurrently but at much lower concentrations. The relatively long half-time for disappearance of L-DOPS from plasma, compared to that of NE, explains their very different attained plasma concentrations. In patients with neurogenic orthostatic hypotension, L-DOPS increases blood pressure and ameliorates orthostatic intolerance. Inhibition of LAAAD, such as by treatment with carbidopa, which does not penetrate the blood-brain barrier, prevents the blood pressure effects of the drug, indicating that L-DOPS increases blood pressure by augmenting NE production outside the brain. Patients with pure autonomic failure (which usually entails loss of sympathetic noradrenergic nerves), and patients with multiple system atrophy (in which noradrenergic innervation remains intact) have similar plasma NE responses to L-DOPS. This suggests mainly non-neuronal production of NE from L-DOPS. L-DOPS is very effective in treatment of deficiency of dopamine-beta-hydroxylase (DBH), the enzyme required for conversion of dopamine to NE in sympathetic nerves. L-DOPS holds promise for treating other much more common conditions involving decreased DBH activity or NE deficiency, such as a variety of syndromes associated with neurogenic orthostatic hypotension.

Incomplete emptying and urinary retention in multiple-system atrophy: When does it occur and how do we manage it?

Neurogenic urinary retention can be a major cause of morbidity in multiple-system atrophy (MSA). However, the timing of its appearance has not been entirely clear, and neither have the medical and surgical modalities for managing patients. We present the data obtained from our uroneurological assessment and therapeutic interventions at various stages of MSA. We recruited 245 patients with probable MSA. We measured postvoid residuals (PVR) and performed EMG cystometry in all patients. The grand average volume of PVR was 140 mL (range, 0-760) in our patients. The average PVR volume was 71 mL in the first year, increasing to 129 mL in the second year and 170 mL by the fifth year. The percentages of patients with complete urinary retention, acontractile detrusor, and detrusor-sphincter dyssynergia (DSD) also increased. The increase in PVR resulted in a decrease in functional bladder capacity, together with an increase in detrusor overactivity and neurogenic sphincter EMG. Clean intermittent self-catheterization (CISC) was introduced in most patients. Bladder-oriented therapy (cholinergic agents) had a limited value, whereas urethra-oriented therapy benefited patients with DSD (surgery) for up to 2 years, but syncope occurred in a subset of patients (alpha-blockers). MSA patients present with large PVR by the second year of illness, and that large PVR secondarily causes urinary frequency. CISC is the recommended treatment for most patients. Urethra-oriented medication and surgery benefit patients who would have difficulty performing CISC, although careful consideration of the short-term efficacy and potential adverse effects of these alternatives is mandatory.

Management of multiple system atrophy: state of the art

Multiple system atrophy (MSA) is a sporadic neurodegenerative disease of undetermined aetiology presenting with parkinsonian, autonomic, cerebellar, and pyramidal signs. Despite the lack of any effective therapy to reverse MSA, some of the symptoms may be improved with adequate symptomatic therapies. Medical treatment is largely aimed at mitigating the parkinsonian and autonomic features. The therapeutic results of levodopa therapy in cases of MSA are difficult to interpret because of their variability. Nevertheless, the simple statement that patients with MSA do not respond to levodopa is false. Clinical and pathologically proven series document levodopa efficacy in about 40-60% of patients with MSA and predominant parkinsonian features. Other antiparkinsonian compounds (dopamine agonists, amantadine) may also be employed, but they are not more effective than levodopa. Orthostatic hypotension (OH) can be suspected from the patient s history and subsequently documented in the clinic by measuring lying and standing blood pressure. The diagnosis ideally should be confirmed with additional laboratory tests to determine the cause and evaluate the functional deficit, so as to aid treatment. A number of pharmacological agents with different mechanisms of action have been used in MSA to reduce OH when this is symptomatic. OH can also be alleviated by avoiding aggravating factors, such as the effects of food, micturition, exposure to a warm environment, and physiological diurnal changes, and by using other non-pharmacological strategies. The treatment of the very common genitourinary symptoms (incontinence, retention, impotence) should also be considered in order to improve the quality of life of these patients.

Therapeutic strategies in multiple system atrophy

This review provides an update on therapeutic principles and their implications for practical management in multiple system atrophy (MSA), a sporadic neurodegenerative disorder characterized clinically by various combinations of dysautonomia, Parkinsonism, or cerebellar ataxia, often associated with other warning features (red flags), and pathologically by cell loss, gliosis, and glial cytoplasmic inclusions in selected multiple regions of the brain and spinal cord. Because of the small number of randomized controlled trials, the management of MSA is largely based on empirical or open-label evidence. Parkinsonism often shows a poor or unsustained response to chronic levodopa therapy, although more patients than previously recognized may experience an initial moderate-to-good dopaminergic response. There is no effective drug treatment for cerebellar ataxia. However, features of dysautonomia such as orthostatic hypotension, urinary retention or incontinence, constipation, and impotence, may often be relieved if recognized by the treating physician. Because no drug treatment consistently benefits patients with this disease in the long-term, palliative therapies are all the more important. Novel symptomatic and neuroprotective therapies are urgently required.

