Treatment of dialysis-induced hypotension with L-threo-3,4-dihydroxyphenylserine

A randomized, placebo-controlled, phase 2 study of the efficacy and safety of droxidopa in patients with intradialytic hypotension

INTRODUCTION

Intradialytic hypotension (IDH) is the most common complication of hemodialysis (HD), and it plays a significant role in the morbidity and mortality associated with maintenance HD.

METHODS

This was a placebo-controlled, parallel-group study evaluating efficacy and safety of droxidopa in improving intradialytic blood pressure (BP) responses in 85 adults with end-stage renal disease (ESRD) and prone to IDH. Following screening and baseline periods, patients received 400 mg or 600 mg droxidopa, or placebo, orally 1 hour before HD for 4 weeks. Primary outcome endpoint was the change between baseline and last 2 treatment weeks in average mean arterial pressure (MAP) during HD. Also assessed were changes from baseline in systolic BP (SBP) and diastolic BP (DBP) during and after HD; number of hypotension-induced interventions and symptoms; and adverse events.

RESULTS

Increase in droxidopa intra-HD MAP were not significantly different from placebo, although droxidopa groups showed significant improvements in mean SBP after HD of +4.8 ± 11.6 mm Hg (600-mg) and +3.4 ± 13.1 (400-mg) compared with -4.4 ± 17.9 mm Hg in placebo, and the drop seen in mean nadir SBP pre- to intra-HD was also reduced. Changes in mean DBP pre- and post-HD, changes in mean nadir SBP post-HD, or intra-HD SBP were not significant over the treatment period. HD terminations decreased 5-fold in the 600-mg group and 2-fold in the 400-mg group, whereas the number of discontinuations stayed unchanged in the placebo group. Overall, treatment with 600-mg or 400-mg droxidopa was well tolerated in this population.

CONCLUSION

These data suggest that droxidopa may have a role in reducing IDH complications in patients with ESRD on chronic HD.

Droxidopa in neurogenic orthostatic hypotension

Neurogenic orthostatic hypotension (nOH) is a fall in blood pressure (BP) on standing due to reduced norepinephrine release from sympathetic nerve terminals. nOH is a feature of several neurological disorders that affect the autonomic nervous system, most notably Parkinson disease (PD), multiple system atrophy (MSA), pure autonomic failure (PAF), and other autonomic neuropathies. Droxidopa, an orally active synthetic amino acid that is converted to norepinephrine by the enzyme aromatic L-amino acid decarboxylase (dopa-decarboxylase), was recently approved by the FDA for the short-term treatment of nOH. It is presumed to raise BP by acting at the neurovascular junction to increase vascular tone. This article summarizes the pharmacological properties of droxidopa, its mechanism of action, and the efficacy and safety results of clinical trials.

L-DOPS and the treatment of neurogenic orthostatic hypotension

L-threo-dihydroxyphenylserine (L-DOPS) is an oral prodrug that is converted to the sympathetic neurotransmitter noradrenaline through a single-step decarboxylation by the endogenous enzyme 3,4-dihydrophenylalanine decarboxylase. DOPS can provide an exogenous source of noradrenaline to adrenergic neurons that are involved in the maintenance of blood pressure. Impaired secretion of noradrenaline at the synaptic junction can result in neurogenic orthostatic hypotension and cause faints and falls. The safety and efficacy of DOPS has been evaluated in patients with neurogenic orthostatic hypotension caused by a variety of neurological conditions that can result in autonomic failure, such as Parkinson’s disease, multiple system atrophy, pure autonomic failure and dopamine-β-hydroxylase deficiency. In this review, we include Phase II and III clinical trials undertaken that have examined the safety, efficacy and tolerability of DOPS in the treatment of neurogenic orthostatic hypotension. Drug mechanisms and pharmacology of the drug are also discussed.

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.

Prolonged protective effect of short daily hemodialysis against dialysis-induced hypotension

BACKGROUND/AIMS

Short daily hemodialysis (HD) has a protective effect against dialysis-induced hypotension (DIH). We examined whether this effect extends beyond the treatment period.

METHODS

We analyzed clinical variables in 6 patients (5 with diabetes mellitus) who underwent conventional hemodialysis (CHD) for 4 h three times weekly for 12 weeks; then short daily HD for 2 h six times weekly for 12 weeks, and then 12 more weeks of CHD. All patients had been given vasopressors for severe DIH.

RESULTS

The severe DIH disappeared during the short daily HD. There were significant decreases in body weight (BW), cardiothoracic ratio (CTR), blood pressure (BP), normal saline solution (NSS) amount (62.8 +/- 26.4 vs. 9.8 +/- 7.4 ml/session, p < 0.05), frequency (0.60 +/- 0.26 vs. 0.10 +/- 0.07 infusions/session, p < 0.05) and postdialysis atrial natriuretic peptide (ANP) (176.8 +/- 56.4 vs. 104.8 +/- 42.3 pg/ml, p < 0.05). Weekly ultrafiltration volume (6.3 +/- 0.9 vs. 7.9 +/- 0.7 l, p < 0.05) was significantly higher during the short daily HD period than during the first CHD period. The vasopressor treatment was therefore stopped or reduced in all patients during the short daily HD period. Because DIH recurred in the second CHD period despite a significant increase in BP, the vasopressor treatment was resumed in 5 patients. BW, CTR, NSS infusion amount and frequency, or postdialysis ANP did not differ significantly between the short daily HD and second CHD periods.

CONCLUSIONS

The protective effect of short daily HD against DIH lasted more than 12 weeks after the treatment ended. We therefore conclude that temporary short daily HD is useful for preventing DIH.