Etilefrine in the treatment of levodopa-induced orthostatic hypotension

Light in a Heartbeat: Bond Scission by a Single Photon above 800 nm

Photocages enable scientists to take full control over the activity of molecules using light as a biocompatible stimulus. Their emerging applications in photoactivated therapies call for efficient uncaging in the near-infrared (NIR) window, which represents a fundamental challenge. Here, we report synthetically accessible cyanine photocages that liberate alcohol, phenol, amine, and thiol payloads upon irradiation with NIR light up to 820 nm in aqueous media. The photocages display a unique chameleon-like behavior and operate via two distinct uncaging mechanisms: photooxidation and heterolytic bond cleavage. The latter process constitutes the first example of a direct bond scission by a single photon ever observed in cyanine dyes or at wavelengths exceeding 800 nm. Modulation of the beating rates of human cardiomyocytes that we achieved by light-actuated release of adrenergic agonist etilefrine at submicromolar concentrations and low NIR light doses (∼12 J cm-2) highlights the potential of these photocages in biology and medicine.

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.

Nonpharmacological treatment, fludrocortisone, and domperidone for orthostatic hypotension in Parkinson's disease

There is limited evidence for the treatment of orthostatic hypotension in idiopathic Parkinson's disease. The objective of this study was to determine the efficacy of three treatments (nonpharmacological therapy, fludrocortisone, and domperidone). Phase I assessed the compliance, safety, and efficacy of nonpharmacological measures. Phase II was a double-blind randomized controlled crossover trial of the two medications. Primary outcome measures consisted of the orthostatic domain of the Composite Autonomic Symptom Scale (COMPASS-OD), a clinical global impression of change (CGI), and postural blood pressure testing via bedside sphygmomanometry (Phase I) or tilt table testing (Phase II). For the 17 patients studied, nonpharmacological therapy did not significantly alter any outcome measure. Both medications improved the CGI and COMPASS-OD scores. There was a trend towards reduced blood pressure drop on tilt table testing, with domperidone having a greater effect.

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.

Orthostatic hypotension in patients with Parkinson's disease: pathophysiology and management

Orthostatic hypotension is common in elderly patients, and is now considered to be an important prognostic factor for cognitive decline and mortality. In patients with Parkinson's disease, the prevalence of symptomatic orthostatic hypotension may be as high as 20%. Two factors could explain this high prevalence. First, dopaminergic drugs may induce or worsen orthostatic hypotension. Secondly, Parkinson's disease is a cause of primary autonomic failure with an involvement of the peripheral autonomic system as shown by the ubiquitous distribution of Lewy bodies and reduced iobenguane [metaiodobenzylguanidine (MIBG)] cardiac uptake. These pathological and pharmacological characteristics clearly differentiate autonomic failure of Parkinson's disease from multiple system atrophy. If autonomic abnormalities appear to be present from the first stage of the disease, early onset (within the first year) of symptomatic orthostatic hypotension in the course of parkinsonism can be considered as an exclusion criteria for idiopathic Parkinson's disease. No specific clinical trials have evaluated the effects of antihypotensive drugs in patients with Parkinson's disease and thus no specific therapeutic strategy can be recommended. The management of orthostatic hypotension in patients with Parkinson's disease should always start with patient education and nonpharmacological treatment. Drug therapy should be reserved for symptomatic patients who do not get benefit from nonpharmacological management. Among the available drugs, alpha1-adrenergic agonists (mainly midodrine) or plasma volume expanders (mainly fludrocortisone) are the most frequently used. There are also some drugs that are currently investigational such as yohimbine and droxidopa. Other drugs such as desmopressin or octreotide may be of interest in some situations. Domperidone is widely used in patients with parkinsonism with no proven effect on orthostatic hypotension.

Pharmacological analysis of positive chronotropic and inotropic responses to etilefrine in isolated dog heart preparations

Positive chronotropic and inotropic responses to etilefrine (alpha-[(ethylamino)methyl]-m-hydroxybenzyl alcohol), an orally active cardiovascular agent, were investigated in isolated dog right atrial and left ventricular preparations. Intravenous administration of etilefrine to a support dog increased heart rate and mean systemic blood pressure, and increased sinus rate and atrial contractile force in the isolated right atrium perfused with blood from the support dog. Etilefrine injected intra-arterially to isolated atria and ventricles induced dose-dependent positive chronotropic and inotropic effects. Etilefrine was about 100 times less potent than isoproterenol. The effects of etilefrine in isolated atria were significantly inhibited by treatment with atenolol, but were not significantly inhibited by ICI 118,551. The effects of etilefrine were partially inhibited by imipramine. These results indicate that etilefrine is a highly selective beta-1 adrenoceptor agonist and suggest a moderate catecholamine-releasing activity by tyramine-like action in the blood-perfused dog heart.

The effect of sympathomimetic agents on noradrenaline efflux from a blood vessel

The effect of several sympathomimetic agents on the efflux of noradrenaline and its metabolites has been evaluated using the ventral artery of the rat tail as the experimental model. This vessel is richly endowed with sympathetic nerves and is therefore well suited to examine the efflux patterns of that transmitter. Etilefrine, tyramine, ephedrine and REN-293 were all found to increase the efflux of 3H-noradrenaline and/or 3H-DOPEG to different degrees from the artery. Possible reasons for this variation in metabolite efflux are discussed.

The neurotoxicity of the rat poison vacor. A clinical study of 12 cases

Oral ingestion of a new rat poison that antagonizes nicotinamide metabolism, N-3-pyridylmethyl-N'-p-nitrophenyl urea (PNU, Vacor), is known to cause diabetes mellitus. I describe neurologic complications of PNU ingestion in 12 patients 19 to 50 years of age who swallowed between 0.39 and 7.02 g of PNU. One died within a day, and five died of chronic complications 40 to 182 days after taking the poison. Apart from the acute hyperglycemic ketoacidosis, the clinical presentation was variable, but orthostatic hypotension, gastrointestinal hypomotility, peripheral neuropathy, and encephalopathy were typical. The peripheral, autonomic, and central-nervous dysfunction could develop either acutely or other several days. It is possible that nicotinamide, given parenterally within minutes, prevents toxicity, but the cases discussed in this paper indicate that the neurologic deficits may progress despite later nicotinamide administration. Neurologic improvement took many months. Full recovery was uncommon, and the orthostatic, hypotension tended to persist.

The indirect sympathomimetic activity of etilefrine--a comparison with tyramine and ephedrine using [3H] noradrenaline

The indirect sympathomimetic activity of etilefrine has been examined using the ventral caudal artery of the rat. This vessel has a rich sympathetic innervation and lends itself to studies on [3H]noradrenaline efflux from these sites. Etilefrine possessed significant indirect activity on the artery and this action, although less than that of tyramine, was equivalent to that caused by ephedrine. Pretreatment of the vessels with a mixture of iproniazid, doca, cocaine and UO521 (3',4'-dihydroxy-2-methyl propiophenone) significantly enhanced[3H]-noradrenaline efflux from the artery.

The effects of etilefrine on blood vessels in the rat tail

Etilefrine was found to constrict blood vessels in the rat tail through a mechanism which was partly dependent on the sympathetic nerves present in these vessels. The response to the drug was enhanced by pretreagment with noradrenaline and cocaine, and totally abolished by the alpha-receptor antagonist phentolamine. When compared with several other sympathomimetic agents which were tested on the vessel, etilefrine appeared to have a low order of vasoconstrictor activity. These findings would seem to have considerable relevance to the clinical situation where an attempt has been made to use etilefrine in the treatment of patients with orthostatic hypotension.