Parkinson disease: an update

BACKGROUND

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

REVIEW SUMMARY

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

CONCLUSIONS

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

Pharmacology of orthostatic hypotension in Parkinson's disease: from pathophysiology to management

Orthostatic hypotension is highly prevalent in the elderly, and affects up to 20% of patients with Parkinson's disease. Pharmacological approaches help to demonstrate that Parkinson's disease is a primary autonomic failure with involvement of the peripheral autonomic nervous system as shown by decreased [(123)I] meta-iodobenzylguanidine cardiac uptake and preserved growth hormone response to clonidine. No specific clinical trial has evaluated efficacy of antihypotensive drugs in Parkinson's disease. End point of treatment should be a reduction in postural symptoms. Midodrine (Proamatin), Roberts Pharmaceutical), a vasoconstrictor and fludrocortisone (Florinef), Bristol-Myers Squibb), a volume expander are first choice drugs. No data are available on their effects on orthostatic hypotension-related morbidity. The usefulness of other drugs remains to be demonstrated. This review will highlight the importance of nonpharmacological measures in the management of orthostatic hypotension in Parkinson's disease.

Norepinephrine precursor therapy in neurogenic orthostatic hypotension

BACKGROUND

In patients with neurogenic orthostatic hypotension (NOH), the availability of the sympathetic neurotransmitter norepinephrine (NE) in the synaptic cleft is insufficient to maintain blood pressure while in the standing posture.

METHODS AND RESULTS

We determined the effect of oral administration of the synthetic amino acid L-threo-3,4-dihydroxyphenylserine (L-DOPS), which is decarboxylated to NE by the enzyme L-aromatic amino acid decarboxylase (L-AADC) in neural and nonneural tissue, on blood pressure and orthostatic tolerance in 19 patients with severe NOH (8 with pure autonomic failure and 11 with multiple-system atrophy). A single-blind dose-titration study determined the most appropriate dose for each patient. Patients were then enrolled in a double-blind, placebo-controlled, crossover trial. L-DOPS significantly raised mean blood pressure both supine (from 101+/-4 to 141+/-5 mm Hg) and standing (from 60+/-4 to 100+/-6 mm Hg) for several hours and improved orthostatic tolerance in all patients. After L-DOPS, blood pressure increases were closely associated with increases in plasma NE levels. Oral administration of carbidopa, which inhibits L-AADC outside the blood-brain barrier, blunted both the increase in plasma NE and the pressor response to L-DOPS in all patients

CONCLUSIONS

Acute administration of L-DOPS increases blood pressure and improves orthostatic tolerance in patients with NOH. The pressor effect results from conversion of L-DOPS to NE outside the central nervous system.

Syncope and orthostatic intolerance

Syncope and orthostatic intolerance remain common and significant clinical problems with many undocumented, misdiagnosed, or cryptogenic cases. Careful clinical assessment and application of advancing laboratory support can further improve diagnosis and treatment. Despite the depth of existing research into these common problems, many underlying mechanisms remain unproven.

Multiple system atrophy: pathophysiology and management

Multiple system atrophy (MSA) is a sporadic neurodegenerative disorder that usually manifests when an individual is in his/her early fifties and progresses relentlessly with a mean survival of 9 years. Clinically, MSA is dominated by autonomic/urogenital failure which may be associated with either parkinsonism (MSA-P subtype) in 80% of cases or with cerebellar ataxia (MSA-C subtype) in 20% of cases. Pathologically, MSA is characterised by a neuronal multisystem degeneration and abnormal glial cytoplasmic inclusions containing alpha-synuclein aggregates. Autonomic and urogenital features of MSA should be identified early on because they can be treated effectively in many instances. In contrast, pharmacological treatment of motor features is often disappointing, except for a minority of patients with MSA-P who derive transient benefit from levodopa treatment. In the future, neurotransplantation may extend or improve the treatment response in MSA-P, but further preclinical evidence is required prior to clinical application. Neuroprotection strategies may slow down disease progression in MSA and the results of the first double-blind trial of riluzole (an inhibitor of glutamate release) in patients with MSA will be available in 2004.

The role of cardiac metaiodobenzylguanidine uptake in the differential diagnosis of parkinsonian syndromes

Scintigraphy with radiolabeled metaiodobenzylguanidine (MIBG) enables the visualization and quantification of functionally intact adrenergic neurons and cells. In Parkinson disease, MIBG uptake of postganglionic cardiac sympathetic neurons is grossly reduced at an early stage of the disease in almost all patients with a clinical severity score of Hoehn and Yahr II or higher. Based on the meta-analysis of studies with a total of 246 cases of Parkinson disease and 45 cases of multiple system atrophy, the overall sensitivity to positively identify patients with Parkinson disease was 89.7%, and the specificity to discriminate them from patients with multiple system atrophy was 94.6%. Quantification of cardiac MIBG uptake is a valuable tool to identify patients with Parkinson disease and to discriminate them from other neurodegenerative disorders early in the course of the disease.